Is there the SP1 profile, the new colt style, and another style that like BM and Armalite etc uses, or is the SP1 profile the same as the type BM etc. uses now?

When you really break it down, there are 2 types, M16 and AR15 carriers.

What are the different types of Ar-15 bolt carriers that exist for 5.56 caliber (not including finish etc)

All bolt carriers is about the same in the AR system, there is some difference between the M16 and the AR bolt carrier.  

You would be able to take a Colt carrier and use it in a Bushmaster and a Bush in a Rock River and a RRA carrier in an Armalite.  It is an interchangeable component.

Just to clarify, since this is an offshoot of a question posted on the full-auto board:

I believe strongmad is asking which bolt carriers will function with a registered lightning link.

I know the link works fine with the SP1 carrier design. I also know it DOES NOT work with some current-production carriers which are milled differently on the bottom (for instance, current-production Colt carriers have more metal milled away, in a specific attempt by Colt to make them incompatible with unregistered LLs).

So: Anyone know which carriers are identical on the bottom to SP1 design?

yes, that would be more my question, thanks Tony K.  

PS Colt is an ATF ass kisser

Know absolutely nothing about the Lightning Link, but will it not work with a standard M16 carrier?  If not, and you'd have to use an early AR15 type, why not just get an M16 piece, and cut back the shoulder 'til it's the right length?

shamayim--Lightning link is for use with std AR-15 parts, not with M16 parts.

[url]http://www.ar15.com/forums/topic.html?b=3&f=14&t=164977[/url]

[url]http://www.ar15.com/forums/topic.html?b=3&f=15&t=164999[/url]

Thanks, SBR7_11. That's the sort of info strongmad needs. I KNEW someone here would know!