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Sorry guys, but after reading conversion threads for the past hour, I have to start another one because I can't find the answers...

I bought a USC from Aviator Dave earlier this year, and I've decided to go with a TBostic fused conversion. I have finally invested into conversion parts, including an HK FBI lower. I would at least like to do the FCG parts swap myself just to learn before scheduling with Mr. Bostic.

Questions:

1. Are there any online docs, hopefully with pics, that document a USC-UMP FCG parts swap, along the lines of the infamous BigBore LEM conversion doc? (If not, I'd suggest it would be great for someone to make one!)

2. Does the Auto Sear/Disconector area HAVE to be filled for it to be legal? Ed at HDPS states on his web site that it does make it a stronger design, along with proof that it's been diabled. Has anyone NOT filled this in and had or know of problems? (I just don't have the stuff or skill to do that- I see from Ed's pics that it has been milled after filling). I haven't heard detail from Mr. Bostic if he does that as part of the conversion....

3. I've read conflicting information on whether engraving on the receiver is necessary for SBR- a few have written that they just have the barrel engraved. I ask because of the very real logistics of engraving my very long trust name all over the receiver, and not that logic applies to Federal law, but the barrel MAKES it the SBR anyway...

Thanks guys- I'm exited to get started!

B.
 

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For your #1 question, see these posts. It is similar to the USC.

HK SL8-1 Trigger Group Breakdown
http://www.hkpro.com/forum/hk-reference-library/116098-how-convert-g36-lower-sl8-fcg.html

One thing to be aware of on a USC/UMP though, is that they use a metal ring retainer imbedded in the plastic on the left side of the lower (opposite side of ejection port) so when you're removing pins, push from left to right and install right to left. It makes taking the pins out easier and probably cuts down on wear for the retainers.
 

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question 1. http://www.hkpro.com/forum/hk-reference-library/116098-how-convert-g36-lower-sl8-fcg.html its for a sl8 but there basically the same except skip the first 3 pictures and the usc trigger only has the one trigger spring on the right the sl8 shown has two but that breakdown is what got me through my usc conversion. question 2. the area does not have to be filled cutting the upper to accept ump triggers is illegal. i did the conversion myself and it works fine unfilled.
question3. For registration your name and whole address must be visible you say you have a long trust name would the name and address be easily seen through the vent holes
 

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...

2. Does the Auto Sear/Disconector area HAVE to be filled for it to be legal? Ed at HDPS states on his web site that it does make it a stronger design, along with proof that it's been diabled. Has anyone NOT filled this in and had or know of problems? (I just don't have the stuff or skill to do that- I see from Ed's pics that it has been milled after filling). I haven't heard detail from Mr. Bostic if he does that as part of the conversion....
Tom does filled the pocket with epoxy on his conversion.

 

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#2: No, it does not need to be filled in order to be legal and so long as you transfer over the USC fire control group with its built-in safeties, the likelihood of it tripping the sear into full-auto is negligibly miniscule. I have the FBI lower, too, and didn't fill it and have never had a problem in the nearly 1000 rounds that have gone through my UMP conversion and don't anticipate any. It's more of a what-if, CYA thing.

#3: You can engrave either the barrel or the receiver but realize that it has to be viewable to the naked eye. As mentioned above, if you engrave the barrel, make sure you also cut those UMP vents in the receiver and engrave the barrel in such a way as you can see it through the vents.
 

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2) it is not required to be filled.
It might be stronger that way, but the gun WAS designed for FA fire, with the hole there, so how much stronger does the SA config need to be?

3) absolutely, positively MUST be engraved. Barrel or receiver, your choice. The location must be readily viewable.
 

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All good info.
I would like to add about #2. I filled the area with jb weld, to just below the axle hole. If I remember correctly, the usc lower had extra bracing in that area that was not there in the ump lower. With the two hammer springs applying pressure on that area I decided to fill it for extra strength. Probably unnecessary, but it puts my mind at ease. That said, it is not a legal requirement.

In terms of engraving, there is a thread under the nfa section about gray laser engraving. I posted a pic of my engraving in there if you are looking for examples. They did good, fast work.
 

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On question 2 - the legal question is whether the firearm can be "readily restored" to fire full-auto if you fill in the autosear area.

You should seek your own legal advice on this question but for informational and educational purposes consider the case of U.S. v. One TRW M14 from the Sixth Circuit in 2005. The case dealt with a M14 that, according to expert testimony, could be made to fire full-auto with four to six hours of work with particular machinery or "readily restored" in two to three hours by hand manufacturing the parts. The Court found that it was a NFA machingun subject to forfeiture. The Court looked at several tests to determine if a machinegun could be "readily restored" under 26 U.S.C. § 5845(b)...

In the context of the NFA and its use as a modifier describing the manner of firearm restoration, “readily” has been read to encompass several elements of restoration: (1) time, i.e., how long it takes to restore the weapon; (2) ease, i.e., how difficult it is to restore the weapon; (3) expertise, i.e., what knowledge and skills are required to restore the weapon; (4) necessary equipment, i.e., what tools are required to restore the weapon; (5) availability, i.e., where additional parts are required, how easily they can be obtained; (6) expense, i.e., how much it costs to restore the weapon; (7) scope, i.e., the extent to which the weapon has to be changed to allow it to shoot automatically; (8) feasability, i.e., whether the restoration would damage or destroy the weapon or cause it to malfunction. See S.W. Daniel, Inc. v. United States, 831 F.2d 253, 254-55 (11th Cir. 1987) (ease and scope); United States v. Alverson, 666 F.2d 341, 345 (9th Cir. 1982) (expertise, ease, and scope); United States v. Smith, 477 F.2d 399, 400 (8th Cir. 1973) (time and equipment); United States v. Aguilar-Espinosa, 57 F. Supp. 2d 1359, 1362 (M.D. Fla. 1999) (time, ease, expertise, and equipment); United States v. Seven Misc. Firearms, 503 F. Supp. 565, 573-75 (D.D.C. 1980) (time, ease, expertise, equipment, availability, expense, and feasibility); United States v. Cook, No. 92-1467, 1993 WL 243823, at *3-4 (6th Cir. July 6, 1993) (availability).

In other words, who knows. Someone should get an opinion letter from the ATF. Maybe Ed at HDPS has already done so. I hope so because I've bought a USC SBR conversion from him.
 

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It really does not matter if the area is filled or not. It is a CYA manuever. If you leave the sear trip in place it will not accept a USC upper. If you accomodate the USC upper to accept said trip you have mfg'ed an unregistered MG. This is what will get you in trouble.
 

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It really does not matter if the area is filled or not. It is a CYA manuever. If you leave the sear trip in place it will not accept a USC upper. If you accomodate the USC upper to accept said trip you have mfg'ed an unregistered MG. This is what will get you in trouble.
Yep, as long as you don't cut into the receiver to make clearance for the trip lever, then it physically can't accept a full-auto lower no matter what.


Even with an AR15, all you need is a drill press and the correct drill bit to make an auto sear fit.
 
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