Grouping problem

[mikecr]

What does it mean when a seemingly well built 1KBR gun and precision ammo combine to produce 1/2moa,ugly) groups -consisting entirely of 1/8moa clusters?

That is, a few here, & 3to4 there, then a couple up here, then a couple back into the 'first few' ragged hole, then another back up there, & on & on.... Always clusters forming..
Never actual fliers, but instead distinct,but unpredictable)POI changes. That's about the only way I can describe it.

I shoot it free recoil off Farley/edgwood, and have swapped barrels/scopes/bullets/front&rear bags/and shooters!! Several 280yd ladders have taken me to the same load, with very low ES, and best overall grouping has been .005 off lands. But of course I've experimented -without success.

Actually, I'm wore out with it. A little afraid of it..
But I'm invited to shoot 5 into 1/4moa at a local contest. So it's time to solve this I guess.

Has anyone seen anything like this?
Thanks

 

[rhino]

could be a bedding issue, or perhaps your barrel has a stress in it thats causing that erratic behavior.

Need a qualified smith like Alan and Dan Warner to look at it.

When in doubt have the experts look at it.

RHINOUT!

 

[mikecr]

Thanks Rhino
What kind of bedding issue might there be?

Here's the thing, I live nowhere near a shooting gunbuilder,as far as I know). This gun was bedded and stock finished by Kavanaugh, and he did an excellent job. It's a BAT RS action & rings in a Shethane-Lee Six stock. The action screws are torqued to 65inlbs.
Both barrels tried are Border 5R, and finished in 6.5wssm by Bryant. They're tightneck chambers, 28" & 8.5tw for 139Lapuas/140VLDs at 3025fps. It weighs 16lbs 6oz.
I've tried 3 NF NXS scopes, various edgewood & Protector bags.
The dies are custom & cut with my reamers. The necks are turned to .013" thick, and the brass is h20cap matched.

Just runnin out of ideas with this one.
Is 65"lbs enough torque?
Maybe I should get a couple more barrels finished..

 

[SPM]

Hey Mike, I have a friend that just had the same problem, it turned out that his brand new scope jacked up. So I would try a different scope before paying someone to look at it. Good luck, SPM

 

[JERRYHM]

Mike,
If the bedding checks out. Try a heavier firing pin spring, BAT's come with weak springs. Also check for firing pin drag on the trigger.

 

[CJ6]

You've tried barrels,bullets,scopes .How about the scope mounts are the base screws loose?

 

[mikecr]

Good ideas fellas, thanks
I really wish the gun just shot badly. That would be easier to fix. It's the clustering so tight that hooks me, as I see the potential expected there.

I use BAT's one piece ring-bases with 20moa incline. There are raised lands machined into the action to accept them with a snug interference fit. Seems so solid to me that I wonder if the base screws could affect anything at all.
The scopes tried have not picked up any type of ring marks.

I've used mostly BR2 primers, but have tried all others. The BR2s have given me low ES. Only thing is, they aren't reliable in the cold, and my headspace needs to be a touch tighter with them compared to other primers. Maybe my firing pin spring is weak. I'll ask Bruce about it.

The bullets tried have been 139Lap, 140JLK, 130Norma.
Initial testing showed promise with IMR4350. It fills the case, gives me good velocity, low ES, and It happened that I had alot of a same lot. Maybe I could start over with another powder and bullet.

 

[Johnboy]

have you tryed changeing primers yet sometimes that works for me

 

[mikecr]

Do you realize this thread is ~10yrs old?
The problem ended up being NXS scope lens bedding.

 

[Homerange]

Do you realize this thread is ~10yrs old?
The problem ended up being NXS scope lens bedding.

What does that exactly mean ?
Loose scope lenses ?

 

[ShootDots]

Three (3) things come to mind: 1.) It may be a "bullet" issue. I have had rifles that would shoot fabulously with several bullets BUT one bullet shot horribly! I can't explain that>>>but it exists! 2.) It may be those 65 inch lbs of torque. Maybe back off to 50? and finally 3.) I have found that the VAST majority of 6.5s shoot best between 2960 and 2990! You may be just over the actual node.. I have shot 260 Ackleys, 6.5 x 284s and such and they ALL like the 140 class bullets in that velocity range. Other than those things, it appears like you have tried everything else. It obviously is trying to shoot, you just have not found the ideal load yet>>>>or like I said, maybe the torque on the screws!

 

[MagnumManiac]

What does it mean when a seemingly well built 1KBR gun and precision ammo combine to produce 1/2moa,ugly) groups -consisting entirely of 1/8moa clusters?

That is, a few here, & 3to4 there, then a couple up here, then a couple back into the 'first few' ragged hole, then another back up there, & on & on.... Always clusters forming..
Never actual fliers, but instead distinct,but unpredictable)POI changes. That's about the only way I can describe it.

I shoot it free recoil off Farley/edgwood, and have swapped barrels/scopes/bullets/front&rear bags/and shooters!! Several 280yd ladders have taken me to the same load, with very low ES, and best overall grouping has been .005 off lands. But of course I've experimented -without success.

Actually, I'm wore out with it. A little afraid of it..
But I'm invited to shoot 5 into 1/4moa at a local contest. So it's time to solve this I guess.

Has anyone seen anything like this?
Thanks

Yes, my short range custom 22-250AI does the same with a certain powder and bullet combo. Had me pulling my hair out. I never did figure out the cause.
I opted to stay with the same bullet and switch powder, groups are now totally predictable at 3/8MOA. Hoping for tighter, but this rifle is only used at 300mtr F-Class.

It sounds to me it may be a heat treating issue, but you have changed barrels.
It’s definitely a head scratcher. Have you thought it may be a vibration issue?
I had a H S Precision stock that would vibrate on every shot, you could feel it through the pistol grip. The bedding block would ‘sing’ and cause 2 distinct groups about 3” apart, always high and right. After fully bedding it, the problem vanished.

Cheers.

 

[mikecr]

What does that exactly mean ?
Loose scope lenses ?

According to NightForce the lens in my primary NXS scope had a 'lens bedding issue'. To me that means it had been intermittently shifting from one position to another & another & back. That's what my grouping had been doing.
They fixed it and got the scope back to me right away (3 days). No more problems after that.
The weirdest part is that before this I had swapped NF scopes and it did not resolve the problem. Then by chance I had picked up another NF NXS on a good deal, that showed me right away that my other scopes were in fact -problem scopes.

I'll have to say that NightForce service is excellent, but I have since sold off all NF scopes and replaced them with Leupold Mk4s. They're just better scopes, and they've all tested perfect.

 

[Homerange]

According to NightForce the lens in my primary NXS scope had a 'lens bedding issue'. To me that means it had been intermittently shifting from one position to another & another & back. That's what my grouping had been doing.
They fixed it and got the scope back to me right away (3 days). No more problems after that.
The weirdest part is that before this I had swapped NF scopes and it did not resolve the problem. Then by chance I had picked up another NF NXS on a good deal, that showed me right away that my other scopes were in fact -problem scopes.

I'll have to say that NightForce service is excellent, but I have since sold off all NF scopes and replaced them with Leupold Mk4s. They're just better scopes, and they've all tested perfect.

Thanks.
I had what you might call a similar experience with an old VX1 1-4x Leopold that would rattle the cross hairs around when you just dry fired the rifle. When new it was fitted to dads .308 and lived there until I found this behavior. It was ~20 yrs old and had had a few bumps hunting but nothing extreme.
Sent it back to Leopold and although both exterior lenses were replaced the worksheet also listed the erector assembly was 'reworked'. As I understand it, it contains the lenses responsible for variable magnification and indeed if this sliding assembly wasn't fully restrained would explain changes in POI. Sure in my case the visible effect was extreme but IMO any vertical or horizontal movement in the assembly will show on the target.

 

[alinwa]

What does it mean when a seemingly well built 1KBR gun and precision ammo combine to produce 1/2moa,ugly) groups -consisting entirely of 1/8moa clusters?

That is, a few here, & 3to4 there, then a couple up here, then a couple back into the 'first few' ragged hole, then another back up there, & on & on.... Always clusters forming..
Never actual fliers, but instead distinct,but unpredictable)POI changes. That's about the only way I can describe it.

I shoot it free recoil off Farley/edgwood, and have swapped barrels/scopes/bullets/front&rear bags/and shooters!! Several 280yd ladders have taken me to the same load, with very low ES, and best overall grouping has been .005 off lands. But of course I've experimented -without success.

Actually, I'm wore out with it. A little afraid of it..
But I'm invited to shoot 5 into 1/4moa at a local contest. So it's time to solve this I guess.

Has anyone seen anything like this?
Thanks

I've seen it from some things;

#1-loose barrel, from hand-tight to "light pop" I learned that what you could get away with with a PPC you could NOT with a bigger case......
#2-loose scope bases. When I say "loose".... I mean not EPOXIED down.
#3-bad scope (why I have 3 scope checkers) but not seemingly relevant in your case.
#4- loose necks and VLD's (ie, over .002 nk clearance) (It took me three years to figger out how to get rid of them selfsame stupidgroups with 108's/6BR)
#5-bad bedding (back when I bedded the Brownell's way)
#6-forgetting to lock down the Farley turret (I once won a 600yd contest with my rest unlocked, just kept jacking the screw back up and wondering "WHY WON'T THIS THANG SET???") cuz I get real dumb when I'm on the line......


real dumb



re problems with MYSELF, I've had similar results from;

#1-rocky bag setup, too light and unstable. A REALLY good gun/tune can overcome this one, sometimes.
#2-trigger overtravel set to zero, the traditional Pete Brownell "glass rod"....... dude that bullet's in the bore FOR EVER!!! long enough I can drive that gun into the next ZIP Code.
#3-gremlins.... ie shooting over snow, shooting in "dead calm" and shooting under moonlight to name a few.

 

[T-shooter]

Is it grouping the shots in order or just randomly making small areas with hits?

 

[T-shooter]

Is it grouping the shots in order or just randomly making small areas with hits?

A few years ago I fired 6 shots at 215 yards. I don't remember what ammo or in what order I shot them but it made 3 touching pairs using the same point of aim. Why???

 

[mikecr]

That's a lot of what I was seeing right there. If I shot 15, I'd have a few distinct but separate (yet tight) groupings. My testing is usually at 200yds.

 

[Dusty Stevens]

A few years ago I fired 6 shots at 215 yards. I don't remember what ammo or in what order I shot them but it made 3 touching pairs using the same point of aim. Why???
View attachment 1049751

sure sign of a scope or base/ring shift. hard to tune that out.