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Discussion Starter · #1 ·
Anybody have the current specs on what is legal for a non FFL 50cal M2HB unfinished rhsp? From talking to people and what I have read, the only legal option is a dummy rhsp that is thicker than what the design specs called for. Then the owner has to cut all the holes and lines and find a way to mill off the extra thickness of the plate in order to stay legal when buying a non ffl rhsp for M2HB 50 cal. This sound correct? Reason for asking is there is a non ffl M2HB kit with an 80% rhsp on GB right now and that rhsp looks like trouble for the buyer.
 

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PhD in Over-Engineering
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I wouldn't be worried about a pre existing 80% plate in a case like this, at least for Title I semi. For Title II, I suppose one can argue it is a bit dicier, the difference being the presence of extra thick denial islands, or their absence making it Title II category. Constructive intent argument being what can be made of it. For a manufacturer in current terms, the 80% semi plate is risky business, given ATF policy. But for stuff that was made "back in the day" I have never heard of any trouble, nor would I expect it. If producing Title II as a maker, one would probably not be playing with the 80% game unless specifically for another properly licensed mfg with proper paperwork.
 

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Discussion Starter · #3 ·
I never bothered to check the thickness of the so called 80% plate on GB until now. With a price tag of 7k I didn't get to far into reading the specs.http://www.gunbroker.com/Auction/ViewItem.aspx?Item=508901879 The concern I had was, this being a non-ffl sale. How complete does the rhsp need to be,to be considered a finished receiver and not a 80% rhsp. Like I said, I remember the 80% specs to be so few that really all it was,was just a plate shaped to fit a 50cal and after the first line was cut or hole drilled it was no longer 80% it was finished and since the only thing left to do on this side plate was top and bottom plate holes. I was thinking it is way past 80% and wanted to get an idea on the specs of what passed for a legal 80% rhsp these days. And how would anyone be able to argue this plate was grandfathered in by being made back in the day without any markings on it?
 

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Don't see a problem here on first look. Get a close up of both sides of the RSP to be sure.

As a buyer your concern should be, "is it a quality part?" Not a legal issue.

If I were bidding on this item, I'd want a lot more detailed closeup views of everything before dropping $7K
 

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Have to agree with Karl - The 50 plate is a big deal - from a materials standpoint. There is no "spec" on what is an 80% plate. Or 80% tube. It will be dependent on what the prosecutor wants to do, and what the BATF "expert" says it is. Now, the steel alloy used to make the plate makes a huge difference, and if not correct can result in anything from the gun binding up right up to killing you. Heat treatment is also an important factor, and this is a subject far to extensive to discuss in a post I have to type. We used oil quenched 4140 for our 1919 post sample plates back when we made the guns. I do not have the spec for the steel in the 50 cal in front of me, but that would be one of the first questions I would ask. Then heat treatment - this is why the parkerizing on GI guns is a different color at the rear where the backplate slots are cut. The pictures in the GB auction look like a Full auto plate. So the gun will be a post sample. $7k seems pretty high for a pile of parts - you will spend $2k easily getting it assembled and finished, assuming all the parts are useable. Cheaper to buy a finished post sample.
But hat is my 2 cents....
 

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PhD in Over-Engineering
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Just took a look at the images. Not a lot of detail for sure. But I'd like someone else to look and see if they see what I think I see! Hard to tell, but that extra plate looks like another Left side to me. Maybe my eyes are out of focus today.

MG08 pretty well summed it up on 80% plates. When those were being made, the specs varied with the manufacturer. ATF generally ignored all this for years, but what they settled on, after closing the Halo case, was the charging handle slot and feedway profiles. They don't have any concern about what percentage of the plate is finished. That is not their criteria, and they refer to that as an "industry term." Their concern is how much time and what kind of tools it requires to be finished. Not that this isn't equally vague, but the major machining that is generally considered to require a mill, is a lot different than just a drilling op. All these discussions we used to have, like once you drill that one extra hole on your 80% plate you now have a gun, has proven to be meaningless.

Note, on material: Drawing calls for these options: A331, A322, 4340 or 4140. Heat treat of last inch and a half, to 32 Rockwell "C" scale. The .30 cal guns didn't get heat treat added until 1942. If that is the same pattern for the 50s, then the heat treat was added later on, after many of these were built and issued with no heat treat. I don't have drawings early enough to confirm that on the .50 cal, but there is enough to indicate this was a revision from original specs.
 

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I don't think there's anything wrong with your eyes today..."O'long haired Ke-mo sah-bee".

Tirediron
 

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Discussion Starter · #9 ·
Damn, that is funny.7k for a M2HB kit with a extra unfinished LSP. That's what I get for posting after midnight. I should have noticed that this was the special Kalifornia kit that uses two LHSP's. And they want 175.00 to ship it. Thanks guys for all the time spent answering my questions
 
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