legal "landmine"?

[fritsch]

I think I might have discovered a technically legal "landmine" with building mg42/53s. If it's already been addressed and I missed it, I apologize.

So the BATF approved way to do a "reweld" is to make the grip slot larger, weld in the blocking stud, and grind off the sear lugs on the bolt. OK, but after you get your receiver welded up and finished, isn't it technicaly possible at that point to just hold the bolt back (with lots of stuggling im sure), put a belt in, and let go of the bolt? Shouldn't it continue to fire until the belt's gone? Am I missing something here? Are people inadvertently making MGs for a short period before they alter their locking wedge?

[roadrunner]

Hi Fritsch, I think what you might be overlooking is that in modifying the bolt for semi auto a floating firing pin is introduced. Along with the trigger group this changes the operating system to a closed bolt rather than open bolt action. Of course if you have a firing pin stuck in the forward position all bets are off. RR

[fritsch]

I'm talking about before you modify the firing pin to float. In the scenario I'm talking about, someone has done their mods required to start welding the receiver (blocking lug, widening grip slot, grinding off sear lug on bolt). Then has successfully welded up and cleaned up the receiver to operate. At that point, before any more work is done to the bolt (and in this scenario the grip pack is irrelevant, semi or full) wouldn't it theoretically be simple to make it fire indefinitely? Just assemble everything except the grip pack, somehow hold the bolt back, put a loaded belt in, and release the bolt.

All this dawned on me after I finished welding up my receiver (with proper mods, mind you) and was using the bolt assembly to put in the rails. I guess what I really want to know is if I should get something modified TONIGHT to alleviate this engineering problem I'm seeing, or if I'm just crazy (and of course crazy is always on the table )

[roadrunner]

I can see your point. In that situation it would definately be a runaway. I know some laws refer to Rounds fired per trigger pull. But others to full auto componants, so anyone want to chime in on a legality question? RR

[shred]

"pull-back-bolt-and-let-fly" FA is also verboten. See the "Sputter Gun" rulings.

Best plan is not to get into that situation and mod the bolt first, but.....

[salt6]

Any semi auto gun can be set up do that.

Sent from my Desire HD using Tapatalk 2

[JBaum]

Gee, it's also possible to rebuild it with no modifications at all and make a machinegun, and it's just as illegal, too.

[fritsch]

I guess I'm not asking "is this legal" because I know operating it in this manner is clearly illegal. It was just something I hadn't seen addressed before. It seams like a glaring problem if you weld your receiver before you do all of your bolt mods, and I just hadn't seen anyone say "make sure the firing pin floats in the bolt before you weld the receiver up". The problem that I'm seeing is the sear lug you cut off to "neuter" it is also the same mod to make it fit in the receiver. The 1919a4 and RPD have two completely different cuts for these two purposes. Are there any other guns that have a neuter and "relieving cut" (for lack of a beter term) in one?

[M1 Tanker]

You can take a 1919 and machine just the sides of the barrel extension, lock frame and bolt to fit in the semi auto receiver and you have an illegal machine gun also if you don't modify the rest. If your worried, modify the wedge first, then grind on the carrier.

[fritsch]

You're absolutely right M1 Tanker. That modification order you described, I believe is stated as illegal by the ATF in the presence of a finished receiver even if you don't operate it like that. It's modifying it to fit in a semi reciever but not modified to no longer be full auto.

And you're right, modifying the wedge would be the way to simply make it not operate in full auto (and don't worry, once that dawned on me, that mod went to the top of the stack). So why in God's green earth did they decide to make it the sear lugs as the thing that no longer makes it full auto and not the locking wedge? Especially when it's also the very same modification that makes it fit in the semi receiver. Am I crazy? There has to be something I'm not seeing here

If I'm wrong about any of this, please chime in. There has to be a thread somewhere deep within the bowels of this place that addresses this.......isn't there?

[JBaum]

When ATFE makes sense, they sometimes later reverse themselves anyway, so trying to understand their decisions is a waste of time. It's their game, they make the rules, and not following their rules can mean jail time.

It doesn't have to make sense, we just have to do it

[M1 Tanker]

Something to remember here, BATF didn't send out a list that said do these things to be a semi auto. A manufacturer sent in a sample saying we want to do this, whats your ruling. They ruled on what was sent in to tech branch, not on what they thought was the best way to go about it.

[fritsch]

Ahhh haa! That makes a little more sense. So let me get it straight. They gave the OK on the end result, and it's up to you what order you make it in to stay legal? And by the way, when I went to drill the locking wedge, I toasted two drill bits. What are you guys doing? Are you using carbide bits? Annealing and hardening? I'll ask in the building section, but I thought I'd post it here, too, because of it's relevancy.

Edit: Never mind, I found the answer in Gungrubbers bolt tutorial. Man, you guys have everything on this sight. It's been such a humbling experience building this thing. I couldn't imagine what it was like back in 2005 pioneering this stuff!

[M1 Tanker]

Correct Fritsch, a FFL07 would send in a sample to rule on the finished product. Its up to us at home to be smart and make sure our build process is safe so at no time do we manufacture something we didn't intend.

[shred]

. The 1919a4 and RPD have two completely different cuts for these two purposes. Are there any other guns that have a neuter and "relieving cut" (for lack of a beter term) in one?

The Sterling semi-auto is done similarly-- milling the bolt for the blocking bar also removes the open-bolt catch shelf for the sear. It is best to remove the firing pin nub from the bolt on one of those before cutting the slot.