I bought a DPMS lower at the gun show and when I went online to purchase parts they mention pin sizes. What are they talking about? How do I determine what pin size this lower is? Also who makes the best DVD on assembly of a AR-15?

Only Colt sporters use the large pins.

Everything else is mil spec. (small pin)

The standard milspec pin size is .250. The Colt Sporter is .312. The hole spacing is different between the Colt and ALL others as well, making the use of non-Colt receivers impossible without either using an offset front pin, or, as I regularly do, re-bush the Colt lower to accept any of the other manufacturer's top ends.

quote:

Originally posted by Swede44mag:
........Also who makes the best DVD on assembly of a AR-15?

Can't answer who makes the best, but you might be able to get by with these. And it won't cost you anything.

Brownells videos

Jim

Older Colts have large pivot pins .315" or there abouts. Newer Colts have large fire control pins .170" or so vs .153" or so. There are a lot of variations as to why I say or so. I have seen the .315 listed as .312 and all between. The .170 is listed .169 - .171.

Your DPMS will be .250" takedown and pivot pins and .153" fire control pins which are both Milspec size.

www.ar15.com has a Build it Yourself section with tons of information/pics.

I think you will find that the pin size being reffered to is the fire control group and the DPMS is a .155", whereas the Colt's are .170".

I strongly recomend the AR15 web site and their build it yourself section's tutorial. It is extremely simple to put a lower together, just becareful with the trigger guard roll pin.

Build it yourself