Thread: Sub sonic

The question of sub sonic hanloads for such and such caliber pops up quite a lot. Is there any particular cartridge that has more going for it than others when it comes to subsonic handloads?

Bigger is better for the bullet.

Smaller is better for the case.

Fatter is noisier/ harder to make really quiet. Softer projectile the better

So a pistol round kind of ticks the boxs

357mag, 158gn +
308Win, 180-204gn 10 twist

I think 30 cal hits the sweet spot of noise vs expanded diameter vs energy.
308 Is about the largest case that is practical to run normal weights subsonic.
Blackout is pretty much designed for it but loses out on supersonic power if wanting to run 2 loads.

Originally Posted by blip

So a pistol round kind of ticks the boxs

Pretty much. You are limited on velocity so have to make up for it with mass and frontal area to get the terminal effect. And you only need a tiny bit of powder to send a bullet out at 1000fps so if you have a large case it needs stuffing with something like trail boss to take up the space. Otherwise the velocities can end up all over the place.

So something like a 243 with a little 6mm bullet and 45gr of case capacity doesn't make much sense as a subsonic cartridge and would be difficult to get consistent.

Whereas a 300 blackout, 45acp, 450 bushmaster, 8.6 blackout are either naturally subsonic or don't need to be significantly down-loaded to make them so (to the point of becoming erratic), and have much bigger harder hitting bullets. Some of which are made to give some expansion at subsonic speeds.

@Pommy i see your signature at bottom of post. Ever tried grendal at sub speeds?

No. I don't see the point. So much so that I haven't looked into whether subsonic expanding 6.5 projectiles even exist. As fas as I know/care they don't.

If you plan on hunting then a bullet that expands at low velocities is the biggest problem.
You can get either go for the specialty copper bullets (expensive) or cast lead in the likes of 308/300BLK/8.6BLK, but pistol bullets are definitely the easiest option.
I played with the cast 151gr bullets in a 300BLK and found them annoying to work with, needed a special die to flare the cases and needing a different seating stem or else you would mark the bullets. They shot like crap too.

Something like 44mag, 357mag or 450Bushmaster is probably the easiest.

If you want to run both subs and supers then 308 is probably the best (.338cal bullets are stupid expensive and give way more energy that you need).
But the lack of Trailboss powder is the main thing holding you back.

Originally Posted by blip

@Pommy i see your signature at bottom of post. Ever tried grendal at sub speeds?

I spoke to Rob (who makes the cast bullets).
He said 6.5cal is too small to practically do subsonics, and that there wasn't too many mold options.

He at least used to do 7mm cast bullets.

are you looking for sub only and shooting to 50 mtr only or are you interested in shooting further out with standard loads for clearings or bush edges 2-300 mtr?
I run a 358 Win, have tried 220gr HP lead with gas checks 1000 fps, not that impressed, tried pistol bullets like 357 cal 158 hr XTP's at 16-1700 fps and been really happy with performance on small - medium game. But still have the option of a load that good to 300 mtr if I need to.
Z

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.