450 Bushmaster vs 458 SOCOM as cast bullet AR cartridge?

[Elkins45]

I didn't really know which forum to put this in, so I settled for this one because it's the one most people seem to read consistently.

I am planning to put together an AR upper in one of the "thumper" calibers for hunting with a silencer. That means subsonic ammo. I had just about settled on the 458 SOCOM (which uses .458 bullets like a 45-70) simply because Starline makes brass. Another option opened up yesterday when I found out they are also now making brass for 450 Bushmaster, which uses .452 bullets like 45 Colt and 45 acp.

I have molds in both diameters, up to 500 grains for the SOCOM and up to 300 grains for the Colt. So I don't need to decide based on bullet diameter. All things considered, is there any particular reason to choose one cartridge over the other?

[prsman23]

No replacement for displacement. Or whatever similar adage can be used for bullet size [emoji4].
I would choose 458. But I love 45-70 and already load for one. I load mostly jacketed for 45 acp. If you load for both. Just get two uppers


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[dondiego]

The .450 Bushmaster cartridge is legal in the "Shotgun zone" in Michigan for deer hunting but I don't believe the .458 SOCOM is legal. I recently held an AR, a Ruger American, and a Ruger # 1 in .450 Bushmaster.

[RPRNY]

With Ruger now chambering several rifles in 450 Bushmaster, it may give more impetus to the cartridge, otherwise, it's really 6 vs half a dozen.

[acoop101]

Why not add to the mix even more and the 50 beo?

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[Elkins45]

Why not add to the mix even more and the 50 beo?

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Because my Form 1 is for a 45 caliber silencer. And because I don't have any molds.

Who makes the brass, or do you have to form it yourself??

[frankenfab]

458 Socom all the way. Be sure and get a case gage from Tromix, and check your fired brass with it as well, to get a reference on what your chamber dimensions are like.

Bottle nose feeds better. It will run flawlessly using Lancer 20 Rd 223 mags with no modification.

I also have a 50 Beowulf, which I like even better. I have no real world experience with the 450, but I got in to big bores way before it came out.

[acoop101]

Because my Form 1 is for a 45 caliber silencer. And because I don't have any molds.

Who makes the brass, or do you have to form it yourself??
*_* starline makes 50 be brass and it seems to come up on sale more often. That said your explanation about the suppressor makes sense.

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[Elkins45]

The .450 Bushmaster cartridge is legal in the "Shotgun zone" in Michigan for deer hunting but I don't believe the .458 SOCOM is legal. I recently held an AR, a Ruger American, and a Ruger # 1 in .450 Bushmaster.


With Ruger now chambering several rifles in 450 Bushmaster, it may give more impetus to the cartridge, otherwise, it's really 6 vs half a dozen.

Twist rate probably needs to figure into my decision. Subsonic heavy bullets probably need a faster than normal twist to stabilize, doubly so since I don't want baffle strikes in my silencer. I think 458 can be had with faster twist, but it also shoots heavier bullets.

[dondiego]

Heavier bullets may help keep you in the subsonic range.

[alping45]

If you are only going to be shooting cast, why not go with the .450 bushmaster and double your options for boolits & molds since you can size down any .458 boolit to .452? I size down the RCBS 45-300 FN from .458 to .452 in a lee push through die and it takes almost zero extra effort as opposed to a .453-.454 boolit.