Re: Marlin 7 round 22lr magazines modified for 4 round
Here's my writeup. I'll post it on RimfireCentral later.
Disclaimer: <span style="font-weight: bold">Perform this procedure at your own risk.</span> There is a very real possibility of permanently destroying your magazine, especially if you are not mechanically inclined. On the same note, I am also not responsible if you injure yourself in the process. Due the amount of variability between magazines and the skill levels of the people reading this, results will vary. It is up to the modifier to be able to make sure the magazine is fully functional, and if it isn't, to make it functional.
Required:
7/10rd Marlin .22lr magazine
Compatible rifle
Dremel tool with cut-off wheels OR a hacksaw
Needle-nose pliers
Vise grips or flat jaw pliers
Metal file
Punch and hammer (optional)
Step 1: Following all applicable safety rules, verify that the rifle is empty. Check both the chamber, and the magazine well. From this point forward, I will assume you are taking the necessary precautions to prevent a negligent discharge or otherwise dangerous situation.
Step 2: Insert an EMPTY magazine into the gun. Using a scribe or fine tip marker, make a mark on the magazine body approximately 1/16" proud of the magazine well. Note the pictures on the following step.
Step 3: Remove the floorplate - Using the edge of the table or a punch and hammer, knock the floorplate <span style="font-weight: bold">forward</span> (see picture) to remove it. The follower and spring will also come out. Make note of the tabs on the magazine body that retain the floorplate. This is what we will try to recreate.
Step 4: Make a rough cut about halfway between the mark you made in Step 2 and the bottom of the magazine. Note the use of tape to prevent marring. I had the magazine in a vise while I used a Dremel to make the cut.
Step 5: Cut from the bottom edges to 1/16" shy of the line you scribed earlier. Note the picture for the cut positions. The cuts should be made on both the left and right side.
Step 6: Using needle-nose pliers and a vise grip (or flat jaw pliers), bend the tabs down as indicated in the picture. The trick here is to make the bend as sharp and square as possible. Get the pliers right up to where you want the bend to go, then bend them 90 degrees outwards. These tabs will form the retaining flanges for the floorplate.
Step 7: Cut off the unbent portions of the cut (the front, back, and middle portions that are still sticking up). Clean up the cuts and use a metal file to make the bottom of the magazine roughly square. (Excuse the rusty, dull file. I can't afford to replace it at the moment.)
Step 8: Clean the metal shavings off the magazine and test the fit in your rifle. It should fit with 1/16"-1/8" of clearance between the tabs and the bottom of the magazine well. This is to compensate for rolled portion of the floorplate. Also note that excess clearance is preferred over too little clearance.
Step 9: Cut the tabs down into retainers. Try to replicate the original flanges. This is probably the most difficult part of this tutorial. You have to use a combination of cutting and filing to shape the flanges. Keep trying on the floorplate. It should fit fairly snugly, but it should also go on with a bit of tapping. Be careful not to remove too much of the tab.
