fabro's
How bout this, an AR15 varminter of your choice, I like the 24" fluted 1-8 twist, and an extra upper in 25 wssm, and later on this year there is a 300 wssm coming out. Not quite the power of the rsaum or wsm but about 2.5-3 pounds lighter and they'll all work off the same lower.
But basicly the story on AR's is, they're all about the same, the only fully In-House manufacture of AR-type rifles is Olympic arms. The rest just contract others to make parts for them and then they assemble, those "others" also sell parts to any other AR distributor who is interested. Now the distributors buy where they get the best price so thats why RRA uses wilson barrels and J&T uses shaw and so on, other than that you could buy an AR of every make and model and they could be made by the same outfit. hope this info helps
RR
Just checked one the links in my fave folder, check this out
http://www.accuracysystemsinc.com/ar10_supermagnum.html
now if you can buy a custom AR-10 upper in a wssm for 1600.00 I'm sure you can get a lower for less than 600.00, you could buy one stripped and get an AR-15 lower kit then you only have to buy about 3-4 other small parts, thats all that don't interchange, and they're just pins and springs.