Just got done testing some jet sizes at an indoor range. Ammo used was 200 rounds of 77gr IMI SMK. I started low and moved up if any issues popped up with 0.8, 0.9, 1.0, 1.1, 1.2 size jet screws. Stock jet size is 1.2mm (corrected in original post). Regulator was left on normal mode as I don’t have a baffled suppressor for this barrel length.
0.8 - FTE
0.9 - FTE
1.0 - FTE*
1.1 - reliably extracted
1.2 - reliably extracted
* 1 FTE in a 20 round mag. I shot an additional 20 rounds on 1.0 using 55gr PPU M193 with no FTEs. Lovely fireballs!
I’ve settled on 1.1mm for further testing. It seems smoother than the stock 1.2mm but not so much that it’s worth swapping screws - I make my own gas screws so no biggie. I also tested with my OSS suppressor and the 15 is surprisingly tame suppressed. I initially had 4 light primer strikes with the IMI ammo but that cleared up as I continued shooting. I will be installing an extra power hammer spring to mitigate this in the future.
After 240 rounds, I’m loving my 15. It shot out a fist size hole at 10yds. My modified PDW stock is solid and I’ll continue monitoring it every session. Next, I need to get the 15 sighted at 50yds and test its accuracy.