stupid newbie questions...

[Nicotine]

I have a few questions relating to custom builds that are probably REALLY newbish.

First, I notice that on some custom builds, there is what looks like a little rubber piece that stretches along the side of the receiver between the FCG pins. What is this and why is it desirable enough to add to a custom rifle?

Second, I noticed recently that an ad in SGN was selling "Retro" AR lowers. What exactly would make a lower "retro"? I was under the impression that only the upper and buttstock has changed since the A1.

That is all for now. Thank you for your time.
-Nicotine

[Robb Jensen]

Those are KNS anti-rotational pins. They were designed to use on 'registered' full auto lowers to keep from wearing out the holes in the lower receivers (since these lowers are $10K+). The side benefits of them are that they make the trigger pulls very consistent shot to shot and the pins can't walk out.

I use them because of consistent trigger pulls, Gen 1 pins work best in this regard.

Gen 1 pins on my LMT. (this is a register SBR, which if I had to replace it would cost me about $400 for a new lower and tax stamp).
http://img.photobucket.com/albums/v408/gotm4/LMTlower-1.jpg

Gen 2 pins on my 3gun rifle.
http://img.photobucket.com/albums/v408/gotm4/KNSpins.jpg

[Nicotine]

Thanks, very nice looking rifle BTW.

IMO, the GEN 1 looks nicer. You say it works better too?

nevermind on the "Retro" lower question. I managed to find an answer myself after all.