Glock 20 Gen 4 failure to feed Underwood 180 TMJ

[G20g4]

Been to the range and 3 of the 4 boxes fed fine. No jams, last box had multiple jambs. Fired one box of 165 TMJ zero failures. Maybe it is breaking in or got a bad batch. Will definitely continue to shoot Underwood ammo.

[mt10mm]

Been to the range and 3 of the 4 boxes fed fine. No jams, last box had multiple jambs. Fired one box of 165 TMJ zero failures. Maybe it is breaking in or got a bad batch. Will definitely continue to shoot Underwood ammo.

Hope it all works out for you, keep us posted.

[chucky2]

Count me in as another who has FTF issues.  I've had it since I first got it new from dealer (GSSF order) March '13.  Happens with off the shelf ammo, Underwood, PBR Premium 165gr, and with .40 Winchester from Walmart (100 rd box) with my .40 KKM conversion barrel.  Decided to just send it back to Glock last week while I still have remaining warranty, let them screw with it.  I'm wondering though if I could have just order 3 new mag springs and solved the problem...who knows...

[G20g4]

It appears I had a bad batch of 180 TMJ I reported it to Kevin which lot # I had no problems with and the one I had the problem with. I shot all the ammo, he would have replaced what I hadn't shot. Have had no problems with the 165 TMJ so will continue to shoot that until he has 155 TMJ in stock. Thanks for all the help everyone.

[PandaBear]

I don't have any issues with FTE with my stock Gen 4. Only experiencing lots of FTFeed with the last round of all 3 of my blocked and pinned magazines (15 to 10 round). I've only used Underwood 165 TMJ and Underwood 180 TMJ. I finally bought a 10 round magazine so I hope my problems will go away.

[Intercooler]

When you say bad lot of 180's. Bad how?

[Gviz]

Just thought I'd give a little update here.  I bought my G20 gen4 a few weeks back, shot it the day of with 40 rnds of 200 grain pmc bronze.  I had 3 FTFs on the very last round.  I had loaded the mag with 10rnds 4 times.  Did some reading on here, saw some guys having similar issues and suggested changing out recoil springs and such but before I did all that I wanted to test mine some more.  I ordered some 180grain HP XTP from Underwood since that is what I wanted to keep in the gun for defense.  This go round I loaded the mag 3 times to capacity of 15 rounds and only had one FTF... the very last round on the very last mag.  So for now Ill probably leave the gun as is and try some Underwood 180 TMJ in the future.

[Mtnfolk75]

  What was the Lot # of the Underwood 180 TMJ's that gave you problems?    I have a Gen 2 Glock 20 and also have problems with Underwood 180 TMJ's.   I have shot 50 rounds of Blazer & 20 Corbon 165 with stock RSA, no problems & no Smiles.  Heard about the stronger spring needed for Underwood so I ordered a Wolff 22lb and a Stainless Guide Rod. 
  Next session with the new 22 lb uncaptured spring, I shot 50 American Eagle & 50 Underwood, alternating by magazine.   American Eagle was flawless with the 22 lb spring.  Only got through 30 Underwood with 7-8 FTFper magazine.  Didn't have the stock RSA with me so went home & changed it out.
  Came back to the range & tried the other 20 Underwood with the stock RSA, same problem.   Finished the 20 Underwood 180 TMJ's along with 10 Buffalo Bore 155 Barnes using the stock RSA. The BB 155's ran flawless, but did shoot low & left by about 4".  8 of the 10 BB 155's had Major Smiles.   FWIW, all the other stuff shot to POA at 15 yards & no obvious Smiles.

Any suggestions?

[Gviz]

Forgive me if this is a noob question/suggestion but, maybe the problem is more with the mag springs than the RSA? Maybe stiffer mag springs are needed? 

[TheOtherMike]

Interesting thread, but has some apparent derp here & there.

Regarding spring wear: Someone already correctly mentioned that cycling a spring is what wears is out, not static loading.

Regarding RSA (Gen4 I think) and handling all loads, weak to strong: Sounds highly suspicious. Hope it works for you.

Regarding frame flex with a stock/light RSA: The case is (should be) already extracted by the time the slide is all the way back. Thus any flex upon slide/frame impact cannot affect extraction.

Regarding stock/light RSA and smilies [I am speculating a bit here and would appreciate thoughtful feedback]: All slow motion video of a round being fired clearly shows the bullet exiting the barrel before the slide begins to move rearward. I suspect that once the bullet exits the barrel, the pressure within the barrel drops significantly. I propose that since the pressure drops, the only time a smilie is produced is while the pressure is high and the bullet is still in the barrel. And since the slide has not moved while the bullet is in the barrel, the RSA strength is not a factor in the occurrence of smilies.

For the record, I have a G20SF (almost 1 year old) and have fired most, if not all, of the ammo mentioned thus far in this thread without issue using the stock RSA. No smilies. No FTF. No FTE. I am not suggesting that nobody else is having issues, but I do suspect user mods have unforeseen consequences and mags/mag springs are often overlooked (also recently mentioned).

So, in summary: user mods and mags/mag springs are likely culprits.


And as a 10mm newbie, I am curious about the accepted practice of replacing the stock RSA. Is there some body of evidence and analysis that indicates it is necessary, or just speculation?

[I may sound a bit like a jerk, but I am seriously trying to learn.]

[4949shooter]

You will know you need a heavier weight RSA if you have malfunctions with hot ammo fired, but not with low powered or medium powered ammo.

Other than that, some guys use the heavier springs because thy feel the extra weight helps keep frame battering down to a minimum with the hot ammo.

[G20g4]

I don't have the info on the ammo I had trouble with. One particular lot number I had significantly more FTF of Underwood 180 TMJ. Still had a few with the other lot number. I ordered a Sprinco Cor-Bon  recoil system, it does significantly reduce felt recoil however I had more FTF. So I switched to 165 TMJ from Underwood, no FTF with stock recoil spring however many with the Sprico. So I increased the mag springs from Wolf. Helped a little. I sent the Spinco system back. I may try it in the future but the std one not the Cor-Bon. I have ordered 30 boxes of Underwood 165 TMJ now and my 20 seems to like it. Just bought a 29 g4 2 weeks ago. It hasn't had a single problem which is good considering that is my carry gun. I may try a box or 2 of 180s in the future if he is out of 165. My defense loads I am carrying is 135 Nosler. Anyone tested this for penetration? It seems like it would be a perfect round.

[Dave84]

I don't have the info on the ammo I had trouble with. One particular lot number I had significantly more FTF of Underwood 180 TMJ. Still had a few with the other lot number. I ordered a Sprinco Cor-Bon  recoil system, it does significantly reduce felt recoil however I had more FTF. So I switched to 165 TMJ from Underwood, no FTF with stock recoil spring however many with the Sprico. So I increased the mag springs from Wolf. Helped a little. I sent the Spinco system back. I may try it in the future but the std one not the Cor-Bon. I have ordered 30 boxes of Underwood 165 TMJ now and my 20 seems to like it. Just bought a 29 g4 2 weeks ago. It hasn't had a single problem which is good considering that is my carry gun. I may try a box or 2 of 180s in the future if he is out of 165. My defense loads I am carrying is 135 Nosler. Anyone tested this for penetration? It seems like it would be a perfect round.

Raggedyman did testing of the 135 Nosler. It didn't penetrate quite deep enough. 8" I think is what it got. I would recommend 155 gr or 165 gr.

[G20g4]

I have some Underwood 155 gr XTP so I staggered the mags with some of those mixed in, I have seen other tests and the 135 gr penetrates almost a foot with 4 layers of denim.  I am sure I will never need it but over penetration is an issue where I live. I am sure what I have will be plenty. Wouldn't mind having some Underwood Gold Dots. They got 180 gr today and plan to load them next week. I have some Buffalo Boar 180 gr so I am sure it's the same basically.

[4949shooter]

I have some Underwood 155 gr XTP so I staggered the mags with some of those mixed in, I have seen other tests and the 135 gr penetrates almost a foot with 4 layers of denim.  I am sure I will never need it but over penetration is an issue where I live. I am sure what I have will be plenty. Wouldn't mind having some Underwood Gold Dots. They got 180 gr today and plan to load them next week. I have some Buffalo Boar 180 gr so I am sure it's the same basically.

Let us know how the Gold Dots do!