10mm fans... Finally a 33round mag that works!!

[Jack-O]

As some of you may know TDI/Kriss had Magpul design a mag extension so the Kriss .45acp SMG could operate reliably with a proper 30 round mag capacity.

http://www.kriss-tdi.com/kriss-store...category_id=12

I ordered two of the extensions to try out and see if I could get it to work with 10mm. This would effectively give all the 10mm fanboys a decent mag for their dream carbines and SBR's. Here's what I did....

Brief overview:
the conversion is a 3 piece deal. A spring, and a 2 piece sleeve that clamps on the bottom lip of the factory mag and locks into itself. The bottom spring support inside the mag is not re-used, but the baseplate does slide onto the conversion even if it does not have a real function in the conversion.

It appears the plastic is identical to the type the Glock mag is made of. There is no metal liner, but that seems to be unnecessary as it has 2 layers of polymer, and the mag body itself is what lock in the gun. Fit in the G20 is perfect with no problems.

I feel it's important to mention that I am in fact a modifying genius, so it's not really fair to compare my works of legend to other peoples.

I ran into some problems trying to get the kit to work on the G20 mags, so I set about with my tools and some common sense and "adjusted" a few things.

First Problem
- the spring is too fat to fit into the g20 mag body without excessive friction.

Solution
-I put the spring into my bench vise and squeezed it so that it was narrower. It doesnt need to go too far, but springs actually bend fairly easily when they are compressed perpendicular to thier intended compression.
You only need to squeeze the fat part of the spring about 2/3 of the way down, as the rest will stay in the body of the conversion add-on and you dont want to mess with the width too much there. There is enough length in the 20 mag to allow for the lengthening that will happen with the sideways shrinkage. Just squeeze it enough to allow free movement in the mag body. test frequently.

Second Problem
-the spring will not quite fit on the g20 follower. Its a WEEEE bit too long and will cause improper feed angle if it's not seated correctly

Solution
- I took a dremel and carved a little notch down in the bottom inside, at the REAR of the follower. The spring now pops in the notch and fits quite nicely. GO SLOW. the notch only needs to be down where the spring will sit, you do not need to make the notch come all the way out.

Third Problem
- The follower gets hung up inside the mag body where the conversion and mag meet. It will feed about 19 rounds then stop and the rest will fall out. The front of the follower is catching on the front lip at the junction.

Solution
- I smoothed the inside front edge of the mag body. There is a 45 degree bevel there stock. Just smooth it even more and give it a nice long angle to follow. A 15 degree would be about right
- Once that was done I put a slight angle on the front of the follower. I just removed the 90's and hard edges enough so it would not get hung up. The lip inside the mag that it was catching on was about 1/8", so I started my angle 1/8"+ from the front and worked it to a nice transition. I also took off any hard angles or corners from the front of the follower. DONT GET FREAKED. the follower in this area does not need to support the round so much that this little bit would sacrifice reliability. You are only smoothing the corner over a bit. It ended up being about a 45 degree angle on the front of the follower.

Note: In part 2 you will note that i put the notch at the rear of the follower, then the front of the follower was hitting. I dont think this was the cause, as I had the same problem before i notched it. If you want to put the notch at the front of the follower, then try it, it may actually help hold the front back a wee bit and further minimized hitting the junction. You will still need the other mods tho.

I have not tried to fire it yet and I am only feeding rounds by working the action by hand. It appears to be operating fine tho. I can get 32-33 rounds into it before my thumb gives out. must get mag loader for this thing.

It's really important to get the spring squeezed down enough. There is some inconsistency with the insides of the glock mags, and you probably should spend a little time smoothing the inside of any bumps, particularly where the metal liner halves has been fused together. There may be some bumps that the narrower 10mm spring has no problem with, but the wider 45 may.

I used a dowel rod to push down the follower and compress the spring a few times before loading. That will help put the coils in place for proper functioning, PLUS it can tell you if it is hanging up on anything.

the provided spring appears to be quite strong so it should help with proper functioning a lot.

I notice that the inside of the liner says it is made by magpul.

Total time to experiment and modify the first one... 1 hour. I got the second one converted and it took about 15 minutes.


Here are the pics of the conversion. Before and after so you get an idea what needs to be done.

Very simple stuff. It can be done with a bench vice and a file or demel. I used all three.

I also added a bit of my favorite silicon spray lube to the inside of the mags. I've started to add this to any mag that I pull apart AFTER i clean it out. It's totally dry, does not attract dust or grime and makes everything work nicely. I recommend it!!


Really big images:
http://img694.imageshack.us/img694/6326/img0008ga.jpg
http://img63.imageshack.us/img63/8153/img00071.jpg
http://img710.imageshack.us/img710/135/img0005dy.jpg

[Jamesb74]

Sweetness. Do you have a range report?

[Jack-O]

couldnt get out today, but I have it planned for next weekend for sure.

These derned things make me want to get a mech tech carbine or one of those add on stock and SBR a G20

[Jamesb74]

All I need is a G20 and would be good to go. I dont think I would want to do this with a G29 but it could happen.

[CaseyJ]

They look very similar to the Arredondo mag extensions I have but mine are only +5 or 6. I thought of doing this but I have no guns that I really wanna run that much 10mm through. maybe if the KRISS came in 10mm!

[Jack-O]

This mod will effectively make a 10mm carbine a possibility!! there is no reason not to make a proper Subgun/thumper that uses 10mm and needs a hi-cap mag now!!

[Zippy]

Ah, the horror, the horror! Wouldn't this qualify as a weapon of mass destruction? Seriously, GREAT posting, GREAT info. Very well done and useful!