How reliable are 33 round Glock mags?

stephen426 · October 23, 2020, 11:04 AM

I just got an AR-9 from Diamondback and it takes Glock mags. I got to try it out at the range last weekend at our practical shooting club. It was able to easily hit the steel from 25 yards aways with the Crimson Trace red dot I put on it (didn’t have time to really shoot for overall accuracy as we were running drills till the end). Mine is of the 7.5 inch barrel variety with the “forearm brace”. The gun ran flawlessly from the first round and recoil was obviously pretty tame given it was standard 9mm. The factory trigger leaves a lot to be desired (I’m a trigger snob) so I have a CMC PCC trigger coming soon.

One of the members is a trainer for the Miami-Dade police department. He mentioned that the high capacity mags for Glocks are not reliable. He had no issues with the gun, but he told me to buy some 17 round mags since those are much more reliable. I haven’t been able to find much info on the mags being unreliable. Are some mags better than others or are all 33 round mags for Glocks unreliable? Please share thoughts and any actual experience. Much appreciated.

Shadow9mm · November 7, 2020, 07:04 PM

In short, get one and try it. It may work in your gun it may not, only one way to find out, its worth a try,

Long answer
I have shot 33rnd mags a handful of times in both glock pistols and ar pistols. I never had a failure in a glock pistol. In my buddies high end AR pistol we had issues, which I don't think were the magazines fault. The 33rnd mag would feed round nose fine, but 147g flat nose would not feed. the flat nose fed hi and hung up on the barrel extension and failed to feed more than a couple rounds at a time. the magazine itself fed just fine. We did not try any HP ammo. the 15 and 17rnd mags we had fed the flat nose fine. not sure what the issue was.

FITASC · November 7, 2020, 07:42 PM

My 32 rounders work well, even in my Ruger 9mm PCC

jmr40 · November 7, 2020, 08:05 PM

I've had 2of them for years and use them quite often at the range in a variety of Glocks, G26, G19, and G17. Never had a failure of any kind

jmhyer · November 7, 2020, 11:58 PM

I've never had an issue with the Glock-branded ones that I own. I can't say for sure, but I have read that the Asian-manufactured ones can be less reliable.

Jim Watson · November 8, 2020, 10:57 AM

The PPC shooters I see at USPSA and IDPA seldom have trouble with their 33 round Glock magazines, or even the aftermarket.
As said, they are not very expensive, try for yourself.

stephen426 · November 8, 2020, 11:02 AM

Thanks for the replies guys. The Glock branded mags are about $35 a piece, which is almost double some of the other brands sell for (on sale). I may get a few Glock 17 rounders as a last ditch back up, but I now have 8 of the 33 round mags. I have SGM and KCI brand mags right now and they have worked fine so far. I haven't done extensive testing due to the cost and scarcity of ammo, but I have run 2 full mags of each brand.

My cost average for 9mm is about $12/box of 50, but I could be selling them for close to $50/box. Hard to shoot too many rounds knowing the market value of ammo right now.

Double K · November 8, 2020, 11:13 AM

I have one for my home defense Glock 19, glock brand, I can't think of a better mag to have in a gun on the nightstand. It's never jammed, I shoot it often. There could be some serious restrictions on high capacity magazines in the near future, either sell them now or get ready to turn them in. Beto doesn't approve of them.

Onward Allusion · November 8, 2020, 11:52 AM

Never had problems with OEM 33 round Glock mags. The Asian 33 round mags work fine with brass rounds. Not so much with steel cased ammo or full length FMJ. Steel cased rounds will seize inside the mag.

One thing to note with these mags. When they are totally fresh, they will work fine with 26, 19, or 17. As they get older, the springs wear a little and will be impacted by cycle speed of the slide. I originally got a crap-load of them for my TNW Aero and it work GREAT in it because the cycle time is slow due to the buffer tube set up.

October 23, 2020, 11:04 AM	#1
stephen426 Senior Member Join Date: March 11, 2005 Posts: 3,840	How reliable are 33 round Glock mags? I just got an AR-9 from Diamondback and it takes Glock mags. I got to try it out at the range last weekend at our practical shooting club. It was able to easily hit the steel from 25 yards aways with the Crimson Trace red dot I put on it (didn’t have time to really shoot for overall accuracy as we were running drills till the end). Mine is of the 7.5 inch barrel variety with the “forearm brace”. The gun ran flawlessly from the first round and recoil was obviously pretty tame given it was standard 9mm. The factory trigger leaves a lot to be desired (I’m a trigger snob) so I have a CMC PCC trigger coming soon. One of the members is a trainer for the Miami-Dade police department. He mentioned that the high capacity mags for Glocks are not reliable. He had no issues with the gun, but he told me to buy some 17 round mags since those are much more reliable. I haven’t been able to find much info on the mags being unreliable. Are some mags better than others or are all 33 round mags for Glocks unreliable? Please share thoughts and any actual experience. Much appreciated. __________________ The ATF should be a convenience store instead of a government agency!

November 7, 2020, 07:04 PM	#2
Shadow9mm Senior Member Join Date: March 21, 2012 Location: Indianapolis, IN Posts: 3,973	In short, get one and try it. It may work in your gun it may not, only one way to find out, its worth a try, Long answer I have shot 33rnd mags a handful of times in both glock pistols and ar pistols. I never had a failure in a glock pistol. In my buddies high end AR pistol we had issues, which I don't think were the magazines fault. The 33rnd mag would feed round nose fine, but 147g flat nose would not feed. the flat nose fed hi and hung up on the barrel extension and failed to feed more than a couple rounds at a time. the magazine itself fed just fine. We did not try any HP ammo. the 15 and 17rnd mags we had fed the flat nose fine. not sure what the issue was. __________________ I don't believe in "range fodder" that is why I reload.

November 7, 2020, 07:42 PM	#3
FITASC Senior Member Join Date: December 6, 2014 Posts: 6,446	My 32 rounders work well, even in my Ruger 9mm PCC __________________ "I believe that people have a right to decide their own destinies; people own themselves. I also believe that, in a democracy, government exists because (and only so long as) individual citizens give it a 'temporary license to exist'—in exchange for a promise that it will behave itself. In a democracy, you own the government—it doesn't own you."- Frank Zappa

November 7, 2020, 08:05 PM	#4
jmr40 Senior Member Join Date: June 15, 2008 Location: Georgia Posts: 10,808	I've had 2of them for years and use them quite often at the range in a variety of Glocks, G26, G19, and G17. Never had a failure of any kind __________________ "If you're still doing things the same way you were doing them 10 years ago, you're doing it wrong" Winston Churchill

November 8, 2020, 11:02 AM	#7
stephen426 Senior Member Join Date: March 11, 2005 Posts: 3,840	Thanks for the replies guys. The Glock branded mags are about $35 a piece, which is almost double some of the other brands sell for (on sale). I may get a few Glock 17 rounders as a last ditch back up, but I now have 8 of the 33 round mags. I have SGM and KCI brand mags right now and they have worked fine so far. I haven't done extensive testing due to the cost and scarcity of ammo, but I have run 2 full mags of each brand. My cost average for 9mm is about $12/box of 50, but I could be selling them for close to $50/box. Hard to shoot too many rounds knowing the market value of ammo right now. __________________ The ATF should be a convenience store instead of a government agency!

November 7, 2020, 11:58 PM	#5
jmhyer Senior Member Join Date: June 19, 2012 Location: MS - USA Posts: 899	I've never had an issue with the Glock-branded ones that I own. I can't say for sure, but I have read that the Asian-manufactured ones can be less reliable.

November 8, 2020, 10:57 AM	#6
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	The PPC shooters I see at USPSA and IDPA seldom have trouble with their 33 round Glock magazines, or even the aftermarket. As said, they are not very expensive, try for yourself.

November 8, 2020, 11:13 AM	#8
Double K Senior Member Join Date: June 16, 2020 Location: Colorado Posts: 486	I have one for my home defense Glock 19, glock brand, I can't think of a better mag to have in a gun on the nightstand. It's never jammed, I shoot it often. There could be some serious restrictions on high capacity magazines in the near future, either sell them now or get ready to turn them in. Beto doesn't approve of them.

November 8, 2020, 11:52 AM	#9
Onward Allusion Senior Member Join Date: November 17, 2009 Location: Back in a Non-Free State Posts: 3,133	Never had problems with OEM 33 round Glock mags. The Asian 33 round mags work fine with brass rounds. Not so much with steel cased ammo or full length FMJ. Steel cased rounds will seize inside the mag. One thing to note with these mags. When they are totally fresh, they will work fine with 26, 19, or 17. As they get older, the springs wear a little and will be impacted by cycle speed of the slide. I originally got a crap-load of them for my TNW Aero and it work GREAT in it because the cycle time is slow due to the buffer tube set up. __________________ Simple as ABC . . . Always Be Carrying