I used "poly fil" on old low velocity 45-70 with cast bullets back in the day...We tried lots of things seems a little wad of toilet paper was even tried.
Don't think it did much good, as I abandoned the practice for some reason I can't remember...probably a waste of time as nothing positive came of it in my limited experiments.
What velocities are ya looking for? Subsonic? 4 grains of Trailboss. Or 11 to 12 grs of AA 5744
1800 to 2000 fps Trailboss balky enough to do the job with out fillers...use it for subs in the 308 (and even in 50 BMG) shoots small groups with 175 MK a fun load. It will not cycle the AR 15 action in 300 blackout, but can be used.
Don't think it did much good, as I abandoned the practice for some reason I can't remember...probably a waste of time as nothing positive came of it in my limited experiments.
What velocities are ya looking for? Subsonic? 4 grains of Trailboss. Or 11 to 12 grs of AA 5744
1800 to 2000 fps Trailboss balky enough to do the job with out fillers...use it for subs in the 308 (and even in 50 BMG) shoots small groups with 175 MK a fun load. It will not cycle the AR 15 action in 300 blackout, but can be used.