Do you live in one of the socialists states that have a 15 round mag limit?
We have a guy in Jersey making legal, 15 round AR mags, $20.
They are 20 round boxes permanently modified. You can't take them apart for cleaning. Really not that big a deal, just compress the follower and load it up with Brakleen etc
And I figured out how to permanently modify a S&W M&P 15-22 mag into a 15 round limit.

I recently got a non New Jersey compliant AR.
AR's are tough to come by here, especially Jersey legal versions. Jersey has the stupid evil features statue. Most of the dealers in the area tell you a 2 or more month wait.
One of our dealers out in the backwoods has given up getting stripped down or fake AR's (bushmaster's version) and gets whatever he can. Then sends them to a gunsmith to make Jersey legal.
I walked in there few weeks ago with a list of 6 AR model part numbers I was interested in.
Turns out #2 on the list was sitting in the rack, already modified and waiting for a sale. The original purchaser ordered it, waited 8 weeks, had it modified - and then didn't pass the NICS check.
Yeah!
The top AR is one of the evil ones, M&P 15, "detachable box magazine" with - pistol grip, flash suppressor, adjustable butt stock, +15 magazine (30).
The armorer replaces the suppressor with a comp and pins it. Pins the butt stock in the position you want, permanently alters (meaning the floor plate is pinned) the P-Mag 30.
Really opens the realm of possibilities for us.