Help Diagnose Issue with Rifle System

[slowelk]

Long, but your help is appreciated.

I'd like to get the obvious recommendations out of the way with, so I'll start with build components and assembly specs. Rifle assembled in May. Issue started at round 508 through the barrel/system. Rifle has been used at PRS and NRL matches this spring, most recent match was 6/14.

Action - Impact 737r short
Barrel - PVA Osprey, Med Palma, 6.5 creed, torqued to 80 ft lb
Stock - Foundation Ezekiel. Action screws paint penned and torqued to 65 in lb
Rings - UM Premier
Scope - NF NX8 4-32, all screws are paint penned and torqued to UM spec (30 ring caps, 45 ring bases)
Suppressor - DD Enticer Lti with Area 419 mounting system

First 100 rounds not included, all rounds have been the same lot of factor Berger loaded 130 OTMs. All shots throughout the issue have been recorded on my Garmin chrono, and velocity SDs have been 11-13fps, so I do not believe it is an ammo issue.

The rifle has not been dropped, or intentionally stress-tested, but has endured several bumps and dings from match shooting without issue.



I shoot large groups to establish zero. Rifle has been supremely accurate since the beginning (see baseline photos. 12-shot group is from 6/19).

Baseline Groups:




Issue started after the first six shots of the group in the next photo. Shots are numbered (nine shots). After this group I checked all screw torques and suppressor, everything was tight.


Head scratching. Decided to start another group. After this group I headed home and cleaned everything. Prior to this I had not cleaned the bore, as I usually don't, but I have consistently cleaned the lug recesses, chamber and throat.


Back to the range and started with this 20-round group. I thought the problem had been resolved.


After this, thinking the problem had been resolved, I moved to do some 300 yard positional work. My correction for 300 is 1.0 mils, and my first shot I was a mil-ish low, but it wasn't me. Moved back to 100 and this group resulted.


During the above group I spun the turret from min to max several times. I then decided to alternate shots between 300 and 100. The below is the resulting group at 100.


I've checked everything I have the tooling to check. My thoughts are the barrel has loosened, but the barrel is well beyond hand tight, or the scope has gone bad.

Let me know what you all think.

 

[wind gypsy]

Head scratcher. I'd guess scope.

Assume the foundation is cut for an impact and not bedded?

 

[slowelk]

Head scratcher. I'd guess scope.

Assume the foundation is cut for an impact and not bedded?

Yes, micarta bedding block for impact action. Very snug fit.

 

[ResearchinStuff]

barrel torque jumps out as being low, if you tighten it to ~100 ft-lbs you'll know it's not loose and it can come off the list as being a potential cause.

I think S2H was having issues with accuracy from a couple of DD cans, but not sure which models. the suppressor being loose, or having a loose baffle, could definitely cause those little shifts. how's it shoot with the can off?

if not fixed by the above, something in the rings/scope, including scope internals would be the next thing i looked at.

 

[wind gypsy]

Yes, micarta bedding block for impact action. Very snug fit.

Side tangent.. I hadn't looked at that stock close prior to this post. It looks sweet for an NRL gun. Have you liked it?

 

[slowelk]

barrel torque jumps out as being low, if you tighten it to ~100 ft-lbs you'll know it's not loose and it can come off the list as being a potential cause.

I think S2H was having issues with accuracy from a couple of DD cans, but not sure which models. the suppressor being loose, or having a loose baffle, could definitely cause those little shifts. how's it shoot with the can off?

if not fixed by the above, something in the rings/scope, including scope internals would be the next thing i looked at.

PVA recommends 75 ft lbs for non-magnum, 308 bolt-faced cartridges. I added five extra.

I wouldn't think it's suppressor. I've never shot it without the suppressor, so I don't know why the suppressor would be the problem now.

 

[slowelk]

Side tangent.. I hadn't looked at that stock close prior to this post. It looks sweet for an NRL gun. Have you liked it?

Very comfortable. I wish my performances would have been a stronger endorsement for it, the stock is not the problem.

 

[Laelkhunter]

It could be the way the photos appear, but:
pic#4 shot #8 hole looks elongated
pic#5 shot #2 looks elongated
pic#6 bottom bullet hole looks elongated
pic#7 shot hole #1 looks elongated
pic#8 bottom shot hole looks elongated

Could be just my old eyes, but looks like the bullets out of the group weren't stabilized leaving a slightly elongated hole. Causes??? Possibly baffle strike in can, but then most of the shots would be leaving elongated holes. Or the holes are normal and we have to find another cause.
Try without the suppressor maybe??

 

[Harvey_NW]

Barrel torque then scope check would be the order I would address it in.

 

[ResearchinStuff]

PVA recommends 75 ft lbs for non-magnum, 308 bolt-faced cartridges. I added five extra.

I wouldn't think it's suppressor. I've never shot it without the suppressor, so I don't know why the suppressor would be the problem now.

My pva 223 is at 110 ft lbs, it's not going to break.

 

[slowelk]

It could be the way the photos appear, but:
pic#4 shot #8 hole looks elongated
pic#5 shot #2 looks elongated
pic#6 bottom bullet hole looks elongated
pic#7 shot hole #1 looks elongated
pic#8 bottom shot hole looks elongated

Could be just my old eyes, but looks like the bullets out of the group weren't stabilized leaving a slightly elongated hole. Causes??? Possibly baffle strike in can, but then most of the shots would be leaving elongated holes. Or the holes are normal and we have to find another cause.
Try without the suppressor maybe??

hadn't considered this. I think the pics could be misleading in terms of the concentricity. I will check alignment. odd that it would just start happening?

 

[slowelk]

My pva 223 is at 110 ft lbs, it's not going to break.

I will take it to 100.

 

[Wrench]

I'd check all torques. If all good pull the can and shoot. I have killed many scopes and usually it's several minutes or mils out. When my nightforce broke....I could hear it rattle when I took it off and shook it. Rolling in a different scope is easy to do and answers questions quickly.

 

[Ramem7mm]

tagging in. removing suppressor seems easy to be able to cross it off, if it is the culprit.

 

[HandgunHTR]

My guess is the suppressor or suppressor mount.

Do you remove it after use? If so, are you thoroughly cleaning the mount and the mating surfaces of the mount and suppressor? If not, start there.

I recommend against shooting groups without the suppressor if the loads were developed with it on. Chances are it won't shoot the same with it off, so there is no way to tell if the variation is due to removing the suppressor or not.

If you have the ability to go direct thread, you may want to try that.

 

[slowelk]

For those of you suggesting suppressor @Ramem7mm @HandgunHTR @Laelkhunter , why do you think it would only just now become an issue?

 

[Ramem7mm]

Another person had mentioned as well that something could have had a strike or possibly came loose internally. I do not own a suppressor so not qualified to put my opinion out there but it seems easy enough to take off just to rule it out incase something happened internally causing the abnormality.

 

[Laelkhunter]

For those of you suggesting suppressor @Ramem7mm @HandgunHTR @Laelkhunter , why do you think it would only just now become an issue?

Buildup of carbon inside creating a possible deflection in the bullet path, mount coming loose if it has a mount, or possibly something else. Stupid question but does the suppressor rattle if you shake it? Possible something broke off/came loose inside. Just trying to help identify what could be causing your groups. You have to eliminate possible causes one at a time until you find out what it is.

 

[Lawnboi]

I have quite a few thoughts.

Try another scope immediately. This will check off one of the easiest variables. Theres good reason to keep a reliable scope around in rings because it’s the most likely to mess up.

How are you cleaning? I have had a 6.5cm barrel do the exact same thing with zero cleaning for ~1000 rounds.

Mirage? I don’t see a suppressor cover. Mirage can cause some zero shift especially when shooting high magnification groups at closer range.

Suppressor clear and mounts tight?


My plan would be to first actually clean the bore. This is going to be an intensive process if you havnt done it at all. I know this is a debated topic on Rokslide but I tried the no cleaning thing and it worked till it didn’t. If I was okay with 1.5moa guns I’d probably not be cleaning, but I’m not.

After that I’d try a different scope.

After that I’d try a different barrel .

 

[Hill Difficulty]

One thing I never see anyone mention is when a front action screw is barely too long. "Too long" is if your finger tip can feel the top of the screw enter the inside of the receiver when finishing the screw rotation. If barely too long, the top of the screw will contact the downward bolt lug and cause the bolt face to lift up from center.

Something to eliminate, anyway.