The AR learning curve is steep- but if I can rebuild an engine I should be able to do this (I think? )

Interested in trying a 9mm build. The other thread suggested just waiting for components to go on sale and that will likely be my nece$$ary approach.

-Are there any components that Brownells cannot sell me? Happy to buy from our vendors but wish to know what choices there are.

- I'm a little fuzzy on the parts between the barrel and the BCG, is there a good exploded diagram around?

- What would the mag size restrictions be for a 9mm build?

PS:I haven't posted here for a while- 'tis like a breath of fresh air