[PTK]

I am aware of a couple of guys who wanted to SBR their Glocks and carry the gun CCW, with the Israeli/FAB stock in a Maxpedition-type bag to have available just in case.

After contacting ATF, their ruling was once the pistol is SBR'd it must be stored and transported in SBR configuration.

You can remove the stock and fire the gun in non-NFA (pistol) configuration for short periods of time at the range for fun, but before you leave the gun must be put back into SBR configuration (stock on). You also must store the gun in your safe in SBR configuration.

Incorrect. Modifications are perfectly permissible even for long periods of time as long as the firearm can be returned to the condition stated on the F1 or F4. The BATFE is very clear on that.

Well, I just got off the phone with the ATF Office in Seattle. Here is the official word:

There is NO--I repeat, NO--Federal restriction to using the Mech-Tech CCU Unit with a handgun lower (1911, Glock), then removing the carbine upper and reinstalling the pistol slide assembly.

The one caution that I got was to "check your State's laws as well".

So, check your State's laws.

And, when cleared, use with confidence and much fun.

Powderman, you just got an opinion from one employee. The law is quite clear. A 1911 or Glock with a rifle upper is a rifle, it has a stock. The law is quite clear that if a firearm designed or redesigned (such as with a CCU) to be fired from the shoulder must have a 16" or longer barrel and at least a 26" OAL or it is an NFA item. Period. If it, at any point, had a stock - it's a rifle or short barreled rifle (depending on barrel length).

If you could just convert things back and forth, there would be a LOT of people with MN 91/30 "pistols". Hey, no stock, so it's a pistol, right? Doesn't matter what it started as, a pistol or a rifle, if it EVER had a stock designed or redesigned to be fired from the shoulder, EVER, it's a rifle. If that is true and the barrel is now less than 16" and/or the overall length is now less than 26", it's a "weapon made from a rifle" - an SBR. Period.