The JR Carbine Thread

I bought a used 9 mm Jr carbine off here and the guy who previous owned it striped the screws on the receiver and messed up the castle nut screw . Does anyone know where I can go to buy new screws and a castle nut screw
 
Just about finished the changes I wanted to make to rifle, put a 3 lb Timney trigger. 15" keymod rail, Magpul CTR stock, Vortex Spitfire 3x scope, still waiting for my Hogue grip to come in

JR.jpg
 
Curtis264 said:
Just about finished the changes I wanted to make to rifle, put a 3 lb Timney trigger. 15" keymod rail, Magpul CTR stock, Vortex Spitfire 3x scope, still waiting for my Hogue grip to come in

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this looks pretty cool. Not a fan of the optic being so far back on the rail though.
 
Curtis264 said:
Just about finished the changes I wanted to make to rifle, put a 3 lb Timney trigger. 15" keymod rail, Magpul CTR stock, Vortex Spitfire 3x scope, still waiting for my Hogue grip to come in

JR.jpg
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Looks nice.

1. Where/who did you get the rail from?
2. Any difficulty installing the rail on your JRC?
 
TripleF said:
Looks nice.

1. Where/who did you get the rail from?
2. Any difficulty installing the rail on your JRC?[/QUOTE

I bought off Ebay, it came with barrel nut, all hardware and 4 shims and I needed them all. But it was a very easy install. But the fit and finish is as good a the 300 dollars rails that I have bought
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Inclined Front Grip (JRC-IFG1C) for Just Right Carbine 7" OEM Handguard

One can download the STL files for 3D Printing at Thingiverse: https://www.thingiverse.com/thing:1635523 (Yes for free):)
 
Thanks for all the posts on the JRC - good and bad - this helped me make my decision to get the JRC 9mm. Got an awesome deal thanks to Clayton at Prophet River! Unfortunately not in stock so a special order... (im)patiently waiting? But this means lots of time time to drool over the upgrades you've all shared!
 
Hoping some of you can provide some insight. I just recently picked up (new to me) a JRC in 9mm. I took it apart and gave it a good cleaning and coated the bolt in a fine layer of gun grease as I figure a lightly greased bolt is better than a dry bolt. I brought it to the range to sight in my red dot using some reloads. I am using Titegroup and CFE Pistol powder. I know the powders are somewhat dirty compared to using factory rounds. I got through about 50 reloads when the bolt became a little difficult to pull back. Shot another magazine and after that the bolt refused to be hauled back to chamber another round. I didn't have a chance to use factory rounds. Continued the session with my M&P 9 using the same reloads with no issues. I went home and took apart the JRC and it was very dirty. I reassembled it and the bolt had no issues. Does the JRC only work well with factory loads that are not so dirty?
 
Bone Dry JRC

gunner065 said:
Hoping some of you can provide some insight. I just recently picked up (new to me) a JRC in 9mm. I took it apart and gave it a good cleaning and coated the bolt in a fine layer of gun grease as I figure a lightly greased bolt is better than a dry bolt. I brought it to the range to sight in my red dot using some reloads. I am using Titegroup and CFE Pistol powder. I know the powders are somewhat dirty compared to using factory rounds. I got through about 50 reloads when the bolt became a little difficult to pull back. Shot another magazine and after that the bolt refused to be hauled back to chamber another round. I didn't have a chance to use factory rounds. Continued the session with my M&P 9 using the same reloads with no issues. I went home and took apart the JRC and it was very dirty. I reassembled it and the bolt had no issues. Does the JRC only work well with factory loads that are not so dirty?
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Personally, the only thing I oil on the JRC (9mm) are the threads. Everything else is bone dry.

When I first got it, I got a single box of every 9mm in one of the local stores and shot it without any issues. Eventually, ended up buying a box of 750(?) 9mm box from Canada Ammo - cheap and dirty Ukrainian made ammo. Gone a couple of times without cleaning before putting through at least 300+ rounds (of the cheap stuff). Aside from the carbon build-up, the rifle runs well bone dry, but definitely gets dirty as a direct blowback. Would not recommend oiling any bolt/receiver/chamber or trigger surfaces.
 
Thanks TripleF. Appreciate the advice. Just never thought that metal against metal, in this situation, is better without a little lubrication.
 
Thought I would share some results of shooting my 45ACP JR Carbine.

I finally got my heavy buffer weight, trimmed recoil spring, and buffer spacer/rubber bumper installed. I had some serious issues with feeding ever since I purchased this carbine! After these items were installed, I have yet to experience a malfunction! It has been more than 350 rounds since the modifications. Very pleased to say the least!


I tried some load development the other day. I tried 3 different powders: Unique, CFE Pistol, and Longshot. I approached the max charges of each powder in 0.3 grain increments. Three incremented powder charges per powder (9 test loads).

The bullet of choice was the 230 Grain Hornady HAP hollow point.

Range these groups were shot at was 50 yards.

The next tests will be at 100 just to see how the loads carry out.

It is great to see some promise in this little carbine!

In each of the tests, the lowest powder charges showed signs of velocity variations of around 100fps+/-.
Each target had a single bullet vertically strung outside the core group. Always low.

The middle powder charges showed immediate improvements to the velocity variations and verticle stringing fliers. The flier was noticably closer to the core grouping.

The highest charges showed the best groupings for all three powders tested. The velocity variations/ fliers, were nearly eliminated. The higher pressures produced a more consistant burn and velocity.

Here are two examples of the max charges. One of Unique (the best results, smallest group), and CFE Pistol.






Average velocities for the maximum "Unique" powder charges were 1024 fps.
Average velocities for the maximum "CFE Pistol" powder charges was 998 fps.
Average for the maximum "Longshot" powder charges was 1002 fps.

I can hardly wait to see what it will do next trip!
 
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