More info. Here's one for the suppressor experts. Update!

[Bear44]

This is not a subtle or inconsistent change. Every time I shot it with gas in the can I was getting about 1.5 MOA groups. Every time I shot it with clean air in the can I was getting 2 to 3 foot groups.

I went through more than 40 rounds experimenting with this.

 

[Bear44]

I did an internet search and found one post on another forum about a similar problem, though it wasn't as bad. However, it was also with subsonic Gorilla ammo, though a different bullet.

Their powder interacting with the oxygen?

Time to try a different ammo.

 

[NWSharpshooter]

Don’t mention to AAC that you’ve shot 223 through it. I own a cyclone and was told specifically not to shoot 223 out of it.

I don’t know why, doesn’t make any sense but when I questioned it they just repeated tyt I should not do it.

 

[Bear44]

Don’t mention to AAC that you’ve shot 223 through it. I own a cyclone and was told specifically not to shoot 223 out of it.

I don’t know why, doesn’t make any sense but when I questioned it they just repeated tyt I should not do it.

Hmm, interesting.

 

[NWSharpshooter]

Hmm, interesting.

Of course they also told me not to shoot it on an AK. I got an end cap strike about a year later shooting it on a 223 AK so don’t listen to me.

 

[Lionheart]

That's what you get for buying that Kulu.

jk.

 

[GAgunLAWbooklet]

Thanks for posting the thread, Bear.
I've never noticed this, but I have never tested the accuracy of my suppressor with exclusively cold-bore shots with regular atmospheric air in the can.
Typically, when I get to the range I take a "fouling shot" into the backstop without even aiming at a target, just to get the light coating of gun oil out of my barrel. Then I shoot groups for accuracy. Normally I'll shoot a couple of groups from the bench (or supported prone) without any significant delay (not long enough for fresh air to re-fill the suppressor). Then, after I check my groups, I'll plink until I'm done with that gun, and then put it away for the day.

I see that I need to work on real-world hunting conditions-- first round accuracy from a cold bore.

 

[batoncolle]

I did an internet search and found one post on another forum about a similar problem, though it wasn't as bad. However, it was also with subsonic Gorilla ammo, though a different bullet.

Their powder interacting with the oxygen?

Time to try a different ammo.

I'd try the same ammo on a different rifle also just to see the results. Cold bore POI shift will affect some cans. There are some suppressor manufacturers, like Thunderbeast, that promote the fact that their cans don't have the issue.

But it's usually repeatable and not as drastic as yours. I have one can that does it, and I don't use it for hunting.

 

[wildbill1973z28]

Try shooting it without the can and see what kind of consistency you get.

TOOK LONG ENOUGH FOR THIS TO GET THERE!

 

[Bear44]

TOOK LONG ENOUGH FOR THIS TO GET THERE!

Not when I was shooting. The first thing I did was zero the rifle without the can and it was consistent and accurate. When I noticed the problem, I took the can off again and it was consistent and accurate.

The only time the problem occurs is with the subsonic load through the can with fresh air in it. All other times the rifle is accurate, though the POI does shift a little with the can on from with it off. But that's normal.