Thread: Subsonic load for 308

It’s a really easy process @jim160. Load up five cases that span the point at which you think you’ll break the sound barrier. Work backwards, i.e. heaviest load to lightest load, and listen for the supersonic crack. It will suddenly disappear. Congratulations, you’re subsonic. Now drop your load to 0.2gr below that, to be consistently below the sound barrier. You’re aiming for about 1,000fps.

Crimping cast lead bullets is essential to maintain consistent pressures.

As Gkp says, your load will be higher than those suggested for lighter bullets. I would start at 10gr and work back in 0.3gr intervals to 8.5gr, you’ll find it somewhere in there.