I have repeatedly seen requests here on how to turn a factory 8-round magazine into a 10-rounder. Hopefully, this is "sticky" worthy and will answer most (if not all) questions about the process.
Converting an 8-round mag to accept 10 rounds is a fairly simple process and can be done with simple tool. As a basic guide, you will need:
1. A factory Saiga .308 magazine.
2. A ruler or tape measure (calipers work great, if you have them)
3. Something to mark measurements with (pencil, nail, pick, etc)
4. A fine tooth saw (copeing or hack). A dremel can be used but not necessary.
5. A semi-coarse file.
6. A craft / hobby / utility knife.
7. Something to push the follower all the way to bottom (I used the handle of a cresent wrench here).
First - magazine disassembly.
Locate the floor plate and find the square detent hole in the bottom.
Using a nail or like-sized punch, depress the square detent about 1/8 of an inch. At the same time, gently slide the base plate toward the back of the mag body. These can be a bit tight on new magazines.
WARNING! DO NOT SLIDE IT ALL THE WAY OFF YET!
Once you have the base plate about half way off, hold it with one thumb and use your other thumb to put pressure on the plate just below it. (These mags are wayyyyy over sprung and under considerable tension - even unloaded.)
After you have positive pressure on the sub-plate, gently slide the base plate all the way off. After that, ease the sub-plate, spring and follower out of the mag body.
Here is the factory follower.
It is 1.837" (inches) tall from top to bottom, as measured from the back of the follower.
Also make note of the raised ridge / rail on the forward side of the follower. It rides in a corresponding track on the inside of the magazine body.
Measuring from the top of the "hump' on the top of the follower, measure down approximately 1.3" (inches). Scripe a SQUARE line forward and cut off the bottom of the follower with a fine tooth saw. Clean and square up the cut area with a semi-coarse file.
WARNING - Leave at least 1/8" - 3/16" (inch) of the track rail on the forward side of the follower! DO NOT REMOVE IT, FILE IT DOWN/OFF OR CUT IT TOO SHORT! It guides the follower up and down and helps keep the follower from "tipping" which will cause it to bind in the mag body.
The battery on my clipers was going out (display flashing), but it ended up being 1.25" (inches) tall after cutting, filing and dressing.
Next - use the file and utility knife to create (scrape) a slight bevel / taper on both the inside and outside of the bottom edge of the follower. The will help keep the follower from binding in the body and help guide the spring up into the follower during compression (loading).
sub-plate and reassembly.
You will notice on the sub-plate that there are two upward protruding "legs". These will need to be trimmed down. The overall height on mine ended up being .85" (inches) after trimming.
After making sure all burrs are removed and everything is nice and smooth and rounded on all of the parts that you worked on, reassemble the mag in reverse order as disassembly. I recommend using a dry silicone spray on the internal components to ease everything going back together and help reliability.
Also - after final assembly, find something to compress the follower all the way to the bottom (not ammo). You may hear some mild crunching or popping. That is just the spring finding it's path to the under / inside of the follower (the taper / bevel you applied earlier should help with this). You should only need to do this once after reassembling the magazine.
Now you should have a fully functional 10 magazine. If it is tight with 10 rounds, disassemble and carefully trim a hair (1/16" - usually no more than 1/8" (inch)) more off of the legs on the sub-plate ONLY. DO NOT cut anymore from the bottom of the follower or screw with the rail / track on the side of the follower.
Part four - final
For those who are curious, the spring in a factory 8-rounder is identical to a FBMG 20-rounder.
Above - The top spring is from a FBMG 20-rounder, the bottom one is from a factory 8-rounder.
Also - The modified factory 8-round (now 10-round) follower works in my FBMG mags, making them 22-rounders.
Hope this helps
Edited by macbeau, 09 February 2008 - 05:37 PM.