I use a MTP military issue Grab bag. 6 Mags upside down with Gripp tabs uppermost.
Used exactly the same Ammo down style with Chest Rigs and Belt kit for past 25 years. Not that I think my Smith would ever need to be carried in with belt kit or chest rigs nowadays.
thanks guys, but trying to stick with kydex type so i can use it multiple types of competitions sometimes i don't want to drop the mag and rather reholster (extra shots if needed)
Most kydex holders for standard metal M4 mags will take a 15-22 mag.
Personally I use California Competition shotgun caddies to hold my 15-22 mags.while not as low profile as a dedicated mag pouch they do work, retain the mag well and I had some spare. With many shooters going to the more exposed double shell clips you should be able to pick up some second hand ones. California Competition Works Shell Caddy Tactical Shotshell Ammo