Was at a gun show recently and got talked out of buying a PWA lower. A guy who didn't buy the lower either said it was actually a M16 not AR15 lower. He pointed out that the M16 lower has more of the area behind the trigger assembly milled out. Anybody know if this is true? Anybody know where I can find actual images of the area?I was looking to buy not bet. Thanks

What you discribe is a normal reciever, some companies began to mill the recievers to prevent an individual from putting auto sears into their weapons, Colt being one company that I know of.
The term is called high and low shelfs(sp?).
In order for a reciever to be Mil-Spec, it will have the area behind the trigger milled out the same as a M-16.


Hijacked this from a thread over at AR15/BIY:
[url]http://www.quarterbore.com/nfa/dias.html[/url]

The key thing you have to look out for on receivers that have been modified is whether or not they have an extra hole drilled in the receiver. This is for the extra pin required to hold the automatic parts in place. If you can compare pictures of a semi and an auto receiver side by side you will easily see what I am talking about.