BATFE compliant aluminum receiver question

[Quest Master]

I've seen solid aluminum dummy receivers for dummy guns like the STEN, MP-40 etc. for years. I don't see any problem there, but I've seen aluminum sideplates for the Maxim, M2 .50 cal. etc being offered recently. Is it BATFE compliant to build a dummy gun on an aluminum right side plate of the same dimensions? Doesn't seen legal to me.

[Don Shaffer]

The Aluminum Receivers I have seen have a raised rib cast on the inside so original parts won't fit ! Check before you Buy ! Don Shaffer N.E. Ohio

[W. Winget]

The other consideration is the cycling of an Automatic firing piece and the effects of steel parts cycling under extreme pressures will render the aluminum pieces out of tolerance fairly quickly...so the amount of machining work put into an aluminum side plate that 'could' function for a short duration wouldn't be a real issue. It might not even stand up to the testing and functioning phase of assembly.
Yeah, some .45's and pistols like Walthers P1's have had aluminum frames for years, but that's a sliding back and forth mechanism, not a guide down, and guide up type of action the Maxim would incur.
Just a thought.
V/R W Winget

[Andy Cole]

From my understanding, having built a couple of semi belt feds, IF it is assembled and unmodified full auto internals will fit and fire one round it is considered a machine gun.

I for one WOULD NOT chance it. Material aside, it makes no difference. 13 years ago when I got my first torch cut belt fed kit, it still had sections of the right side plate attached. Even though a large chunk was missing from the side plate, the bolt could still cycle. I have no idea when it was cut originally, but had not been "de-miled" to ATF specs on the books at the time I acquired it. I didn't know better, until a very reputable Class III dealer informed me that as it sat it was contraband. It was immediately dismantled and the right side plate destroyed per ATF guidelines.

Thankfully I was later able to build the then legal kit into a beautiful and legal Semi-auto 1917a1. That gun is what started me down the rabbit hole of semi-auto belt feds.

[Loganr]

I saw that web site the steel 80% plates have the 1/2 inch
Dummy island
The aluminum no but looks Un drilled and some machining
So he might get by selling it as is because it can not be fitted but if you finish it then who knows.
If he’s honest he will send you a copy of the BATF
Approval letter.
I think he’s right up there with solvent traps but I could be wrong