Quoted:
8.5” CMMG 1 in 7 twist 300 Blackout is the platform. No can as of yet.
View Quote
You don't say, but there's not much point having with a short barrel rifle in 300Blk if you're not going to use a suppressor, so I assume that you are planning on getting one in the future and are accordingly looking to load sub-sonic.
When you made the decision to sacrifice both barrel length and velocity, you will need to look to bullet weight for your terminal effect, so that means optimizing a powder choice to a heavier bullet.
Also, a 1:7 twist rate is a fast rate for a 22 caliber barrel, it is super fast for a 30 caliber barrel. A fast twist rate is needed to stabilize long projectiles (which are also heavier since the only way to get longer projectiles of a given diameter is to make them longer - but twist rate has to do with length). But, as the diameter of a projectile increases, the speed at which the outer edge of the projectile is moving increases. At sub-sonic velocities this is not a problem, but if you were shooting 30 caliber projectiles at high velocities out of a 1:7 barrel, you could easily have your bullets coming apart on their way to the target.
I am expecting more out of this set than it can give me as far as accuracy goes.
View Quote
A suppressed short barrel rifle is essentially a pistol with a buttstock. It is a weapon for police and special operations forces to use in a surprise assault that may lead to close quarters combat. Typical ranges would be across a room or front yard; 5, 7, maybe 12 yards. It is not for distance use. Personally, I would practice with it at the distances where it could (and would) be reasonably employed.
I’m reloading so what’s the best load to load for this specific set up and what should I expect.
View Quote
Well, you ask for the
"best load" and then constrain the selection to a single powder. Nobody knows what the "best load" for your rifle is. And certainly nobody can say whether that "best load" is going to be achieved with Lil'Gun. You need to discover the "best load" by following a proper load development process.
Personally, given your super fast twist rate, short barrel and need for subsonic velocities with your future suppressor, I don't think Lil'Gun is an optimal choice. Based on my past experience, I would look to powders such as H4227/IMR-4227, Accurate Arms 5744, Accurate 1680, or H4198/IMR-4198. Keep in mind that even though I reference them as H4227/IMR-4227, because they are similar, H4227 and IMR-4227 are different powders and the load data is not necessarily interchangeable.
You can accept powder recommendations, but
don't ever accept a load you get off an internet board. You don't know if I've got 40 years reloading experience with no failures or am a sadist looking to give you the nickname
"one eye" or
"lefty". Based on published information, select a powder that looks suitable. Beginning with the Starting Load (
and if no Starting Load is published, take the given load and back off 10% for your Starting Load) and then incrementally heavier loads looking for accuracy and pressure signs. Stop if you reach the Maximum Load or if you get pressure signs.
Good luck.