reconabe,
I too have an M1 with a pistol grip, a CQBSolutions SOP and CQB sling . I agree totally with Tacman that the SOP is very comfortable and works well. It adjusts to my frame like a glove and is impeccably constructed. It also comes with fitting instructions and the web site has frame by frame instructions on how to use the slings. The CQB sling has a narrower strap that hangs a bit better, but not better enough for me to switch from the SOP sling. I bought mine direct and had the slings in two days. Good luck in whatever you buy,
CW
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"As to the species of exercise, I advise the gun."
Thomas Jefferson