Allow me to suggest you check out (google) the Ratmag made by z71rat over at the hide. About the same price & excellent work, also.

I have a ratmag for my 10 FLCP-K...a 10 rounder. Believe he makes 'em in 12, 15 and 17 round capacities, too.

Uses existing (factory) bottom metal & a factory Axis/Edge mag (you provide) that is then grafted to one of several types of mil-surp mags depending on your long or short action rifle.

I'm currently waiting on CTD to send another Axis/Edge mag which I'll forward to z71rat to convert for me so that I'll have a couple 10 rounders for my Savage. The first one works so well, I decided I needed another one.