You could try the MDT 223 polymer mag. I have a 350 legend and the polymer mags worked great but your cartridge is a bottleneck so it may or may not work.
Like new Sig P226 with the following upgrades
short reset kit
SiCo threaded barrel
comes with the factory barrel, case and mags
$825 shipped to your ffl
Brand new unfired Spartan Rifles (Bartlein) - 6mm GT barrel
1:7.5 twist
Original contour: 1.250" for 5" then straight taper to 1.000" at 28"
Finished at 27"
5/8x24 muzzle threads
This was not a prefit
$850 shipped-SOLD