Problems with TF 41 Round Glock Mag Extension

[Greg5611]

Just finished a Steel Open Challenge with 20 stages using my JP GMR-15 carbine.  Very frustrated in that 70% of the stages I had failure to feed malfunctions from my Glock magazine with a TF extension (41 rounds).  It seemed like the 3rd round into the stage failed to feed each time so I started to back off and load 3 less rounds into the magazine.  This helped but I still experienced occasional failure to feed.  I was shooting Delta Precision 124 gr JHP bullets loaded at 1.150 OAL.  Anyone have these problems with TF mag extensions in a Glock magazine fed PCC and if so, what is the fix?

[L9X25]

If my recollection is accurate, the follower starts to enter the base pad on the 35th round, so rounds and the follower are

transitioning from the extension to the tube from 41 to 35.  Once there is 35 or fewer, the follower is completely in the tube.

If all of your problems occur with more than 35, take a hard look at the transition areas, if you are having problems with fewer

than 35 rounds too, you may have other problems too, like a bad mag.

[ChuckS]

Make sure there is no plastic slag extending into the mag tube and slightly bevel the top follower edges that may try to catch on the bottom of the mag tube. OAL may be a tad long also.

[alvinsmith75]

1 hour ago, ChuckS said:

Make sure there is no plastic slag extending into the mag tube and slightly bevel the top follower edges that may try to catch on the bottom of the mag tube. OAL may be a tad long also.

This is probably it.  I believe this description and fix was on the instructions that come with the extension.  I load a short oal and have not had any issues.

[ChuckS]

Just now, alvinsmith75 said:

--- snip --- I believe this description and fix was on the instructions that come with the extension. --- snip ---

I was going to say RTFB but I am in a gentle mood this morning since I identified my problem with the Russians. 

 

Due to a pudgy RN bullet base, I load to 1.085". It works fine with a ramped and non-ramped barrel.

[alvinsmith75]

14 minutes ago, ChuckS said:

I was going to say RTFB but I am in a gentle mood this morning since I identified my problem with the Russians. 

 

Due to a pudgy RN bullet base, I load to 1.085". It works fine with a ramped and non-ramped barrel.

EXACT oal of my 125 BBI in my Faxon barrel.

[Old3GNR]

Why would you be using 41 round mags for a steel challenge event?

[Greg5611]

Was not a “Steel Challenge” but the Berry’s Steel Open.  Kind of a USPSA format but steel only.  20 stages 600 rounds.

[ChuckS]

17 minutes ago, Greg5611 said:

Was not a “Steel Challenge” but the Berry’s Steel Open.  Kind of a USPSA format but steel only.  20 stages 600 rounds.

Fun match, wasn't it? I was RO on stage 2...

[Greg5611]

Yes, I RO’d stage 5.  Fun time.

[Snopczynski]

What is your OAL OP?


Sent from my iPhone using Tapatalk

[Greg5611]

1.150

[Snopczynski]

Check the length of your extension. I have a buddy who had this problem and had to start loading to 1.125” because his rounds were getting wedged in the extension. He was loaded at 1.135”

 

is your extension pladtic or aluminum?

[Greg5611]

Aluminum.

[L9X25]

Mine is aluminum and works fine with 1.170 

[alvinsmith75]

Is there any reason as to why people load such a long oal to begin with?  I only ask this because after shooting CZ's and Faxon I have to load short(1.085 and 1.075).  My guns run flawlessly, no mag issues, and my loads have run flawlessly in several other guns.  Plus I get to use less powder to make the same power factor as people loading longer.

[L9X25]

I did not have a press set-up to load 9mm, so I was purchasing the (WWB) Winchester White Box 200rd bulk packs to see if I would like to continue shooting PCC.  

The rifle ran perfectly with it, so when I dedicated a press to 9mm, I started by duplicating the WWB ammo.  To my surprise, it was loaded at 1.170 OAL.  I thought SAMMI was max at 1.160", but I was wrong, it is 1.170" for that bullet profile.   IMO, the longer the round, the closer to the chamber that it is and the better it will feed in the gun.  Obviously, the round has to fit and work in the magazine and chamber,  but longer is usually better as far as feeding in the gun is concerned.  

 

I am now shooting a different projectile, and load shorter out of necessity, but can attest that the extension ran over 1,000 of the 1.170" without issue.  

 

 

[Greg5611]

Conflicting advice, most suggested shorter OAL.  I think I will try an experiment,  I did file off some “slag” in my Glock mag.  I will rerun some 1.150 and reprocess a 100 rounds to shorten them to around 1.060 OAL.  See if there is a difference.

[L9X25]

I don't think that OAL will have much to do with your problem unless you get over 1.170".  

 

You problem is likely in the transition and you may have solved that. 

[MikieM]

Sometimes the polymer on the inner bottom of the magazine will scrape off at the inside corners. Over time this can build up and slow the follower enough to reduce spring tension and inhibit proper feeding. This was especially true with MBX extensions.

Clean the bottom inside corners really well at least a half inch up, or so. Down to bare metal if necessary.

 

Like L9 said. It isn't an OAL problem. These extensions are just tight on space.

Edited April 12, 2018 by MikieM

[1911luvr]

I don't think that OAL will have much to do with your problem unless you get over 1.170".  
 
You problem is likely in the transition and you may have solved that. 

It will if you use it in an ETS mag. The mag inside diameter is tighter and lead or coated projectiles can drag in the mag.


Sent from my iPhone using Tapatalk

[L9X25]

I run 2 ETS mags and the 1.170 FMJ  115's work fine, even with a 56 rd extension.

[1911luvr]

I run 2 ETS mags and the 1.170 FMJ  115's work fine, even with a 56 rd extension.

Yes, FMJ’s aren’t the problem. Lead or poly coated lead projectiles seem to have an issue with dragging on the plastic magazine housing. It usually happened once the spring tension relaxes, somewhere passed half way through.


Sent from my iPhone using Tapatalk

[AndrewGK]

I had two new TF extensions which exhibited similar problems intermittently. I started with manually filing the internal base of each magazine which helped a little but didn't quite do the trick. After that i took the follower and LIGHTLY filed any sharp corners, especially at the front and back of the follower, and haven't had issues since.

[Greg5611]

Thanks Andrew!