Suppressors Suppressed cold bore shot

[wildfowler]

I would welcome anyone to take a stab at this issue I am having.

AAC 762SDN-6
Used on three rifles:

10" Noveske 300BLK factory upper

20" 270AR (wildcat ar15 platform) user assembled.

20" LR308 black hole barrel, user assembled.

To be honest I have not touched my 300 blackout in over a year but I don't remember having this issue that I am currently seeing on the two 20 inch rifles. All three rifles use brake mounts although the 308 Mount appears to be a newer design.

I am getting what I consider to be an excessive cold bore shot with the suppressor. With either the 270 or the 308 my first shot and only the first shot is high and off-center.

The 270 is about 6" high and two inches left. The 308 is about three inches high and two inches right.

Both the 270 and the 308 do not have the first cold bore shot problem when fired unsuppressed.

I can actually take the recently fired hot suppressor off of one rifle and switch it to the cold rifle and not get the same problem so I am comfortable saying the error is not shooter induced.

I have no idea what is going on but I am speculating that it takes one shot to either heat the suppressor or pressurize the system to be able to fire shots that group normally.

It occurred to me since the two rifles in question do not have the same shift point it may be related to the timing of the suppressor and I am going to try and adjust the timing of the brake mount to see if I can at least have the cold bore variation contained within the same vertical line as the rest of the group.

Has anyone else ever encountered anything similar to this and is there a fix?

This is my only 30 caliber suppressor but I do have a friend with some other choices that I intend to test out as soon as possible.

Thanks.

 

[fdkay]

Cold bore Pop, not unusual as long as it is repeatable in each rifle.
Probably didn't see it with the blackout as the volume of gas is much smaller and the ranges typically shorter.
It has to do with replacing the atmosphere in the can with the gases from combustion.

 

[Icallem]

"AAC 762SDN-6" I have 2 of these.


"Has anyone else ever encountered anything similar to this and is there a fix?" I encountered the same issue, I bought a TB-30P, problem gone.

 

[SABuzzard]

WOW... 6" POI shift from first to second shot??

Take a look at how the can's ratchet mount is lined up when you put it on (pre first shot) and after the first round. You may be tightening it on a tooth that isn't holding after the first shot. I have an SDN-6 and on one mount I had a similar, but not nearly as extreme, problem. I would put the can on. It would be snug and after the first shot it would slip back to the next tooth in the ratchet mount and have a little play in it. I found that if I put the can on, but didn't force it to tighten up (leave a little wiggle) it was much more consistent. AAC's 51 tooth system is anything but precision oriented. For anything other than short range carbine work I go to one of my thread on cans. 6" still sounds crazy.

 

[RELOOP]

I have no noticeable shift with my xm-3 / Surefire can.

 

[Name Enough]

I have the same can and do see a very noticeable cold bore POI shift. About 2 1/2" high and 3/4" left. The next two shots will be about 3/4 inch high and then it settles in. I had my gunsmith grind down the mounts so it locks up better which greatly increased accuracy.
I have the least POI shift with an SBR in 6.8 SPC. On that rifle it is less than 3/4 of an inch. Never the less there is a POI shift.
Long and short of it is that my next suppressor will most likely be a Surefire.

 

[KYpatriot]

Hmmm. My TBAC is 1/2 in high and centered on the cold bore. So practically no shift at all. I'd consider replacing the can. Have you tried a direct thread?

 

[wildfowler]

For now this is the only suppressor I have, I do have a harvester in the works but it'll be a while for that to come to pass. I know this is not a high precision suppressor but the atmosphere or gases in the can is a new explanation for me.

The mounts on the two rifles in question were actually very tight straight out of the package and did not require any home gunsmithing. The original mount on my blackout did require honing to get it to lock up tight. Both mounts in question are holding properly and are not skipping teeth.

I rotated by one quarter turn the brake mounts on both rifles and that seems to have removed some of the horizontal shift but the vertical shift is still present. So I do consider that to be an improvement

The 308 is the newer of the two rifles for me and I have only loaded rounds using CFE223 powder.

I really didn't even notice this was occurring in the 270 rifle until I started using CFE223 powder.

CFE223 gave me about 100 ft./s boost in the 270 wildcat rifle. My previous load was using much faster burning1200R powder. I went back and looked at that load this week and there is a vertical shift but it's not as bad and very manageable and I honestly didn't make the association previously.

Going to try a regular flashhider mount in the meantime to see if that has any effect at all but ultimately I am planning on moving to a lighter weight direct thread suppressor for these two rifles.

I'll probably look for a faster burning powder to see if that changes anything in my 308 if I can't get it worked out otherwise. And I guess I'm going to switch back to the 1200R powder for the 270 wildcat.

I want to add that once I am past the first shot both rifles are exceptionally accurate even with this suppressor. I've got no other complaints with the accuracy of the suppressor itself.

Thanks.

 

[wildfowler]

Okay I am a dumbass I can admit it. I knew the AAC 51 tooth mount could have issues. And combined with the fact that there is an old thread that got bumped up by someone else caused me to rethink this.

I tightened up both amounts as tight as they could be through a series of trial and error while honing on my drillpress.

No more cold suppressor shot variation on either rifle and both are now printing 1 inch or less multishot groups.

I sure feel stupid because I thought both mounts were good to go since they were very tight however there was a tiny amount of wiggle. No more.

Thanks for the help with this.

 

[3DHUSKER]

All I am going to say is it is a common problem for some manufactures. When I bought my cans for precision shooting that is one of the things I could not have. Evey shot needed to go in same hole cold bore or not. I bought accordingly and I didn't buy the can you did. I can give recomendations if you need them.

 

[wildfowler]

Thanks I think I know which ones would be good choices from a precision standpoint. But always am open to recommendations.

For now, I feel like I am as repeatable and accurate as my suppressor will allow and am very happy.

Thanks.