Glock 20 recoil spring for hot HC ammo

[mcseal2]

I recently got a Glock 20 Gen 4 handgun.  It feeds the 180gr Fiocchi JHP ammo I've been shooting fine with the stock barrel or the 6" KKM barrel I got for shooting HC ammo.  With the 200gr Underwood HC ammo I got to try it is jamming after the 3rd round with a full magazine.  The slide is coming forward and hanging up about the middle of the case, leaving the round pushed down in the magazine.  I'm guessing from some online research this means I need a stiffer spring?  What would you recommend and should I also change the guide rod?

Thanks for the help.  I am trying to get the Glock set up to carry on some Alaska and other hunts.  I'll be hunting with a rifle, but want to have a handgun also for when I'm fishing or don't have the rifle within arms reach.  I like shooting the 10mm and am lucky enough to be able to shoot it in my yard.  I want to get a reliable set-up figured out to practice with and carry.

[The_Shadow]

Well those HC may be part of the issue.  Can you measure the MEPLAT and the cartridge overall length...
Some of the Wide Flat Nose bullets 0.300" and wider needed to se seated a little shorter to improve the tipping angle as the cartridge feeds from the magazine, and as the case head tries to exit the magazine and start up the breech face...
Are you having the feed issue while racking the slide or as the next cartridge is being fed after shooting and ejecting the empty spent casing?
If it is not feeding the next after a shot it could be related to the slide velocity as well...

[4949shooter]

My Gen 4 G20 and G40 feed the Underwood hardcast loads.

If it's not the bullets as Shadow suggests you might want to try the 24 pound RSA from Glockmeister.

https://www.glockmeister.com/Glockmeister-Stainless-Steel-Recoil-Spring-Assembly-for-Gen-4-20-21-40-41/productinfo/G4SS20CS/

I use it in my Gen 4's and it works great with Underwood.

[mcseal2]

Thanks. The bullets feed fine when I rack the slide. I dont have batteries for my calipers now. I will get some and maybe order the spring too.

[sqlbullet]

Thanks. The bullets feed fine when I rack the slide. I dont have batteries for my calipers now. I will get some and maybe order the spring too.

Probably...

Your magazine is hanging up/too slow to present the round to the top of the mag.  This is why they cycle fine by hand, but not in firing.  First we need to establish if the rounds are hanging up in the magazine at #3 or not.  The fact that it is consistently at that round count makes me think there is some kind of binding.  If there is binding, rectify and test again.

If not....

The higher slide velocity is causing the slide to rebound off the impact abutment at the end of travel, causing it to try to feed from the magazine much faster than with lower impulse data.  As a result the magazine has not yet fully presented the base of the round to the slide face (bolt) and it is slipping under.  Why this only happens with the 3rd round could be due to a number of reasons, and probably is not relevant to the fix.

There are two possible solutions.  Slow down the slide, which requires a stronger RSA, or speed up the magazine with a stronger mag spring.  Or both may be needed, though I doubt it since this only happens relatively rarely (1 in 15).

[mcseal2]

I might not have been clear enough.  It was not only on the 3rd round, it was on the 3rd round and all past that in the magazine.  I think round 1 and 2 may have fed ok just due to the increased spring tension in the magazine with it almost full.  I'm guessing this means the recoil spring is the most likely issue? 

[sqlbullet]

I would suspect the slide is out-running the mag due to rebound.  +10% mag springs, or an stiffer RSA or both.

[mcseal2]

Thanks.  If the recoil spring doesn't do it I'll see about mag springs.  Hopefully this does it. 

[mcseal2]

Well the 24lb spring didn't fix the problem.  Called KKM and they suggested a 22lb spring for the 200gr ammo.  They said the 24lb is best with really hot 220 or 230gr loads.  I ordered a 22lb spring assembly from Glockmeister.  I also have a couple boxes of 220gr Underwood ammo and a +10% mag spring on order from Midway.  Hopefully some combo of these is reliable in my Glock.  I had free shipping on the Midway order so I added the mag spring, it's cheap enough I didn't want to find I needed it later and have to pay more to ship it than the spring cost. 

Shot more of the 180gr stuff and I'm through 3 full boxes now.  I still haven't had a failure of any kind with either barrel with it.  It's apparently just the hot bear loads it has issues with. 

[sqlbullet]

What happens if you just unload a magazine by thumbing the rounds out?  Does the next round pop right up, or do they sometimes hesitate a bit.

[mcseal2]

The rounds pop right out with no hesitation.

The 220gr ammo from Midway came in today.  I tried it and had the same issues with both the stock and 24lb recoil spring.  I put it up and did some work for a while.  Toward evening I got the +10% Wolf mag spring put in one magazine and tried it again.  With the KKM barrel, stock recoil spring, and that mag I got 5 of the Underwood 220gr rounds to feed fine.  I had a buddy show up to borrow a trailer then and didn't get any more shooting done.  Those 5 landed in the 3"x3" piece of cardboard I had stapled up on my target board to shoot at 15 yards, so it was showing promise.  I need to get more shot, probably be Sunday before I can do that.  Helping a friend drag calves tomorrow and it will be a long day. 

Maybe I'm finding a solution.

Thanks to everyone for your help.  I'll post again after I get more rounds fired.

[4949shooter]

I might try a few round through the stock barrel and see if it improves. I realize we aren't supposed to fire lead in a Glock barrel, but you can fire a few through it with proper cleaning afterwards. I have done this without issue.

I also have fired powder coated ammo it has not been a problem in my Glock(s).

[Iceman]

I have been thru all the same problems you are experiencing and have found solutions!  I have a G20 gen3.   Had feed problems with UW200HC.
Tried 22 and 24lb captured recoil springs, no better.  The problem is that the mag spring isn't strong enough to push the stack up with the higher slide velocity.  The 24lb spring aggravates the problem as it returns the slide faster. I have a friend who experimented with all types of fixes and we agree on the solutions.

The +10% mag springs didn't work!   What does work is a 19 or 20lb uncaptured Wolf  recoil spring on a Wolf guide rod coupled with using two G20 mag springs.  The "double spring" mag will hold 12-13 rounds not 15!   I have also tried mag springs from a company that does comped conversions to Glock 45cal (promised friend I wouldn't reveal their name) that work just like the double spring.  Another forum member found success using a double spring from a Glock 19 (9coil).  With the G20 double mag spring I got 50% slide lock back with one round remaining, problem being the follower pops up further and catches the slide lock. The solution is to cut down the little"nub" on the follower that engages the slide stop.


So, with the 19lb recoil spring and double G20 spring  mags with the followers modified my G20 now functions 100% with the UW200Hc and all the other ammo I've tried. The only downside is you lose two rounds of mag capacity.  I am going to try my new Glockmeister +2 mag extensions with the G20 double spring to see if I can find a 15rd solution.


Hope this helps from one who has done extensive testing to fix this problem!

[mcseal2]

Thanks very much, that is sure worth a shot.  I'll give it a shot when my 22lb spring arrives if that doesn't fix the problem.  I'll try the double mag spring with the stock and 22lb springs first since I already have them.  I'm not worried about capacity, the chance of getting more than 2-3 rounds off if I have to deal with a bear is pretty small.  I just want reliability and accuracy for those rounds. 

[mcseal2]

I should add, I tried the factory barrel, recoil spring, mag, stock everything with the 220gr Underwood HC earlier today also, 2 failures to feed in 5 rounds.