Twist Rate for .357 Magnum Subsonics?

[Scoop]

Anybody got any info on optimum twist rate for a .357 magnum carbine launching 180 gr projectiles at subsonic velocities? Thinking of building a Contender Carbine to hunt with and figured 180 gr Hornady XTP's @ 1000 fps might perform well on eastern-sized whitetails.

[320pf]

Scoop,

I check in the Speer reloading manual, they list a twist rate of 1:18.75 for 38 special and 357 mag. pistols. The 38 special loads are all subsonic. The 357 mag in rifle is listed as 1:16. Since all of the pistol bullets are short and fat you can probably use the same rate of twist.

Interestingly, the rate of twist for the 357 maximum is 1:14 in a 14 in barrel. The Speer manual list some heavy (200gr) bullets that are some what longer than the 158 g pistol bullets... but the slowest mv listed is about 1300-1400 fps. So I would guess that you will want a twist rate at lease as fast and the 357 maximum (1:14)... probably more like 1:10 to 1:12.

From the Speer data I calculated that the 200 gr bullet out of a 14 in 1:14 twist barrel 357 Max is doing about 1200 to 1300 rev per sec (rps).

At a MV of about 1000 fps the bullet would spin about 800 to 900 rps. If you increase the twist to about 1:12 the bullet rotation is about 1100 to 1200 rps. If you increase the twsit to 1:10 the bullet will spin at about 1400 rps. This assumes that I did not screw up my math.

I hope this helps

320pf

[Scoop]

Thanks 320pf. The barrel I'm getting is a 14 twist. I think it's gonna work out perfect with 180 gr Hornady XTP's or Nosler Partition-HG's. It'll be here on Friday. Hope to be shooting this weekend. I've got some 180's loaded on top of 5.0 gr of Titegroup. We'll see what happens. Should make a very interesting 50-75 yard suppressed/subsonic deer load. Should be very quiet through my Phantom as well.

[sharps54]

Scoop,
How did this work out for you? Since you are using a single shot I wonder if you could use some 358 rifle bullets in it. You would probaby have to either lengthen the throat or maybe use short 35 remington bullets in 38 special cases. I have a 357/44 B&D cylinder for my Blackhawk and I have thought about picking up a rifle and trying the rifle bullets with this round (since I have the reamer and dies), it should be able to punch 225s or 250s out subsonic.

editted to add the short 35 rifle bullets might have been for the 350 Rem Mag not the 35 Remington, I'm not sure off the top of my head.