Colt 6520 $899

[120mm]

Make sure you have that rail perfectly aligned with the upper, or you're going to have quite a time getting that T1 to properly zero. Honestly however, I would simply get a good rail with solid lockup to the receiver (anti-rotation barrel nut) and simply attach the T1 there. Seems to be what you're going for and doesn't permanently destroy a perfectly beautiful Colt rifle.

Meh, it's just an upper receiver.

I have access to a nice milling machine that would true up the upper.

I hate railed forearms.

[rob_s]

There are any number of options that wouldn't require a fully-railed forearm. Troy TRX Extreme and VTAC Extreme, Apex Machining, Samson and Rainier Evolution, the new Daniel Defense, etc.

I'm actually surprised we don't see more of this. Every month I see guys with optics mounted on top of the carry handle, when in fact mounting forward of the carry handle in a lower 1/3 mount on a free-float handguard would probably be the better solution.

[markm]

I love the strength of the carry handle... it's the skinny, non NFA barrel that I'd have no use for.

[ST911]

I have always wanted a 6520. Next time I'm in the states I may find one, chop the carry handle and mount a piece of rail toward the front of the upper. I like the idea of the combo of permanently affixed BUIS and T-1.

I remember guys doing that in the days before railed uppers. The carry handle was chopped the received leveled and trued, and a rail section was attached to the upper. Quality work did well. Lesser jobs performed as expected.

A friend had his done somewhere in AZ as I recall. Last I knew, it was still going strong.