He's asking you "How would you modify an M16 upper to fit an AR lower???" because in your post (#27) you stated "If you modify an M16 upper to fit an AR15 lower". As far as I know the only difference between an M16 & AR15 upper is the early model M16 used a larger front pin, there might be more differences but this is the main one I know of that needs addressed to mount the two together, other then that that fit together.
Not sure what you are trying to say? It would appear as if you just contradicted yourself though. The 1st line you are saying it can't be done???
No you never said "don't do it".
I never said "it is illiegal don't do it" I said it goes quite aways towards making a "readably convertable weapon". The link does not address modifications to the receiver....
Doing mods to the upper itself doesn't mean anything, you can mod it to take a completely different bolt if you want (let's say a square one). The lower is a different story, any mods to allow FA parts to function in an AR is illegal.
Exactly. The ATF has done a lot of testing and feel (and most likely proved) that simple installing FA fire control parts, even if there is no auto sear, you can make an AR fire multiple shoots with one pull of the trigger.
... only that M16 parts in your AR15 is not legal.
1) That is correct
1) but I do know that anything you do to an AR lower to make it accept an Auto Sear turns the receiver from an AR to an M16. 2) Modifying it to fit an M16 upper would do this.
2) Modifying what, and how are you modifying it?
Sorry if this reply sounds like an argument but it's not, I'm trying to see your point of view and what you mean.