I have a new 10.5 inch 5.56 upper from PSA for my pistol lower.
I have been playing with Quickload to find a way to have NO flash, No super loudness or percussion from the short 10.5 inch barrel.
Flash comes from unburned powder in a standard 5.56 round.
Excessive loudness is from the bullet leaving the barrel at roughly 15,000 psi instead of something normal like half of that.
So far, a promising load candidate is:
Cartridge: 5.56x45 NATO
OAL 2.2 inches
Barrel Length 10.5 inches
Default case capacity of 28.50
Alliant HERCO powder - 10.5 grains. Case filled 73.3 percent. (might first try 10 grains)
Bullet Hornady 55 gr GMX #22273 (this should expand at velocities over 2000 fps)
Max Pressure 49525 psi
Velocity 2199 fps (yes have to give up some velocity to get no excess loudness/flash)
Muzzle Pressure 8664 psi
Propellant Burnt 100% (no flash)
I have not tried this load.
I do not know if it will cycle the AR.
I do not know for sure it is safe.
I do not even own any HERCO powder yet.
I do not want to go to the gunclub during this pandemic.
This is all theoretical for now.
I have been playing with Quickload to find a way to have NO flash, No super loudness or percussion from the short 10.5 inch barrel.
Flash comes from unburned powder in a standard 5.56 round.
Excessive loudness is from the bullet leaving the barrel at roughly 15,000 psi instead of something normal like half of that.
So far, a promising load candidate is:
Cartridge: 5.56x45 NATO
OAL 2.2 inches
Barrel Length 10.5 inches
Default case capacity of 28.50
Alliant HERCO powder - 10.5 grains. Case filled 73.3 percent. (might first try 10 grains)
Bullet Hornady 55 gr GMX #22273 (this should expand at velocities over 2000 fps)
Max Pressure 49525 psi
Velocity 2199 fps (yes have to give up some velocity to get no excess loudness/flash)
Muzzle Pressure 8664 psi
Propellant Burnt 100% (no flash)
I have not tried this load.
I do not know if it will cycle the AR.
I do not know for sure it is safe.
I do not even own any HERCO powder yet.
I do not want to go to the gunclub during this pandemic.
This is all theoretical for now.