SMK is a FMJ target bullet, not designed for sub expansion. Are we talking bullets to hunt sub sonic?
Bullets that stabilize sub sonic?
Or a load for low recoil?
What twist rate is your barrel, you will need that info so you can pick the pills you want to shoot, which will then determine the powder.
I have a good sub load for my MRAD but its a 1/7 twist shooting 190's. My 1/11 twist won't stabilize anything over 175, but at a sub velocities it won't...
Send me a PM, I might be able to help you with that. I might know a guy or two from Benelli and a shop... we have been working on all sorts of M4 "things" hint hint
LMT also won the contract so they will be using both MRGG and LMT. Mostly because of the patent LMT has on their mono rail allowing return to zero for SOCOM goodies they run.
It will cycle fine! A can increases back pressure, so don't worry. Besides the M4 was designed to run over gassed so it would function in all types of weather
I would save a few more months and get a larger budget then you open yourself up to lots of good options. 1-8 power, used NF, the new Eo Tech 3-9, Arken, Credo, etc
Of course if it's rejecting in front of the face, a .22 rifle would do the same. If you're right handed like a civilized person 🤣 there isn't much of an issue