Hi guys, I'm new to AR's. Hope this isn't a stupid question. I'm sure at least one person will tell me it is ;o). I went to a gunshow here in Denver today (Crossroads) looking for a lower receiver. I saw several but I also saw something that confused me a bit. I was looking at 2 complete lowers (one bushy, one Rock River Arms). They appeared to be identical until I viewed them from above. The bushmaster had a distinct hump on the inside wall of the receiver (on the right hand side near the rear) while the RRA receiver had straight inside walls on both sides of the receiver. I was under the impression that both of these companies made "mil-spec" lower receivers but now I'm confused because of the obvious difference between the two. The dealer gave me some bullshit about the bushy having "extra metal left over after it was forged". Whatever. What is the true significance of this hump and is it desireable or not? Thanks in advance for any responses...

Matt

Thanks!

Matt