Project KAR-46
By Jess, Range Team Member
For those of you who are remotely familiar with firearms this month’s title may have thrown you. What on Earth is a KAR-46? You aren’t losing it, this gun is not in production and only exists as a one-off project. Normally I like to review firearms which anyone would be able to hunt down and purchase for themselves and this rascal goes against the grain. Taking this slight detour, I’m going to use it as an example to celebrate the modularity of the AR-15 platform which allows the KAR-46 to exist. Welcome, readers, to where genius meets insanity. Or something.
It started with my love of straight pull actions.
The problem is the market doesn’t have many of them and the few which exist don’t offer much of anything for customizing. Right out the gate the AR-15 solves this problem. In fact, there are some ban-state models which have already been made into straight pull actions and these are readily available to purchase (but they’re also quite expensive and rare.) AR’s are so versatile as to have been turned into single shot rifles, pump action rifles, belt-fed rifles, even some ban-state conversions where you would have to break it open like a shotgun in order to load a fixed magazine. Wild stuff going on here! But with good reasons. The base platform is very flexible, affordable, and parts are easy to come by. They can also be made nice and lightweight and chamber affordable cartridges and even easily change out to different calibers, all huge benefits.
What to do for the charging handle? The part of the action which is going to be seeing the most direct interface with the shooter? It’d be possible to use the T charging handle but frankly I hate them. Constantly having to pull on one of those seemed like a terrible idea, not to mention the spot where an AR’s charging handle latches to the upper receiver can wear down over time being the uppers are aluminum. There’s also something called the Cali Key but that wasn’t doing it for me either, it lacked class and uniqueness. No, I had my sights on imitating the best straight pull action ever made: The Swiss K31.
For the fellow introverts here, yes, this is where “KAR-46” came from. It’s a silly answer to the question “what happens when you combine an AR-15 with a Swiss K31?” Not to be misleading with the fancy label, this isn’t a rifle where every part is custom machined in a shop. Still, I couldn’t resist mashing the two designations together. The K31 is what inspired the entire project while the AR made it possible so it only seemed appropriate to have a name inspired by both.
Why not just get a K31, though? They seem to be fantastically built rifles and I’ve heard great things about them, but from where I stand there are some problems. The K31’s are huge, heavy, and are chambered for an increasingly difficult to find cartridge. Trying to modify them is difficult and expensive with next to no support in this country. Even finding a spare factory magazine can be a challenge. The thought of turning one into an affordable to shoot platform nested into a fancy aluminum chassis seemed impossible. Still, the “beer keg” shaped charging handle is iconic of Swiss rifles of this era and I wanted it.
Yes, I based my entire project off the shape of a bolt handle. Inspiration can take many forms.
Thanks to this wonderful thing called the internet I soon had a surplus K31 charging handle sitting in front of me. How to make a gun which uses it, though? It was time to put a theory and my madness to its first test. The K31’s charging handle sure looked like it could fit inside of the channel for the AR’s charging handle with minimal trimming. Sure enough, it fits with room to spare. Paired with an upper receiver which has a shell deflector (because I didn’t fancy brass smacking my knuckles) but no forward assist and a custom machined notch along the side for a little added clearance (the K31 handle had to mount at a slight angle for better clearance) and the action was figured out.
The bolt is the heart of the action so the new charging handle had to fit in a secure manner. Bonus points for finding an affordable solution. I don’t have access to a machine shop nor the knowledge of how to use these machines so I reached out to MJ Gunsmithing out of Hubertus to help me with the shop work. Eli and I spent some quality time working out the nuts and bolts as I laid out my vision. What we agreed on was to use the existing mounting points for the gas key with an aluminum riser so the K31’s charging handle could bolt directly into place with existing threading.
Removing the semi-automatic bits from an AR was far easier. Delete the gas tube and install a gas block backwards to seal the gas port. Originally the port had been soldered off but the pressure generated from shooting it popped that plug out at some point.
Next up was the buffer. It would have been easiest to use a standard buffer and spring for an inherent bolt forward assist which has been done in other straight pull conversions, but that’s not what I was after. I wanted the full manual experience. The spring had to go. Without the need for a buffer in a typical manner I popped the weights out of a carbine length buffer to make it weigh about as much as a feather. Removing the spring presented a brand new dilemma in that the buffer itself would be free to slide about within the tube.
The fix? A piece of PVC pipe. I already had this lying around from a twenty year old potato gun, how fortunate! The same diameter of pipe which had been used as a ram rod for spuds was the perfect fit for the narrower part of the buffer. After wrapping a piece of pipe in a small strip of adhesive backed Velcro (the fuzzy part) it made for a good snug fit within the buffer tube. Getting closer! In order to keep the two pieces together I simply backed out the buffer’s roll pin enough that the PVC sleeve would stay put, and thus so would the buffer within the receiver extension.
Why use a buffer at all? The bolt needs something to connect with when running the action. If a carbine buffer is good enough for the forces of a semi-automatic design then I figure it can hold up to me manually throwing the bolt about like a madwoman. Time will further test this theory but so far it’s holding up.
While this configuration does indeed work it presents a few issues, mainly that the weight of the bolt and carrier aren’t being held into battery by much more than the friction of the gas rings. I had tried a super lightweight bolt which helped considerably but made the action far more “sticky” feeling and I didn’t want to drop several hundred more to figure out whether it would or wouldn’t work with a different brand. Staying affordable was important! The bolt which I had originally bought for it was one of the lowest priced offerings through Palmetto State Armory (and it was on sale, go me!) and the bolt throw was … smooth enough.
This is a range toy though, I’m not hiking or hunting with it. The simplest answer to keeping the bolt in battery is for the hammer to hold it in while at rest, which means keeping the chamber empty until ready to use. Not a huge deal. With this in mind I went with mil-spec trigger parts as a too light hammer spring would be counterproductive to what has effectively become an internal safety. Plus, mil-spec triggers are affordable and I had a spare set.
With the important functional bits out of the way it was time to move into aesthetics and the user interface, and here is where I was really excited to play. The K31’s characteristics were important to me, I wanted to keep that old school military bolt action feel where possible. First up: Caliber. Since the K31 is within the .30 caliber family the closest I could get without breaking the bank is .300 Blackout, which also happens to fit perfectly into another idea I’ve had brewing for this project. Another added bonus is how great .300 is for suppressor use which is almost impossible to beat when paired with a manual action. For a barrel I settled on a lightweight offering by Faxon since keeping it light mattered more than retaining zero during brisk firing.
Having a chance to make this rifle properly unique, there are some other uncommon bolt guns out there which had a nifty feature: The ability to carry a spare magazine right on the gun. The Steyr Scout and far lesser known but cool as hell German DSR-1 both did this and I love the concept. As luck would have it, FAB Defense has two different AR-15 stocks which have a built-in spare mag holder. The ten round mag which comes with these stocks is kind of garbage but Lancer L5 mags can be had both in ten round sizes and optimized for .300 Blackout. Two of those went straight into the shopping cart and turned out to be a perfect match for the FAB Defense stock, easily retaining a fully topped off spare reload in the back.
For the handguard I went with a 15″ Aero Precision Atlas-One S. The S in particular omits much of the Picatinny rail which further lightens it up and lends to that old style wooden handguard appearance which ran right up to the muzzle. With a 16″ barrel and .300 Blackout a flash hider is kind of unnecessary but PTR makes a very neat looking birdcage hider for their HK 91/G3 clones which lent the right look of an old battle rifle configuration (and it was cheap!)
The K31 could fit a bayonet so naturally I had to work this into the design as well. Of all the things, Sig Sauer has an affordable aluminum M-Lok bayonet lug (which I sure hope they continue to make!) The bayonet would be positioned well south of the barrel but I can’t have everything. With the long handguard it still mounts the pointy stabby bit far enough forward to look good, and there’s the bayonet mount solved. Next!
Iron sights. I wanted to do something special here and Eli came through. See, the K31 has iron sights. If you look closely the K31’s front sight kind of looks like an AR-15’s front sight while the back sight looks more like an AK pattern with a leaf spring and tangent slider.
I wanted this for my project. As it turns out, Picatinny mounted AK rear sights DO exist. Just…not in this country. And, well… Russian sanctions. Not a great time to import oddball rifle parts.
The solution here turned out to be a surplus AKM rear sight base, an aftermarket adjustable rear sight, a spare red dot riser mount, and a resourceful local gunsmith or two. Another aluminum riser and a couple of bolts later and I ended up with a quick detach Picatinny mounted windage adjustable AK pattern rear sight which was the perfect height for standard rail mounted AR sights. Score! For the front sight I went with a Daniel Defense fixed front sight post out of my parts box which was a great fit and matched the K31 aesthetics pretty darn well.
Another unforeseen issue popped up here. Unlike an AK where the front sight has a rounded sight profile, the AR’s front sight wings are straight and far more vertical. When shouldering the KAR-46 it became far too easy to mistake one of these wings for the actual front sight. Cool, built in windage adjustment! But the actual sight post needed to be easier to pick up. This was easily solved with an aftermarket high visibility orange polymer front sight post.
Hey, remember when I mentioned selecting the .300 Blackout? As it turns out, a supersonic .300 has very similar ballistics to a 7.62x39mm, the cartridge which my new custom made rear sight leaf had originally been calibrated for. In a wonderful twist of coincidence, mounting the rear sight to the back rails of the Aero handguard gave it the exact same sight radius of a typical AK rifle. I couldn’t have asked for a better result!
The rifle was now together, all parts working and iron sights adjusted. It needed one more piece of trim: Color. Since the K31 was a focal point for inspiration I could have gone with a wood trim Cerakote but as the gun itself was pretty funky I wanted to get a little funky with its trim. In short order I settled on “Black Cherry” Cerakote which is a lovely maroon hue with some natural reflectivity. It sorta kinda suggests something like cherrywood or purple heart wood but also provides a newer chassis-like sort of vibe, another merging of old and new.
Finally getting to shooting the KAR-46, I went into it not knowing what to expect. What I had was a VERY lightweight rifle with a manual action and an intermediate .30 caliber round. Getting the full recoil of the .300 Blackout was more than I was honestly expecting but it wasn’t bad. In fact, the more I shot it the more I came to decide that it was just the right amount of thump to make this gun shine. It provided the illusion of shooting those old military bolt guns where the recoil was heavier but so were the guns.
The action isn’t nearly as smooth as I would have liked, the KAR-46 has NOTHING on a Swiss K31, but it worked! Manually running an AR completely changes up the sound experience as well, taking on very distinct bolt racking notes which draw a fair bit of attention at the range. After running through the first ten round mag the action would start to feel a bit sticky, I can only guess it’s due to the chamber heating up and making the brass fit a tad more snugly. Half of the fun of a straight pull is running the action like you mean it and the KAR-46 does deliver here. By the time all twenty rounds are spent and you need to reload the chamber has a chance to cool down some.
The heavier and slightly less refined feel of a basic mil-spec trigger also lends nicely to the old military bolt gun feeling. The AR’s standard safety and bolt catch still work wonderfully so you know when you need to swap out mags if you forget to count or run standard capacity mags.
It took a while and some proper gunsmithing help but my pipe dream had finally become a reality. A super lightweight straight pull which I could afford to feed and shoot, an insane amount of aftermarket parts and mods for decades to come, my beloved Swiss beer keg charging handle, an aluminum chassis-like body, and at a weight so minimal you have to experience it to believe it.
But… Why? Why take a perfectly functional and clearly superior semi-automatic rifle and hobble it so? Since the beginning this project has been incredibly polarizing for those who heard about it. Some thought it was cool and some thought I was out of my mind to make such an abomination. The answer to “why” is simple: Because I wanted to. Building a fully custom gun which ticked all of these boxes would have been expensive and vastly beyond my capabilities to make.
In yet another showcase of how versatile Stoner’s design is, the AR and its prolific nature allowed me to step outside of the Armalite box and do something wild and possibly stupid but certainly unique, and it didn’t require any mortgages to finish. Like it or hate it, everyone who has a chance to shoot the KAR-46 walks away with a huge smile. I’ve been having so much fun that I’m starting to consider another upper. Perhaps .350 Legend…
Decades later when I’m gone and this one-off rifle may well end up at some gun auction or on an internet channel like Forgotten Weapons, now there’s some documentation on what had spawned the zaniness and the steps taken in order to get there. Go forth and enjoy some creative expression through firearms!
