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Rifles Semi Auto

Just Right Carbine Review

by James Tarr   |  February 14th, 2013 9


Pistol-caliber rifles and carbines have been around for decades and have always enjoyed some popularity. There are a number of different reasons for this. Not only is pistol ammunition cheaper than rifle ammunition, it is much easier to hit something with a long gun than a pistol. Between that, the lack of recoil and quieter report, pistol-caliber carbines are a great choice for new shooters.

They also have a utility beyond that of simple target shooting, namely self-defense. Depending on the caliber and load, you’ll see an extra 100 to 300 fps boost when firing pistol ammo out of a carbine-length barrel. Depending on the laws in your locale and the added boost in velocity you get, hunting might be an option as well.


The JR Carbine can be changed from right- to left-hand operation by unscrewing the charging handle and swapping the ejection port cover. The charging handle can be held back by parking it in the receiver notch.

I was introduced to the JR (Just Right) Carbine at a recent industry event and was surprised to learn it had already been around for a few years. Ironically, when I got a carbine in to test and showed up at the range with it, friends from Canada I shoot with knew all about the JR. They told me the JR Carbines are very popular up there, as they do not have the same restrictions on them as true AR-style rifles and carbines.

While it will take AR trigger groups, stocks, pistol grips and fore-ends, one look at the carbine will tell you it is not designed around the AR receiver. The JR Carbine is a straight-blowback carbine designed to feed from the Glock magazine.

Reliability is first and foremost, and the designers of the JR did a smart thing building it to feed from ultra-reliable Glock magazines. Even if you don’t own a Glock, Glock magazines are everywhere, are reasonably priced and hold a lot of rounds. Even the Glock 33-round 9mm magazines aren’t too expensive or hard to come by (if legal where you live, of course).

I obtained a 9mm carbine for testing for this article, but the JR is offered in .40 S&W and .45 ACP as well. If you want to change calibers, you don’t have to buy a whole new gun. You can buy a conversion kit for $250 that includes a new barrel and, in the case of moving from the 9/40 to the .45, a new magazine well. That makes this a really versatile system.

This carbine is specifically designed to be simple, which is a good thing. Also, simple usually equals inexpensive, and such is the case with the JR. To keep their carbine inexpensive ($699 suggested retail for the basic model) the designers use a simple magazine release on the left side of the magazine well, similar to the layout you see on Glock pistols.

Both the charging handle and ejection are completely reversible. The handle just unscrews. Moving the ejection port cover from one side of the receiver to the other changes the ejection because the ejector is built into the inside surface of the cover.

The upper receiver is secured to the lower with two hex-head screws. The bolt handle reciprocates when firing, and it can be locked back with the use of a notch.

Both the upper receiver and fore-end are railed, so you can mount whatever optic you desire, but the carbine does not come with any sights. Versions are available with threaded barrels so you can install the AR muzzle device of your choice.

I have fired three JR Carbines extensively, two in 9mm and one in .40 S&W. All of them were completely reliable. In fact, I was shooting one 9mm carbine with my two boys and we put so many rounds through it in an afternoon (at least 500, most of which were steel-cased) it got so dirty I couldn’t work the bolt by hand without smacking it loose, and yet it still kept running.

Prior to the next range session, where we put another 200 or so rounds through it, I didn’t clean it but merely lubed the bolt through the ejection port, and we never had a problem.


The carbine can take a lot of AR lower parts such as triggers and stocks, but it’s a blowback-operated gun that feeds from ultra reliable Glock magazines.

However, all three JR Carbines suffered the same problem: The fore-ends got loose and unscrewed under recoil. This is a simple fix with Loctite, but it’s something that should be addressed at the factory.

My two boys (ages 14 and 10) have fired several brands of AR-style pistol-caliber carbines, but they liked the JR Carbine better because the controls were simpler. They liked the bolt handle on the side of the receiver—they knew right where it was, and with the notch it was easy for them to figure out how to lock it back—something to consider if you’re planning on buying a carbine kids will shoot.

Personally I prefer the look of a true “AR-15”-style pistol-caliber carbine over the JR Carbine, but those cost hundreds of dollars more than the JR and aren’t any more reliable or accurate—or fun.

  • Phil

    How accurate is it at 100 yards?

  • Mazryonh

    I never understood why the Just Right Carbine can’t handle high-pressure cartridges like the 10mm Auto, while others like the Thureon Defense carbine or the Mechtech Carbine Conversion unit can.

    • JMoors

      Directly from their site: When will you offer the JR Carbine in 10mm?
      The JR Carbine is a direct-blowback design. The bolt is entirely
      inertial and does not lock when in battery, and the barrel breech does
      not depress upon firing, so there is no mechanical action to absorb some
      of the recoil energy as there is in the 1911 or Glock, for example.When
      the gun is fired the bolt’s mass is not enough by itself to
      sufficiently slow the bolt’s recoil, even when using the standard AR-15
      aluminum buffer with its own internal sliding weights. In order to
      adequately slow the JR Carbine’s bolt down the bolt in the JR Carbine it
      has a solid steel buffer to augment the mass of the bolt. Our buffer is
      significantly heavier than the standard AR-15 aluminum buffer, and is
      sufficient for the energies developed by the 9mm, 40S&W. and
      45ACP. Unfortunately, the full power 10mm generates too much energy
      (37,500 psi) to accommodate through increased buffer mass within the
      limited confines of the buffer tube and still permit sufficient
      fore-and-aft bolt travel for the gun to function. Using a significantly
      denser material for the buffer – like tungsten, for example – might
      accommodate the higher power of the 10mm, but it would be cost
      prohibitive. Using reduced power 10mm cartridges might work, but then
      the performance would be much like the 40S&W and the advantage of
      the 10mm would be lost. For these reasons we do not plan to offer the JR
      Carbine in 10mm (or other high power cartridges such as .357 Sig, .40
      Super, or .460 Rowland, for example).

      Hope that helps

      • Mazryonh

        I mentioned the other PCC models because they managed to solve the high-pressure round problem, while the JRC stubbornly refuses to go that route. It’s not like the laws of physics are different for the Thureon Defense or Mechtech companies, so how did they manage to do it with making their PCCs prohibitively expensive/heavy?

        • AZShooter85

          I think I have an idea why; in order for JRC to offer their rifle in the “higher pressure” calibers, it will require that they invest in R&D and tooling for a redesign. I’m assuming that their sales and revenue forecast does not allow for this kind of investment or risk. Either that, or they lack the engineering talent and experience to solve the problem.

          • Mazryonh

            That’s too bad, really. Magnum Pistol cartridges like the 10mm Auto have a lot to gain from the longer barrels of PCCs. Lower recoil than handgun platforms chambering the same, easier handling due to handguard/foregrip and buttstock, easier aiming, etc.

          • ijdfc

            You can reload with a slower powder and stronger primer to take advantage of the longer barrel.

  • varminthunter43tx

    I now own a Remington TACTICAL 700 (threaded) in the 300ACC BLKOUT and I sub-
    crbe to all the above magazines plus American Rifleman(Life Member), American Hand Gunner, GUNS and HANDLOADER and have yet to read any articles on this weapon. Why is that? I built my 300 ACC BLKOUT on the AR platform and had only found 300 each Primed Rem. brass and having to make more brass from GI 5.56. I’m enjoying doing so. When I get my Suppressor it will make it better to hunt feral hogs and coyotes at night. So how about it all you gun writers what gives? I been hand loading since 1964 was a COMBAT UNITS ARMOROR in every unit I served in even
    as Company First Sargent. Active and Reserve served over forty years. I am 70 now.
    J.J.Huro 1SG. USA RET.

  • Mikial

    Ultra reliable Glock magazines is accurate, but the JRC has consistent FTF problems from Glock mags, even though those same magazines work just fine in Glock pistols. Having owned one and had no end of problems with it, my advice is buy something else.

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