AR10 Handguard kit, Tactical, 15 inch MPN:10TACHGD15-MLOK UPC: 815718022516 The AR-10 Competition Handguard kit is ultra-light and is designed with a slim profile for maximum comfort with minimum weight. The rail features full-length M-LOK attach
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I don't think the rails that fit that lock ring thing have been made for quite awhile
And, if you are referring to pic rails that interface with those slots, it’s entirely possible that those slots are just for cooling, with no provision for attachment of accessories.
It's been a while since those came out and I no longer have the catalog from that time frame. If memory serves correctly those are lightening/cooling vents, not mlok slots. You could possibly make something work with those bit it wouldn't be worth the money and effort in my opinion. The Armalite tactical handguard is very well made, affordable and light. They are also thinner than that fiberglass handguard, it would be a huge upgrade for $200 spent.
I had a JP rail left over from one of my other Jp rifles a mounted it on the 3oclock posistion. It’s ok at best. Good enough for a laser or light I guess