What's going on here

[Buckoman]

Ok weird stuff happening. Gun is zeroed at 100 yards, groups less than 1/2 MOA. As I move from 100-200 on out to 600 yards I find that my groups are consistantly drift to the right. This happens on calm no wind days and its a 260Rem with 142SMKs with a high BC.

If I move the scope to another gun, say my 308, same thing. I figure either my scope is canted or I'm canting the rifle, but I betting its the scope. I'm 99.9% sure I'm not pulling the gun either. Any thoughts here?

Lets say the scope is canted. If I have right drift, which direction is the scope canted?

Here's how I mounted the scope: I put a bubble level on the rail. I then hang a plumb line out at about 20 yards. I then vertically align the crosshiars to the plumb line.

The weird thing is crosshairs should look like they are cutting vertically through the middle of the bore of the gun, but the optical illusion is such that it appears offset. Is this normal?

 

[USMCj]

Re: What's going on here

Why do I have a feeling you are using a Leupold.......

Sounds like the reticle in your scope is canted, pretty common with Leupolds. This is why you should use the feeler gauge method of aligning a scope. You have to pick and choose between your reticle being plumb, or the scope (erector system)

If you are dialing elevation, plumb the scope using the feeler gauge method and live with a canted reticle. If you are holding for elevation, plumb the reticle.

 

[Buckoman]

Re: What's going on here

Its actually a Schmidt and Bender PMII. Hmmm Feeler gauges? Please expound sir.

I shoot both holdovers and dial. I found that to hit at 600 I have to hold exactly .5Mil to the left to get hits with my 308.

Is this a good tool? Reticle Aligner

 

[Niles Coyote]

Re: What's going on here

here you go

http://www.snipershide.com/level

 

[kcbird]

Re: What's going on here

Could it be the action and base is not in line. I dont know if this could be a diagnosis but someone on here might know.(scope not in line with the bore)

 

[OptedOut]

Re: What's going on here

In my experience in years past when a windage problem surfaced and progressed at longer distances it came down to the fact that the rail was not parallel with the bore/barrel. I've seem many "expensive" rails that were off in their drilling, of course some receivers also.
(I'm referring to quality military scopes over the years)

 

[steve123]

Re: What's going on here

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Master_Blaster</div><div class="ubbcode-body">Ok weird stuff happening. Gun is zeroed at 100 yards, groups less than 1/2 MOA. As I move from 100-200 on out to 600 yards I find that my groups are consistantly drift to the right. This happens on calm no wind days and its a 260Rem with 142SMKs with a high BC.

If I move the scope to another gun, say my 308, same thing. I figure either my scope is canted or I'm canting the rifle, but I betting its the scope. I'm 99.9% sure I'm not pulling the gun either. Any thoughts here?

Lets say the scope is canted. If I have right drift, which direction is the scope canted?

Here's how I mounted the scope: I put a bubble level on the rail. I then hang a plumb line out at about 20 yards. I then vertically align the crosshiars to the plumb line.

The weird thing is crosshairs should look like they are cutting vertically through the middle of the bore of the gun, but the optical illusion is such that it appears offset. Is this normal? </div></div>

If your base is not parallel to bore an easy fix would be Burris signature rings with inserts.Provided that your S$B is 30mm not 34mm.

Is your scope dialed way to one side to zero it?If it is then it's gunsmith time.

If you shoot in a location where the wind is primarily left to right and there appears to be no wind that could be part of the problem.There's almost always some sort of wind especially with 308.

Steve

 

[gugubica]

Re: What's going on here

Try this...

Go out and shoot groups at 100, 200, 300, 400 and 500. Dail your elevation correction.

Go out and repeat and hold all your corrections.

Which method drifts, or do they both?

Then, have another shooter do the same thing with your setup.

 

[Hellbender]

Re: What's going on here

I was having the same thing happen with 2 different guns, made me pull my hair out.

Take the SH online training course and it will disappear....seriously.

It's trigger and recoil control.

 

[JL]

Re: What's going on here

how much drift to right?

spindrift will make 0,1mrad or slightly more, and coriolis adds perhaps 0,05mrad- Thats what it is here, about MN height. Roughly 1/3 of spindrift.

So I'd say that total drift to right in death calm day should be between one or two clicks to right.

I used 8" RH twist and 3000fps MV in calculations.

 

[Buckoman]

Re: What's going on here

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hellbender</div><div class="ubbcode-body">I was having the same thing happen with 2 different guns, made me pull my hair out.

Take the SH online training course and it will disappear....seriously.

It's trigger and recoil control. </div></div>

Can you elaborate here? A fellow shoot suggested the same thing so I started shooting open rear palm just finger on the trigger. Same thing happened. I've heard spin drift but, I'm getting like one whole MOA drift. Seems a bit much for that. As for dial and holdovers, I tried both and both have the same thing. If I dial, I have to dial 1 MOA windage. If I hold, I'm holding on the 1/2Mil line. Does that calculate to near the same?

Does the Surgeon 591 not have issues with base alignment since its built in or is it still a possibility?

 

[Lowlight]

Re: What's going on here

If you watch the video on Trigger Placement, pad versus joint you'll see just moving my finger on the same rifle, with the same ammo over a course of 6 targets each, I observed 1/2" group difference by just changing from the pad to the joint. This 1/2" did not show up until 300 yards, and was invisible at 100.

Very few people define what "Straight Back" on the trigger means, and because of that each person has a different understanding of what trigger control really is, forget follow through because most don't realize they are in fact not following through.

One thing we like is the fact that ExBal and Gerald Perry understand what is often mistaken for spin drift is in fact because of other factors. So in ExBal when you want to adjust for spin drift you actually go out and shoot your target at a range like 600 and input the drift recorded so ExBal can calculate the "Shooter Drift" as combined with the other influences. In our opinion this is the correct approach to this often used reasoning.

At the same time, we have found, proper application of the fundamentals, most importantly, that often misunderstood trigger control and follow through will greatly reduce the horizontal component of ones shooting. But you have to know what you are doing wrong to correct it. Most can't even tell when their finger flies off the trigger during follow through, so it is very difficult do diagnose alone.

You can dial your shooter errors and call it spin drift, that is the scientific way to explain away your problems, especially 600 yards and in... or you can learn to drive the rifle correctly. If you have an error in your rifle's construction, well then ExBal can help you account for that, especially when you consider how small the cant in a base is to give the shooter 20 extra MOA at 100 yards. Its' only about .020" from front to back.

Watch the videos, a lot of stuff is explained away with the proper fundamentals.

http://www.youtube.com/user/SHLowlight?blend=2&ob=1

 

[Cigarcop]

Re: What's going on here

Its cold outside...maybe your just shivering so much its magnified at the further distances..

I know you don't handle the cold too well!!!!

JK bud

 

[CanPopper]

Re: What's going on here

There could be several reasons.
1. Cant of scope relative to barrel
2. Scope adjustments are non linear

What I would do is this:
1. Hang a target at 100 with a bubble level attached so I know the target is level.
2. Have an anti cant device on rail
3. Check crosshairs against target at 100. Make sure reticles line up while scope base anticant device also centered. (adjust scope as needed)
4. Start shooting groups at the aligned target while dialing in elevation in 2 inch increments. Dial in both above bull's eye and below.
5. Also dial in vertically at bull and shoot 2 inch increments to left and right (basically shooting a cross by dialing turrets)
6. Check to see if groups form straight lines, horizontally and vertically. A problem scope could shoot parabolic curves as the dial gets turned.

 

[brand692]

Re: What's going on here

Well, this is an intersting problem, not real common with high end optics and actions.

This was a real problem with the LCS scopes as many of them had canted reticles (Both of mine did and had to be sent in for service). Never heard of that with a S&B.

My first inclination would be that you have a rail/bore alignment issue. Even though the rail is built in on the Surgeon, if the barrel was not installed properly, your issue would be at the barrel/action joint. Sure the scope is perfectly aligned with the action, but the barrel may not be aligned with the action, hence, a barrel/scope misalignment.

I don't know if you can do it with your trigger, but I would suggest that you turn it down as low as it will go (for a Jewell, down to 2oz) and shoot a group using the free recoil method. This is the method that was used during all of the Houston Warehouse Project testing and provided .035-.070 groups. It eliminates nearly all of the human factors when shooting. This will give you a base line to work with and hopefully determine if its human error or mechanical in nature.

If its human error, then training is in order.

If it is mechanical, then I would say it needs to go to a smith. You can correct some issues with the Burris rings mentioned above or a set of USOs, but in the end, they are a bandaid, not a fix for the real problem. While a MOA at 500 yards is a lot on the target, it is hard for a non qualified gunsmith to determine where the issue lies. We are talking thousandths of an inch at the action. It could be as simple as needing a crown done on the barrel or as complex as rechambering and threading a barrel.

One last comment, as this is already dragging on. When using rings that adjust for windage in the front AND rear, such as the USOs or the Burris, you can set the front ring to one side and the other ring to the otherside, simulating a canted rail. Make sure, if you are using this style ring, to set both rings to either full right or full left. Same thing can also happen if you install the rings with the rail bolts facing opposite eachother (one to the left, one to the right).

Best of luck figuring it out. I'll be interested to hear what it turns out to be. Keep us, or at least me, posted.

EDIT: Damn, took to long to type, had five posts before I submitted!

 

[Buckoman]

Re: What's going on here

Wow thanks for all the helpful responses here folks. I"ve got a lot to figure out. I'll keep ya'll posted. Thanks for the info

 

[gugubica]

Re: What's going on here

I am thinking that it is not a mechanical issue. Nothing against you, it may just be an aquired habbit that you don't know you have.

The online training offered here is worth way more than what you will pay. Compared to what most poeple have in their sticks, its next to nothing. Give it a shot.