Low Velocity on First Shot with Subsonics

[parsky1]

Any comparison with and without the suppressor?

So I bought a wilson combat 16" 1x7. Shot 208gr ELD with 7.5gr of N110 at a COAL of 2.200". I only got 600fps out of them. Before they were 900fps. That seems scary slow to me. Thoughts?

[dellet]

Any comparison with and without the suppressor?

So I bought a wilson combat 16" 1x7. Shot 208gr ELD with 7.5gr of N110 at a COAL of 2.200". I only got 600fps out of them. Before they were 900fps. That seems scary slow to me. Thoughts?

I would probably want to compare with a second chronograph just to be certain, too many of your numbers don’t seem to make sense.

Checking bore size when there is a discrepancy like this is always a good idea.

On your first round, low velocity issue, is that cold and clean bore only or cold and dirty ?

[parsky1]

Any comparison with and without the suppressor?

So I bought a wilson combat 16" 1x7. Shot 208gr ELD with 7.5gr of N110 at a COAL of 2.200". I only got 600fps out of them. Before they were 900fps. That seems scary slow to me. Thoughts?

I would probably want to compare with a second chronograph just to be certain, too many of your numbers don’t seem to make sense.

Checking bore size when there is a discrepancy like this is always a good idea.

On your first round, low velocity issue, is that cold and clean bore only or cold and dirty ?

Cold and Dirty. My previous barrel was a blackhole weaponry 16" pistol gas and it had horrible cold bore shot performance. -200fps on the first shot. Cold bore shots were 6-8" low cold bore and then everything grouped up just fine. Supers were always fine. If you let the barrel cool down it would do it again. Can, No can, gas off, factory ammo, it didn't matter. I tried A1680, lil gun, H4198, N110

The chrono is good. I use it for all my other rifles and it doesn't do this. I have a 10.5" 458 socom that shoots subs just fine.

I bought this barrel hoping the rifling would be better suited for subsonics as the blackhole was polygonal. This barrel is better but it seems I'm the only person on the internet who has this problem. Part of it is everyone is shooting shorter barrels and I question those who are shooting 16" barrels if the groups they post have a true cold bore shot in them.

BTW this is all done single fed from the mag. I drop 1 in the mag and hit the bolt release for every shot to be consistent.