I have 3 rifles made to accept my .30 Ops Inc 3rd model:
- Rem 700 in 260 with a match chamber, Heavy Palma, 25" Bartlein 1:8" barrel.
- GAP10 Gen 2 in 260 with a 20" Bartlein 1:8.2" barrel
- Armalite AR10 in 308 with a 20" WOP 1:10" barrel
Both gas guns use adjustable gas blocks and are adjusted so that it reliably cycles to an open bolt with a magazine inserted.
Shooting the GAP10 today doing load development with 140SMKs and H4350 from 42.0-43.0 in 0.2gr increments. Without the can on, I had NO ejector marks on the brass ... at ANY load level. I had an extra 5rds each in 42.4, 42.6 and 42.8 and wanted to see POI shift and accuracy difference with the can on. EVERY round fired with the can had ejector marks, some even swiped enough to raise a pretty good burr. Since I FL sized all the brass to the same headspace dimension (1.629-1.631) and I load powder to +/-0.1gr, sort bullets by ogive dimensions so that my Base-to-ogive dimension is +/- 0.002" I can discount the ammo being the cause.
Since the un-suppressed rounds show no signs of ejector marking, I assume the bolt is locked for the duration of the pressure in the barrel. I have to wonder, knowing a very little about the Ops Inc can design, if the first baffle and the large chamber that sits over the barrel are creating a secondary pressure wave that comes back down the bore either after the bolt has started to unlock or more likely when the brass case has "sprung" back to a somewhat smaller size, and thrusts the brass back into the bolt face.
I have been less-than directly behind enough muzzle brakes to be very familiar with the pressure wave from them. This is the only thing I can think of to explain the difference between unsuppressed and suppressed rounds. The raw pressure difference within the barrel cannot be significant enough of a difference as there is only a 15-30fps increase in velocity with the suppressed ammo.
Top-to-bottom rows:
42.6gr H4350 - avg. vel = 2685fps - no suppressor
42.4gr H4350 - avg. vel = 2688fps - suppressed (I rotated the raised ejector marks that I filed down to the 6 o'clock)
42.8gr H4350 - avg. vel = 2701fps - no suppressor [IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/farm5.staticflickr.com\/4313\/35303029984_ffa7a378fa_b.jpg"}[/IMG2]
OP Seberger patent drawing for Ops Inc can: [IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/farm5.staticflickr.com\/4329\/35751345890_004a42b16e_b.jpg"}[/IMG2]
What says you folks???
- Rem 700 in 260 with a match chamber, Heavy Palma, 25" Bartlein 1:8" barrel.
- GAP10 Gen 2 in 260 with a 20" Bartlein 1:8.2" barrel
- Armalite AR10 in 308 with a 20" WOP 1:10" barrel
Both gas guns use adjustable gas blocks and are adjusted so that it reliably cycles to an open bolt with a magazine inserted.
Shooting the GAP10 today doing load development with 140SMKs and H4350 from 42.0-43.0 in 0.2gr increments. Without the can on, I had NO ejector marks on the brass ... at ANY load level. I had an extra 5rds each in 42.4, 42.6 and 42.8 and wanted to see POI shift and accuracy difference with the can on. EVERY round fired with the can had ejector marks, some even swiped enough to raise a pretty good burr. Since I FL sized all the brass to the same headspace dimension (1.629-1.631) and I load powder to +/-0.1gr, sort bullets by ogive dimensions so that my Base-to-ogive dimension is +/- 0.002" I can discount the ammo being the cause.
Since the un-suppressed rounds show no signs of ejector marking, I assume the bolt is locked for the duration of the pressure in the barrel. I have to wonder, knowing a very little about the Ops Inc can design, if the first baffle and the large chamber that sits over the barrel are creating a secondary pressure wave that comes back down the bore either after the bolt has started to unlock or more likely when the brass case has "sprung" back to a somewhat smaller size, and thrusts the brass back into the bolt face.
I have been less-than directly behind enough muzzle brakes to be very familiar with the pressure wave from them. This is the only thing I can think of to explain the difference between unsuppressed and suppressed rounds. The raw pressure difference within the barrel cannot be significant enough of a difference as there is only a 15-30fps increase in velocity with the suppressed ammo.
Top-to-bottom rows:
42.6gr H4350 - avg. vel = 2685fps - no suppressor
42.4gr H4350 - avg. vel = 2688fps - suppressed (I rotated the raised ejector marks that I filed down to the 6 o'clock)
42.8gr H4350 - avg. vel = 2701fps - no suppressor [IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/farm5.staticflickr.com\/4313\/35303029984_ffa7a378fa_b.jpg"}[/IMG2]
OP Seberger patent drawing for Ops Inc can: [IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/farm5.staticflickr.com\/4329\/35751345890_004a42b16e_b.jpg"}[/IMG2]
What says you folks???
Last edited:
