450 vs 5.56 bolt

[roli24]

Are the BCG's interchangeable between a 450 and 5.56?

[Hoot]

Welcome Aboard Roli!

Short answer: Yes the bolts and barrels are different however.

Hoot

[Bmt85]

Just to clarify what Hoot said. The BCG is the same, except for the bolt.

[roli24]

What is the difference with a 450 bolt?

The one in my rifle looks identical to my other AR bolts. Although I have noticed that the barrel extension is wearing where the bolt locks up.

I am beginning to wonder if this rifle doesnt have the right bolt.

[Bmt85]

The face of the bolt is hogged out a lot more on the 450 bushmaster because it’s a bigger round. Not even close to looking the same as the .223 bolt.

[Hoot]

The 5.56/223 bolt face fits the .378 OD rim of that cartridge, The 450b rim which was originally spec'd at .473 OD, would not fit into the bolt of a 5.56/223. So, the 450b bolt is "hogged out" to an internal diameter that fits the .473 rim. The outside of either caliber's bolt is the same. Either one will fit into the AR 15 barrel extension. In the normal operation, there will be some shining of the points that rub against one another. That is to be expected as they get "broke in".

Hoot