I’d like to take a large frame Glock subcompact and turn it into a 19x style gun that will run full size mags but with an abbreviated barrel.

I have a 29 and I use full size mags in it when hiking with Xgrip or similar gap extender but I was curious if there was an actual frame available.

I can’t find one from Poly80 or Lonewolf but was wondering if I’m missing someone.

Unless I'm misunderstanding, this should work:
https://www.armorally.com/shop...45-pistol-frame-kit/

You either cut down the dustcover (rails make that easy), or you buy a threaded barrel, and add a comp.