I noticed that my Glock mags for my .45 JR carbine weren't always feeding reliably when fully loaded, but never had an issue with my JRC factory mag. The 'bad' mags still had original springs so I ordered some Wolff +10% xtra power springs. But they weren't much heavier or longer than the stock .45 springs, so I ordered another set directly from JRC. Those JRC springs are much heavier and approx. 2 to 3" longer than stock or Wolff. I wound up using the Wolff springs in my G19 mags since Wolff sells the same replacement spring for G19 (15 rnd 9mm) & G21 (13 rnd .45). In the G19 it's a pretty significant upgrade but about the same in a G21 mag.