Here's a cook book post on the ambidextrous extended mag release from Carolina Shooting Supplies, This thing is so slick and easy to use, anyone can make magazine changes almost as good as Sopmod!!!
It comes with the extended release, a rivet and a cap screw assembly with lock nut (if you prefer it over a rivet) a capture pin to hold the spring in place whit mounting, and a ball bearing to pound the rivet to flare it.
First take a 1/4 inch drill and drill off the flange of the existing rivet. (sorry about bad pic)
Then drive the rivet out of the mag release housing with a punch
Place the old catch and new catch on a pivot pin and mark the amount of excess metal on the area where the catch rests against the trigger guard and where the catch engages the locking lug of the magazine. The new catch has excess so it can be fitted to any AK.
Then file off excess almost to the marks. You will want to do the final fitting with the catch mounted (without the magazine spring mounted in the catch) so you don't do too much. Once it is filed, hit files areas with cold blue.
After fitted and checked with a variety of magazines, then do assembly with spring per the enclosed directions (Why repeat it here?). I tried mine with 6 Circle 10 Bulgarians and 16 assorted Mil-Surp metal mags. All worked, and all cycled several rounds through them after installing the extended mag catch.
I get no kick back on this from CSS. I am posting this because I am genuinely excited about this catch. I am not given over to tacti-cool stuff, rails, etc. I believe in practical, real world stuff that works and serves a purpose. This is heavy duty, mil-spec, and I would bet my life on it. THis is the best modfication for an AK I have ever seen! This latch works so well, I am surprised the Russians didn't adopt it. It makes an "emergency magazine change," as they now call it, much easier to master. Instead of having to hit the magazine release tab with the loaded magazine and timing it just right, you simply push down on the mag release with the trigger finger and slap the empty magazine forward with the loaded one. It does not have to be as exactly placed and timed as it does with the current method. I mastered it with this release in about 5 to 10 minutes tops!