K31 "Tanker" Conversionby Rich Stern
The K31 carbine is a really cool military surplus item. A Swiss built, inexpensive surplus rifle, known to be accurate, with a unique pull-bolt action. Every once in a while AIM Surplus (aimsurplus.com) will offer "shooter" grade rifles at clearance prices. The subject of this article is just such a specimen. I had been hoping to find a suitable milsurp candidate to try an unusual dye color for the stock; this K31 seemed ideal. When the rifle arrived, I found it was in good shape. It had average blue loss, an unremarkable beech stock with a pretty good assortment of dents and dings, but generally solid. A functional shooter, as AIM had advertised. Here it is after hardware removal and sanding the stock:
Prior to getting the K31, I had been viewing "tanker" sized versions of Mausers, Enfields, and Garands on the web. A tanker is a main battle rifle with a shortened barrel and stock, meant to be kept in the cramped interior of an armored vehicle for crew use. Some of these are gunsmith projects, while others are legitimate surplus weapons.
Looking at the K31, I began to think about what it would look like as a "tanker." I was already going to try an unusual stock color. The risk? Sixty seven dollars, shipping included. Not a lot to loose if the project went bad. I am an unapologetic tinkerer when it comes to opportunities like this.
For purists who are groaning about "Bubba" sporterizing...yep, groan away. But let's keep this in perspective: K31s are widely available, for less than $100 in very good condition. This particular rifle was unremarkable, with a 1952 date, no soldier tag to identify who carried it, a beat up beech stock, and fair bluing. It's low on the totem poll of collectable K31s.
Another objection to the conversion is recoil. Would the smaller, lighter K31 kick too hard? With Swiss GP11 surplus ammo, it probably would be painful. I handload 7.5x55mm Swiss ammo, which means I can tailor the the recoil to my taste. I load and shoot Ed Harris' "The Load" (10 to 13 grains of Red Dot behind a cast bullet) in .30 cal milsurps, and the very light recoil is similar to a pistol caliber carbine. That recipe is known to work well in the K31.
Here's the barrel clamped in a vise and marked for cutting. I used a Dremmel tool with ceramic cutting discs. It took about 10 discs to get through the barrel. That's a lot. I have undone a hefty padlock shank with just a couple of discs. The steel in these rifle barrels is stout.
I removed enough to leave the K31's barrel at 16.5 inches, measured externally.
I used a bandsaw to cut down the front stock and handguard, and spliced a piece of scrapwood into the stock where the barrel band retaining clip would normally reside.
Handguard and front stock rough sanded and countoured:
The rifle looked unbalanced with the standard length of pull. I removed 3/4" at the butt.
Here's the tanker after all the major wood and metal sizing, still in rough form.
My workshop is set up for woodworking, so metal working machinery, such as a lathe, is not readily available. I used a benchtop belt/disc sander with simple jigs to finish the muzzle at 90 degrees, and to grind the barrel diameter to accept the front sight.
Here's the muzzle, nearly ready for the front sight.
Front sight back on. I used a level across the rear sight and the front sight to align the sights. I have no idea how a gunsmith does it. I assume there are jigs and fixtures for such operations. My method worked well enough, because the gun still shoots true to the sights without any windage adjustment on the front sight.
I polished the muzzle and then used a fine Dremmel stone at slow speed to add a very slight crown to renew the rifling ends.
My first attempt at the "unusual" dye color was a total bust. I got an ugly, puke green:
My wife suggested tinting the shellac I was using over the dye with black tint. It worked pretty well. Each coat of tinted shellac produced a darker green. It is now more of a forest green.
Overall, I am happy with the tanker conversion. Handling is a big upgrade over the full length K31. It's still heavy, but it has a length that's similar to a Ruger 10/22. It's easy to handle and point. It shoots well with either jacketed or cast loads, and the recoil is perfectly acceptable. If I had to do it again, I'd try for a more traditional stock color. The green is fine; it's a bit strange but still looks pretty good, and has the added benefit of matching the local woodlands, for a camo effect.