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Semi auto accuracy.....what's the secret?

TRPAUBREY

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Minuteman
Feb 27, 2011
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I have a Robinson Arms XCR-M in .308 (piston driven) and I cannot get it to shoot a tight group. I hand load all my ammo and I can shoot 1/2 MOA groups from my bolt gun. I am currently trying to develop a load for the XCR with IMR 3031 and 168g A MAX bullets. I have tried 39.0 gr up to 43.0 gr in 1/2 gr increments with no solid groups. Here and there I will get a 2" group and I chronograph each shot (2-10 fps deviation). I made sure the barrel was not getting too hot and there seems to be a slight improvement with the gas shut right off. I have mostly loaded for my bolt guns, is there something I am missing for a semi auto? I do realize that a semi auto will never shoot as good as my bolt guns, but I would like to think I should be able to get it close to 1 MOA. Any suggestions will be appreciated.
 
No, it's very inconsistent....sometimes the first shot it the worst. I have checked the torque on the barrel retaining bolt and gas tube as well. (I know that if they are loose it will definitely cause accuracy issues.)
 
If the gas block is attached to the barrel, and the op-rod affects the harmonics in any way, you will have a hard time getting such a gun to shoot.

Are there any accuracy guarantees from Robinson Arms? Do the bolt lugs have uniform contact with their pressure-bearing surfaces in the receiver? Is the chamber cut for reliability, and what is the jump?

Is the crown uniform and clean? Do you have a muzzle device on it? Is it averaging about 2 MOA at 100yds?

What optics and mount are you using? Are you bagging the gun in the rear, with solid frontal support? Lots of variables with this scenario that we need to know.

For comparison, I feel cheated and down if my precision gas guns shoot 3/4" at 100yds for 4 rounds, and I will barely be satisfied if they shoot that way for 5 rounds. I have pages of groups through my GA Precision AR10 in .260 Remington that are .4" - .6" 5rd groups, but it has a Bartlein, precision single-point, CNC cut-rifled and hand-lapped barrel installed by GAP.
 
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I was shooting off an Atlas bipod on a seated bench and have a bag under the hand grip. I took the muzzle break off and just have a thread protector on it. I am using a Sightron SIII 8-32 scope on Burris 6 screw mounts. The jump is something I have not checked due to the fact that the rounds have to be 2.80" to fit in the magazine. (I was concerned about the jump).
 
Are semi autos quite sensitive to being dirty? It is not really dirty but not squeaky clean either.
 
I had my best groups with amaxs @ 2.78" in my ARs.

Honestly I have heard good and bad about the XCR-M. The few people that have them are not getting the greatest groups out of them. There was a guy getting near MOA with his on ARFCOM I think but I don't recall exactly. You should be able to get around 1.5MOA with it though.

Try a bag under the buttstock rather than under the grip for starters. Try not to torque the pistol grip and let the rifle recoil straight back into your shoulder while focusing through the scope at the target the entire time.

It could also be that your rifle absolutely hates 3031. If possible try to get your hands on some factory match ammo to use as a baseline for comparison.
 
Have you tried factory ammo? How does it compare? A box of FGMM could help you to know if its something on your end or the guns end.

Have you tried different bullets? Some guns just dont care for some bullets and will shot poorly with one.

Tried different powders? Again perhaps the gun just doesnt care for that powder.


Ive found bolt guns are a bit more forgiving ot get good groups out of. They just shoot more accurately, easily with a wider variety of components. Of course when you hit subMOA more things come into play but getting to MOA seems pretty easy.

Now semi autos, in my opinion and experience, can be a bit more temperamental. My 300 blackout i had three different bullets all pretty similar. Hornady 150gr FMJBT, Hornady 150gr interlock, and 147gr FMJBT pulldowns. All pretty similar, same OAL, charges, ect. But the interlocks i couldnt get to shoot all that well. 1-2MOA. The other two shot ~1moa and even there ive found the (least this batch) of pulldowns to shoot slightly better.

Just something to consider.
 
Follow through is much more important in a semi b/c lock time is much slower than in a bolt gun. My groups tend to go vertical when I lack follow through.
 
Like others have said try a box of factory Ammo first like the Federal Gold medal match in 168. Do it with the gas port turned off and place each round in the chamber by hand. Then run the bolt forward and shoot away. Some piston actions are very violent and you may need to crimp your bullets too. It will be evident if hand feeding the rounds gives a better accuracy than mag feeding. What twist, barrel length, and type(SS or Chromelined) barrel is your rifle?
 
There is nothing wrong nor secrets either, trying to get bolt gun accuracy out of a gas gun like the XCR is a wasted of time. Those rifles aren't designed to shoot tight groups but rather hit everything you aim at, once you accept that fact, life will be a lot easier.
 
I usually use Varget, however it is very hard to find at the moment but I do have some Benchmark I could try. The barrel is a 20" chromed lined with a 1:10 twist. I did try some Federal gold match ammo..... with the gas off it shot 2 MOA...with the gas on it was about 2.5 MOA (that is better than anything I had loaded even though my hand loaded velocities had a lower spread). I will try a couple different bullets with the Benchmark and bag the rear as you say. Next time out I will remove the bipod and use my Caldwell rest. I do have slightly more of a vertical string than horizontal so I will pay close attention to the recoil.

Thanks guys.
 
I usually use Varget, however it is very hard to find at the moment but I do have some Benchmark I could try. The barrel is a 20" chromed lined with a 1:10 twist. I did try some Federal gold match ammo..... with the gas off it shot 2 MOA...with the gas on it was about 2.5 MOA (that is better than anything I had loaded even though my hand loaded velocities had a lower spread). I will try a couple different bullets with the Benchmark and bag the rear as you say. Next time out I will remove the bipod and use my Caldwell rest. I do have slightly more of a vertical string than horizontal so I will pay close attention to the recoil.

Thanks guys.



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Just a suggestion. If you're going to shoot single-shot, put the cartridge in the magazine, don't just drop it in the chamber and let loose the bolt. Can you spell slamfire??? Hold the trigger until the rifle returns to battery, then release just enough to re-set. I've learned this, and a lot more on this site, for which I am grateful, but still not a very good shot... Good luck.
 
This may sound odd but try this. After you lock & load a round in the chamber, aim off to one side of the target on purpose and shoot into the backstop. Then see how your shot group looks like. The reason behind this technique is there is a slight difference in the seating of the round when you lock & load vs when you shoot and the bolt blow back loads the next. I don't know if this fix your issue but at least allow you to start to eliminate potential issues.
 
The xcr-m is pretty common up here in canada due to its nonrestricted status.
In short, accuracy isn't good.
The barrel attachment method is a Mickey Mouse affair and does nothing for consistency. They typically display vertical stringing.
I went from 3-4 moa groups with the xcr-m to sub moa with an lmt mws overnight. Same shooting setup, same technique.
It's not you, it's the gun in this case !
 
Consistency, consistency, consistency, trial & error, ammo development, consistency, consistency, consistency. I've always said this as an estimation for 100yards, it's 40%shooter / 40% rifle / 20% ammo. The further you shoot past 100yards, the more wind & mirage variables come into play and the shooter% & ammo% exponentially increases.

1.) AMMO: If you're not reloading, then you should in order to come full circle as a precision shooter. Shooting the wrong ammo can totally screw with your head, making you think the issue is all on your when it is actually just the ammo. Until then, it's total hit or miss unless you're paying a stupid amount of money for stupid expensive factory ammo. Being able to control all aspects of the AMMO variable PLAYS A HUGE PART in this game. If you're not reloading, then do yourself a favorite and get-r-done as I enjoy reloading just as much as shooting my rifles. I've found that 168amax & 168 HPBT (you pick brand) works wonders in my LMT 1:10twist. Never had much luck with 175's. Once you find a bullet that obviously performs well in your rifle, then it's the never ending quest of hunting down the perfect powder & the amount of powder to drop. Once you lock down the powder, then it's off to the races with bullet seating depth and f#cking around with bullet jump. When it comes to reloading, everything falls back on consistency. Consistent headspace shoulder bump, consistent OGIVE seating depth, and consistent powder drop. Just for pure example, if you bump one pc of .308 brass to 1.623 and the next pc of brass to 1.628 for your fired brass of 1.632 = there goes your group in one shot. If I'm going to 5shot groups, everything I do is in increments of 5. Hell, even sometimes I'll even weigh out my bullets in batches of 5each (for 5shot groups) that all weigh the same (and actually doesn't take that long to do once you get a method to your madness) if you're going for ultimate accuracy (as I've even seen 168 amax bullets range all the way from 167.6 to 168.4 grns).... Once you get 5 bullets that weight exactly the same, move those 5 off to the side as a group of 5 (will use an extra loading tray for sorting bullets), seat those 5 & keep them together in your ammo box & will shoot just those 5 in a row. Even the smallest tricks of the trade such as keeping your brass in order while dropping powder (to minimalize scale drift) all the way through to seating & storage in your ammo box & loading into the magazine / taking the 5shots can make a .25moa difference.

2.) CONSISTENT SCOPE SHADOW, VIEW, SCOPE SET UP, & CHEEK WELD: Scope shadow is your friend & enemy actually. Once you have 100% clear glass with no scope shadow, then lock in that cheek weld. If going for groups, DO NOT move your view / cheek weld for nothing while taking your shots. If you move your head during your shots to scratch your ass, pick your nose, or say hello to your friend = 100% guarantee your P.O.I. will change with a semi-auto and your group will go to hell. Also, play around with your side focus. Just because your side focus says 100 for 100yard shooting doesn't mean you should use it. Try setting up your rifle in a rear bag & dead nuts zero on your bullseye. Bob your head left / right, up / down, and see if you're crosshairs move off your bullseye as you bob your head. I have found that I actually have less parallax with my scope set at about 75 to 80 setting on my scope, rather than 100 for sidefocus for shooting on the 100yard mark @ the local range. Once you get your side focus set up, screw around with your zoom, double check side focus, and then go to town.

3.) BI-POD.. TO LOAD OR NOT TO LOAD? SANDBAG ON THE FRONT? BIPOD SIZE!!! This topic is a strange one for me & I've found it to be a total trial and error type stuff. ALL of my AR's don't like bi-pod loading BUT for my RRA EOP varmint rifle.. Why? I seriously have no clue. You just need to take a couple 5shot groups both ways and see what works better for you. Heck, even try a sandbag on the front. It's all trial and error. EVERY ONE OF MY AR RIFLES likes to be shot differently. I swear they are more picky than my girlfriend. Finally, I have found the lower the bipod = the better. Also, the more level the rifle is once in the rear sandbag while using either a bipod / front sandbag = less bipod / muzzle jump = more accuracy. I noticed a HUGE difference going from 9-13" to 6-9" harris bipod on my AR's (just need to keep an eye on longer magazines so they don't hit the bench). Might need to kick the legs out a notch or two. My last LMT MWS on the 100yard shootout thread that was sub-moa all day long was with NO bipod loading on an ultra flat bench & allowing the recoil to more "naturally flow" into my shoulder with little pressure on the grip. Now, I could never do that with my RRA EOP varmint rifle. She likes an ultra firm hold for some damn reason.

4.) TRIGGER RESET OR NOT? Some, if not most, say to trigger re-set. For some damn reason I shoot like crap when I trigger re-set, BUT I totally understand it's purpose. Try it both ways, and see what works better for you

5.) REAR SAND BAG.... BEING REALLY AGRESSIVE OR NOT WITH THE RIFLE DURING YOUR SHOTS??: This is a strange one for me. I use an owl ear rear sand bag and I prefer a squeezable canvas style (not leather as they are too hard for elevation adjustment). When it comes to SOPMOD style stocks I actually run my owl ears front to back and "cup the point of the sopmod stock" in the pocket of the rear bag. This has proven great results for me with my SOPMOD style stocks as they would obviously just fall off the sandbag once the shot is taken. As for my A2 stock varmint rifle, then I run the ears left to right and allow the recoil to naturally flow into my shoulder. Once again, all trial and error type stuff. Try an aggressive hold, try a more relaxed hold & allowing the recoil to more flow into your shoulder. Some of my AR's like a more aggressive hold, but my LMT when shooting off of a flat bench (not ground / soil), likes a more "natural flow recoil" into my shoulder with little pressure on the grip for some strange reason. Once again, all trial and error, and remembering how that rifle you own works with you as a shooter. Not sure about bolt actions, but for me and my AR's... they are all different.

6.) SIZE OF YOUR BULLSEYE FOR THE YARDAGE BEING SHOT: This is just how I do it as a recreational shooter with my 16x scopes. I personally like shooting circles as they don't give a crap if they are level or not. 1" for 100yards, 2" for 200yards, 3" for 300yards, 4" for 400yards, and so on for my 16x scope... On the other hand, my 1-4 power scope on the 4x power works great with a 4" circle for 100yards & 8" circle for 200yards. I think you get where I'm going here. Once again, it's all about consistency. I try not to make the circle too big so you're not 100% sure if you're dead nuts zero, but not too small that your crosshairs cover up the damn circle. I've found that at 16x scope power, a 1" circle is just about perfect for 100yards. Once my crosshairs cut the circle into 4 perfect 1/4 pcs of pie = shot taken once dead nuts still in my rear bag.

7.) WHEN TO CLEAN THE BARREL?? Once again, another trial and error. Each rifle is different. I'm starting to come to the conclusion that my LMT 7.62 rifle with it's chrome lined barrel LOVES copper fouling. I haven't cleaned the copper out of my LMT in a while & will only run a snake down the barrel once with CLP after each trip to the range. Now, my 5.56 AR's (like my 3G1, RRA EOP varmint, and RRA ATH) with their 18" 1:8 twist barrels, I start to see accuracy drop off after about 400 to 500rounds. I seriously think this has something to do with a carbon ring right after the chamber & ripping the copper jacket off my bullets. Once I start to see accuracy fall off (and my RRA EOP varmint rifle is notorious for this), it really needs the entire barrel scrubbed down & will take about 20 to 30 rounds for my groups to get tight again once the barrel has been totally cleaned of all copper / carbon. This is when I bust out my foam bore cleaner when I need to remove all copper / carbon... Not everyone uses snakes, but I do. Keep those snakes clean about every 10th cleaning by cleaning them with soap / water & let dry for a couple days. Making sure to the snake out of the muzzle of the barrel as straight as possible. Name of the game is = less times you run the snake down the barrel = the better. I just got done screwing around with this with my RRA EOP as the accuracy was totally going to hell (like 1.25moa groups and not .75moa) due to not cleaning the copper / carbon fully after about 500rounds. It took 2 total 15min sessions of foam in the barrel to get it tip top again. Once again, trial and error. Each rifle is different.

http://www.snipershide.com/[email protected]


I have a Robinson Arms XCR-M in .308 (piston driven) and I cannot get it to shoot a tight group. I hand load all my ammo and I can shoot 1/2 MOA groups from my bolt gun. I am currently trying to develop a load for the XCR with IMR 3031 and 168g A MAX bullets. I have tried 39.0 gr up to 43.0 gr in 1/2 gr increments with no solid groups. Here and there I will get a 2" group and I chronograph each shot (2-10 fps deviation). I made sure the barrel was not getting too hot and there seems to be a slight improvement with the gas shut right off. I have mostly loaded for my bolt guns, is there something I am missing for a semi auto? I do realize that a semi auto will never shoot as good as my bolt guns, but I would like to think I should be able to get it close to 1 MOA. Any suggestions will be appreciated.
 
#1) Heavy Match Barrel (1/7 or 1/8 twist)
#2) Reloads developed with correct bullet & powder for "YOUR" rifle
#3) 2-stage target trigger
#4) Tightness between the upper and lower with bump bushing.
#5) Your trigger finger ????
#6) NO BIPODS!!!!! only good benchrest target rest up front & good rear rest on top of rock solid bench.
#7) No sling swivels that can touch the rests or bags.
#8) OOPS, the highest power scope you can put on top

Anyone care to add??
 
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I found something out when working with Leupold Mk 4 scopes. If I shot at those red/orange sticky dots that have a black dot in the center, my groups sucked. I noticed that the edges of the dots were difficult to resolve. I changed to black targets, and my groups immediately improved.

Apparently, some scopes use coatings that make it difficult for the optic to resolve either the red/orange, or blue/green end of the spectrum well. With the Leupold Mk4 that I have, it doesn't resolve the edges of red/orange target dots well. As a result, it is very difficult for me to get good groups when using those targets. Changing to black, or dark colored dots that aren't in the red/orange end of the spectrum solved my problem. That is just something else to consider.
 
IMO if the OP can shoot 0.5 moa with his hand loads in his bolt gun I would bet it is not his hand loads that is causing the unsatisfactory groups. From all the comments subsequently posted on the inherent accuracy XCR-M I would suspect it is a problem with the rifle especially since he has tried FGMM and can only get 2-2.5" groups with it. I would send it back to Robinson for a check up if was my rifle.
 
IMO if the OP can shoot 0.5 moa with his hand loads in his bolt gun I would bet it is not his hand loads that is causing the unsatisfactory groups. From all the comments subsequently posted on the inherent accuracy XCR-M I would suspect it is a problem with the rifle especially since he has tried FGMM and can only get 2-2.5" groups with it. I would send it back to Robinson for a check up if was my rifle.


2 to 2.5 " with fgmm is pretty standard for a five round group. Heck thats actually better than average !
A check up is not going to reveal anything, they're just not an accurate rifle...
 
The xcr-m is pretty common up here in canada due to its nonrestricted status.
In short, accuracy isn't good.
The barrel attachment method is a Mickey Mouse affair and does nothing for consistency. They typically display vertical stringing.
I went from 3-4 moa groups with the xcr-m to sub moa with an lmt mws overnight. Same shooting setup, same technique.
It's not you, it's the gun in this case !

Just wondering if you were the same guy that I remember who insisted shooting using the mag as a mono-pod is good way to test for groups?

Op this rifle is a battle rifle. I can get 1.25 moa consistently, sub moa just under half the time with my xcr-m. My friends rifle in my hands is 2.5 to 3 moa at best. The quality control on the rob arms line do not focus on the things that make a rifle shoot submoa groups. Im guessing mine has a chamber that was cut with a brand new reamer one of the better factory barrels and a tighter barrel extension to receiver tolerance. I dragged an xcr kicking and screaming into a precision role and got lucky in that mine is reasonably accurate, but wont be winning any matches with this thing. Basically some are accurate others are minute of upper body mass to the 800m 7.62 iron wall
 
I think I may have mentioned that it was a common technique up here, hardly insisted. It was tried in everything from monopodding it on the mag to the usual bipod/rear bag to a full on ransom rest.
The use of the mag for a rest stems from the fact that the barrel attachment method was designed by a three year old that had very limited gun smithing talents.
There is no recoil lug, the barrel does shift within the reciever.
On mine I could see the rubbing where it was doing so regardless of the barrel retention screw torque.
No contact on the forearm does positively influence groups on some xcr's.
As you mentioned quality control isn't awesome, you can consider yourself lucky to have an example such as yours. The majority have a hard time consistently shooting an average of 3moa 5 round groups.
Personally, I traded the xcr-m off on an lmt mws (also a "battle rifle") and went from a 3moa average to a .75 average over night. For the same price. The lmt at 7000 rounds has less wear than the xcr-m did at 600.
Not even in the same class. Not even on the same planet.

Just wondering if you were the same guy that I remember who insisted shooting using the mag as a mono-pod is good way to test for groups?

Op this rifle is a battle rifle. I can get 1.25 moa consistently, sub moa just under half the time with my xcr-m. My friends rifle in my hands is 2.5 to 3 moa at best. The quality control on the rob arms line do not focus on the things that make a rifle shoot submoa groups. Im guessing mine has a chamber that was cut with a brand new reamer one of the better factory barrels and a tighter barrel extension to receiver tolerance. I dragged an xcr kicking and screaming into a precision role and got lucky in that mine is reasonably accurate, but wont be winning any matches with this thing. Basically some are accurate others are minute of upper body mass to the 800m 7.62 iron wall
 
Once sight alignment and trigger control are mastered the most important thing to good shooting is to make recoil resistance consistent; yet, most folks just don't get it. They don't understand that their miniscule shot to shot divergence in the relationship between shooter, gun, and ground is making recoil resistance unpredictable; and, thus making their shot groupings bigger than what would be possible with a really solid position. Since these folks no nothing about proper shooter/target analysis, they cannot measure the effect of their inconsistency; and, being ignorant of their error origins, they attribute the cause of their errors to inferior equipment, defective ammunition, or wind. The bottom line is a shooter who masters a steady position will get awesome results with any match conditioned action type. The message here for the inexperienced shooter is focus on marksmanship not equipment.
 
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2 to 2.5 " with fgmm is pretty standard for a five round group. Heck thats actually better than average !
A check up is not going to reveal anything, they're just not an accurate rifle...

I have to disagree with ^^^^^on the 168 FGMM. I have an LMT MWS, POF-P308, SIG 716, HK MR762 and a DPMS SASS and while I shoot mostly my hand loads I have shoot FGMM 168 and each one shoots 1 moa or better (depending on the rifle) with 168 FGMM. I do agree that the OP's problem is the rifle.
 
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Once sight alignment and trigger control are mastered the most important thing to good shooting is to make recoil resistance consistent; yet, most folks just don't get it. They don't understand that their miniscule shot to shot divergence in the relationship between shooter, gun, and ground is making recoil resistance unpredictable; and, thus making their shot groupings are bigger than what would be possible with a really solid position. Since these folks no nothing about proper shooter/target analysis, they cannot measure the effect of their inconsistency; and, being ignorant of their error origins, they attribute the cause of their errors to inferior equipment, defective ammunition, or wind. The bottom line is a shooter who masters a steady position will get awesome results with any match conditioned action type. The message here for the inexperienced shooter is focus on marksmanship not equipment.

Amen!! Teach this to the masses who are ignorant.
 
I have to disagree with ^^^^^on the 168 FGMM. I have an LMT MWS, POF-P308, SIG 716, HK MR762 and a DPMS SASS and while I shoot mostly my hand loads I have shoot FGMM 168 and each one shoots 1 moa or better (depending on the rifle) with 168 FGMM. I do agree that the OP's problem is the rifle.


I'm speaking of fgmm in an xcr-m.
It doesn't matter how high quality the oats are that you feed to a three legged horse, it's still not going to win any races...

168 fgmm is a solid 1moa average in my mws. It's decent stuff.
It really likes 168 Amax over 44 grains of varget in a lapua case though, I have to screw up badly to make that shoot over 1 moa.
But I digress, back on topic, the average xcr-m has the same accuracy potential as the $425 Chinese m14 copies we have here. Good enough for a battle rifle ?
Maybe.
Good enough for a precision semi auto ?
Hell no !

To the op, don't beat yourself up, trade that thing off. You'll never be able to refine your gas gun technique if you're wondering if that flyer was you or the gun...
 
I'm speaking of fgmm in an xcr-m.
It doesn't matter how high quality the oats are that you feed to a three legged horse, it's still not going to win any races...

168 fgmm is a solid 1moa average in my mws. It's decent stuff.
It really likes 168 Amax over 44 grains of varget in a lapua case though, I have to screw up badly to make that shoot over 1 moa.
But I digress, back on topic, the average xcr-m has the same accuracy potential as the $425 Chinese m14 copies we have here. Good enough for a battle rifle ?
Maybe.
Good enough for a precision semi auto ?
Hell no !

To the op, don't beat yourself up, trade that thing off. You'll never be able to refine your gas gun technique if you're wondering if that flyer was you or the gun...

I thought you were referring to GMMM in general, my bad. Then we are in total agreement.:)
 
The xcr-m is pretty common up here in canada due to its nonrestricted status.
In short, accuracy isn't good.
The barrel attachment method is a Mickey Mouse affair and does nothing for consistency. They typically display vertical stringing.
I went from 3-4 moa groups with the xcr-m to sub moa with an lmt mws overnight. Same shooting setup, same technique.
It's not you, it's the gun in this case !

You are 100% correct. The XCR-M is nothing but a blaster and you should use only a red dot on it. Sell it and buy a SCAR 17s . See Video.

SCAR 17 at long range - YouTube
 
Amen!! Teach this to the masses who are ignorant.
Give me a friggin break......................the man has already established he can shoot 1/2 MOA with a precision rifle. It's a 1 1/2 MOA gasgun.........period. You can dress a pig any way you want, in the end it's still pork.