Met a guy on Armslist who wants to trade his AR build for my R700 AAC-SD .308.

I'm looking for another AR as I never get to the range with my Remington, nor do I want to spend a $1 a bullet.

My issue is, I don't know much about his build. He says it is a LAR skeleton lower, nickel boron bolt carrier, and colt 6940 1x7 barrel.

However, from my very rough understanding the 6940 requires a proprietary barrel nut, the barrel extension and gas tube are also unique to the 6940??
Apparently only the barrel is from the 6940, the rest of the upper he simply describes as "milspec." If so much of the barrel is proprietary to the full 6940 upper, would it be possible to do just the barrel on a stock AR upper without a botch job?

I want to make sure I'm not trading for some hobbled together AR with parts that aren't supposed to fit together jammed into place.

I personally wouldn't trade a nice gun for a build from someone I don't know.

Yeah me either, you're better off selling the gun for cash, using the cash to build an AR correctly.

Yup.

Always trust your gut. If you think something seems "off" then it more than likely is.

Yeah I think you'd be coming out on the short end on that one.... LAR are ok but nothing special per se.  A 6940 barrel had to bave come from another rifle, and NiB name-brand carriers are $200ish, so unless there is a Geiselle trigger and a UBR stock and nice FF handguard you're better off trading for a complete, name brand rifle of comparable value to your 700.