Hello,  
I'm new to posting questions at this site.  I've read the forums for a few months,but this is my first Q.  Hopefully it'll work ok.

i was wondering if there is a simple way to distinguish a pre-ban from a post-ban ar15?  

One more question.  My friend has a colt ar15, and it has a red piece of plastic in the lower behind where the hammer is pulled in the cocked position.  What is the purpose of this and why don't all ar's have it?

Thanks

The only feature that can distinguish between pre and post ban is the serial number.  

The red piece of plastic is there to tighten the fit between the upper and lower.  I can't remember the name of the product right now.  If your upper/lower fit is tight there is no need for it.

Welcome to AR15.com

I think that the product you're referring to is an "Accuwedge."

There's a review of the product on the Fulton Armory site, in the FAQ section:

http://www.fulton-armory.com/AccuWedge.html

Do a search on this forum, or on the net. There is a fair wealth of information on the lower receiver serial number designations for preban vs. post-ban from various mfg's. Be aware that the ATF has stated that, "...in their opinion...", a preban serial #'d lower must have been assembled in a complete, preban config'd firearm prior to Sept. 13, '94 to qualify as a legit preban; if it was assembled after that date, it is considered by them to be post ban legal only. How the assembly is determined to have occurred before vs. after the pivotal date is subject to the gov't's good graces (Of which it most likely has none).

I know that a preban Colt can be generally distinguished by a 2-letter prefix in the serial number; post bans will have a 3-letter prefix. Other mfg's have their own designations.

A reputable dealer will be up on all of the details (mine certainly is) and only sell you what is legal. Stick to a reputable dealer, follow the law.

Good luck.

Do a search on this forum, or on the net. There is a fair wealth of information on the lower receiver serial number designations for preban vs. post-ban from various mfg's. Be aware that the ATF has stated that, "...in [their] opinion...", a preban serial #'d lower must have been assembled in a complete, preban config'd firearm prior to Sept. 13, '94 to qualify as a legit preban; if it was assembled after that date, it is considered by them to be post ban legal only. How the assembly is determined to have occurred before vs. after the pivotal date is subject to the gov't's good graces (Of which it most likely has none).

I know that a preban Colt can be generally distinguished by a 2-letter prefix in the serial number; post bans will have a 3-letter prefix. Other mfg's have their own designations.

A reputable dealer will be up on all of the details (mine certainly is) and only sell you what is legal. Stick to a reputable dealer, follow the law.

Good luck.

Quoted: I think that the product you're referring to is an "Accuwedge." There's a review of the product on the Fulton Armory site, in the FAQ section: http://www.fulton-armory.com/AccuWedge.html

Thanks IMHO - couldn't remember for the life of me.  And I have one.  Gotta do something about these migraines...