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Thread: 50 caliber receiver
09-15-2010, 07:10 PM #1
50 caliber receiver
I'll start with I'm not a gunsmith, don't really want to be a gunsmith, and I own guns but not into them that much anymore. With that said, a friend of mine brought over a barrel and a drawing for a receiver over a year ago asking what I thought it would take to make the receiver. I told him a firearms license to start! The gun is a one-shot 50 caliber sniper type I guess (BMG?). My friend has done me a number of favors over the years and he isn't getting any younger so it's probably time I do something with this.
First question is how much of the receiver can I make without getting into trouble? Second, is it legal to let him finish it here on my equipment after hours? The gun is for his own personal arsenal.
Next, the drawing he brought requires 90 degrees rotation of the bolt (which you have to remove to load/unload). He started talking about a tri-lobed bolt that wouldn't require as much rotation. I think he had seen one somewhere that was like this. I know zilch about gun design - is there a tried and true design like this? If so, where could I get it?
My friend has all kinds of guns (and a canon!) - I think at this point he just really wants to make one. Any help is much appreciated.
09-16-2010, 06:51 AM #2
Very Gray Area
Just a note like yours to start...I'm not an attorney or an FFL holder, but here's my take as someone who has built a few guns:
You could potentially make part of the receiver for your friend legally. Problem is, there is no defined point where the project goes from a hunk of metal to a receiver. The ATF makes this determination on a case-by-case basis and it has to do with their interpretation of the intent. Once it's at a point where it's clearly a receiver (in the eyes of the ATF) you have made a gun.
Since you don't hold an FFL and/or pay a SOT (Special Occupational Tax) as a manufacturer, you can't make a firearm except for personal use. If there is sufficient proof that you created the firearm for resale or giving to someone else, I believe you have committed a felony.
Now, I'm not sure, but I have heard (from my experience building a silencer) that you can have parts made for you, but you need to be present the entire time the parts are being made and they cannot reside in the possession of the unlicensed machinist. He can use your machines as much as he wants to make it himself as well, no matter who owns the machine.
Frankly, I'm not one to advocate willful disobedience of the law, but if you did machine the parts for him and he was present the whole time, how could anyone prove which one of you actually ran the machine?
As far as the design, I'm not really qualified to comment...never built a big fifty. I would recommend checking out the Bill Holmes design. Many seem to have been built successfully over the years.
09-16-2010, 08:04 AM #3
As far as the actual receivers goes if it were me I'd machine it out 4140 prehard and then have it heattreated to around 42C on the Rockwell scale.Do all your machining before HT.Warpage shouldn't pose a problem.If it's going to be a bolt action I'd use 4130 for the bolt but I forget the HT number on that.Again do your machining before HT.The only way I'd first fire something like this(basically home made)is strap it to a tire with a long string on the trigger and plenty of space and a tree between me and the new rifle.Afterwoods,providing both gun and owner are still intact I'd check for stress anywhere in the receiver/bolt area of the gun.
09-16-2010, 02:38 PM #4
Materials and heat treatment specifications
I have worked in the firearm industry for several years as a design engineer. Lots of parts for U.S. machineguns and assult rifles are made of 8620 (or 8620H)steel and are carburized for hardness and durability. The following parts are all made from 8620 (or 8620H) steel and carburized:
M16 barrel extension
M16 bolt carrier
In the case of the M16, the parts are carburized to a case depth of 0.010" to 0.015" and a final hardness of HR15N 89-91 (maybe 89.5 to 91.5). I think the parts for the M14 are similar. I am also guessing that the M14 hammer and trigger are also made from 8620 steel.
The only operations performed on the parts after heat treatment are grinding operations. Galling isn't an issue with either firearm.
If you would like the specific heat treatment and material specifications for the M14 or M16, just ask. I'll gladly give them to you.
09-16-2010, 06:15 PM #5
Legal or not?
I am a class 7 FFL (Manufacturer and dealer)
I could not build the reciever and give it away or sell it without it going onto a form 4473 but I can build up to 50 guns a year without paying excise tax on them...
That said, You are not a licensed dealer so you are not held to these limitations, You can make your friend his reciever and give it to him without breaking any laws (just don't sell it to him)
If you decide to mark it (and I would) stamp in the caliber of the gun or have him do it and give it a unique serial number so that if it gets stolen he can report it with a possability of some day getting it back.
09-17-2010, 05:10 AM #6
Thanks for clearing that up...I have heard multiple versions from many people of questionable authority about the rules of gifting a homemade firearm. It's clearly illegal to manufacture it with the intent of selling it (without a license) but I have never heard a clear answer on gifting until now!
09-17-2010, 06:15 AM #7
Thanks guys, I appreciate the info. I didn't want to break the law trying to return a favor (favors).
09-18-2010, 06:19 AM #8
If you give it away you have to serial number it. If you keep it for yourself it requires no markings, but you can not give it away without marking it.
09-21-2010, 08:59 PM #9
The type of action you are describing is a shellholder action.
Ones with 3 lugs are available complete guns on GB, the
Vulcan 50 cal for 1500-1800 bucks.Ed