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Made a 25 round mag out of a 20 Tapco, actually holds 27

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1mlt:
I've been wanting to do this for some time. Considered several ways to do it. Came up with this one.

Started with a regular Tapco 20


Added a damaged 20 that I have (2 of them from my experimenting with the adapter)


Cut the damaged one into 4 parts. The pic is missing one part because it is already in the 25


Cut the bottom 1/2" (or so, actually right across the mold mark) off the good mag. Super glued the top part of the first mag to the smaller "section" cut out of the damaged mag. Then glued the bottom of the original mag to the now inserted section. replaced the unmodified spring and follower and slid the floor plate back on. Look very close to the bottom 1/4th you can see the seams. If you do this, you MUST clean up all the "slag". The edges have to be smooth, straight and square. Be sure the follower slides easily before you glue up everything. And if you do it all correctly, you end up with this:


Side by side comparison


And last a 20 round mag on top of the 25 (27actually) round mag. I'm going to take the 25 round mag apart and make a real one, now that I know my dimensions work


I wanted to do this so I could carry 6-25round mags=150 in those AR mag pouches that hold 6 mags, instead of 6-20mags=120. One scrap mag will yield 3 inserts and one bottom in case you mess up one. I did it this way because the follower never gets below the insert. I figured if the follower doesn't go below any of the glued seams it can't hang up on the way up as the gun cycles. It hand cycled fine. I'm going to make one more and go to the range and see how they run. I may glue a piece of flat polymer on the outside of the mag as reinforcement. I'll give you guys a report afterward.
Marcus

martin08:
I can't count past thirty....   :cry:

Lollygagger:
On my Tapco 20's, I commonly trim my follower bottom & "spike" in the floor plate lock to have them load & feed 22 rounds reliably -that is, load 22 rounds and lock in the action with the BOLT FORWARD.

I looked at the mag, and I'm pretty sure that a max trim on the follower & dropping the floor plate locking piece out (securing the floor plate otherwise)...would yield 24 rounds, if that mattered.

I did not go beyond opening up to 22 rounds as the amount of material needed to be trimmed seemd a bit much -and, the stresses were increasing a bit over proportionally (I played around with the mag -as I have done others like the cobray in the past).

The *added chunk* is a workableapproach if a fella just has to have the rounds. This was a approach worked out to make hi-cap AK74 (bakelite) mags (over 30 rounds) some time ago.

Jus' a little history.

LG :? (some will recall that I did the opposite with a Promag duckbill -making a short mag out of one)

martin08:
I'm wondering how well they will hold up over time and spring "fatigue".  I'm sure that the mags were designed to incorporate some loss of extension on the spring after a certain number of loadings....

... your thoughts, Marcus?

1mlt:
I honestly don't know. It seems to function fine right now. I don't think I'm as worried about the spring as I am about the mag coming apart. I doubt the spring is compressed any more than at 20. I really did this just to see if it could be done. Also, the 5 extra rounds make the mag heavy. After doing this, I think I'm going to stick with 20.
Marcus

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