Glock 21SF issues...

[Musubi1000]

Did you check the FP channel? If it were just the FP spring you would have solved the problem completely. Since your mom had a light strike I would still inspect it. If it is clean I would then check the FP block and trigger bar to ensure the trigger bar is moving squarely to the FP block. Remove and inspect the FP block to make sure it is a stock unit. The titanium ones can wear out and cause light strikes. Good luck.

[Bill Steele]

Did you check the FP channel? If it were just the FP spring you would have solved the problem completely. Since your mom had a light strike I would still inspect it. If it is clean I would then check the FP block and trigger bar to ensure the trigger bar is moving squarely to the FP block. Remove and inspect the FP block to make sure it is a stock unit. The titanium ones can wear out and cause light strikes. Good luck.

I agree, grip has nothing to do with light strikes.

[kenl]

OP, good that you fixed the light FP strike problem. Failure to eject? I bet the previous owner installed a heavy recoil spring. Try swapping in an ome spring.

Good luck

[fritztkatt]

Detail strip and clean everything. Again. Like others have said, light strikes are spring cups, channel, pin, and spring.

Ensure there isn't a burr or otherwise mangled plunger, and that the trigger bar is fully releasing the plunger.

If it still has light strikes, I'd replace the pin.

Is there any way to check firing pin protrusion on a glock? Like an actual go/nogo gauge? If it's a seriously high mileage gun, it could just be worn.

I've heard rumor that the maritime spring cups reduce friction (and trigger pull weight), which should help the firing pin slide. The ghost brand ones don't seem to help during a function check, but did ever so slightly improve trigger feel in my gun after install.

FTEJ is probably from bulk ammo or lighter reloads, compounded with that aftermarket recoil spring.

[Thepug99]

How about getting your money back from seller

[deadcoyote]

I believe the red spring is for running military ammo designed for sub-machine guns in countries that issue sub guns and glocks. I would not recommend using the red spring in a pistol.

Edit to add: After consulting my glock book here the red and blue spring are both for sub gun ammo and are not sold in the United States. I'm sure you could obtain one, as the magic of the inter-webs has essentially made anything possible. I would point out that besides not being a real fix for the problem it would also probably significantly increase the weight of your trigger. Note I say probably, never done it so I don't know, but understanding how the different springs interact to make your pull weight I am assuming it would increase it significantly.