Carpenter-1
Member
Look for a sling mount to fit the tube. Like to buy one for a decent price that i don't have to modify.
Midwest Industries Rear Sling Mount Adapter Ambidextrous Loop AR-15 Carbine Aluminum Matte - MidwayUSA
This is the best rear mount I've found for the 15-22. You just have to remove the butt stock and slide this over the rear "buffer tube" and tighten the bolt down. Easy. It's tough and extremely well made. No modification required. Fits nice and tight so you'll never have to worry about it moving.