Greetings from Finland!
I recently finished my .300-221 AR15 build.
Test rounds were loaded to cases made from .221 Rem cases with Redding dies.
On first test bullet was molycoated 220 grs SMK on top of 12 grs N120 and CCI small rifle primers.
Accuracy was fairly good (5 shots/18mmC-C@50meters) but there was still some room for improvement as load was still supersonic.
Velocity was not measured but one can sure tell difference between super and subsonic...
Second test rounds were loaded with same components but now with 11.5 grs of N120. Average velocity was 320 m/s but this time accuracy was not tested.
On next test I'll drop powder charge maybe 0.1-0.2 grains to get some safety margin to keep velocities well in subsonic territory.
Other possible step in load development is to use N110 powder but I'm not sure if it's necessary.
Barrel is custom made by Finnish gunsmith from Lothar-Walther .30-8" stainless blank. Reamer came from PTG.
Gas system is is pistol length and barrel length is 420mm to keep gun within rifle dimensions according to local legislation.
Silencer in picture above is BR-reflex suppressor.
This forum has been very useful during my build project so I thought it's time to share the outcome of my project with you.
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