Gentlemen, please pardon if I offend, but I know what I want, just can't afford the $1400+ being asked for SP1s.
I see a number of SP1 uppers being offered, and I can see me -- here it comes -- removing the nasty lug and shortening the barrel(as little as possible).  I know this would offend collectors out there, but:

1. - would I be breaking any laws?
2. - would putting it on a post ban lower be legal?
3. - is it only the front "pivot" pin that is   large? -- or is the rear pin a problem too, when  putting it on a post ban lower?  I assume I could "bush" the pivot pin.

Thanks for your help.

 

1 & 2 - not a problem, legally, as long as you remove the bayonet lug and muzzle threads.
3. only the pivot pin is large - rear is standard.

Thanks for the response.  I know that in the AK world there is a barrel nut to cover the threads -- usually fixed with a spot of weld.  I haven't seen any such thing for the AR.

Again, thanks

So why not cut the flash suppressor that's already there back to the muzzle,and spot weld, or even better, permanently mount one of the lookalike muzzle brakes?

spot welding is not legal for removing muzzle threads under the AW ban.

The spot-welded ak muzzle nuts were pre-1994 - they must come in bare-muzzled since then, or with a post-ban compliant brake attached in ATF approved fasion (seam welding, 1100F silver solder, or blind-pinned and welded).

Permanent attachment of a post-ban legal brake of some kind (even a 'lookalike' like a cavcomp or kurt's tac-brake) will do the trick.  You could also make up a muzzle nut instead of a post-ban legal muzzle brake, and have that permanently attached.  With so many decent-looking and (more important) reasonably functional post-ban brake options, most people don't bother with a simple muzzle nut - although they could make/use one if they chose to.