benfranklin1787 wrote:So you cant just buy the mag tube extension, that would be illegal?
In trying to find an answer to my question, I've found about fifteen answers to yours. None of which are the same. Seems the M4 was not on the ATF's list of banned import firearms, so much confusion exists about the topic. 922r, however, refers to any non-sporting models (which include anything with a fixed mag over 5rd capacity)
Long story short, common consensus, as well as "I'm not sure, so I'll play it safe and keep myself out of jail" says that just the magazine tube or an extension would be illegal. Seems everyone out there interprets that differently, but that's what seems to be the larger number of opinions, as well as how I would personally interpret the law (having no legal authority in any way).
Next to that, though, if you replace the magazine tube entirely, it would only require two other parts be replaced with US made parts to make it legal. The M4 has 13 (some people say 11, I say assume 13 to be safe) imported parts, and to be legal it has to have 10 or fewer parts.
Here's a list of the imported parts on a stock M4:
1) Receiver
2) Barrel
3) Bolt
4) Bolt Carrier
5) Gas Piston
6) Trigger Housing
7) Trigger
Hammer
9) Disconnector
10) Buttstocks
11) Forearm
12) Magazine body
13) Followers
Replace any three of those and you're good to go. Magazine, follower, and the forearm would probably be the easiest/cheapest (without actually doing any price research).
http://www.autoweapons.com/photos07/jan/1780sbr.html
