KRISS mag extensions for G21 (G20) [Archive] - Glock Talk


View Full Version : KRISS mag extensions for G21 (G20)

06-15-2010, 06:11
Anyone out there using these? These are made for the G21 mags (which just happen to be the same as the G20 mags, or so I thought). In any case, two of these things show up and I promptly disassemble two of my stock G20 mags. I had two identical NOS old school LEO ONLY stamped ones so I decided to use those. As I'm stuffing the new spring up into the new much longer tube assembly, I realize the spring is actually rubbing on the inside of the top part (of the stock tube). I figure it'll break itself in and press on. Well, I proceed to stuff 31 rounds of 10mm in there and am very pleased until I try to unload it. About 20 rounds come out as advertised then stop. There were a few rounds that became jammed in the tube at a slight angle. I fish them all out but the follower appears to be stuck. I disassemble the mag and I had to actually pull pretty hard to free the new spring from the old section of the mag tube.

A brief online investigation reveals that there have been a few problems with the new springs rubbing the inside of the older stock mag tubes. OK, I have a brand new, recently manufactured one. I drag it out and same thing all over again and the spring sticks in the new one too; not nearly as bad but still sticks.

Question: has anyone A) used them with any success as intended in a G21 (.45 ACP) or B) done what I'm trying to do and/or can tell me why it's not working here.


06-15-2010, 12:31
KRISS magazine extensions are designed and intended for use in the G21. You installed a KRISS mag extension in a G20 magazine and it failed. That has a lot to do with the follower design.

I talked with KRISS regarding this subject. I was informed they intend to introduce a 10mm kit late this year. If you do not want to wait for the kit you will need to work the bugs out of your current follower. Look at the difference between the G21 follower and the G20 follower. Try to modify the G20 follower to resemble the G21 follower and you will have a good start.

06-15-2010, 12:36
The follower doesn't *appear* to be the issue. The actual spring is what's hanging up. IOW, the OD of the coil of the spring is ever so slightly larger than the ID of the factory mag tube.

My original thoughts were that if the G20/G21 factory mag tubes were the same except for the holes in the back, it should work. Am I missing something else?

06-15-2010, 12:45
Standard G20/21 mags use the same spring (#448) in Gen 1/2/3 magazines.
Current SF mags (and a few gen 3) use a special spring called the wide base (#1300) designed for use with 1304 (#1,2,3 followers).
I discussed this issue with the KRISS crew. They informed me the only requirement was a new 10mm follower.
If they are aware of the difference, this means I do not have to make one. I guess I am content to wait for them to develop it for me.

06-15-2010, 12:54
OK, thanks for the help. I guess I'll just contact them and explain the spring issue. It has three very distinct OD changes, maybe the ones I got were just made a little large in error.

06-15-2010, 14:44
Maybe they changed the design? Maybe they plan another change? All I know is the 10mm is finally on the drawing board.

I can tell you this much: The KRISS system is excellent for use on G21 mags..... Should be great for G20's as soon as they make the modifications.