Weird first shot inconsistency with can

[Samsquanch]

Im posting here as a last resort to see if anyone has an explanation for this odd behavior. I have a 308 scar 17 that has been a good reliable 1" gun for a long time. I recently added a sandman S, and my groups actually improved to a consistent .8-.9 which is great for a scar, but the first round cold shot is now exactly 5" to the left consistently. The second shot and all subsequent shots will be exactly on my zero until i pause long enough for everything to cool down. I suspect its something to do with the atmospheric change inside the can after the first shot, since it only ever takes 1 round to fix, and doesnt "walk in" to my zero over a series of shots.

I checked concentricity with a rod and bore scoped the can. I've rechecked torque on everything. I rarely ever clean, but i went ahead and did that just to see if it would change anything. The scope is a nightforce and i moved it to another rifle to make sure its not broken somehow. I also repeated this 5 times over the course of the day yesterday by just letting the gun sit a while, so its not a jumpy shooter problem.

At this point all i can do is ditch the can, but that's a bit of a bummer so hopefully there's something I'm not thinking of that's correctable. Thanks for any suggestions.

 

[msgriff]

I'd probably check concentricity with the rod while the barrel and suppressor are hot, during the time frame that your second and subsequent shots are consistent, and compare that with the cold bore alignment check.

 

[MSTN]

How do you load your first round into the chamber?

Try putting the gun in your shoulder with the bolt locked to the rear and the magazine locked in position, loading up the bipod, getting completely set to fire, and then hitting the bolt release.

This seems to help eliminate first round fliers in some gas guns.

 

[db2000]

POI change on first round suppressed is very common. Some cans more than others. I’ve read on here (take that with a grain of salt) that TBAC are very consistent throughout all shots. I don’t own a TBAC so can’t say personally. My SiCo Omegas and 36M depend on the caliber I’m shooting. All will be off by some amount first cold shot. Not 5” but I’ve seen as much as 3”. Usually about 1-1.5 MOA off. I just keep a record where it shifts as this is repeatable. Realistically, hunting, I’ve never worried about it for closer shots. When elk hunting, I haven’t risked it suppressed.

 

[mgoodrich]

I would talk with the Sandman S manufacturer to see what they have to say. This is not a direct thread attach suppressor and I would suspect that the mount hardware may be having an issue. I would try to get another mount and see if the same thing occurs.

I personally have not seen a cold bore shot be different with my suppressor mounted compared with it unmounted, other than the POI shift. I have a direct thread mount and have used it on a GAP PRS rifle in 6 CM to a ruger american predator in 22 CM. The GAP rifle has the best overall group compared to the others, which I would expect.

 

[B Man]

I’m testing one now having this issue. Have a few things left to test but haven’t gotten it back to the range yet. Maybe this week.