I have the parts coming for my high quality decicated 22LR upper.  I need help on what mags to go with for it.  I looked at the CMMG mag $25, and BD Sonic weld with steel lip $20 both of 25 round capacity.  I also looked at the BD Gen 3 30round mag which is $30, and has the SS feed lip. I'm using a Aero precision upper and a CMMG  dedicated Bolt Carrier.  which mag would be best to go with?

That's what I would do if I didn't already have a big stack of black dog mags.

But my black dogs have been great. I don't think I've ever had a magazine related malfunction with those.

Edit: These. https://www.midwayusa.com/product/847319/black-dog-machine-sonic-x-conversion-magazine-with-nylon-feed-lips-ar-15-cmmg-ciener-tactical-solutions-sig-522-rimfire-conversions-22-long-rifle-polymer-smoke Haven't tried the metal feed lip ones.

What is different between the 15-22 mags and BD?

Well you can look them up online and see the physical differences.  I would say, in my opinion, these are the advantages of the 15/22 Mags with the Boonie Packer adapter:

1) 15/22 mags are typically less expensive and abundantly available from multiple vendors with few variations (BD mags seem to have a thousand different configuarations - hard to tell which ones are good to go)
2) The combination of these 15/22 Mags and the Boonie Packer adapter provides reliable LRBHO with standard bolt catch, especially with the CMMG bolt.
3) 15/22 mags are easier to load manually than BD mags

Again, all in my opinion.  Others may not agree with me, but these are the reasons I went in this direction.

I'm with Josh on the Boonie Packer/15-22 mags... the 15-22 mags use a fan fold spring and the follower is guided  by the shouldered "loading" tab... this allows a much better control of the follower than those with a smaller diameter coil spring... the bolt hold open on the Boonie packer uses the AR bolt catch, and saves wear and tear as the follower of the others when they protrude to catch the bolt

I agree about the superiority of 15-22 magazines, they are easier to load and all for a fully functional bolt latch.  Two solutions that permit use of the 15-22 magazine in an AR lower.  Both solutions employ Smith & Wesson 15 – 22 magazines, hold the bolt open on the last round and release the bolt with the same operation as a stock AR. This function may be important to the durability of the firing pin and the barrel breach face.

The BMA is a well conceived and precisely produced solution. In my rifle it does not work reliably with high velocity ammunition and the magazine well adapter can involve getting the magazine past a new hump in the magazine well that regular AR 15 users will not expect.

The Catch 22 is a simpler more direct solution that gave me more reliable function.

Redi-mag Better Mag Adapter (BMA)

The Gizmo
This device requires no modification of a standard AR lower. This was the draw for me; if my experiment with a dedicated 22 LR barrel was going to be a failure, I did not want to modify a lower only to have to reverse the modification later.

An aluminum magazine well sleeve holds a very small bowl to catch that operates off the spring pressure of a stock AR bolt catch. On my Anderson lower, this device was so tight that I could hear the scraping of the anodizing as I pushed it in with an empty magazine.

Its Virtues
Over the course of nearly 10,000 rounds, I operated this device in conjunction with a Rock River two-stage trigger with a full power hammer spring, a Larue two-stage trigger with a full power hammer spring, and each with various reduced power hammer springs. At times I have run Lakeside heavy-duty recoil springs. While I had read about these rifles requiring high-speed ammunition in order to function reliably, my experience, all of it with 16 inch barrels, has been the contrary. My best function has been with standard velocity or subsonic ammunition, and by best I mean flawless.

Problems and Limits
The problem I did encounter with the BMA was a failure to hold the bolt back on the last round of Remington Golden Bullet, Thunderbolt or CCI mini mag. My theory was that the bolt speed was too great and did not permit the chain of bolt catch spring, AR bolt catch and BMA bolt catch enough time to rise and block the returning bolt. This inability to use the really hot stuff was not a great loss to me because the accuracy with high velocity ammunition was much reduced.

In a second build, I re-examined whether I had made the right choice with the BMA. I removed it from the rifle, cleaned it and put it away. It came out looking as if it had been dipped in motor oil and dropped on a beach. The catch itself showed no sign of wear.

The Catch-22 (C22) bolt catch and magazine well adapter

The Gizmo
The C 22 is a bolt catch with a dogleg that allows it to grab the face of the ubiquitous Ceiner/CMMG bolt. The magazine well adapter is a self retaining piece of polymer that looks as if it may have been 3-D printed.

My First Thousand Rounds
I installed the C 22. Over the course of the first 50 rounds (10 magazines) of Aguila SV, I had several failures to hold open. I switched to the worst, most abusive round I had, Remington Golden Bullet, for several magazines and was rewarded with reliable function. I congratulated myself for having found the solution to the limits of the BMA. I switched back to standard velocity and the bolt now held open every time. I can only guess that there may have been some part-to-part polishing happening. My next session of 300+ rounds was failure free.

The C 22 swings through a greater range of motion than the stock bolt catch, so you may notice the release tab sticking out farther. The extended dogleg also means that the release button has less leverage; it feels like a grittier trigger with longer travel compared to a stock bolt catch release tab. That is not a problem in operation, but you may notice it. The C 22 also has a larger hole through the middle of it than a stock catch. IlHondo noted that and made a shim for his. I wonder whether that larger hole was intended as part of the design to confer some benefit.

My third session had a few failures to keep the bolt open, but worse the bolt dropped every time I dropped a magazine, sometimes immediately after I pressed the magazine release, and sometimes just a moment after the magazine dropped. I assumed this was a problem with the C 22, the only new element.

Customer Service Squared
That Saturday, I left an email for customer service at the Catch 22 website asking whether this was a known issue and whether there were any recognized fixes for this condition. My hope was that someone would see the note and give me some guidance when they got into the office the following week. Instead, I received a reply from Alex in less than one hour. He had read and understood my email (I do not consider this a trivial accomplishment given the difficulties so many have with online communication) and had questions about the operation of my rifle and the appearance of the bolt catch.

You might imagine that the bottom of a CMMG bolt is a simple 90° turn with a sharp edge. It isn’t. Instead, there is a very small bevel between the bottom of the bolt and the bolt face. That tiny bevel had its mirror image impressed at the top of the C 22 bolt catch. When I was dropping my magazine, the bolt catch was dropping like a too aggressive trigger job and releasing the bolt. I tried it with each of my magazines with the same result; if I could get the bolt to hold back after the magazine dropped, the bolt would drop as soon as the rifle was bumped. If I engage the catch manually, I could easily push it in far enough that it would hold the bolt safely.

Alex asked me a number of questions over the course of a couple of emails. This was not only a person who understood the bolt system and how the C 22 interacted with it, but who was reading the responses and thinking about them before he responded. He posed a basic question, “have you tried it with other magazines?”. Of course I had! I tried it with the other magazines I always use. Only then did it dawn on me that the first diagnostic step of trying a different magazine isn’t satisfied by trying a different magazine with exactly the same wear.

I thanked Alex for spurring this epiphany and let him know that I would buy a new magazine to test the Catch 22. At this point I was genuinely thankful to have someone who understands this system take the time to understand the problem and suggest a solution, and over a weekend no less. Alex wrote back that he would send a replacement Catch 22 so that I would have that to test as well. I made mild protest that I am not owed a new part where the original part may not even be the problem, but he assured me that that isn’t a problem and that he would be sending the part anyway.

The new Catch 22 and new magazine came on the same day. The new magazine pushed the catch up to solidly hold the bolt. I compared the new magazine to the old magazines, specifically the little orange leg that pushes the bolt catch upward. I detected no difference in the length of the old and new leg. I disassembled an old magazine and the new magazine and reassembled the parts with the following results:
1. Old magazine body + new spring + old follower = failure
2. New magazine body+ new spring+ old follower= failure
3. New magazine body+ old spring+ new follower= good function
4. Old magazine body+ old spring+ new follower= good function

Despite the appearance of the old follower, it must have have been the problem. I used a pair of fingernail clippers and clipped a bit of weed wacker cord to glue to the follower leg. This gave correct function with all of the old components.

I was able to get all of this to the range today for testing. Almost immediately, the little piece of weed wacker cord I had super glued to one of the legs came off, but the others held. The only failure to hold the bolt back on the last round with the new or fixed magazines was with one of six magazines of Remington Golden Bullet. This also happened when the Catch 22 was new. The CMMG bolt has many virtues, but I believe that one of its vices is excessive bolt velocity that makes it difficult for any bolt catch to do its job. The Catch 22 was again uniformly holding open on the last round with CCI standard velocity, Aguila standard velocity, Aguila high velocity, Seller & Bellot subsonic, Federal match and Remington subsonic.

What exactly did this test anyway?

Aside from my analytical failure to function check not just with a different magazine, but a materially different magazine, this tested two things, 1) the durability of Smith & Wesson magazines and 2) Catch 22’s customer service. Smith & Wesson 15 – 22 magazines are very good, but they are not immune to age and wear. More importantly, this episode reveals Alex’s focus on seeing that people are happy with this product.

The BD and CMMG and S&W mags are roughly the same price within a 2-3 bucks. I just have no experience with any of them. Since it seems like the  consensus is the S&W mags are better quality, and tends to have less issues I’ll go with them.

I second the Better Mag Adapter and SW 15-22 magazines. I like how you can use the McFadden quick loader by pulling the follower down and quickly loading it without any extra resistance. I found that without pulling the follower down with one hand while you are quick loading with the other hand that the quick loader would unseat the bullet slightly and put a dent in the copper plating.

I'm personally using both a modified BMA and the Catch-22 since my build is a lefty and the BMA wouldn't work with a left handed CMMG .22lr bolt.

I've found that if I take my time and load only one cartridge at a time (SW15-22 mags), and release the follower, they will alternate noses, and I perceive a better feeding with my CMMG dedicated upper...