22rfAR’s - bolt hold open devices?

[terryh]

Gents,

I currently use a Booney hill hold open device in a ‘metal’ 22rf AR, which works, most f the time, with the S&W MP-15 magazines as they have the ‘prong’ on the back of the follower.

now looking into the top of a Kriss 22rf AR the other night they have a much simpler modified hold open catch that works with the Kriss magazines and the M&P (think the Kriss magazine had a separate ‘tongue’ that popped up when the mag was empty??). Just and add on to an standard AR hold open (and therefore simpler to run/keep clean etc.)

There is also a ‘Catch-22’ version of the  Kriss simplified item.

So here are my questions:

Does anyone know if the Kriss hold open catch will work in any ‘mil spec’ AR lower?

Is the Catch-22 item basically the same as the Kriss item?

What other magazines for 22rf AR’s are there that will work with hold open devices? Obviously M&P,  Kriss and Black Dog Mk3’s -what others?

Which magazines, other than the Kriss items, look like ‘solid’ AR magazines not the skeleton M&P’s?

Thanks in advance

Terry