My friend (who's a welder by trade) and I are researching making our own springs. Pretty deep subject, that.
Initially, I'll scavenge springs from a similarly sized magazine - Cetme, M14, FNAR, etc (I have many potential suitable 308-cartridge donors)
The follower, similarly, we'll "borrow" from an existing design; if we don't find one that we can make to work, I'll machine a set of dies and we'll just hydraulically press metal ones. (The cheaper the better, in each case; I'm hoping to reclaim CETME parts, as I have several dozen 20-round CETME mags).
I'm not married to exactness of the magazine design or follower; etc. In fact, I don't believe I can even re-construct the magazine as it was built, without building a great deal of tooling to do it. So I'm drafting up a new design, which will be dimensionally accurate but easier to construct.
The best I can tell, the SCAR magazine is constructed from a single sheet of metal which is run through a forming process involving rollers, folded, and the final "seam" is formed on the rear right edge of the magazine. The magazines body is a single piece that is crimped together, not welded.
A length of steel insert is also present (spot welded to) the inside of the rear of the magazine which serves to make the magazine body more rigid as well as provide a notch for the follower to travel along. The rear of the follower (the notched part) is exposed through a U shaped notch in the top of the rear of the magazine, allowing the follower to activates the bolt-hold open lever.
The feed lips are rolled over at 90 degrees (probably by ramming the assembled mag in to a forming die hydraulically). I can machine a die and insert (to keep the magazine body from fexing) and replicate that process. After bending the lips, the top opening will need to be profiled the front and rear of the lips will need to be tig welded for strength (this is where my welder friend comes in... that's an artform.)
We'll plasma cut the floor plate and trim to fit by hand.
So...
Starting with the appropriately sized sheet of steel;
#1 roll the ribs
#2 cut the magazine catch notch and punch the stop
#3 Fold the floorplate catches
#4 Fold the magazine "rear"
#5 Fold the magazine "front" (completing the "box")
#6 Mig weld the seam on the right edge (where there is additional clearance on the SCAR receiver for a "rib")
#7 Spot weld the rear notched insert in place (this will require a pass on the mill to cut the notch on the strip of metal)
#8 Trim the bolt hold open notch (dremel)
#9 Insert mag body in to retaining blocks, clamped together, hydralically press the feed lips to the appropriate radius
#10 tig weld the feed lips front and rear, clean up welds
#11 trim follower to fit.
#12 cut (or adapt) floorplate to fit
#13 assemble and test.
We'll be missing the plastic part on the bottom of the mag that "levels" it out, but I don't mind.
