Rifle Scopes How Critical Is Sight Base Alignment With Bore?

[lestersurv]

Two weeks ago I decided to remount a couple of scopes had mounted on AR-rifles.

Switched two scopes from bolt rifles to the AR-10s. One of the bolt rifles has a Leupold Mk4 picatinny rail, other one Weaver Steel bases. Since the AR-10 rifles (flat-tops) both were equipped with LaRue LT 110 QD Risers, using low 30mm type rings, I figured just to check the reticle alignment with a boresighting tool.

Scopes were removed from all 4 rifles, rings left unchanged. Checking the first AR-10 scope moved to the Leupold Mk4 base I found the reticle was registering WAY RIGHT on the boresighter grid. I checked the second AR-scope on the Leupold base and found about the same Far To The Right position.

I put the scopes back on the LaRue Risers in same slot positions removed from and moved boresighter to each AR. The scopes were then registering correct and much closer to center of the boresighter grid.

I then took the bolt rifle scope orig on the Leupold mk4 pic rail noted the position of reticle on the grid and then mounted the scope on both AR-10 rifles w/o the LaRue Riser. The reticle remained in same alignment on boresighting grid. Then mounted the LaRue riser on the AR-10 and checked scope on grid. Reticle was 8 MOA right of position when mounted on bare AR-10 flat-top or the Leupold Mk 4 Picatinny rail.

Repeated the tests with the other AR-10 and found same results.
My tests show that the LaRue QD Riser model LT 110 QD shifts the axis of scope mounting 8 MOA Right compared to scope mounted on AR-10 integral picatinny rail which is machined/cast integral to receiver.

Have been using these LaRue risers for couple years, but never checked bore alignment of base with receiver... Rifle shot well at range when zeroing, but that is how a Zero works; ain't it?

If the scope is 8MOA right of bore and sighted-in/Zeroed at 100yds, how much error is there gonna be at 300yds or more? Probably quite a bit? This led me to conclude the 3 LaRue LT 110 QDs that I own are useless.

Wonder if this is a problem with other LaRue QD scope bases? Seems like they are all designed the same with the QD levers on left maybe being the reason for the 8MOA shift to right.

I have gone back to using 30mm high rings on the ARs that were setup using these risers. Have 5 rifles need to confirm zero. Don't shoot the ARs from bench very often. Now seems likely that my shooting with the AR rifles will likely improve since scope will track bore and not be 8 MOA Off at distances shorter and longer than zeroed-range...

 

[Redmanss]

Re: How Critical Is Sight Base Alignment With Bore?

8moa is not that much of an offset, especially when you're still talking about your bore sight. Put the rounds downrange and see where you actually fall at. I say quit over thinking it on the work bench and get to the range.

Lateral offset becomes an issue when it's to a degree that it causes your erector tube to hit the side wall earlier on elevation adjustments than it would if it were centered. If you're still able to run your scope all the way up as far as you need to, you're fine. This will depend on what scopes you're using and how much elevation travel they have in the first place too.

By the way, an 8moa shift at 100yds will still be 8moa shift at 300yds or 3000yds. MOA is an angle, not a distance, and range to target has no relevance on it.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

If reticle is not aligned with bore, reticle is at an angle to bore when zeroed and only in alignment at exact point zero, unless you don't mind impact being inches from your point of aim; in this case 8" distant from strike of bullet.

Not desiring a weapon that places bullet 8" consistently to right of point of aim, I returned the 3 risers as LaRue salesman instructed.

If you imagine the angle between scope offset to zero point as a line like this: \ you can tell that your impact will be to right at range impact occurs before your zero and to left after the bullet passes point of zero.

Even were the error NOT multiplied by the yardage factor it would remain objectionable. The error though is multiplied because the further past the zero-point bullet travels, the greater the angle and thus the error.

Had I not changed all these scopes at same time and compared AR scopes on the Leupold bolt gun MK4 rail, would have continued to believe the impact errors in my shooting w/AR were my fault or the rifle's...

 

[Redmanss]

Re: How Critical Is Sight Base Alignment With Bore?

Your question was "how critical is sight base alignment to the bore". I answered that question, and you may have misunderstood my answer thinking that I'm incorrect. I'm not always the most eloquent and thorough in my responses. You don't have your profile's location filled out, but something tells me we may have a language barrier here because I'm having a hard time comprehending exactly what you're saying.

Your scope tube might be offset from your bore, but the erector tube would be in line after you adjust it. It's like running a canted base for elevation, only yours was offset for windage. Like I said before, if you were still able to run it up to the elevation you needed for your maximum range you intend to be effective at and you had the available travel, you could run with it. Having enough available right windage might still be an issue at the elevation fringe, that is if you dial for wind at distance instead of holding for it. You may encounter this further with a 30mm Leupold running on a flat base.

Basically when you zero you're lining up your lateral line of departure with your line of sight. This is done in the erector tube or movement of the reticle (depending on scope design), not with the scope tube/base itself. Obviously you want it to match as closely as possible, but having an offset in there is not always a fail of the system.

Something tells me that with all three bases being off to the same degree, it wasn't the bases that has the problem, it's your receiver where the bases were making contact. Maybe a small burr, bump or recess is causing the misalignment with those bases, but when you use another base that doesn't make contact at the same point you don't see it. I'd say it was a good idea returning them and going with an alternative that works.

Glad you found your solution so you don't need to deal with the problem in the first place. Happy shooting.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Here is the deal:

Scopes that came off bolt guns were basically in correct alignment with AR-10 bore, when mounted on the AR-10 flat top receiver w/o the LaRue riser. Put them on the riser and the boresighter showed an 8moa shift to the right.

Scopes removed from AR-10 rifles orig, then placed on boltgun bases showed 8moa to right positioning.

It ain't a matter of either the AR-10 flat top receiver or the boltgun weaver or Leupold Mk4 base. Scopes zeroed on the boltguns held same relative position with right orientation of reticle.


Erector position aside since we are not discussing windage or reticle movements, what matters is that zeroing any scope on the LaRue Riser results in an 8" shift to the right of bullet impact. Dialing the scope to Left 32 clicks (1/4 moa) to be Zeroed or On-Target at 100yds means the barrel is out of alignment and will be grouping right at any distance under 100yds and grouping left at any distance past the zero yardage.

At 200 yds, group will be 8" to left. At 300yds 16" at 800yds impact would be 56" to left.

The scope is on one plane, 8" to right of bore-line. Scope cannot bend-over or shift alignment. If out of alignment it is out of alignment.

Precision Shooting article compendium book discusses the alignment of base, reticle, and bore for most precise shot delivery. TJ Jackson wrote "To Insure Centered Optics". Jackson uses a collimator and epoxies bases, laps rings to be certain that benchrest competition gun he built is oriented perfectly to bore. Jackson makes sure to note "the collimator cannot be disturbed from start to finish of the job, even while epoxying the bases and possibly milling screw slot to add some windage for the zero on collimator.


more later

 

[Redmanss]

Re: How Critical Is Sight Base Alignment With Bore?

I've done it down range and made it work just fine, all the way out to 1000yds. I don't have any epoxy or collimators here in the sand box, but what I do have is less than perfect rifles and scopes I'm required to work with. Don't get me started on how long it takes to get a replacement when something is broken or out of spec, but we make it work. Funny, I zero a scope and it requires a 10+ moa windage adjustment for its 100yd zero, yet I can hit targets at a wide variety of ranges by dialing elevation and holding windage. It's a good thing it didn't know about that article of yours, it might have had a lapse in self confidence and driven those rounds into Logar Province.

Food for thought... Think about the difference between physical and angular separation of two planes. Don't come back when you figure it out, just have your own "ah hah" moment quietly to yourself and move along.

I'm going back to the range. Suggest you do the same, right after you fill out your profile. Cheers.

 

[Lowlight]

Re: How Critical Is Sight Base Alignment With Bore?

8" at 100 yards is a little less than ten thousandths of an inch at the scope. And standard rings are slightly different than QD rings due to the locking levers which would account for your difference.

Comparing anything a bench rest shooter is telling you needs to be taken with a grain of salt. At least when it comes to this. Bench rest is a lesson in engineering based on a lot of theory used to buy results. At the end of the day because of how bench resters operate, the scope could be mounted offset by a foot and it would not make any difference. You are zeroing for the single range shot and the angular deviation is accounted for by use of the internal adjustments. As long as you know the adjustment for the range it doesn't matter. Think of an offset scope on an M1D.

When you zero a scope on your field rifle you are accounting for more than just the alignment over the bore. You are accounting for the deviation caused by the shooter. In the past, at a precision rifle class we took a rifle zeroed in a mechanical rest at 100 yards. Letting 10 shooters, shoot the rifle there was 4" of horizontal dispersion between the 10. That deviation would be removed if you let each person rezero. The worst the shooter, the more adjustment goes into a zero.

What you saw is common and not worth worrying about. The only time it would be an issue is if the scope was not tracking vertical because it was getting side pressure from the tube. You simply have to check vertical tracking with a level line across 100% of the necessary adjustment range. If it tracks vertical the shot will go where the reticle is. You are not compounding that 8" if you zeroed the scope, any deviation at that point is probably shooter induced.

 

[Augustus]

Re: How Critical Is Sight Base Alignment With Bore?

Lesterserv, you are suffering from a severe case of analysis paralysis.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Have owned a Badger AR riser in the past and a couple of Swan's including one with fold-down rear sight. Never thought to test those, but their design with the hex head through-screw and base that is essentially a plate fits over the AR-10/15 flat-top is probably not Off-Set.

So Forum-Owner takes time to tell me how it is. I appreciate the "don't worry about it", but am not convinced. M1-D with offset mount is about as precise as a Winchester 94 with a side-mount. Not the thing for precision shooting.

Not talking about "making-do". I don't want to induce any error in alignment of any sort on a weapon I intend for longrange precise bullet delivery. Am I a "sniper"? No...

Have owned a Badger Ord rem 700 +30moa picatinny base. It was out of spec. Found this out after I parted out the .300win Sendero It was mounted on for 5 years. Never could get that rifle to group well at 300yds. The .308 I had at same time w/Badger mount system would deliver 5rds under .4" at 100 and under .7" at 200yds. The .300 win groups were decent at close ranges but out at 300 went to shit. Two years later comparing several scope bases, found the BO base slots were not cut square to base..

Tell me why it don't matter...
Scope position, LowLight says, is .0001" off to right on the mount. This produces an 8" shift right at 100yds. I put two .05 shims under a Steel Weaver or Leupold QR base to get 20moa cant. This translates to .1 delivering 20moa at 100yds; roughly. The 20moa gain adds 200moa at 1000yds so can get extra elevation scope does not have to compensate for great amount of bullet-drop at longrange; or to keep scope reticle/erector from being bottomed-out.

If reticle has to be canted left, to compensate for scope being off-center of bore to right; and the cant or compensation of windage is 8moa at 100yds; then how is that error not magnified as range increases?

 

[E. Bryant]

Re: How Critical Is Sight Base Alignment With Bore?

You have an angular offset, not a linear offset. We know this because your scope is not offset from by bore by 8".

Because you have an angular offset, you can easily correct for it with an angular adjustment of the scope. This will not cause a POA/POI change at varying ranges, because making the angular adjustment in the scope to compensate for the angular offset of the mount will put the optical axis of the scope in parallel with the barrel axis. If there is any remaining linear offset due to minor manufacturing errors in the mount/rings/receiver, then it will still be inconsequential at any practical distances.

If this still troubles you, I would suggest that you either sit down with pencil and paper to draw things out, or that you actually get out to the range and figure things out for yourself. The good news is that your hypothesis, however flawed, should be very easy to test and prove or disprove; if you're right, you will be off by a whopping 4" at 50 yards and 16" at 200 yards. You won't be off that far.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Here is what I understand about scope geometry:
-- A .1" addition under rear scope base adds approx 20moa to elevation by positioning reticle 20moa below where reticle would register w/o additional lift upon rear base. A .15" lift under rear base adds approx 30moa of cant.
-- Scope is essentially a telescopic optic with crosshair that moves a given value in vertical and horizontal positions.
-- Scope cannot compensate or approximate it can only move reticle, when correctly adjusted, according to specifications.
-- Any error in alignment or position at shortrange will be magnified.
** Scope shift in vertical position (cant) tracks trajectory arc by using otherwise unavailable scope tracking by shifting zero from say 105 clicks down from top movement to 10 clicks down from top movement to zero scope at 100/150yds. Scope then has 55moa out of maybe 60moa (240 1/4moa clicks) of usable elevation to better track the arc of bullet and thereby be on-target at greater distance w/o resorting to hold-over.
-- If scope does not track bullet in alignment w/bore, error is magnified with distance and (seems to me, but I did not test at range to prove...) if shimming base changes orientation of scope, but retains scope/bore alignment then the "error" induced is beneficial. Error in scope base horiz alignment can Never Be Beneficial.


There are many variables at work everytime a bullet is fired. Shooter variables, ammunition variables, temp/elev/humidity variables and any rifle platform elements that could have changed or "adjusted"...

If you have to make-do, you have to make-do... But why select gear that induces variables that aren't beneficial to shooting equation?

Why wouldn't mfr of "precision rifles and mounts" (IE LaRue) not verify that their mount was plumb/perpendicular with bore and exactly in0line with integral base of receiver; or enable end-user/shooter to adjust the mount so it was in-line?

 

[Lowlight]

Re: How Critical Is Sight Base Alignment With Bore?

Isn't ten thousandths .01... and not .0001 ?

Anyway, you are way over thinking it...

Did you ever think you could shoot well with a 308 and not a .300WM because you weren't very good with the extra recoil. That is a much more common occurrence and something we see all the time. Heavier recoiling rifles influence the shooter much more, hence bad groups.

I would like to know how the scope being off center, then zeroed to center is causing bad groups ? It's a good excuse for bad shooting and I will be sure to include in my list of excuses.

Generally speaking the average person is a terrible semi-auto shooter when compared to a bolt gun. it is much more sensitive to bad form due to the multiple recoils. So saying the Larue mounts were causing bad accuracy because they needed some extra windage when zeroed is a bit out there... and trust me I am usually the first one to go on about Larue, but here, not so much. I think the problem is, you, over thinking things.

How is Larue supposed to know how your rifle is assembled, built, etc, to verify plumb... that is what the windage knob is for. If .1 is 20MOA at 100, then .05 is 10 inches... the mount is not the issue here. That little off center is not causing a variable, once it is on and tightened how is it moving to be a variable.

I have a bunch of Larue QDs, I have a Bobro, GDI, etc, as well as more time behind a rifle than most, and in case, you're thinking is not holding up to scrutiny.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Scope that is positioned off-axis in amount that equals 8" at 100yds can, likely will induce tracking errors or limit vertical tracking at bottom range of movement (most distant range).

Scope only tracks full 60moa elevation range of movement when reticle is closely centered in erector tube. Likely that unless you have scope rings that can be windage shifted, you will have some windage shift in getting your zero.

Lots of variables affect setting up a zero. Ammunition being the largest variable, followed by change of shooters. Unless sight base or barrel component has changed in some way rifle should track trajectory arc correctly in an enclosed range w/o wind effects and w/o shooter induced error.


How much "marksmanship" at higher levels is really a matter of mental confidence? I say "plenty".

What shooter whose purpose is to deliver precision riflefire is going to be pleased having one additional factor to deal with or perhaps nag them when the pressure is on?

The M1 Garand was not designed to be be scoped. The M14 was not designed to be scoped, but was adapted for that purpose. AR-10 flat-top A3 receiver is best semi-auto platform for scoped use, but there is no reason to opt for a mount system that takes scope out of alignment with bore.

 

[Lowlight]

Re: How Critical Is Sight Base Alignment With Bore?

So regardless of how straight the base / bore alignment is, if a shooter adds any windage to the scope it will not track straight ... at least that is what you are saying based on my read of your explanation ?

If I add even 1 minute of windage to my scope when zeroing the scope will be off.

That about sum up your explanation that scopes should be zeroed with 0 windage ?

 

[wnroscoe]

Re: How Critical Is Sight Base Alignment With Bore?

There's more to scope base / bore alignment than you think. Chances are, the scope base holes are straight when compared to the receiver center line. In factory, un-tuned bolt rifles, the receiver threads, barrel threads and recoil lug usually play a larger role in misalignment than scope base holes. Recoil lugs being the biggest culprit in the equation.

The Larue or any other flat top upper AR10/15 have the advantage of being designed and manufactured on CNC equipment, they’re going to be 100% straighter than a factory bolt gun.

When a barrel is installed on a bolt, gasser or piston type rifle, if the muzzle isn’t clocked at 12:00 on every one, there’s no way you can/could expect a scope that was taken off rifle A and placed on rifle B to be looking in/at the same spot. The rifles will simply print targets with a POI shift from rifle A to B.

If you want to check scope base holes to bore alignment simply center your scopes windage knobs L/R and compare that to your bore. It wont be 100% scientifically correct but, it will be closer than what your trying to do.

Simply put, your bolt guns are looking in a different direction than your AR’s, the Larue QD’s are fine, they were CNC‘d too.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

A human hair is .003" or three-thousandths
Thirty ten-thousandths would match thickness one human hair.
.01 is one-hundredth of an inch

The Badger ord 700LA scope base was .05" out on the right side of the mount when compared to NightFoce, Warne, and Near mounts also of LA type. I will never again by a split slot scope base.

Probably am OverThinking it, but when I put the Leupold mk4 or viper PST scope onto the AR-10 and have no offset, it raises my confidence that the gear is in correct alignment and will track correctly.

The TJ Jackson article is worth reading and considering.
A boresighter w/collimator grid is a great tool to have access to for many reasons

As to the offset issue again, how is the LaRue offset any different from scope mount holes in a receiver not being centered or the Badger Ord slots not being perpendicular to the receiver or bore? One side .05" out of alignment with the other.

I don't think the recoil of the .300win mag was the issue, as groups went to hell further from zero that I fired them. Never occured to me to test the base, it was a Badger... In 2001, they were about the best I knew of...

I have seen some rings that have windage shift integral to each ring. I would prefer not to have need for such ability or have to pay for it to correct a problem that shouldn't be there in the first place.

LaRue has had my gear for almost two weeks and I have called 3 times to find out about the refund I was promised. If the salesman could have told me how to adjust them to bring them in-line I would have kept them.

I am not interested in owning gear that induces any new variables unless I decide I might use them to my advantage.

 

[Lowlight]

Re: How Critical Is Sight Base Alignment With Bore?

Okay, so answer my question... if a scope has any windage dialed in at Zero, according to your logic it will not track true.

A scope zeroed on any rifle with 1 MOA of windage will trend off center at distance ... at least according to your math. This is what you are saying, true ?

And ten thousandth of an inch is, .010 like i said, look it up. You are showing one ten thousandths of inch.

 

[Lowlight]

Re: How Critical Is Sight Base Alignment With Bore?

Oh and how did the groups, "go to hell" the further from zero... all that would have happened if it wasn't the shooter would be... they would deviate from center, and not spread the group out.

if the base was off and the scope was not tracking true, the group would just be left or right of center by a certain degree... they would not "go to hell" they would be the same, just off center.

Read what you are writing, that your accuracy, "groups" as you put it is opening up at distance... That does not hold water in explaining your dilemma here. Nothing is moving, according to everything you are describing they are just slightly shifted off center. Grouping has nothing to do with center line.

I could mount my scope on its side and zero it and the rifle will group the same. If I then dialed my rifle with the windage knob it will still "group" the same.

Nothing you say makes sense... I think your reading comprehension is a little at fault here causing you to overlay errors in shooting toward these mysterious problems with plumb and center lines.

 

[E. Bryant]

Re: How Critical Is Sight Base Alignment With Bore?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lestersurv</div><div class="ubbcode-body">How much "marksmanship" at higher levels is really a matter of mental confidence? I say "plenty".</div></div>

Well, now we've at least made some progress - you are correct in determining that the problem exists in your head, because it almost certainly does not exist with your setup. Putting rounds on paper at various ranges would have already proved this, if indeed you were interested in finding an answer.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What shooter whose purpose is to deliver precision riflefire is going to be pleased having one additional factor to deal with or perhaps nag them when the pressure is on?</div></div>

Why would this be an issue at any point after the rifle has been zero'd? It won't. Set the thing up, select a zero at an appropriate range, acquire data at various other ranges to confirm the perform of your setup, and move on with life.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Frank,

Sorry for misunderstanding about the thousandth, ten-thousandth thing.

What I am concerned with is not the dialed-in windage of the scope, it is the off-centered mount. If the mount is one-hundredth to right of the bore, the mount is no-good.

Aren't receiver scope mount holes that are not correctly aligned a problem? If we had a receiver that was flat on both receiver bridges and the scope mount holes were drilled .01 to right of center of the receiver, would the receiver be acceptable? Who would really see the offset until they began having problems and investigating?

I'm saying that because the scope is not aligned with the bore that it won't track true to the bore and the only time it will be on-target by dialing constant values is when the scope is at distance it was zeroed at.

The scope is .10 or more to right of bore-line, so windage that would otherwise not be applied (IE 8moa at 100yds) is applied and because the scope has to be corrected for offset, the offset effects the windage at every distance but where it is zeroed-in.

If the scope were in alignment with the bore, with a perfect base and rings, there would be no need to apply windage because scope was positioned in alignment.

I have used Brownells scope alingment rods to setup my scope rings very often. These gizmos are 1" and 30mm rods that fit in each scope ring and are machined to a precise point. When points touch, they are in alignment and concentric. On a canted base the rear rod is higher than the front, but with tips still in alignment you know your scope is squared to the base and rings are perfectly aligned. If your scope is horizontally at center, it should remain so with rings so oriented to base when you use bore collimator grid to align reticle.

This is the same sort of issue with using an adjustable front sight base on an AR-15 service rifle to preserve the center-mark of the rear sight at your zero. The front sight is adjusted at the distances being fired so shooter has full windage R & L. If the front sight is cocked, the sight post can be filed and then height adjusted so still have correct aperture w/flat post sight picture.

When scope is offset from centerline though the entire sight is cocked or minutely out of alignment. Since you can't bend the scope tube into alignment with the bore and you have MOA magnified error induced from the misalignment, you have lots of problems...

If you're zeroed at 100, you've already dialed in 8" left to offset the 8" right causes by the misaligned sight base. The only windage clicks that will be correct unless by chance will be at your zero distance. None really ever apply at 100yds, unless shooting in a hurricane...

Scope can only track one line horiz and one line vertical. If the scope is out of alignment by 8moa at 100yds before bullet is even fired, the scope cannot track bullet path because it is cocked to begin with and out of alignment.


Overthinking this shit? Maybe. By ditching the junky equipment that moves my scopes out of line with bore I figure I have eliminated a bunch of variables and brought scope mounting and tracking back to something I can verify and understand. That makes me a more confident shooter because I know my scope tracks true to the barrel with no offsets.

 

[Lowlight]

Re: How Critical Is Sight Base Alignment With Bore?

Ok, you're clearly smarter about this than a lot of people, it's amazing people can hit anything following your logic. Any scope zeroed on a rifle that has any Windage dialed in suspect. I suppose for people like me ignorance is bliss.

Ask a gunsmith to explain to you timing of the bore, and then find out how many rifles have timed barrels, as Roscoe alluded to above. Which is part of it, forget the shooting part.

Still doesn't explain how a group can go to hell, no matter we don't need another book written.

Best of luck with your search for zero deviation.

 

[Redmanss]

Re: How Critical Is Sight Base Alignment With Bore?

And is why I dropped from the conversation earlier...

 

[E. Bryant]

Re: How Critical Is Sight Base Alignment With Bore?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lestersurv</div><div class="ubbcode-body">Overthinking this shit?</div></div>

Underthinking - or at least incorrectly-thinking - seems to be a far greater problem here.

Once again - go hit the range and prove your hypothesis with some actual hits on targets.

 

[treebasher]

Re: How Critical Is Sight Base Alignment With Bore?

Fuck it, I'm throwing my rifles in the trash and going to slingshots...

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Probably should have posted this in the gunsmithing section.

What is the purpose of building a rifle with trued boltface, trued barrel threads to receiver assuring firing pin strikes perfect center on primer if the fucking scope is offset by so much that it takes 8" correction to bring it online with the bore at 100yds?


You guys say no biggie, just go shoot it kemosabe and fugedaboudit.

The problem is the scope is entirely off axis with the barrel. Like a tube on-side of a spotting scope. It gets you in the neighborhood of what you're looking for but it ain't precise.

As long as the scope is precise and on-axis with bore it can track the bullet no matter where it goes. Bullet can only go so far off-tangent from the bore upon exiting. Yet, the bullet if crown isn't good or bore is dinged can leave barrel cocked...

Scope is already cocked from the bore, because it's out of alignment. Scope is cocked so is already at miniscule angle to register to the bore.

Almost like artillery. Registering the gun. They are shot without sights, no? Scope on the LaRue don't track the bore, so it is registered at 100yds. Like arty, has to be re-registered for any other distance because sight don't track the bore and only intersects the bullet path when registered to do so...

You guys follow?

Bullet cannot veer to left .01" immediately upon exiting bore. Bullet cannot be tracked by scope because scope plane and bullet traverse are not aligned. Close but not aligned.

Scope when adjusted 32 clicks left to compensate for being mis-aligned does not track the bullet. 32 clicks only gets it to center of boresighter. Scope w/o the LaRue is fine. All 4 scopes on plain picatinny rail boresight to about same spot on grid collimator Put them on the LaRue and theyr are 2 grid to right and 1 grid equals 4moa.

= see the two lines. one is barrel, other is scope. If scope isn't vertically aligned with barrel it cannot track bullet. Scope being .01" right of barrel can only parallel the bore, or if shifted to intersect the bore line, can only intersect/intercept at one spot; one bullet diameter along the line of bullet trajectory...

Make any sense to you?

parallel lines. they never intersect.
Any scope that isn't plumb, perpendicular, and squarely mounted to bore is not going to track bullet with precision.


One other thing about the LaRue 5/8" riser. It also adds another .5875" to the distance your optic is offset from the bore. The additional height adds to the angle and exaggerates even more the effect of the offset.

The weapon is only zeroed at one specific distance. Registered on target. Shoot at another known distance, have to register again because the offset requires scope to move at angle to the boreline and bullet trajectory.

 

[Lowlight]

Re: How Critical Is Sight Base Alignment With Bore?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">= see the two lines. one is barrel, other is scope. If scope isn't vertically aligned with barrel it cannot track bullet. Scope being .01" right of barrel can only parallel the bore, or if shifted to intersect the bore line, can only intersect/intercept at one spot; one bullet diameter along the line of bullet trajectory...</div></div>

Ok, let's say we agree with you,

How do the groups, "Go to Hell" .... Still haven't answered that one. It tracks parallel, but how does that effect the group? It will only effect where the center of the group lands, not the size. nothing is moving.

Also go as Sterling Shooter on here in the marksmanship section about recoil pulses and how the recoil pattern against the shooter effects the angular deviation of the shot. As in how will a shooter print in a different location between two rifles with different recoil pulses, or in other words, coming full circle. How does a rifle zeroed on a mechanical rest strike as much as 4" from center depending solely on the shooter? Scope and bore are registered as you put it.

 

[treebasher]

Re: How Critical Is Sight Base Alignment With Bore?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lestersurv</div><div class="ubbcode-body">Make any sense to you?</div></div>

Yep, I put my time in at the Colorado School of Mines.

Thing is you are over thinking it. When you go out and put it to practice the small amount of deviation that you are talking about doesn't matter two shits.

If the 0.050" off of the bore center-line to scope center-line is bothering you why don't you just zero your rifle 0.050" left/right of center? That way the bore axis and the scope axis are parallel?

There, problem solved. BTW, I charge $200/hr for consulting fees...

 

[USMAGator]

Re: How Critical Is Sight Base Alignment With Bore?

If you're seeing a noticable shift in POI at any distance due to a .01 (one one-hundredth) of an inch difference between the axis of your bore and your optic/mount, then thats some pretty impressive shooting. If you draw this out on paper and apply simple trig I think you'll find that you're only going to pick up .01 inches of deviation for each additional 100 yards (assuming a 100 yard zero). So at 1000 yards you're talking about a tenth of an inch difference in your zero. At a MILE you're looking at .172 inches difference. Good luck noticing that in terms of practical accuracy.

Maybe you're a good enough shooter to notice this difference. I'd wager that you'd be better served by spending some more time behind the trigger and reading the wind before you get too worked up about that difference.

 

[Redmanss]

Re: How Critical Is Sight Base Alignment With Bore?

Hey Lester, is this you? Multiple accounts here? What was your screen name previously? It seems you don't like us professional sniper types, me being an 8541 and all, so no wonder you don't want to take the advice from us now.

http://lunaticoutpost.com/Topic-New-Blog-Lester-On-Survival

http://lesteronsurvival.blogspot.com/

http://www.counter-sniper.blogspot.com/

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Over the years, I have been banned several times from snipershide forum. The bans were for disclosing the ineptitude of vendors in comments to persons considering purchase of product. None of my postings were ever different in tone or exaggerated from what you will read here; just that the forum with 70,000 members who had been "conditioned" by the Old Salt Experts to revere the vendors they touted could not be informed of mistakes or frauds that might sway opinion and impact their business.</div></div>

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The abuse heaped upon the 8541 Scout-Snipers by those running the program is really there to shake-out the men who might come to question orders and fail to obey them blindly.

Interesting to interact with those who achieved their Hunter Of Gunmen or Professional Gunman status AKA HOGS & PIGS. Not much tolerance, not much gunsmithing or handloading inquiry or pursuits, and did I mention not much tolerance? </div></div>

Guess I'm not tolerating you here either.

 

[Lowlight]

Re: How Critical Is Sight Base Alignment With Bore?

Wow, you guys are good,

I must be getting old as I don't remember this guy but he sure likes to drop my name. Like here he knows just enough to get himself in trouble and is generally wrong in what he states.

Oh, Lester, SH never authorized IOR to use the name and you'll note it does not appear in their literature or on the box. It was SH members who took part in that, not me.

What a tool, LOL some people.

 

[dogman]

Re: How Critical Is Sight Base Alignment With Bore?

Someone has a man-crush on Frank...

 

[Augustus]

Re: How Critical Is Sight Base Alignment With Bore?

Lesterserv, my god give it up. If you center the reticle on your scope before mounting per instructions of manufacturers then put it on a rail integral to the action such as a Surgeon, then mount it with rings of highest quality you will still have to zero your rifle. I have never mounted a scope on any rifle that was perfectly zeroed without any adjustment. I have seen custom rigs with rails and centered scope reticles be off as much as you are talking about. That's one of the main reasons adjustments are on scopes.

I have seen a few factory rifles with rails on them that required far more adjustment than you are describing. This can present problems if the offset is severe enough. If you center your reticle, mount your scope and you only need 8 Moa to get to zero, you are good to go.

 

[eracer]

Re: How Critical Is Sight Base Alignment With Bore?

So lestersurv, this is a LaRue-bashing thread, right?

Pretty long-winded, if you ask me.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

What a good bunch of guys, and sharp as a pin too: the whole bunch!

LaRue bashing? Not really... Have spent about $25 on long distance phone calls and postage to return the gear their guy told me to return. Have had warranty, return make-goods from Leupold, Warne, Ross Williams, and McMillan. Defective gear they made good, replaced at no charge; with no runaround or hassle. Not same philosophy at LaRue I'm learning.


Don't think having scope in tight alignment with bore matters?
That is your decision.
Benchrest concerns aren't germaine at the hide or any other place hunters of gunmenn gather... Heard about the benchrester who shot a 1.25" group for record at 1000yds? Betcha his scope is aligned with bore...

Not like I've measured how far offset the LaRue base is from centerline. The effective shift shown on the grid translates to 8moa. Might be 8moa offset at barrel which would be MORE Objectionable, no?

I am sure not buying that the scope sits only .01" to right of bore. Try to be polite to the forum owner here. Guess there is a lot to calculate, but the boresighter grid is about 6" beyond muzzle. With an 18" barrel, the boresighter sits about 12" ahead of the scope objective.

The grid in the boresighter says 1=4" 2 grids to right is where a boresighted or zeroed scope will register on a LaRue base...

Are they junk? Their gear is well-made and at a decent price; it is just too bad they didn't engineer the QD stuff to be inline with receiver and bore...

 

[VJJPunisher]

Re: How Critical Is Sight Base Alignment With Bore?

pull your head off the internet and go shoot proffessor

 

[BigJohn141]

Re: How Critical Is Sight Base Alignment With Bore?

Ok easy solution to end this. Go out and buy you a set of windage adjustable rings, zero the windage on the scope, mount it, adjust the rings till you scope is zeroed, and then everything should be aligned to your specs.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Sorry BJ-OK, not possible to do so with and AR flat-top. Scopes were being used on risers so could be swapped to bolt gun picatinny rail or Weaver bases. Have to use a riser to keep low or medium height scope which makes scope usable on bolt gun.

See guy, Scope zeroed at range or only setup on borescope shows a 2 grid or 8" shift to right when mounted on LaRue Riser.

STD base cannot correct if scope mount is completely off-axis with bore. STD windage screw on rear base just allows sloppy mount set to be used w/o dialing in lots of windage to get a zero... No way to mount on pic rail even if would work.

Got a boresighter? You can record your range-fired zero by noting the reticle position on boresighting grid, remove scope from base, if don't move rings, you can use scope on another rifle, then return to orig rifle and reset scope reticle to your noted grid position and be dialed-in again.

Scope from my boltgun transferred to the bare AR-10 flat-top base (integral to receiver) will stay in same approx alignment on boresighter. If use the LaRue, the boresighter grid shows scope that was in approx alignment is now registering 2 full grids right of where was before being mounted on the riser.

If LaRue riser was in-line w/bore shift would not be 2 full grids which equals 8".


Have not yet sighted-in/zeroed the AR-10s or the boltguns scopes were shifted between and no longer have the LaRue risers. Probably LaRue will send them back, but I still haven't heard...

I will test the Leupold mk4 pic rail scope shifted to AR-10 receiver. Will report any shift in vertical position of reticle.

 

[Killswitch Engage]

Re: How Critical Is Sight Base Alignment With Bore?

"see what happens when you have no practical experience doing something... you end up playing with calculators and looking stupid on the internet."

seems i've seen this somewhere before....

 

[BapZander]

Re: How Critical Is Sight Base Alignment With Bore?

From left to right:

1. Scope mounted with 8" poi shift at 100 - 16" at 200
2. Scope mounted with windage zeroed - no shift at any distance.
3. Scope mounted parallel to barrel but with 8" offset
4. Scope zeroed at 100 but still off at 200.

You seem to be thinking what happens is 3 and 4. What really happens is 1 and 2.

But what do I know, the image was photoshopped...

 

[Lowlight]

Re: How Critical Is Sight Base Alignment With Bore?

and if you think about it, being off by .15" that means you are only off by 3.8 millimeters, and if you think about that you are off by 1/2 the bullet width. (Picture 3 & 4 that much ala Larue)

If you can hold / notice 1/2 the bullet width, wow... still doesn't explain how the groups are opening up and Lester refuses to answer the accuracy question as he stated in more than post on here, how the above caused his groups to "go to hell" ...

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

There is shift in vertical position on each mount I checked.

I remain convinced that evidence seen when scopes were removed from LaRue risers and installed on their respective AR-10 rails w/o risers shows significant offset of scope from muzzle and receiver when riser is used.

Will not be using LaRue risers again.
Thanks for your time and comments.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Not really sure the grid correlates to 8" at 100yds. The tool is a boresighter and the grid is used to check scope reticle alignment and reticle movement. Should correlate but does barrel length, distance to sighter grid from reticle (in scope) affect the geometry?

I appreciate your analysis. I think 3 & 4 is exactly what is happening if I use the LaRue riser. The LaRue moves the reticle 2 grids Right from where reticle registers when using the built-in rail. If the LaRue riser were in-line with bore, why would it move each scope register 2 grids to right?

Theoretically, if you could sight using a scope mounted UNDER the bore, the scope could still track bullet path. Scope just has to be in-line with bore to track bullet, if not the situation is as you show in illustration 1 & 4.




<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BapZander</div><div class="ubbcode-body">

From left to right:

1. Scope mounted with 8" poi shift at 100 - 16" at 200
2. Scope mounted with windage zeroed - no shift at any distance.
3. Scope mounted parallel to barrel but with 8" offset
4. Scope zeroed at 100 but still off at 200.

You seem to be thinking what happens is 3 and 4. What really happens is 1 and 2.

But what do I know, the image was photoshopped... </div></div>

 

[ShakyDave]

Re: How Critical Is Sight Base Alignment With Bore?

I like Door Number 2. Slap the scope on the LaRue and center the erector?

 

[E. Bryant]

Re: How Critical Is Sight Base Alignment With Bore?

Lester,

You don't know how a collimating boresighter works, and I'm not going to bother explaining it to you as you have weaseled your way through every response to your inquiries. If you are interested, download the Leupold ZeroPoint instructions. The conclusion you should draw is that offset does not matter with a boresighter - only angle impacts the crosshair's position on the grid, but you will probably surprise us all by drawing some other conclusion.

As the situation related to BapZander's drawing, you can easily figure out which of the two scenarios applies if you SIMPLY GO TO THE RANGE AND PUT SOME LEAD ON SOME TARGETS! Since you lack the necessary knowledge of the theory behind optics and scope-mounting geometry, the practical feedback provided by range time will be a far more valuable tool.

When you start missing Tom Sarver's stunning 1000-yard record group by a tenth of an inch or less, then you may spend this much time pondering the geometry of your mounting system. Until then, please stop wasting everyone's time.

 

[pwc001]

Re: How Critical Is Sight Base Alignment With Bore?

Lester, less running you mouth, and go shoot the damn rifles. You are very wrong, and most of what you say does not does not jive.

Listen to what everyone is telling you, if you don't believe them then try it for yourself.

From your thinking, very few factory Remington 700's would be able to hit anything past 100 yards, as they do not bother to time their barrels, or make sure scope base holes are straight, or inline with the barrel. But they still hit at 1000 once sited in at 100, and dialed for elevation.

Stop swapping scopes and just shoot.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Boresighter is a tool to get rifle on the paper at some distance.
The collimator adds a grid to track scope movement.
Can boresight w/o any device, by removing bolt at range and centering bullseye or aiming point as best you can when sight down barrel and move reticle to center on aiming point.

Trying to quantify all the variables that come into play whenever a shot is fired is impossible. Human element, ammunition element, conditions element can all change or fail in some way.

If you are interested in precision results, don't you try to blueprint every aspect of your rifle to eliminate all the variables you can in that portion of the shooting equation? What else can you control, maybe the ammunition, but that has dependencies on temperature and other factors just like bullet trajectory is impacted by conditions.

If you aren't concerned about using gear that shifts your scope 8" Right from where that scope would register if it were mounted straight to the receiver; that is your affair.

I don't use a harrell's powder measure or wilson arbor press dies, but I do try to use best gear and loading practices I can to handload my ammunition.

The bushnell collimator has aided me greatly over the past 20 years and sure will continue to do so. I will not use any gear that induces error of any kind in my rifle or sighting system.

Thanks for all the replies. Wish all you guys the best results and happy shooting!

 

[USMAGator]

Re: How Critical Is Sight Base Alignment With Bore?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lestersurv</div><div class="ubbcode-body">
I will not use any gear that induces error of any kind in my rifle or sighting system.
</div></div>
Good luck with that quest...
Just go shoot. Bookwork and theory are wonderful things, and are about as significant as a pimple on a gnats ass if you can't execute when you get behind the trigger. The most imprecise and flawed component of your rifle/scope/base/ammunition setup is most likely the guy pressing the trigger.

 

[E. Bryant]

Re: How Critical Is Sight Base Alignment With Bore?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lestersurv</div><div class="ubbcode-body">Boresighter is a tool to get rifle on the paper at some distance.
The collimator adds a grid to track scope movement.</div></div>

Congratulations - you have described the general purpose. But if you really knew how they worked, you'd understand that they are referred to as "collimators" due to the fact that they output collimated light - that is, light with rays that are parallel. Thus, collimating boresighters are not sensitive to linear offsets between the barrel and the optic - they only reveal angular differences.


<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">If you are interested in precision results, don't you try to blueprint every aspect of your rifle to eliminate all the variables you can in that portion of the shooting equation? </div></div>

No, I don't "blueprint every aspect" of my equipment. Limited resources forces me to concentrate my attention on the things that matter most, and not spend days worrying about minutiae.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I will not use any gear that induces error of any kind in my rifle or sighting system.</div></div>

Good luck with that quest. No matter how good the hardware, every human is still burdened with that error-prone mass of jello between their two ears. This thread is some pretty good evidence of that.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Thanks for all the replies. Wish all you guys the best results and happy shooting! </div></div>

You should try doing some of that shooting stuff once in a while. It's highly instructive.

 

[lestersurv]

Re: How Critical Is Sight Base Alignment With Bore?

Mr Bryant,

Why the wise-ass line by line replies to my almost every remark and second-guessing every post I've made here? Got a financial stake in LaRue bigger than the $375 I've got.

Incidentally, talked to their "returns" gal on Tues with her promise to get back to me soon. Still no call or msg from them as of Fri eve.

Perhaps using gear which shifts rifle sight system so far to right from the integral AR-10 picatinny rail that reticle registers 8moa difference is Of No Concern To You??? I respect your perogative.

Have used the Bushnell 74-3333 tool to mount scopes and diagnose scope movement functions for years. No, it's not a Zeiss optical lens collimating tool, but for the $49 I paid for it in `91 it has been the best gun accessory I ever bought, running a close second to Dewey boreguides and coated cleaning rods.

I have seen big differences in performance within a single rifle depending on sight base & ring mounts. Talking sub .4 moa with .308win once the sighting components were better matched to scope and rifle.

Certainly there is no reason to accept a large lateral shift in scope orientation boresight grid registry just to use a piece of gear that can be worked around. Of course, this is just my conclusion and decision; please know I support your decisions to use whatever gear you choose.

 

[E. Bryant]

Re: How Critical Is Sight Base Alignment With Bore?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lestersurv</div><div class="ubbcode-body">Mr Bryant,

Why the wise-ass line by line replies to my almost every remark and second-guessing every post I've made here? Got a financial stake in LaRue bigger than the $375 I've got.</div></div>

I don't own a single piece of Larue gear, and never have. I also harbor no ill will towards the company. It's a completely neutral attitude.

The "wise-ass" responses are simply due to your inability and unwillingness to accept the facts that have been presented to you, as well as your lack of interest in proving/disproving your own hypotheses by putting rounds downrange.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Perhaps using gear which shifts rifle sight system so far to right from the integral AR-10 picatinny rail that reticle registers 8moa difference is Of No Concern To You???</div></div>

It is indeed of no concern to me, given two conditions:

1) That the POA shift comes from an angular misalignment (which can easily be compensated for within the optic)

2) That my scope has sufficient adjustment range to allow for the adjustment without running out of travel.

You're also ignoring the various other sources of alignment error (such as anything between the mount and the barrel bore), which in most cases are of similar magnitude to the mount issues which causes you so much grief.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Have used the Bushnell 74-3333 tool to mount scopes and diagnose scope movement functions for years. No, it's not a Zeiss optical lens collimating tool, but for the $49 I paid for it in `91 it has been the best gun accessory I ever bought, running a close second to Dewey boreguides and coated cleaning rods.</div></div>

Good for you. Regardless of whether you've been using it for 21 years or 21 minutes, it still works the same way - it produces (roughly) collimated light, which means that it only sensitive to angular offsets. If your Larue mount had a linear (parallel) offset, then you'd have never noticed the problem by using your boresighter.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I have seen big differences in performance within a single rifle depending on sight base & ring mounts. Talking sub .4 moa with .308win once the sighting components were better matched to scope and rifle.</div></div>

And do you know why this happened? Have you completed the hypothesis/observation loop? What does "better matched" mean in this context?

I seriously suggest that you take some time to read through the responses here, and think about why no one else but yourself is concerned. It could be that you are operating on a much higher level than the rest of us, although the fact remains that everything about this "problem" can be easily explained with some understanding of geometry at a middle-school level.