Thread: Sub sonic

Pretty much this for me is one of the issues with subsonics - you really need to pick the right platform to launch them from and then get a good reliable source of components and once you've gone through that exercise you've normally ended up with a similar solution to everyone else.

Easiest is usually .308Win in 1-10" twist or faster - anything smaller for diameter is usually very difficult to get a reliable pill that's heavy enough, right profile and right hardness and it usually ends up with the rifle's twist not being fast enough to stabilise the length of bullet you end up with. Anything bigger is more expensive to drive, louder and worse for recoil.

Powder is usually fairly easy, TrailBoss is the first port of call but according to the news from Aussie it's not likely to be rolling off the lines until 2025 so I hear (and that schedule is probably a bit dependent on things like wars as well!). That leaves one of the fast pistol or shotgun powders, such as Red Dot or Titegroup or whatever is available. The only real advantage to TrailBoss over anything else is that it's formulated to be really bulky, meaning that the case is a lot more full with the average load of powder for a subsonic round. This has advantages when thinking about things like powder column position and not having as much variation when shooting uphill or downhill. Also makes it harder to double-charge a case... In practice though, the faster powders don't seem to be that sensitive to the position in the case and generally all the grains have ignited prior to the pill travelling very far in the bore.