accuracy issues with 338 suppressor

[Powderman]

Quick question. I built a 338 Lapua can with stepped cone baffles that are symetical. 8 Baffles total in a ten inch long 2" od tube 316 SS, 37 oz.

It is built for the TRG 42 Rifle.

The rifle shoots great but when I install the supressor the point of impact shift is not the same from shot to shot.

I built the same can for the 308 TRG22 and the only difference is that I used straight conical baffles not stepped baffles and it works great both with sound reduction and consistent point of impact shift.

Is there something different about using stepped cones instead of straight cones that could cause this problem?

My other questions are about point of impact shift. Is there an amount of shift that is acceptable say for a 308 can? ie an industry standard that is acceptable?

What can be done in the design to reduce the shift?

Thanks

[Bendersquint]

Quick question. I built a 338 Lapua can with stepped cone baffles that are symetical. 8 Baffles total in a ten inch long 2" od tube 316 SS, 37 oz.

It is built for the TRG 42 Rifle.

The rifle shoots great but when I install the supressor the point of impact shift is not the same from shot to shot.

I built the same can for the 308 TRG22 and the only difference is that I used straight conical baffles not stepped baffles and it works great both with sound reduction and consistent point of impact shift.

Is there something different about using stepped cones instead of straight cones that could cause this problem?

My other questions are about point of impact shift. Is there an amount of shift that is acceptable say for a 308 can? ie an industry standard that is acceptable?

What can be done in the design to reduce the shift?

Thanks

What kind of grouping are you getting?

37 ounces is ridiculously heavy and the TRG42 isn't designed to take that much weight on the barrel!

Stepped cones aren't that effective on the big bores better to use straight cones, I am not sure why everyone is so fascinated with stepped cones.

There is no such thing as an industry standard in the silencer industry. The ONLY thing is proper sound testing procedures, thats it.

Recore it and put it on a treadmill for a good year or 2.

[Powderman]

Thanks Bendersquint

I based the overall weight of the design on the AAC Titan SS which is 38oz. My tube is slightly larger in diameter than the Titan.

What would you suggest is a weight that is not rediculous for the TRG42?

I am pleased with the dB reduction. It is metered at 35db reduction and is a pleasure to shoot with out hearing protection.

My 308 is a straight cone design, but I thought that the stepped cone may provide more turbulence.

I certanly am not fascinated with stepped cones or anyother design I just want the best performance possible.

The point of impact shift is 7" low and three left at 100 yards. The problem is that it did not groop there it would then shift up and down by apprx. 5 inches.

I understand that there may not be an industry standard accepted for the point of impact shift, I was just curious at what would be an acceptable shift and what would not.

Thanks

[Bendersquint]

Thanks Bendersquint

I based the overall weight of the design on the AAC Titan SS which is 38oz. My tube is slightly larger in diameter than the Titan.

What would you suggest is a weight that is not rediculous for the TRG42?

I am pleased with the dB reduction. It is metered at 35db reduction and is a pleasure to shoot with out hearing protection.

My 308 is a straight cone design, but I thought that the stepped cone may provide more turbulence.

I certanly am not fascinated with stepped cones or anyother design I just want the best performance possible.

The point of impact shift is 7" low and three left at 100 yards. The problem is that it did not groop there it would then shift up and down by apprx. 5 inches.

I understand that there may not be an industry standard accepted for the point of impact shift, I was just curious at what would be an acceptable shift and what would not.

Thanks

I have seen accuracy and ridiculous POI shifts with anything over 30 ounces on the TRG42(my basis is a TRG22).

Best performance would have been with straight cones.

You are definitely dealing with issues with the baffles if your impacts are all over the place.

Acceptable shift at 100 yards is around 1.5-2 inches. Out of a Sako TRG I would expect less as it is a much higher grade weapon than most are running.

[Powderman]

It sounds from you last post that weight is the issue.

I can certanly reduce the weight on my next suppresor build and will try a straight cone design.

I will attempt to get it to 30 oz.

Thanks again.

[Bendersquint]

It sounds from you last post that weight is the issue.

I can certanly reduce the weight on my next suppresor build and will try a straight cone design.

I will attempt to get it to 30 oz.

Thanks again.

Weight and baffle design is the issue. Downside for trying to save money by doing a Form1 is having to make a new can to try a new design legally.

If you have a problem getting it down below 30oz then I don't know what to say.

Good luck.

[Powderman]

I don't mind the cost of another can and will do it legally.

I am a car guy. When I make something I tend to overbuild it for strength...making it as light as possible doesn't come naturally to me!

Thanks for the info.

[Wicked]

When I make something I tend to overbuild it for strength...making it as light as possible doesn't come naturally to me!

Quoted for truth.


I once used a 10lb box of nails while building an 8' x 8' yard barn. The air nailer didn't help my OCD.

We were able to get it certified by the DOD as a nuclear blast shelter though!


My first cans were built with the same methodology: brick s--t-house construction made for a lifetime of abuse!

You may be able to overcome this affliction, but it will require professional help.

[Capt. Link.]

If you are getting poi shifting from shot to shot it has nothing to do with the weight of the can.You may be getting baffle strikes or you have bedding issues with your rifle brought on by the weight of the can.With the increased turbulence of the step baffles did you allow for increased bullet yaw.

[daviscustom]

I am not personally familiar with the rifle past having fondled one a few years ago, but I assume the barrel is free floated.....is the stock close enough to the barrel that the extra weight could be causing it to contact the stock when you fire the rifle? Related to the Capt.'s questioning about a possible bedding issue....I would think either one could cause similar symptoms.

[Bendersquint]

I am not personally familiar with the rifle past having fondled one a few years ago, but I assume the barrel is free floated.....is the stock close enough to the barrel that the extra weight could be causing it to contact the stock when you fire the rifle? Related to the Capt.'s questioning about a possible bedding issue....I would think either one could cause similar symptoms.

I would seriously doubt a bedding issue with a Sako TRG42. The bedding on the TRG's i used were absolutely solid and no room for flexing. It has to do with the weight of the can and flex in the barrel, they aren't the heaviest profile barrels afterall and the step cone baffles.

[Capt. Link.]

I am not personally familiar with the rifle past having fondled one a few years ago, but I assume the barrel is free floated.....is the stock close enough to the barrel that the extra weight could be causing it to contact the stock when you fire the rifle? Related to the Capt.'s questioning about a possible bedding issue....I would think either one could cause similar symptoms.

I would seriously doubt a bedding issue with a Sako TRG42. The bedding on the TRG's i used were absolutely solid and no room for flexing. It has to do with the weight of the can and flex in the barrel, they aren't the heaviest profile barrels afterall and the step cone baffles.

I threw out the bedding as a possibility.The bedding bolts should be checked for proper torque to rule it out and the barrel hitting the stock is a possibility as well.My basic point was that a fixed weight on the barrel will have the same shift of impact for every shot it would not change randomly.
On another issue my experience with high performance baffles has led me to using fewer baffles for the same performance.Eight baffles in a ten inch can in .338 must be a tight stack.I normally use 4 in a .308 but have not done much work with step baffles.

[Hoop]

Something is moving. Either the attachment or the baffles...

Or...

How is the first blast baffle constructed and how far is it from the muzzle?

What is the ID of the tube and what are the OD of the baffles?(baffle to tube clearance is what I am after)

Aperture hole diameter?

Is the suppressor shouldering up squarely on the barrel shoulder?

What method of assembly did you use to put said suppressor together?

[windchaser]

Is the torque on the action screws correct? Is the stock pillar beaded? If so you might want to check to make sure the recoil hasn't broken them loose, also check the recoil lug area, I always use a beveled and heavy duty rcoil lug that is ground flat. Wind chaser.

[jimmym40a2]

Also check for loose rings. I've seen it happen.

[Powderman]

1st baffle is a stepped baffle. 1.75 inches from the muzzle.

Hole dia is .406 inches.

Thanks for the tip on the rings. I did not think about that.

The baffles are a tight fit to the id of the tube. Plug welded along the length. The end caps are circumferentially welded to the tube.

My 1st thought was that the cone vs. stepped baffles made a difference in accuracy. My 308 is a cone baffle design with the same dimensions and construction. Point of impact shift is 2 inches max at 100 yards. and is super quiet.

I based the weight of the suppressor on AAC's Titan SS thinking it is acceptable for the TRG42.

Thanks

[Capt. Link.]

1st baffle is a stepped baffle. 1.75 inches from the muzzle.

Hole dia is .406 inches.

Thanks for the tip on the rings. I did not think about that.

The baffles are a tight fit to the id of the tube. Plug welded along the length. The end caps are circumferentially welded to the tube.

My 1st thought was that the cone vs. stepped baffles made a difference in accuracy. My 308 is a cone baffle design with the same dimensions and construction. Point of impact shift is 2 inches max at 100 yards. and is super quiet.

I based the weight of the suppressor on AAC's Titan SS thinking it is acceptable for the TRG42.

Thanks

After your suppressor is mounted the poi should not change I don't care if it weighs 10 lbs.
Have you thought of turning a stub on your lathe the same size as your threaded barrel and then check the run out at the muzzle of the can.I have one for every size.

[Hoop]

If the rifle shoots fine until the suppressor variable is added, most likely not the rings.

If the POI shift starts to change after a few suppressed shots, I suggest you fire another group after a cool down. Sometimes barrel harmonics take a few shots to become consistent.

If you still get a varying shift, something is under stress in the suppressor and when it heats up it is trying to move to where it is unstressed. Common when welding something.

Did you use an alignment jig when you welded?

I still did not read anywhere that showed exactly how much shift you are experiencing.

One other thing to consider is blast baffle construction. You really need gas expansion holes around the edge of the blast baffle so when that area fills up and is under pressure, it does not effect the bullet's flight path. The gasses are traveling a lot faster than the bullet when they escape from the muzzle behind the bullet.

[Bendersquint]

If the rifle shoots fine until the suppressor variable is added, most likely not the rings.

If the POI shift starts to change after a few suppressed shots, I suggest you fire another group after a cool down. Sometimes barrel harmonics take a few shots to become consistent.

If you still get a varying shift, something is under stress in the suppressor and when it heats up it is trying to move to where it is unstressed. Common when welding something.

Did you use an alignment jig when you welded?

I still did not read anywhere that showed exactly how much shift you are experiencing.

One other thing to consider is blast baffle construction. You really need gas expansion holes around the edge of the blast baffle so when that area fills up and is under pressure, it does not effect the bullet's flight path. The gasses are traveling a lot faster than the bullet when they escape from the muzzle behind the bullet.

The point of impact shift is 7" low and three left at 100 yards. The problem is that it did not groop there it would then shift up and down by apprx. 5 inches.

I understand that there may not be an industry standard accepted for the point of impact shift, I was just curious at what would be an acceptable shift and what would not.

Thanks

Here you go Hoop!

[Shift1]

Quick question. I built a 338 Lapua can with stepped cone baffles that are symetical. 8 Baffles total in a ten inch long 2" od tube 316 SS, 37 oz.

It is built for the TRG 42 Rifle.

The rifle shoots great but when I install the supressor the point of impact shift is not the same from shot to shot.

I built the same can for the 308 TRG22 and the only difference is that I used straight conical baffles not stepped baffles and it works great both with sound reduction and consistent point of impact shift.

Is there something different about using stepped cones instead of straight cones that could cause this problem?

My other questions are about point of impact shift. Is there an amount of shift that is acceptable say for a 308 can? ie an industry standard that is acceptable?

What can be done in the design to reduce the shift?

Thanks

What kind of grouping are you getting?

37 ounces is ridiculously heavy and the TRG42 isn't designed to take that much weight on the barrel!

Stepped cones aren't that effective on the big bores better to use straight cones, I am not sure why everyone is so fascinated with stepped cones.

There is no such thing as an industry standard in the silencer industry. The ONLY thing is proper sound testing procedures, thats it.

Recore it and put it on a treadmill for a good year or 2.

One thing that has never really been addressed here is a minimum baffle wall dimension. We are all pretty comfortable with the .065 tube wall and a spacer wall of .050-.065. We as I recall have never really discussed the thickness of the baffles. Obviously the blast baffle needs to be a bit more robust just because it is subject to more abuse, but what about the nominal baffle wall thickness of a normal cone....could we speculate that the .065 dimension would be sufficient?

[delta9mda]

mine seems to work perfectly fine though it is on a 300 winmag

[hunter2]

Sounds like something is loose or as said above is stressing - can not square to barrel ( shoulder ),internals loose. If you are having strikes, you should be seeing something by now. Too heavy? Maybe.. Have one that weights a lot more than that for a CheyTac from Liberty that shoots great. But the barrel is a little bigger.

[mscott]

I would try a ladder test and work up a new load with the can on. You may have affected the barrel harmonics enough that it just won't shoot your present load any more. All of my rifles shot fine with and without the can, but I've heard of others having problems like yours. Is there any chance you could put someone else's can on your rifle or your can on a different rifle?

[Hoop]

Stop wasting ammo, rebuild the suppressor lighter.

Plenty of manufacturers making 20-25 oz. 338 suppressors.

[Dan Carey]

I just threw the targets away showing key-hole bullet holes. I took the can apart and checked every baffle carefully, couldn't find a bullet strike anywhere. I stuck the suppressor in the lathe reamed it to .265" which was the original hole size anyway. Very little material was removed. The key-holing stopped. I don't often line bore a suppressor because the tolerances are so tight I gave up doing it.