My first tests using the Lee C309-160-R with the 300AAC cartridge is looking promising.
18.0gr of 2230 is pushing the powder coated 166gr gas checked projectile averaging 1492fps in the 16” AR barrel and 1371fps in the 11 1/2” single shot pistol barrel.
Seating the bullets at 1.940” seems to be fine. This falls in the middle of the upper lube groove. Seating in crimp groove would put the OAL at 1.855”. The bullet touches the rifling at 1.955”.
100 yard groups were not tight or even different when used in the rifle or pistol. Then again it was very windy during the test, blew the chronograph over twice. This test was more for function and velocity.
Also set up a trash can at 100 yards filled with sand and recovered the 4 projectiles.