[archy]

So the Aussies have a bayonet that fits an M4 but we don't?

Nope. The Aussies use their F88 AusSteyers, which use the Eickhorn KCB-70 bayonet. The M4s are USMC M4 rifles with ACOG sights and the old issue M9 bayonet, now being replaced by the USMC by the OKC-3S bayonet, seen here on M16A2 rifles.

[Buffalo Head]

One of us seems confused. I am certain that bayonets that fit M16’s, M16A1’s and M16A2’s do not fit M4’s. You seem to be writing that the new OKC-38 bayonet fits both M16’s and M4’s. The distance between the flash supressor and bayonet lug is quite different between M16’s and M4’s.