Groupings not playing nice

[Cinders]

Hi all!

Wasn't sure what sub-forum this belonged in, but I could use a pointer in the right direction to figure this problem out:

Criterion 18" M118 hybrid

Precision Arms M11 muzzle brake

built a new AR308, trying different ammunition in it, and the one consistent thing that I'm getting is tight, separate groupings.  Plus a few flyers about every 5 rounds.  This was with Hornady Match grade 168 gr.  (Lower grade ammo produced exactly the same results just with more flyers and a looser group).  In effect, if I adjust my crosshair to center the separate groups, I'd have 3 round tight group to the left of the crosshair and a 3 round tight group to the right of the crosshair and a few flyers.

My friend shot this rifle and got similar results.  Tight groups that won't stay in one place.  

Is this just inaccuracy of the rifle showing random patterns?  Shoot a 20 round group and look for an average?  I did the scope mount to specs, but tighten it more?  

 

[Radioactive]

Are you saying that the same ammo brand, type, and load is moving it’s groups? Or are you saying each type / brand of ammo is grouping differently? The second situation is not uncommon as each load behaves differently due to powder and bullet differences resulting in speed variations etc. If the first is true I’d look for something loose on the gun (barrel/scope) or at shooting technique. Are you resting the barrel on something? Are you loading the bipod the same, same grip, same body position etc.

[98Z5V]

1 hour ago, Cinders said:

Hi all!

Wasn't sure what sub-forum this belonged in, but I could use a pointer in the right direction to figure this problem out:

Criterion 18" M118 hybrid

Precision Arms M11 muzzle brake

 

 

What other components were used to build this gun?

[Matt.Cross]

What optic are you using?

[Cinders]

Timney trigger

Aero Precision upper and lower and handguard

Zero Fail BCG

Vortex Diamondback 4-16X scope 

American Defense Recon straight scope mounts (tightened to 18 inch-pounds) (this model has 2X quick release lock downs)

 

My only 2 guesses are:

1) The gun is not accurate and these are simply part of the cone of fire.  They just look like there is a tight pattern but are random.

2) The scope is moving, despite very tight brackets and no discernible movement upon physical inspection.

 

 

[shooterrex]

I'd try a different scope and mount first. Use a scope you know is good. I just threw away a scope I've had for years. The groups went to hell real quick on a rifle. When I took the scope off I can hear something loose inside the scope.

 

[billymagg]

7 hours ago, Cinders said:

Hi all!

Wasn't sure what sub-forum this belonged in, but I could use a pointer in the right direction to figure this problem out:

Criterion 18" M118 hybrid

Precision Arms M11 muzzle brake

built a new AR308, trying different ammunition in it, and the one consistent thing that I'm getting is tight, separate groupings.  Plus a few flyers about every 5 rounds.  This was with Hornady Match grade 168 gr.  (Lower grade ammo produced exactly the same results just with more flyers and a looser group).  In effect, if I adjust my crosshair to center the separate groups, I'd have 3 round tight group to the left of the crosshair and a 3 round tight group to the right of the crosshair and a few flyers.

My friend shot this rifle and got similar results.  Tight groups that won't stay in one place.  

Is this just inaccuracy of the rifle showing random patterns?  Shoot a 20 round group and look for an average?  I did the scope mount to specs, but tighten it more?  

 

We need a little more data, you stated you had 3 round groups to the left of your intended point of aim??? so the first three rounds are to the left? and the second three rounds for the next group to the  right?? so all bullets from the same group are together, correct???  and every 5 rounds you have a few flyers???

Many magazine fed weapons have a "first round flyer", in other words the first round off the top of the magazine will have a different point of impact away from the main group of the rest of the rounds in the magazine, due to manually cycling the action of the weapon, as opposed to the weapon cycling the following rounds mechanically more consistantly.

we typically fire 3 round groups because a barrel, especially a lighter profile barrel will begine to "string" rounds as the barrel heats up, if you fire 5 or 10 round groups that effect will become noticable as your bullets begin to "walk" away from the initial grouping of the first rounds in a cool barrel.

 

I do agree that the scope or mounts are the first point of likely failure, check that first.

 

Edited August 3, 2020 by billymagg

[Cliff R]

Here might be an example of what you are describing.  The center group in the pic below if from my 308-AR.  It has a light profile 14.7" barrel. 

The first two rounds are nearly in the same hole and down at the 6 o'clock position.  The next two round nearly in the same hole at 3 o'clock.  The last round or "flier" is outside the "box" at 12 o'clock.

Compare that group to the same loads fired thru my DPMS to the left where it just shoots a "group".

I didn't take any other pics but the 14.7" rifle does this with enough consistency that it is not coincidence.  Most likely just the "nature of the beast" and comes from heating up.  It's topped with a Leupold scope in a "rock" solid mount.

Matters not in the big scheme of things.  At the end of the session I backed up to 300 yards, leaned over a big round hay bale up near the barn and fired 5 rounds thru it as fast as I could get back on target.  The resulting "group" fell just inside of 6", well on a Mule Deer or Elk, which is what the rifle was built and is used for........Cliff

Edited August 4, 2020 by Cliff R

[edgecrusher]

I agree with check your scope and mount. 

17 hours ago, billymagg said:

We need a little more data, you stated you had 3 round groups to the left of your intended point of aim??? so the first three rounds are to the left? and the second three rounds for the next group to the  right?? so all bullets from the same group are together, correct???  and every 5 rounds you have a few flyers???

Many magazine fed weapons have a "first round flyer", in other words the first round off the top of the magazine will have a different point of impact away from the main group of the rest of the rounds in the magazine, due to manually cycling the action of the weapon, as opposed to the weapon cycling the following rounds mechanically more consistantly.

we typically fire 3 round groups because a barrel, especially a lighter profile barrel will begine to "string" rounds as the barrel heats up, if you fire 5 or 10 round groups that effect will become noticable as your bullets begin to "walk" away from the initial grouping of the first rounds in a cool barrel.

 

I don’t agree with this. Magazine fed weapons do not have first round flier issues. That’s operator error, anticipation or other. A cold bore shot may have POI difference from the following shots but once you send a few your fine. I shoot ten rounds groups with no stringing. Not sure what the issue there is but lighter profile barrels should have no issues with this as long as your not shooting full auto, mag dumps or allow some cooling following two magazines of group fire. Mechanical action of the weapon is the same from the firing pin to the primer. Action has nothing to do with a flier. Reference a shooting sled. Get three rounds down the pipe and then shoot a five round group. Once your barrel has temp, the group is consistent as it can be to ammo tolerance. 

[billymagg]

On 8/3/2020 at 5:04 PM, edgecrusher said:

I agree with check your scope and mount. 

I don’t agree with this. Magazine fed weapons do not have first round flier issues. That’s operator error, anticipation or other. A cold bore shot may have POI difference from the following shots but once you send a few your fine. I shoot ten rounds groups with no stringing. Not sure what the issue there is but lighter profile barrels should have no issues with this as long as your not shooting full auto, mag dumps or allow some cooling following two magazines of group fire. Mechanical action of the weapon is the same from the firing pin to the primer. Action has nothing to do with a flier. Reference a shooting sled. Get three rounds down the pipe and then shoot a five round group. Once your barrel has temp, the group is consistent as it can be to ammo tolerance. 

Fair enough, but I'm going to stick with the "first round flyer", as well as bullets walking as barrels heat up... of course ammo is also a factor, and its consistency shot to shot, even in the same box of factory ammo, but I've honestly found the Hornady to be very consistant, not to mention reloads and different brass.  I'm also going to throw in different magazines, not only different types, but individual magazines may affect your group.

So the separate  left right groupings where in the same magazine of ten in your group??? yes??? so were you able to change out your scope, could you give us some specifics about your scope and mounting? thanks billy, and good luck, these sudden issues can be very frustrating until you get it sorted out, hang in there!

Edited August 6, 2020 by billymagg

[98Z5V]

On 8/3/2020 at 3:04 PM, edgecrusher said:

 I shoot ten rounds groups with no stringing.

Vertical stringing, if it were that, is a breathing problem - firing at different times during your breathing cycle.  Always fire on the full-exhale.  Always.

19 minutes ago, billymagg said:

Fair enough, but I'm going to stick with the "first round flyer", as well as bullets walking as barrels heat up...

Only if they're machine guns.  Times are different now.  If you're still quoting Viet Nam Logic - those were light profile M16s with a 1:12" twist rate and with 55 grain projectiles. That was even before "Government Profile" was invented.

"First Round Flyer" is a cold-bore shot.  It CAN be different, over a warmed barrel shot, but most modern barrel-manufacturing technologies mitigate this, as much as they can. 

Walking as the gun heats up... That's only a thing now if it's a pencil-profile barrel, and you rapid-fire the shiit out of it.  I have a 16" Faxon Pencil-Profile 5.56 gun - and it doesn't walk as the barrel heats up.  Once it's warm - you are right there, everytime.

Technology and times are different from what you're preaching, my man. 

 

[98Z5V]

The guy here in this thread is placing 3 shots left.  Then he places 3 shots right...

He's changing his sight picture.

The mount is good, the scope is good.  That's a very minute ("My-Noot") change in sight picture - inconsistant sight picture - between groups.

Shoot 10, see where they fall. Shiit, shoot 5, see where they fall.  Make scope adjustments from that.  Repeat.  Don't change your sight picture.  Dial your magnification DOWN... 

Edited August 6, 2020 by 98Z5V

[edgecrusher]

56 minutes ago, 98Z5V said:Only if they're machine guns.  Times are different now.  If you're still quoting Viet Nam Logic - those were light profile M16s with a 1:12" twist rate and with 55 grain projectiles. That was even before "Government Profile" was invented.

"First Round Flyer" is a cold-bore shot.  It CAN be different, over a warmed barrel shot, but most modern barrel-manufacturing technologies mitigate this, as much as they can. 

Walking as the gun heats up... That's only a thing now if it's a pencil-profile barrel, and you rapid-fire the shiit out of it.  I have a 16" Faxon Pencil-Profile 5.56 gun - and it doesn't walk as the barrel heats up.  Once it's warm - you are right there, everytime.

Technology and times are different from what you're preaching, my man. 

 

That’s what I’m saying. Unless you’re shooting full auto this is operator error.

[edgecrusher]

1 hour ago, billymagg said:

Fair enough, but I'm going to stick with the "first round flyer", as well as bullets walking as barrels heat up... of course ammo is also a factor, and its consistency shot to shot, even in the same box of factory ammo, but I've honestly found the Hornady to be very consistant, not to mention reloads and different brass.  I'm also going to throw in different magazines, not only different types, but individual magazines may affect your group.

So the separate  left right groupings where in the same magazine of ten in your group??? yes??? so were you able to change out your scope, could you give us some specifics about your scope and mounting? thanks billy, and good luck, these sudden issues can be very frustrating until you get it sorted out, hang in there!

Magazines have absolutely nothing to do with what comes out of the muzzle. I can’t get behind that. Sounds like Internet boogaloo.

[Matt.Cross]

I'm of the opinion that the only way a magazine can affect your group is by feeding badly enough to mangle your round somehow. 

Gas guns are extremely unforgiving in terms of the fundamentals of accuracy from a technique standpoint. Slight errors will produce profound changes in your POI, that's the nature of the beast. It's also one of the main reasons I love this platform so much, it absolutely will make a shooter out of you if you commit to it.

[billymagg]

13 hours ago, Matt.Cross said:

I'm of the opinion that the only way a magazine can affect your group is by feeding badly enough to mangle your round somehow. 

Gas guns are extremely unforgiving in terms of the fundamentals of accuracy from a technique standpoint. Slight errors will produce profound changes in your POI, that's the nature of the beast. It's also one of the main reasons I love this platform so much, it absolutely will make a shooter out of you if you commit to it.

Yep, my AR came with a 10 round ASC magazine, my first outings with this mag were abysmal, at my first opportunity, I took it to our local Central Obamastan Rock River dude, we cycled several magazines through, and that magazine dinged every last round as it was chambering! threw that one out of the pile and things got all better

[billymagg]

13 hours ago, Matt.Cross said:

I'm of the opinion that the only way a magazine can affect your group is by feeding badly enough to mangle your round somehow. 

Gas guns are extremely unforgiving in terms of the fundamentals of accuracy from a technique standpoint. Slight errors will produce profound changes in your POI, that's the nature of the beast. It's also one of the main reasons I love this platform so much, it absolutely will make a shooter out of you if you commit to it.

and your second point is my point exactly. If you were to take a look at all of Brandon Collier's, of Wilson Combat's groups, this spring and summer?? (they are posted on almost every ad for a Wilson Combat WS-10 rifle in 308 or 6.5 Creedmore that is posted on Gun Broker. Brandon's name is on almost every Wilson Combat's rifles 3 shot group as the shooter. Nine out of Ten have a 1st round flyer, and two snuggled together like amorous rabbits. That first round is manually cycled, likely by releasing the bolt, being held back by the bolt stop? the remaining two are cycled by the gas from the proceeding expended round, cycling the action. That is a huge difference, and I'm the noob here, but I've done a fair share of shooting, and a fair share of attempting to understand weapons, and the operating systems.

I also recall several tests, where a pistol was snugged into a ranson rest, targets at 25 yards, and a 5 or so magazines were fired with no changes to the set-up, out of the same box of ammo.. they hand cycled the first round of each magazine creating a small group, away from the large group fired by the remaining automatically cycled rounds.

I've got ONE heavy barreled rifle, all the remaining are light sporter profiles, since I carry my rifles more than I shoot them. Starting with a clean cold bore, and shooting 10-20 rounds, they will all walk as the bore heats and fouls, even that damn near new Wilson..

this is a very competent and opinionated group of operators here, confident as well, I'm certainly NOT saying that is the OP's problem, I don't know, and as mentioned above, breathing and where you park your eyeball behind those cross hairs will make a difference.

Breathing is where I've had to make the most changes with my 308 AR, that and a much better front bag than I was using before...

15 hours ago, edgecrusher said:

Magazines have absolutely nothing to do with what comes out of the muzzle. I can’t get behind that. Sounds like Internet boogaloo.

If you have a magazine fed weapon of any sort? the magazine is the second largest variable behind ammo, supposing that your shooting form remains consistent, on your weapon, this is purely subjective, but I've had the best luck with older Colt 20 rounders on the 5.56 AR platform, and as mentioned elsewhere, I had an ASC that consistently dinged bullets as they were chambered...

I would add that you should consider where your ejected empty cases go, my 5.56 usually puts the first one around 2:OO o'clock, the remainder of a 5 round mag usually about 3:30 to 4:30?? your milage may vary??

So Chief, do you feel like you are any closer to what has changed to cause this sudden group divergence, I mean you've got lots of trigger time? you are leaning toward your scope aren't you??

[98Z5V]

6 hours ago, billymagg said:

.

If you have a magazine fed weapon of any sort? the magazine is the second largest variable behind ammo, supposing that your shooting form remains consistent, on your weapon, this is purely subjective, but I've had the best luck with older Colt 20 rounders on the 5.56 AR platform, and as mentioned elsewhere, I had an ASC that consistently dinged bullets as they were chambered...

I would add that you should consider where your ejected empty cases go, my 5.56 usually puts the first one around 2:OO o'clock, the remainder of a 5 round mag usually about 3:30 to 4:30?? your milage may vary??

So Chief, do you feel like you are any closer to what has changed to cause this sudden group divergence, I mean you've got lots of trigger time? you are leaning toward your scope aren't you??

I have almost 40 of these things, different sizes, different calibers - magazines don't affect my accuracy, at all.  In fact, in only have one bolt gun that's not detachable-magazine fed, and I have a big pile of bolt guns.  Doesn't affect them.  The accuracy on these guns is quite nice, ARs, bolts, all of them. 

Magazines are not going to ding your accuracy. 

It's pretty far from purely subjective.

In an AR, where your ejected, empty cases go has everything to do with the buffer system components, and nothing else.

[Cinders]

On 8/5/2020 at 10:49 PM, 98Z5V said:

Vertical stringing, if it were that, is a breathing problem - firing at different times during your breathing cycle.  Always fire on the full-exhale.  Always.

Only if they're machine guns.  Times are different now.  If you're still quoting Viet Nam Logic - those were light profile M16s with a 1:12" twist rate and with 55 grain projectiles. That was even before "Government Profile" was invented.

"First Round Flyer" is a cold-bore shot.  It CAN be different, over a warmed barrel shot, but most modern barrel-manufacturing technologies mitigate this, as much as they can. 

Walking as the gun heats up... That's only a thing now if it's a pencil-profile barrel, and you rapid-fire the shiit out of it.  I have a 16" Faxon Pencil-Profile 5.56 gun - and it doesn't walk as the barrel heats up.  Once it's warm - you are right there, everytime.

Technology and times are different from what you're preaching, my man. 

That's what throws us!  Only to point out some credibility for the human side of the gun, both my friend and I were Marine snipers (amazingly ran into each other again at the same job years later).  

Now, having said that, I was used to everything being provided by gun-savvy people.  But I'm very good with parallax, stock weld, scope relief, etc.  We tested the parallax down to the smallest change, have steady breath holds, slow trigger squeeze.  My friend has stayed in the gun community and builds AR-15s while I'm coming back to the community after a long break.

I'm going to borrow his scope and mount again.  I used his for the break-in and got groups about 2.5 MOA at 100yds.  Got my new scope and mount and suddenly I'm seeing ~1 MOA groups.  If I shot 5 rounds, I'd see a 3-group touching and a 2-group touching, separated by an inch or so.  

He produced the same thing.  We both had a flyer every 10 rounds or so.

Just enough to make us question if it is us or the rifle is quirky.

[98Z5V]

12 hours ago, Cinders said:

Just enough to make us question if it is us or the rifle is quirky.

It could be - quickest way to find out is to swap that scope out with your buddy's scope. If it's still doing it after that - it's the gun, somehow.  Something in there is messing with it.

Post a pic of the gun, if you would please.

[edgecrusher]

Barrel nut then? Maybe not torqued to spec? Receiver extension (on the upper, maybe an blem that got through)? Barrel extension. Does the rifle have a free floating barrel? Taking you out of the equation with these....

[Cinders]

11 hours ago, 98Z5V said:

It could be - quickest way to find out is to swap that scope out with your buddy's scope. If it's still doing it after that - it's the gun, somehow.  Something in there is messing with it.

Post a pic of the gun, if you would please.

 

17 minutes ago, edgecrusher said:

Barrel nut then? Maybe not torqued to spec? Receiver extension (on the upper, maybe an blem that got through)? Barrel extension. Does the rifle have a free floating barrel? Taking you out of the equation with these....

I'll get a pic up.

We used his AR-15 vice block to torque it to specs (the barrel).  It is free floating except for the heavy duty compensator on the front.  

Should I look at taking off the compensator to test?  It's on there right and tight with shims, according to specs.

Thanks for advice so far.  I'll try some more groups with pics to help you all help me, lol.  I can recall seeing this *once* before like 15 years ago in the service.  I don't know what the real problem was, but they sent the rifle in to be re-barreled and it came back working fine.  The theory was the barrel fiberglass bedding was compromised, but nobody that really confirmed that.

Last question: I think this is purely a barrel issue, does that compute?  The compensator is unlikely to produce this randomness.  I'll try re-torquing the barrel nut and test again.  

[DNP]

What sort of spread are you seeing and at what range?  I re-read  few initial post, but didn’t see that data. Was curious how much you’re seeing in the shift. 

[98Z5V]

8 hours ago, Cinders said:

Last question: I think this is purely a barrel issue, does that compute?  

Nope, not at all - not with the barrel you're using. 

On 8/2/2020 at 1:09 PM, Cinders said:

Criterion 18" M118 hybrid

Doesn't make sense, for that barrel, at all.  That's the Fulton Armory profile and specs, that Criterion makes for them.  Clint McKee wouldn't let a bad design get out, not with his history. 

Change the scope - do the easy thing first.  That's the Vortex budget scope, that you have on it. Bad ones can and do get out, from every scope manufacturer, once in awhile.

[Cliff R]

There will always be some human error when bench resting a weapon no matter how you are set-up to keep things from moving. 

Experienced shooters know how to minimize the problems associated with breathing, sight alignment, grip on the weapon, trigger control, etc.  What we try to do as dedicated enthusiasts is to minimize the variables that we have the most control over, the quality of the weapon and it's parts, barrel, trigger pull/smooth/crisp, scope mounts, high quality optics, and ammunition.  It goes without saying that tighter groups at shorter distances play a big role when you really start stretching things out some. 

It's still not a perfect science and reminds me when I used to shoot on the rifle team back in my military days.  For the most part most folks did quite well in the prone position "locked-in" and slow fire.  Some typically did better their as they had their sight dope down pat and better at judging the wind, etc, but for the most part you see higher scores on that part of the course.

It's when you go to the standing position where you really start seeing some HUGE deviations in the scores, and I suppose it's still like that in 2020........Cliff