Multiple "groups"?

[mercervillerental]

I've noticed that I often find 2 seemingly distinct groups appear on target which leads me to wonder, is it the load (I assume not) or me (probably?).

I try to shoot 10 round groups as often as possible. Typically somewhere between shots 3-5 another slightly more distinct group seems to form next to, below (less often above) the original group.

Anyone else experienced this before? If its typically shooter error, is there something common that makes this happen that I should look to correct?

 

[RTH1800]

I see it on groups that are not bad but sub groups are far better. Say a 10 shot group at 600 meters is 4.5" but 7 of the shots are 2.25" and the other 3 are clustered in 1.25" but positioned to enlarge the overall group. I suspect it is the shooter but have never figured out a way to isolate it. If not the shooter it is more likely random than the equipment my intuition says. Again, just a guess.

 

[Tx_Aggie]

What sort of rifle are you shooting?

I'm not a gunsmith by any means, and hopefully someone more knowledgeable than I will comment, but IIRC, a rifle splitting shots into two distinct groups is often caused by a bedding issue.

A "bedding issue" could be anything from a poor fit between the action and stock, pressure on the barrel, uneven or incorrect torque on the action screws, uneven pressure on the recoil lug, interference between the trigger assembly and the stock/chassis, etc.

I suppose it could also be a problem with the scope mount (i.e. not properly torqued), or possibly the scope itself.

 

[ShtrRdy]

If you can repeat this behavior multiple times then it's likely not you but the rifle/scope/ammo.

 

[Erno86]

Barrel & receiver heating up???

May I suggest for accuracy testing --- Limit yourself to 3 shot groups ---- Shoot in a fairly rapid pace before the receiver heats up.

One minute time sequence for an approx. 3 shot group??? Then let the big gun cool.

 

[Klemm]

Loose rear action screw and or cheek weld

 

[mercervillerental]

Thanks for the suggestions all.

I should clarify one thing, I find it happens more often when I'm shooting an AR vs a bolt gun, and possibly because that is when I usually shoot 10 round groups, whereas on my bolt gun its usually more like 5. However its now happened on two AR's hence why I'm thinking its me somehow, but still not sure what to look at.

I'm going to check my cheek weld and also fire sequential rounds a little more quickly and maybe cut my initial # of shots per group down as per another recommendation here.

Thank you all!

 

[Tx_Aggie]

Shooting fewer rounds per group isn't really a fix.

 

[b6graham]

Shooting fewer rounds per group isn't really a fix.

says the dude who's mascot is some dog lol

kidding aside, caliber, rifle, barrel contour??

 

[Tx_Aggie]

says the dude who's mascot is some dog lol

kidding aside, caliber, rifle, barrel contour??

Haha, damn straight she is!

I assume the second bit is directed at the OP.

 

[buffalowinter]

I suspect "parallax"...i.e. you are not looking through the scope consistently each time. Changing cheek pressure, stock weld, etc will result in shifting groups. You can test this by purposely looking through the scope using different cheek pressure, head position, etc. This results in multiple groups depending upon the angle the eye is at as it looks through the scope/sight.

definition: the effect whereby the position or direction of an object appears to differ when viewed from different positions, e.g. through the viewfinder and the lens of a camera.


A simple everyday example of parallax can be seen in the dashboard of motor vehicles that use a needle-style speedometer gauge. When viewed from directly in front, the speed may show exactly 60; but when viewed from the passenger seat the needle may appear to show a slightly different speed, due to the angle of viewing.

The further the distance, the easier it is to observe this effect.

Target shooters have used small apertures on their scopes to reduce parallax error. Here is a home made one.

Congratulations, you have just made your scope virtually parallax free. If your head is in the wrong position you won’t be able to see anything through your scope. Now move your head around until an image appears. This is your perfect head position.

White Oak Lens Reducer
Our unique “ghost ring” design is a lens with a chamfer around the center hole. It ships with two lenses, a clear and a smoke tinted. Both are transparent which allows you a full field of view so you can still see surrounding targets and target numbers but acts as a ghost ring centering your eye in the 3/64 diameter hole.

There are obvious disadvantages to this fix , even for target shooting, but it does demonstrate that this is a common problem and that the fix is consistency in looking through the scope with the same head position every time.

 

[Dthomas3523]

Look at the shooter first.

Vertical = breathing (breaking trigger at different points in the breathing cycle)

Horizontal = trigger (not 90 degree and straight back)

Unless you are sure your fundamentals are solid, you cannot begin to assess an equipment problem.

 

[mercervillerental]

Shooting fewer rounds per group isn't really a fix.

I should have been clearer, I plan on shooting the same number of rounds per group but per an earlier recommendation I'll break it up allowing my barrel to cool in the meantime

 

[mercervillerental]

says the dude who's mascot is some dog lol

kidding aside, caliber, rifle, barrel contour??

6.5 Creedmoor stock RPR

 

[mercervillerental]

I suspect "parallax"...i.e. you are not looking through the scope consistently each time. Changing cheek pressure, stock weld, etc will result in shifting groups. You can test this by purposely looking through the scope using different cheek pressure, head position, etc. This results in multiple groups depending upon the angle the eye is at as it looks through the scope/sight.

@buffalowinter going through my old threads here - I think you nailed it. As I've paid more attention to setting my parallax correctly and getting more consistent head placement in relation to my scope all of my groups have tightened up considerably. Thank you! Hopefully this helps someone else down the road as well

 

[Dthomas3523]

@buffalowinter going through my old threads here - I think you nailed it. As I've paid more attention to setting my parallax correctly and getting more consistent head placement in relation to my scope all of my groups have tightened up considerably. Thank you! Hopefully this helps someone else down the road as well

If you had proper sight picture (no shadowing and such), it likely wasn’t parallax.

 

[mercervillerental]

If you had proper sight picture (no shadowing and such), it likely wasn’t parallax.

Its been a while so I can't remember to be honest with you. If that was the case (shadowing) what would that likely indicate?

 

[Dthomas3523]

Its been a while so I can't remember to be honest with you. If that was the case (shadowing) what would that likely indicate?

Shadowing indicates you’re not behind the optic properly.

If you have a completely proper sight picture without shadowing, parallax matters much less.

 

[JakeM]

Look at the shooter first.

Vertical = breathing (breaking trigger at different points in the breathing cycle)

Horizontal = trigger (not 90 degree and straight back)

Unless you are sure your fundamentals are solid, you cannot begin to assess an equipment problem.

^^^^ this. I thought it was a cold bore shift, I was just me. Video yourself shooting and go over the fundamentals as you watch it.