I have a used XM177 style upper for sale 10.5" with a permanently attached 5.5" Flashhider. I'm pretty sure it has a 1:12 twist rate. It'll shoot 40grn just fine but key hole a 55grn. I've shot about 1500 rounds though it without any problems.
"L" and "M" on the A1 Upper; Large Button Forward Assist; Bolt and Carrier are marked "Y" with a circle around it.
Not currently interested in parting out.
I would like $ 500.00 shipped USPS Flat Rate. That includes insurance and delivery confirmation, Buyer will have to sign for package upon delivery.
I will not sell to ban states due to the Bayonet Lug.
USPS MO or Discrete Paypal Gift for Payment.
Sorry for the pictures, can email you better ones in needed.