I'm currently looking at the Black Dog web page for the Gen III 32 round magazine. I'm confused on a few things that's in the description.

First off, I'm wanting to build a dedicated 22 building using Milspec Aero upper and lower receivers with a Right to Bear Arms dedicated bolt and barrel.

I'm curious if this magazine will A) fit my reciever set up and B) work with the .22 conversion setup. It doesn't specifically mention this in the details.

There is a reference to a Catch22 device, but the link only takes me to the homepage. What is the device that they are speaking of?

The magazines will fit a standard AR-15 magwell and work with a dedicated 22LR bolt/barrel assembly, or a conversion.  The Catch22 is a LRBHO device that will lock the bolt back after the last round.  If having LRBHO is not an issue for you, just ignore that part.

They work great with my PSA lower, RTB complete upper. Buy them.

Is this what your are talking about?

That is what he is talking about.  The ARCatch22 site warns that the BDM magazine may not actually work the Catch22 though.  https://arcatch22.com/

That magazine is the gold standard for AR22

RCA

Hi! Alex with AR Catch22 here.

We had originally been working with BDM on that Gen3 design, but it ended up falling short of working properly with the Catch22.

The spring tension is too weak and the follower doesn't stick up high enough for a true LRBHO. Here's a video of the function: https://www.youtube.com/watch?v=ZbsCT7D-k0k

Personally I recommend running S&W 15-22 mags with a shim in a .22lr setup as it'll give you the most consistent LRBHO. https://www.youtube.com/watch?v=IVyvr_Ra2eE

Weak spring tension seems to be a common issue as the new CMMG magazines have the same issue. I know @Renaissancemann has replaced the CCMG mag spring with a S&W 15-22 spring and that combo seems to work.

Yes a fully functioning LRBHO with BDM magazines would be nice, but as long as I can still manually lock the bolt back with the Catch22 I will be fine.

Yeah, swapping the CMMG spring for a 15-22 one works great. The main challenge there is that it's super hard to find standalone 15-22 springs for sale.

As far as manually locking the bolt back though - that's not mag dependent so you'll have that functionality with whatever you use.