Malfunctioning Glock 20SF

[COinCO1818]

I recently purchased a new glock 20sf and during my first range session experienced the slide locking back after every round. Upon inspection of the pistol the slide catch seems to have proper tension downward onto the frame. This did not happen with all the ammo I tried only with fast 180/ 200 grain Underwood ammo. The ammo is commercial loaded and is supposed to be shooting in the 1300/ 1200 fps range. Is this an ammo related problem or do I need to change to a stiffer recoil spring? I also tried some BVAC and Hyperclean ammo and experienced no trouble. No pressure signs with any of the ammo. A couple of the Underwood cases look like the slide caught them. Thanks for your time.

[dmaxfireman]

Was the malfunction happening with more than one magazine?

[SW-Shooter]

Are you a new Glock handgun shooter? You could be inadvertently pushing up on the slide stop/lock. I'd check mags, disassemble then reassemble. Rule all of the above out then start replacing the recoil rod with something like a Lightning Strike, and go from there.

[misanthropist]

I do shoot a G20sf quite a bit myself although I don't know if that makes me especially qualified to comment here, just throwing it out there, I guess...my inclination is to say that the ammo is the issue. Does it feel noticeably hotter than the other stuff? Is the recoil extremely sharp? I'm just wondering if the slide is slamming back hard enough to move the slide release around.

Another possibility might be that the stiffer recoil is causing your thumb to hit the slide release.

I can tell you that I had a G20 that my gf at the time squibbed and fired, causing an extremely slight barrel bulge that caused the slide to lock back every time. It was tough to figure out and most people insisted on telling me I'd reassembled it incorrectly with the spring on the wrong side of the pin.

But it locked back on every shot, regardless of ammo. Anyway if you think there's any chance you could have squibbed it, you can always check the barrel. That is unlikely to be the problem but I mention it because I have been there.

[Mike from Texas]

Have you field stripped it lately?


Sent from iPhone/Tapatalk

[RiflemanBobcat]

This seems an unlikely possibility, especially in light of your multiple-ammo experiences and reduced problems.
However, I had a "locking back at odd times" issue with my formerly-issued G22C, and I was being *damned* careful to avoid the slide stop and to not "limp-wrist." A department armorer (who's been a shooter longer than I'd been alive at the time) experienced the same issues.

Turned out, the upper locking block pin (not sure if that's the official name for it) had sheared in half. The left side, which was bearing on the top of the slide stop, was missing. I'm about 99% sure it happened at that range session (thank God it didn't happen elsewhere!). It certainly caused some confusing premature-lockback issues, and fortunately the same armorer who test-fired it had a spare handy.

Again, that seems unlikely to be the case this time. But I figured it was worth mentioning just in case.

[R0CKETMAN]

Ensure the tip of the slide lock wire is under the pin.

If so, remove slide lock and inspect wire for propper bend.

Remove slide, insert empty mag, inspect timing/slide stop tab contact.

Remove slide, view slide stop tab while inserting full mag and again once seated.

Have someone video left side of gun while you shoot to ensure you're not riding it.

[R0CKETMAN]

This pic shows the point where the bullet is closest to SS just pior to full insertion on G20sf

http://i57.photobucket.com/albums/g219/rocketmanmtb/71312234.jpg


and now fully seated

http://i57.photobucket.com/albums/g219/rocketmanmtb/68058830.jpg