AUG question

[darvish]

Hello,  I’m order for a select fire bolt carrier and trigger group to be used in a semi auto upper, it looks like the lower rear of the upper needs to be machined to allow the sliding disassembly button to close, securing the upper, when using the select fire stock count aiming the trigger pack and select fire connecting mechanism from the trigger, running down both sides to the trigger pack. 
 

it seems the common solution is to machine the shelf on the bottom rear of the upper wider to allow the button to slide closed.    Would machining the button mechanism itself  be a viable alternative?   
 

if the upper is so modified , does it become an NFA item?  I have a trigger pack ( Post Sample) and an surplus AUG parts kit.  (With what appears to be a select fire trigger pack) bought from APEX.  
 

im guessing my post sample trigger pack is only a machine gun if installed into an AUG that will allow it to function FA.  
 

would a modified upper, forever be an NFA item? I hate to turn a nice Title 1 gun into an essentially worthless post sample if I can help it.  
 

thanks I’m advance.  

[jbntex]

The AUG platform has a couple of differences between the full auto and semi auto guns to preclude their interchangeability of parts with the intention of making a conversion of a semi-auto into a full auto more difficult.

From a firearm receiver perspective (what I believe you are referencing as the "upper") the stock locking latch width cutout is different.  The full auto receiver has a wider stock latch cutout that corresponds to the wider stock locking latch in the full auto AUG stock. 

The semi-auto receiver has a narrower stock latch cut in the receiver and a correspondingly narrow stock locking latch in the semi auto stock.

This change is specifically so that you cannot put a legal semi-auto receiver into a full auto stock.  (more on why this is important below)

So to answer your question, "can I mill the stock locking latch cutout on the semi-auto receiver wider to fit the wider stock locking latch found in the full auto stock and does this make the receiver a machinegun?"

The answer to milling the receivers locking latch wider is unequivocally...YES... you just made machinegun out of that semi-auto receiver.   Milling the stock latch cutout on a semi-auto AUG receiver is analogous to milling and drilling an AR lower or removing the shelf and drilling a hole in an HK semi receiver.

Back to the full auto stock discussion and why does widening the latch cutout on the receiver make it a machinegun.   So there are also difference between the full auto and semi auto stocks besides just the locking latch.  The recoil thruster rods are a different lengths (longer in the semi stock), but more importantly there are protrusions inside the semi auto stock that prevent a factory full auto hammer pack from being installed.

Once you cut a semi AUG receiver to fit a full auto stock you can now combine an unregulated full auto hammer pack and the semi receiver making a machinegun.  Just like once you remove the semi-shelf on an HK it will mate up to a full auto HK trigger pack.

So to answer your next question, can you mill the stock latch found in the full auto stock  narrower to fit the narrower slot in the semi receiver.    Yes you can, but this modification is a legal gray area. 

There are gunsmiths out there who do this type of full auto stock latch conversion so that folks with conversion sears/hammerpacks can use a full auto stock without having to deal with the recoil thruster rod length issue. (As full auto carrier with anti-bounce rods installed won't function in a semi auto stock as the thruster rods in the semi stock are too long)  The legal claim is that modifying the full auto stock latch is no different than prepping an HK pack for a conversion sear  or milling an FNC lower for an FNC sear. i.e. you are not modifying the "receiver" just other surrounding parts to enable the use of a conversion part.

There are other folks who feel this stock latch modification is more like cutting away the front of an HK full auto trigger pack so it will fit a semi receiver.  Sure you are not modifying a firearm receiver.....but you are making a machinegun conversion part unto itself which should be registered.  The argument being, once you modify the full auto stock latch you have effectively made a "AUG machinegun conversion stock" that a semi auto receiver will drop right into and mate up with a factory full auto hammer pack.

Personally I think modifying a stock latch is a bit of a legally risky proposition so I don't so it as a non-licensee and best case it marries your registered conversion sear/hammerpack to that now modified full auto stock.  However, its probably not as big of a deal for a FFL/SOT.

If your post sample pack was built off a semi-auto hammerpack frame than my suggestion is you use a semi-receiver, installed in a semi stock.  You will need to deal with the stock recoil thruster rod length issue. The recoil thruster rod issue can be resolved by either cutting and shortening the anti-bounce rods down in the full auto carrier thruster tubes, cutting/shortening the recoil thruster rods down inside the semi stock, or transplanting recoil thruster rods from a full auto stock into the semi stock.

If your post sample pack is an unmodified factory full auto hammerpack than it won't fit into a semi stock as is. Your only options are either a legal gray area modification to a full auto stock latch or you could try and mill notches in the front of the hammerpack in order to clear the full auto hammerpack blocking protrusions in a semi stock.  Then make the necessary modifications to the semi stock recoil thruster rods or anti-bounce rods in the carrier.  However, it may be really tight not to mill away the autosear pin holes in the hammer pack while also removing enough material so that the factory full auto hammer pack will fit a semi stock.

Hopefully this information helps.

 

 

 

 

[darvish]

That was incredibly helpful and exactly the information I was looking for.   I can easily register the modified stock as a post sample. And sell, surrender or destroy when I give up my ffl/sot.   The stock was cheap enough.   

[jbntex]

Glad to help.

If you are an 07/02 and plan to use an unmodified hammer pack with a semi-auto receiver,  I would mill the full auto stock latch to fit the semi receiver and then register the modded full stock latch as a machinegun in the NFRTR on a Form 2, as that is really the machinegun "conversion" part at that point.

Registering a non-modded AUG full auto hammer pack would be like registering an unmodified HK full auto triggerbox..... neither of which are technically a conversion parts as they can't be used with a semi-auto receiver as is.  Now mill the AUG stock latch or notch the front of the HK full auto triggerbox and you have got yourself a machinegun conversion part as the rest of the unregulated parts needed for full auto all drop into place for use with an unmodified semi-auto receiver.

Edited December 8, 2020 by jbntex