.338 Win Mag subsonic loads

[Nick4050]

To start, I understand that this is a horrible cartridge to load subsonic.

I have a .338 win mag brush gun with an Alaskan360 can on it. I'm wanting to load some subsonic rounds just to have for fun plinking around the cabin. I'm thinking a 300 grain projectile, something cheap like an interlock or speer sp. Does anybody happen to have any experience with loading this cartridge subsonic that could help offer a starting point for powder/charge?

I've done a bunch of .308 subs with Titegroup, and it seems to work really well. I know that position sensitivity is a concern with the 338 WM's larger case capacity, but Titegroup seems to be pretty insensitive.

 

[A382DWDZQ]

I would take a look at the Lyman Cast Bullet Handbook. It has 338WM in there, but for 249gr as the heavier. You can take a look at the 300WM & 375 H&H for comparison. The Lee Modern Reloader 3rd edition has some info on reducing loads, but I’d guess the 4198 and 4895 powders would probably get you some reduced loads. Hodgdon has h4895 loads for the lighter bullets.

 

[HandgunHTR]

Do you think that you would be able to stabilize a bullet that big going that slow?

In regards to position sensitivity, using a filler can help with that.

 

[longrangelead]

Do you think that you would be able to stabilize a bullet that big going that slow?

In regards to position sensitivity, using a filler can help with that.

1:10 will stabilize 300gr for short range. I've done several 338 Thumpers (338/223) with 1:10 take off barrels.

 

[TaperPin]

I’ve had great luck with drastically reduced loads for 338 and others published for cast bullets. Of course jacket bullets have a lot more friction than greased up lead, but it’s a starting point that’s easy to find. Case fill becomes a problem with consistent ignition so some add a little Dacron cotton ball to keep the powder in place against the primer. It seems like I used a lot of powder that’s typically considered slow pistol powder like IMR4227. Detonation from small charges of slow burning powder is a thing and can wreck a gun so stick with fast powders. It can’t be stressed enough to drop powder in all cases and carefully check them all with a flashlight for double or triple charges before seating bullets. The low case fill can allow multiple charges to fit in the case and more than one rifle has been blown up that way.

The guys at castboolits will have a lot of reduced loads for everything and someone there has done what you’re after already.

In the 338 you won’t be burning up the barrel, but with other large capacity magnums reduced loads, which are relatively large amounts of fast powder, will cause significant heat and burn out the throat as fast as full power loads. I was all in for shooting reduced loads all summer only to be quite disappointed when a barrel burned out quickly. Live and learn. lol