Should I get the 20" or the 24" barreled upper?  I know the only difference is generally going to be the velocity but can't decide which would suit me better.  Those who have one or the other I would like to hear from you.  And should I get the 1:8 or 1:12. I am leaning towards the 1:8 since I could shoot the heavier bullets for two legged varmints. How does the 1:8 shoot the lighter bullets?

I have the RRA 1:12 24" SS Varmint upper. If you are going to be packing the gun over a half mile I would say go lighter. Myself, I shoot from the top of a pickup so weight is not an issue. I got the longest barrel length for the improved accuracy and velocity. I got the 1:12" twist because I will be shooting primarily 35-45 grain bullets.A 1:8" twist is not going to handle the lighter bullets too well.

We would need to know your purposes for the weapon to make an informed suggestion. I would go w/ 1/8 it will shoot light stuff just fine and heavy stuff great as well. I wouldn't shoot under 45gr w/ the 1/8 though.

I think I will go with the 1:8 now I just need to decide which length to get.

Longer is better (just ask the wimminz)....if "varmint" hunting...long range accuracy and velocity go together....