Model 1 Sales made a pair of custom 10.5" x 8" twist 300 Fireball barrels for me. I made them into left and right hand pistols using Stag arms uppers and Spikes Tactical pistol lowers with GSE pistol buffers. The gas ports are in the standard "pistol" location and use the pistol gas tube and low profile gas blocks from M1S. I got them in about six weeks but that was last year before the post election panic.