450 bushmaster questions

[Fist_gonzo]

So I'm thinking of starting my second build, thinking of doing one in the 450 bushmaster, anybody have any experience with this round? Also would I need a 5.56/.223 lower or another lower? From what ive read its pretty much the barrel, mag and bcg that are specific to the 450 and everything else is 5.56 spec? Thanks guys

[SideShow Bob]

Go .458 SOCOM, Barrel and BCG, no special mags needed. The .450 and the .50 Beowulf have had some extraction problems due to the almost straight walled cases. The tapered case of the .458 SOCOM tend to extract better. And the bullet choice for reloading is better.

[SA Friday]

Go .458 SOCOM, Barrel and BCG, no special mags needed. The .450 and the .50 Beowulf have had some extraction problems due to the almost straight walled cases. The tapered case of the .458 SOCOM tend to extract better. And the bullet choice for reloading is better.

Is it the full BCG or just a bolt swap?

Agree with the SOCOM over the other two.

[SideShow Bob]

I got mine complete, as in the whole rifle, so that would be a question for someone that did the piece together thing.

[meatman]

Go poke around at http://www.450bushmaster.net/viewforum.php?f=2

Some of the active people in the forum are pretty helpful with builds and what parts are different than the 223/5.56 AR's. I bought mine as a complete upper direct from Bushmaster.

[M14lover]

If your reload or planning to, the .458 bullet selection is the difference maker.

[MarkCO]

Baloney, the .450 is a great cartridge with a nice bullet selection. After shooting, reading and talking to people who actually had both and reload, the answer for me was the .450BM.

So if you have a complete functional AR-15, these are the mandatory changes: barrel, bolt, mill top of ejection port, modify magazine. Nothing has to be altered in the lower.

Really nice parts to have...full mass or weighted hammer, full mass or M16 bolt carrier, adjustable gas, comp. If you reload, a stab crimp is a really nice tool as well.

The .450 BM is a straight wall rebated rim cartridge. If you don't take off 1-2mm from the front of the ejection port to the dust cover notch, you will have ejection issues. There are three ways to mod the magazines. Put a blue single shot follower in a steel bodied GI style mag, grind out a .223 follower in a steel mag, put a .450 follower in a mag. I really like the AR Stoner mags and the Lancer AWM mags for these since they have smooth and thick steel lips.

The .450 is overgassed, but does have less bolt head thrust than the .458 or .50. Mine ran 100% at 1600 fps with a 230 slug, so at 2300 fps, it is WAY overgassed. A lot of guys with these large caliber ARs add up to 3/4 pound to the buffer and or carrier. I found just turning down the gas was a much better solution. The light hammers in match triggers will take a thumping. Best choices are the RRA NM 2 stage or the Jard weighted hammer triggers. Most guys use the Ross comp which is about $40.

While the .450 BM is the most accurate of the heavies, the stab crimp does improve accuracy by having consistent case neck tension.

I have one in 16" and I have built a few other uppers. If you need any help, direction, feel free to ask. If you want to shoot mine, that is doable as well.