I like the HD (heavy duty) ones from Midwest Industries. HD ones have a much larger "button", and to me are easier to push.
MIDWEST INDUSTRIES, INC. : Heavy Duty Swivel, each (100-003-224) - World's Largest Supplier of Firearm Accessories, Gun Parts and Gunsmithing Tools
I choose the Midwest Industries, because I used one of thier mounts (so I was sure it would fit). I think many mfgs make these. I've been told everything from they are all the same, to they only work from the same mfg (in my limited experience, this is not true).
The Midwest Industries HD QD I list above fits the original M&P15OR front gas block perfect. I am actually surprised how expensive these are, but they are nice pieces.
The only one I've tried besides the MI one is:
1 1/4 Quick Detachable Sling Swivel - Black Rifle Works
It works, but the "locking balls" are further down the shaft. So it works, but sticks out a little bit, so not ideal. I've always liked Black Rifle Works, but I'm a little annoyed at them as I've asked them several times in e-mail who makes this QD, and although they have offered to refund, they have not been willing to tell me the mfg. I just wanted to know the mfg, so I could start figuring out who's were compatable with who's.
Sorry, that's about all I know. I've been hoping a expert would jump in here and tell us the real deal.
