I have a 450 Bushmaster in the 16" Ruger American bolt rifle.
Sun I swaged down some 300 grn Hornady HP .458 bullets to .452 in a Lee push through sizer.
They came out perfect.
Horn brass, Rem 7 1/2 primers and Li'gun powder and a fairly heavy taper crimp.
I started at 31 grains, 3 shots through the chronograph set up in my driveway. My open fronted woodshed is 30 yds from my porch door and makes a good backstop. I set up rock maple and beech chunks to line up with the chrono and got to it. 2 shots checking vel was all it took to split a 16" long, 5" thick chunk in half. Most shed some jacket and lead and continued on into the piece set up in back of it.
Any way, went up in 1/2 grain increments. When I reached 33.5 grains ( still not compressed,but near full) the extreme spread dropped to 18 fps. Velocity for a 5 shot ave was 2112 fps at 20 ft.
The primers are less flat then the factory ammo, brass goes in and comes out like it isn't there.
Next is the 350 grn Speer and Horn. I expect 2000 fps is very achievable. I used a 45/70 Marlin loaded with 350 Horn at just over 2000 fps to shoot broadside through Kudu, Gemsbok, and had no problem dumping a big bull eland hit quartering to me. 60 yrd run and down he went.
This is a potent little cartridge in a bolt gun that is short, light and has very little recoil.
I'll try it without the muzzle break at some point, but like it as is.

Nice; I never considered it because I assumed it just fired pistol bullets. Sounds like you have made it a real contender.
Small c.

Years ago I did the same thing, pushed some Hornady 300/.458” bullets through the 0.452” Lee die and fired them in an M94 .45 LC carbine. Shot fine but were a bit hard for .45 LC velocities.


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Seems like this simple act/fact hasn't gotten around to everyone just yet...or the fact that "RIFLE" type bullets are available and have been available for quite some time...just not as prevalent as .458 sized bullets.

Check out Fury and Hawk bullets.

Don't know HOW the BM got such a bad rap and all that BS between it and the SOCOM...they're two peas in a pod...and the arguments are just arguments to argue over minutia, and even more inane/mundane if you are shooting a bolt gun.

Good Hunting

That's a lot of punch in a small package. Wonder how your loads would do in an AR.

Bill...Check out the 450 Bushmaster forums and online url's AND checkout the U-tube vids...450 BM barrels and complete rifles are available from Brownells and several other places...it is a very popular AR conversion, I have one I tricked out I like very much.

One problem with the AR conversions is the SAAMI pressure of ~39 Kpsi is near the top for the AR-15 platform while you can go MUCH higher pressure wise in a bolt gun...one fly in the pie is the CASE VOLUME , like many of the 60 gr cases, CC limits the amount and type of powder to about 3...Lil'Gun, WW296 and H110, bullet weights in the 300-400 gr REALISTICALLY, (yes you can go much heavier and have a higher SD, but MUCH lower velo/energy) which also limits velocity and max energy.

That being said my 450 BM and 500 S&W Mag with 300-350 gr bullets will put the hurt on anything I care to plug. These are 45 to 50 cal bullets at 1800-2500 fs...I just have a hard time with shooters thinking "pistol" bullets and cases are just pip-squeak "girly" guns. I don't think they actually figured out the energy released by a ~1/2" bullet traveling at that velocity...if you say 45-70, 50-90 loaded at SAMMI specs, their eyes get big..and EVERYBODY knows what a factory Rem 45-70 405 gr slug can do....say 450 Bushmaster/AR-15 and the noses go up.

The 450 BM has limits just like any other caliber, but it's a whole lot better than throwing rocks.

AR's and funny sounding cartridges are not for everyone.

I like the 10 round, Semi-auto functions also...you can send 10 - 300 gr Nosler Parts/2075 fs/2880 ft lbs rounds down range very quickly. I think that ~2900 ft lbs muzzle energy will do nicely within 200-250 yds for anything on the planet...

Good Hunting