Suppressors Empty Can first shot vs follow up Shots, POI Shift

[big_beau13]

Anyone out there experiencing a big jump from an empty can first round shot, to the follow up(s)? I have always seen a slight difference in speeds, but never a POI jump like I experienced yesterday.

Shooting a CF Proof 24" 6.5PRC w/a TB Ultra 7, 144 Hybrids, RL26 @2880fps, SD of 6.

Ran a few plates from 280-870y, first shot would be on my hold or center plate...Follow up shot would be .4-.6 right depending on distance. It was extremely consistent, I ran a 5 shot group at 711y, first shot, again dead center, follow up 4 shots were a half mil right, but all stacked on top of each other.

None of this shows up at 100 yards of course...only at distance.

Anyone else experience this? Anything I can try to take some of that out of it?

 

[Zak Smith]

Hi,

Bring it back to basics, if the POI is actually changing, it has to show up at 100 yards. If it's not, then something else is happening.

POI changes are due to something moving shot to shot, re-verify that everything is tight! We can, of course, examine and test fire the can, but it's almost always something else going on.

Give me or Ray a call to discuss if you'd like.

 

[Supersubes]

Have you run this same test without the can?

 

[Cascade Hemi]

A half mil is 1.8" at 100 yards. Are you saying you can't see a half mil shift at 100 yards?

 

[big_beau13]

Have you run this same test without the can?

No, that is a good idea. I will throw the brake on and see if that changes anything.

 

[big_beau13]

A half mil is 1.8" at 100 yards. Are you saying you can't see a half mil shift at 100 yards?

I am saying at 100 yards it shoots excellent groups, sub 1/2". At 711 yards I had a half mil jump to the right.

 

[big_beau13]

Hi,

Bring it back to basics, if the POI is actually changing, it has to show up at 100 yards. If it's not, then something else is happening.

POI changes are due to something moving shot to shot, re-verify that everything is tight! We can, of course, examine and test fire the can, but it's almost always something else going on.

Give me or Ray a call to discuss if you'd like.

Thanks Zak! Everything is tight, I double checked that. I cannot get it to replicate at 100 yards...Its very odd. I have had this can for a while, I love it!! This is the first time I am running into these issues and its also my first carbon fiber barrel. Not saying the two are related, but its interesting...

 

[Huskydriver]

Do you use a mirage cover? What direction was the wind blowing even if barely any wind was present?

 

[big_beau13]

Do you use a mirage cover? What direction was the wind blowing even if barely any wind was present?

Yes, I just picked up a new Cole Tac cover, its a little thick, but works great. We lucked out yesterday, not much wind out there. So had to adjust for some spin drift only.

We shot from 300-870 yards, around 10 targets everywhere in between and I consistently had the issue. Take my first shot, center mass, follow up shot would jump far right. My buddies would all shoot, giving my barrel time to cool down and the can too clear. Then I would move out to the next furthest target, issue would repeat itself.

I have had this can on probably 6 different barrels, this is the first one with the issue.

 

[Huskydriver]

Any chance the barrel is contacting the stock/chassis inlet?

Pics of the supressor mounted on the barrel close up?

 

[Hateca]

Personally I think it’s just this particular set up. Can gets gassed up after first round and shifts to the new poi. Seen this on other setups.

You said the shift is repeatable. After the shift what’s the group size? Is the group size stay tight after the shift and were they repeatable?

Try a different load. Try it without the can. If there is no shift without the can I would say it’s the can pressurizing after the first round causing the shift.

 

[big_beau13]

Personally I think it’s just this particular set up. Can gets gassed up after first round and shifts to the new poi. Seen this on other setups.

You said the shift is repeatable. After the shift what’s the group size? Is the group size stay tight after the shift and were they repeatable?

Try a different load. Try it without the can. If there is no shift without the can I would say it’s the can pressurizing after the first round causing the shift.

Yes, its repeatable, the group size after the shift is tight. I didn't go down range to measure, but it was stacking shots at 711y. Did the same thing out at 870.

I think I am going to play with the load some and see if anything changes. Also I plan on testing without the can as well.

 

[big_beau13]

Any chance the barrel is contacting the stock/chassis inlet?

Pics of the supressor mounted on the barrel close up?

It is in a manners PRS2 stock, the barrel is floating all the way back...It is a brake attached can with the Area 419 adapter kit. Like I said its been on a bunch of different rifles, never had this issue. Even with other barrels in this Manners stock, no issues...bit of a head scratcher.

 

[Mordamer]

If you can't replicate it at 100 yards then it isn't happening.

What's the logic here? Is the suppressor reaching and slapping the first shot to the left at some point between 100 yards and 700 yards?

 

[Zak Smith]

Try it without the 419 adapter.

On the gas theory, here's some data:
2 milliseconds- main pressure wave dispersed, another 10-20 ms, the evacuation of the trailing gas is done.
On a PULSE SLM, we can see that the entirety of the pressure events are done (ie back to baseline) after 100 ms, but that includes reflections, etc.
It should take just a couple/few seconds to the air to homogenize inside the can, at least from the density perspective.