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.
I have to go with PTK on this one. It's the whole reason I did my build in a certain order. Started with an AR pistol. Custom DI .357 SIG with 9" barrel. No problem, totally legal. Then got it certified as a SBR. Tax stamp came, changed buffer tube and put on a stock. But one of the big problems with any NFA item is the way you have to plan ahead to take them over state lines. You have to do the paperwork. But the rules clearly say that I can remove the stock, change back to a pistol buffer tube, and then travel where I like with no tax stamp. At that point it's just a pistol again.
Now it would be a different story if I had the stock and buffer tube in my car with me and the pistol!
Them's the rules!