Custom Build: The N23 HVY PDW Build in .400 Legend

I like short guns and I cannot tell a lie. Ever since I saw the Recoil article on the N23 concept, I’ve been enamored with the idea. Basically they envisioned what a PDW version of the M16 would have looked like had the government made one during Vietnam.

I did my own twist on one, but chambered it in 300 Blackout and called it the N23A1. Then I did a Micro M16A2 build. I started thinking something with a bit more punch would be fun and this year’s project was the N23 HVY, a 400 Legend-based build.

It All Starts at SHOT

I get some of my best — or maybe worst — ideas at SHOT Show every year. I always see something there that stirs my “need” to buy or build something ridiculous. At SHOT Show 2024 I had a chance to shoot a suppressed Ruger American in 400 Legend. I loved the big bore, soft shooting cartridge and was very interested. Being an AR guy the idea of a big bore semi auto based on the basic AR-15 platform was intriguing. I kept looking throughout the year but AR barrels and ammo were a little scarce.

Fast forward to the 2025 SHOT show. Ammo supplies had settled in by then and there were a few loads readily available. That just left me looking for barrels. I’ve found in recent years that the Vendor’s Showcase, which is only set up the first two days of SHOT, is often a treasure trove of smaller companies with some great products. It was there that I ran into the folks at Hitman Industries. It turns out that they make barrels in a whole bunch of unique calibers. They were who I got my .380 ACP barrel from for my goofy .380 AR PDW that I did earlier this year. They also had .400 Legend barrels in a couple of different barrel lengths so I ended up grabbing a 10.5 inch one of those too.

The Usual Suspects

With barrel in hand I turned to my usual suspects for the rest of my parts. I picked up a slick side carry handle upper and rear sight kit from Luth AR. The Mini Mil Spec buffer assembly was from KAK Industry. The .400 Legend uses bolts with the same case head diameter as the 6.8mm and I picked up a BCG  from KAK as well. I used a basic Anderson lower parts kits. I’m going to miss Anderson, I used a bunch of their LPK’s in builds.

Since this was a carry handle inspired build I needed a front sight post for the barrel. Rather than mess with drilling and pinning a FSB I used a set screw model from American Icon. This just slides on like any other gas block and set screws in place. The set screws are recessed out of sight under the sling swivel and bayonet lug. Once in place you can install the sling swivel. You can see from my pics that I still needed to do that in some of my pics. I’ve used this FSB set up before and like to make sure my gas block is aligned right and things run reliably on a couple range trips before I rivet the sling swivel in place.

On my last N23 build I 3d printed a handguard, lined it with heat shield tape and painted it with high temp engine paint. It’s an okay, but not great handguard solution. The problem is, no one makes short, pistol length CAR-15 handguards with a proper heatshield. Well, the folks at American Icon have been looking at the concept and had a few sets of prototypes made. These were professionally 3d printed and fitted with a proper heat shield. I was fortunate that they let me check a set out for T&E and feedback. They’re a nice handguard but the cost isn’t reasonable for serial production. They’re hoping to partner with someone to get injection molded ones made, which would bring costs down considerably. Molds are expensive though, as I’ve learned from folks in the industry. It’s a big gamble for a small business, on a niche product.

For the buttstock, I cut down a B5 Systems CAR-15 stock to fit the short KAK buffer tube, and cut down an old original A1 grip to the stubby length like the US used on the 608 carbines.

A Proper Lower

I used a custom lower from Bad Attitude Company for my N23A1. I had it engraved with the N23A1 markings, and the .300 Blackout chambering. Recoil called their gun the N23, which comes from the concept that they built a gun that “Never Was.” The N is obvious and the W from was is the 23rd letter of the alphabet. Playing on the “Never Was” concept, I had my daughter, a graphic designer, make a unicorn logo in the style of the Colt rearing horse. It seemed appropriate to use an animal that never was to represent my builds that never were.

I caught Bad Attitude right as they were relocating to North Carolina. They also were in the process of tooling up to make proper A1 lowers as well. If you’re a clone builder you know A1 lower are tough to come by. Since Brownells stopped selling their retro lowers, you basically have the H&R lowers, and the Intl Mil Co ones, or you try and find an old one floating around on the secondary market. H&R’s are fine, and I’ve used a lot of those, but they’re all going to be marked H&R. So if you want something different stamped on your gun you’re out of luck. The Intl Mil Co ones are excellent by all accounts, but again you’re limited to certain markings that they offer. They’re considerably more expensive too. Not saying they’re not worth it, but they’re not for everyone.

Bad Attitude saw an opportunity with this vacuum of A1 lowers and has done a great job of filling it. They tracked down a set of original Colt blueprints, and found a forge that would do the lower, and had the proper molds made. These are true A1 lowers. Made from original Colt blueprints. They just don’t have the third hole drilled for obvious reasons. But they’re otherwise spot on for a clone build. BAD sells a number of pre engraved lowers with common model designations that are readily available for order from their website. They also do custom engraving at a very reasonable cost too though, which is what I was after.

I used an A2 pattern lower on my N23A1, which was fine for that build. First since it was a “Never Was” gun anyway, there really was no “correct” configuration. Second, my “A1” version used a C7 upper and modern caliber so an A2 lower was fine. Despite the caliber though I intended my N23 HVY to look older, thus the slick side upper. I thought an A1 lower was more appropriate for this build, so I waited until the A1 lowers were rolling out to get one.

I ended up going with my daughter’s unicorn logo, a model designation of N23 HVY, indicating the heavier chambering, and the .400 Legend caliber marking. I also got my NFA markings done by BAD. That saved me time getting them done later since I knew I was SBR’ing this build, and saved me a few bucks over having it done separately later as well.

Finishing Touches

My upper came with a basic black anodized finish. I could have gotten my lower in black as well, and did consider it. After all, I keep going back to the fact that this isn’t a true clone so it can be whatever I want. With that said, I wanted it to look retro so I decided on a gray finish. The old Colt XM gray is hard to find these days. H&R does do gray uppers and lowers. Stripped gray uppers aren’t always in stock though, and the shades of gray can vary. That’s just the nature of the beast. I do use Norrell’s Moly Resin to paint and cure gray finishes on some builds like I did with my recent 605. I decided to try something different with the N23 HVY.

I’ve used Brownells Alumahyde II in FDE on a couple builds and their Gray parkerized color for some parts. I decided I’d give that a go for the whole gun this time. It’s a more gray/green shade like WW2 parkerizing than a Colt XM gray. But that played into the whole theme for this build. I just got my BAD lower in raw aluminum since I knew I was going to paint it anyway. I painted the upper, buffer tube, and small parts while I was waiting on my lower. Overall I think they came out pretty good. I did find once the lower came in and I started assembling everything that the Alumahyde is a thicker finish than Moly Resin, so I had to do some fitting of parts like the selector lever and take down pins.

For the stocks I wanted to do something different as well. I turned to Cheating Death Customs for that work. I have a set of their brown fakelite stocks I’ve used on another build and really liked the way they came out. Since then I had seen a green bakelite finish that they used, which is based upon some Eastern European AK furniture. They made some AR stocks in that style and it looked good. I sent off my chopped grip and CAR stock, along with my American Icon handguards and had them work their magic on those. The finished product looked amazing, and went with the Brownells Parkerized Gray Alumahyde great. It definitely made for a cool retro vibe, even if it was a finish combo that never actually existed.

It Lives

With all of the pieces finally finished and assembled I headed to the range. The .400 Legend is a big, satisfying straight wall cartridge using a .40 caliber bullet. There aren’t a lot of .400 Legend options yet, but I had three different loads to try out. First was the Winchester Super Suppressed 300gr JHP. Next was the Winchester Power Point, a 215gr Soft Point supersonic load. Last was another Winchester load, the Deer Season XP 190gr Polymer Tip “Extreme Point” supersonic load. At this point Winchester is one of the few companies loading .40 Legend, but at least they have a variety of loads and it seems to be readily available online.

I picked up three Duramag 10 round mags for my build. They’re nice and compact, but I have to admit I’m hoping they do come out with 20 round mags soon as well. The first round I tried from the N23 HVY was the 300gr subsonic load. Recoil and report were pretty pleasant, but it didn’t cycle the action. I manually fired a magazine and initially set the N23 aside. I was thinking I must not have my gas block aligned right and was planning on taking back home and re-seating it before I tried it again.

Luckily I had another .400 Legend AR I was working with that day. This was a factory Bear Creek Arsenal rifle and I soon found that it too wouldn’t cycle the subsonic rounds. When I switched to the supersonic rounds everything worked like you’d expect. When I finished sighting in the BCA I went back to the N23 with the supersonic rounds. With supers the N23 functioned and cycled fine. I’ll admit, the first round startled me a bit. Whereas the subsonics were pretty mild and pleasant to shoot, the supersonic rounds went off with a boom and a pumpkin ball sized flame out of my 7.5 inch barrel. Recoil still wasn’t bad but there was definitely a lot of bark and blast. I had some failures to feed over the first couple of magazines but then things seemed to settle in. I do find that my N23 preferred the polymer tip, pointed profile bullets over the blunter lead Power Point load. I’d still get an occasional round hang up on the feed ramp with the latter. That may improve as I get more rounds through the gun, but I’ll probably lean towards just buying the XT load that I know feeds best.

This is a 7.5 inch PDW with iron sights so I didn’t bother with shooting groups. Yeah, yeah, for science and all I probably should but this wasn’t a review gun, this was my personal build. I sighted it in and then shot at “stuff”, which I love to do. I mostly was using the Caldwell self healing reactive targets at 25 and 50 yards. These consist of a 5 inch ball and square that move and bounce when you hit them. For anything I’m going to do with the N23 that’s good enough.

The .400 hits hard and you know this isn’t your typical AR when you pull the trigger. I honestly shudder at the thought of ever firing this thing without ear pro. My initial plan was to run the 300gr subsonics but I hadn’t factored in the cycling issue. With the fixed FSB I can’t exactly put an adjustable gas block on this build. I think I’m going to have to accept that this thing is a firearm and flamethrower wrapped all in one.

What’s it Good For?

With all that said, what is a 7.5 inch .400 Legend AR actually good for? Well, the main thing is, it amuses me. When I Form 1’d it, I put in the reason block “Personal defense against robots, cyborgs, rhinos, and genetically re-created dinosaurs and all other lawful purposes.” It’d certainly pack some punch against any of those things, but it’d also make a neat brush gun for hogs or whitetail. Is it the most practical thing for that? No, probably not, but it’d be fun. And fun is really what I built it for. While it will make for a slick, compact camp rifle that packs some punch this was mostly a build exercise.

I love the N23 aesthetic and have had fun exploring what I can do with it. I now have a .300 Blackout, a 5.56mm, and a .400 Legend build on some variation of the N23 concept. Of the three, the .300 is probably the most practical set up. I’m going to put the .400 in second though, ahead of the 5.56 out of a 7.5 inch barrel. The 5.56 might be most correct for the concept, but the other two rounds don’t suffer as much from the short barrels of the build. So, am I done with N23’s at this point? For now. Who knows though what might pop into my head if I see something new at the next SHOT Show in 2026!