Suppressors any ideas on my groups?

[mlw332]

alright first off rifle is
SAC 308 built from ground up by Mark Gordon
groups without my suppressor are never over 1/2" at 100yd... 3-5 shot groups... best I have been able to shoot it got a .147 5 shot at 100yd
groups when I put on the suppressor open up to 1-1 1/4" at 100yd
ammo is FGMM 168s.
Suppressor is AAC 762 sd
Muzzle break is the 3 prong flash hider 51 tooth adapter.

when taking suppressor off there is a very faint mark on the top prong of the flash hider as if the thread of the suppressor touches occasionally, if this occurs when I remove it or actually during firing im not sure.... no baffle strikes noticed... bullets hit target straight and true

what in the hell could be going on here? does the FGMM not like being shot thru suppressor or is it my suppressor?

 

[mlw332]

Re: any ideas on my groups?

also after taking the suppressor off it takes about 2 shots normally for the gun to "calm down" and start grouping like normal again

 

[762frmafr]

Re: any ideas on my groups?

Action screws tight?

 

[mlw332]

Re: any ideas on my groups?

every thing seems tight as normal

 

[762frmafr]

Re: any ideas on my groups?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mlw332</div><div class="ubbcode-body">also after taking the suppressor off it takes about 2 shots normally for the gun to "calm down" and start grouping like normal again </div></div>

This statement makes me think loose action screws. Or possibly they are tight but a smidge too long and the extra weight on the end of the barrel makes things loosen up a bit.

 

[M C]

Re: any ideas on my groups?

does the can have 'play' when attached (slight wiggle) or is it completely tight?? also how many rounds did you put through it before you pulled it off?

 

[mlw332]

Re: any ideas on my groups?

can has no movement.... i put 40 rounds thru it attempting to get it to group with the can on Thursday

 

[M C]

Re: any ideas on my groups?

i don't have any other ideas, typically it would take maybe 5 rnds and you should notice the groups tighten up if it IS wobbly (loose like a kac can)
by now its probably 'effing with your head, have someone else shoot it and see if they can group it...

 

[lroseen]

Re: any ideas on my groups?

It could be due to mirage if your not using a suppressor cover or taking time for the suppressor to cool between shots to reduce mirage when not using a cover.

It may also be due to the threads on the rifle, barrel or both being out of alignment with the bore of the rifle and suppressor. Also the threads might be in line but if the shoulder of the suppressor or barrel is not a smooth and squared surface when the two surfaces mate together it can cant the suppressor causing the same effect. This can cause instability in flight.

This could also have to do with the actual structural stresses in the barrel reacting to quick heating. The only thing I know of that can help this is cryo treating a barrel.

This could also be all mental. If you know of any local friends who are known to be very good shots have them test it. I would recommend not telling them of the problem you are having just have them shoot it and see the results both suppressed and un-suppressed.

Best of luck.

 

[mlw332]

Re: any ideas on my groups?

I had a guy with me who is one of the police force snipers/marksmen and he put the 40 rounds thru it on thursday.... i had shot it about a week before trying myself....
the mirage is bad but we were trying to wait until it cooled enough to give a good line of sight ..... i have a cover on order so maybe that will fix my problem.
i would not think the threads or anything are out of line because of who built the rifle.... mark is a great smith in my book.

and yeah it has my head all messed up lol it makes you lose confidence fast when your groups open up like that

 

[Pappasniper]

Re: any ideas on my groups?

Just for the heck of it. Take the bolt out and look through the barrel and see if it appears concentric. I had an AR that was jacked up like that. I pulled it before I had a baffle strike. I think Hi BC's R A Crutch may be on track here.

PB