I purchased a G21 Gen 4 last September. I took it to the range and ran about 2000 rounds of ball without a hiccup. Every January, I cycle all my duty ammo and get new stuff (I have several other guns that have duty ammo). My G21 ran steel, aluminum and brass ammo but I got failure to feed (FTF) from my Hornady Critical Duty, Federal HSTs, Winchester PDX1's. Every other round nose dived in my magazines or caught under the ramp of the barrel. I took it to my gunsmith and he polished the ramp. I still have FTF's, just not as many. My G21 does well with Federal HSTs, Remington Golden Sabers and Speer Gold Dots at the moment. I have no luck with my Hornady Critical Duty. I won't carry my G21 in public (as I'm not confident I won't have a FTF at the wrong moment). I'm still researching the possible causes. I've got five Glock OEM 13 round magazines (no modifications). Any thoughts? Thank you in advance.
Polishing a feed ramp will not help a nose down in the mag
problem, the round has not got to the feed ramp yet.
I have that problem with the more powerful loads too and
other jams also with most Glocks I have owned.
I think there is too much slide speed and the mag spring
can't keep up, holding the gun very tight with a very stiff
arm I believe also causes that.
It makes the slide run faster and more violent.
Things that can usually help in combination or by itself,
adding weight or a comp to slide and or barrel,
stronger magazine spring,
not holding the gun too tight and with a stiff arm.
With an auto pistol it's a balancing act, you have
to keep the ammo within the design limits of the
gun or change the limits of it's design for different
loads, be they weaker or stronger loads.