At the risk of coming across as a "smart ass," I'm going to suggest stronger thumbs are needed to load the magazines in question.
They use the same magazines and very difficult to fill! There are dozens of speed loaders for pistols but none that work on the .223 sized mags.
The 4 Best Rifle Borescopes ? Bore Scope Reviews 2023
https://www.reloaderaddict.com/best-...-scope-review/
What entities would have old NOS replacement 99E barrels?
Due to lousy 300Savage round availability, I thinking of buying a .308Win,, chambered
25 round .22LR magazines for .223 conversions or .22LR uppers.
Red, more info as to manufacture. I have CMMG for my drop in.
S.A. Boggs 05-08-2024, 10:07Sam