WTB 18" or 20" 6.5 Barrel with Rifle-Length Gas System

[RebelLibertarian]

Howdy, I'm new to the 6.5 world and looking to buy an 18" or 20" barrel in any 6.5 chamber (.264 LBC, 6.5 Grendel, &c.) for an AR build. I'd really prefer a rifle-length gas system for reliability, especially with an adjustable gas block.

Thanks,
Caleb