How to add length to magazine box

I am building a custom rifle in 7mm Rem mag on a Stevens 200 LA centerfeed action. I plan on shooting the 180 berger hybrids and although the mag box is pretty long at 3.5", it would be nice to make it a bit longer if not too much hassle. I was thinking of making a block that fit tightly in the mag box (my rifle will be blind mag for weight savings) and heating the front of the mag box w a torch and stretching the metal in this region only, even if just 0.1". Has anyone ever tried this? I am waiting on my manners stock still so hard to know how exactly it would line up, but my other savages make me think it would work. Input???


PS, My barrel will be throated to the dummy rounds I send the smith, so no worries there.

I have seen the center of the front of an AR15 6.8 spc mag cut out to seat those long. I'd do that over stretching.

Better option would be to cut the box in half vertically down the middle, then weld it back together to the length you're wanting. You may have to relieve the receiver at the front edge as well.

Correction: Another option. Not necessarily better.

Quote:

---

Originally Posted by troutdodger

Better option would be to cut the box in half vertically down the middle, then weld it back together to the length you're wanting. You may have to relieve the receiver at the front edge as well.

---

i was told this was the option my reputable savage gunsmith uses, buts it's about $200-250 for him to do that I guess. For the price of a mag box I might just try the heat and stretch technique with some auto body filler in the well and release agent on the metal, this would keep the stretch to just that exact area I think.

I dont think you will have much luck stretching the mag box.
At least I would not try it.

What I did with an axis 223 mag is take it apart and sand down the plastic part in the case head end and then reassemble.
Didn't quite get me .1 but if I did both side and then epoxied or similar while pushing it farther back it would give more than .1.
Not sure if your mag is similar though.

I lengthen my long action builds to "unlimited".....................also known as single shots, via SS sled.
Faster, Easier, Stronger, Cleaner..............Better.
Repeaters are over-rated.

Well, I decided to give my heat and stretch theory a try, and it worked great! Box was 3.5" max and now have a 3.6" max box. The trick i found is that the mag box is considerably wider in the front than needed, and you only need to stretch out the 50-60% of metal in the middle of the box. Of course, this box will not work on detach mags now, but mine is blind. I dont think i will need to modify the recieved either, there is enought extra room up front for this mod.

I first cut a piece of hardwood to the length of the mag box and filled the voids with a hard plaster putty and let it dry, then put it in a vice and hit it hard with the torch until the front of the box was red, pryed a large flat screwdriver in from the top and bottom and puched against the wood to "stretch" the box out to 3.6" max COAL. I think I did stretch it some, but also narrowed the front 1/2" of the box out a little bit and move the extra width out to gain lenght. I was done in 30 minutes, but spent a bit more time heating and trying to make it all look nice. I did have to very slightly sand the edges of the mag follower in the front to feed smoothly from the slightly narrowed front end.