JR Carbine - Gun, Ammo or Me? *BIG PICS*

geclark

geclark

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So - I picked up a JR in .45 and took it out to put a few rounds through it this weekend. After a quick cleaning and inspection I loaded one and shot one. I repeated that twice more checking things out between shots and everything looked ok.

So I loaded three rounds into the magazine, and took a shot. Something didn't feel quite right. It had ejected the casing from the first round, and the second round was jammed partially into the chamber.

I extracted the round partially seated round and it looks pushed back into the case, and the case looks a bit mashed up. The rim is also slightly bent.

Photos below:
hrm-45-1.JPG

hrm-45-2.JPG

hrm-45-3.JPG


A quick check of the gun and everything seemed ok, I got through the other 94 rounds without incident.

I inspected the other brass, and found one with a nick out at the top. It fired without a noticeable incident, though I'm wondering if there's a clue in there about what's going on?

nicked-case.JPG


In general the brass seemed to be taking a bit of a beating. I've never fired reloads or the JR before, so there are a at least a couple variables at play.

The only thing that I know I'm doing against JR's manual is using reloads. This was Wolf 230gr TMJ, so I'll try and stick with some factory ammo next weekend to see if it makes a difference. I was also being cautious about over inserting the magazine, and usually pulled down after inserting.

So - anyone have any thoughts on what's going on here? Ammo, Gun or user error or a combo?

The JR is a treat to shoot, and I'm glad everything when smoothly for the last 95 rounds. :)
 
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I am having issues with mine as well.
Mine has failed to feed 4-5 times in 60 rounds.
Two of the failures/jams actually punctured the cases through to the powder! Wow is this gun hard on brass! These are factory rounds as well.

The rifle is suprisingly accurate though!
I fired a sub 2" group at 50yds, and just over 2-1/2" at 100yds.
That impressed me.

Now if I could just get this rifle to consistantly feed for at least 4-5 magazines worth of shooting, that would satisfy me.

I plan on reloading eventually, and by then I hope it feeds and treats the brass better.
 
hmm, the marks on the brass kinda look like the same shape as the feed ramp....maybe. I wouldnt think its mag related... does it bite a chunk out or every round? the first few from a fresh mag? I assume your using the glock model?
 
By the way, a few of my fired cases look just like the 3rd picture.
Its like the feeding is so violent that it drives the bullet back into the case, wrinkling the case below the bottom of the bullet.
 
just for the fun of it, pull your buffer out and post a pic... I was dealing with JRC regarding a feeding issue with mine, he said they are having a hell of a time slowing the action down. My issue was fixed by the new heavier buffer. From what I understand there has been three versions of it so far. Mine didnt damage the brass but it was getting hung up in the feed path. 9mm is a lot smaller then 45acp so its gotta be getting tight in there.
 
I dont think the speed of the action could cause the bullet to slid back in the case, maybe on reloads that were not sized properly.....Im wondering if the round is contacting the feed ramp in such a way that its being pushed in to the case a bit, unce the nose clears the sharp edge of the ramp the casting catchs.....My feed ramp had a bit of sharp edge on it but shooting the shiat outta it has smoothed things out
 
I copied this info from JR's web site , I had a problem with my 9 mil bump firing , it turned out to be the steel case ammo . It was being feed buy the individual I had let shoot it.



Q: My JR Carbine is having feeding problems. What should I do? Feeding problems are almost always traceable to either magazine or ammunition.

Magazine Issues:
The JR Carbine is designed to use either genuine Glock or 1911 milspec-dimension magazines. Aftermarket Glock-compatible magazines or 1911 magazines not manufactured to original 1911 milspec dimensions may not perform properly or consistently. Even genuine Glock magazines have gone through several generations, and they may not all perform the same. See our comparison of two Glock magazine springs.

Glock-45ACP Magazine Adjustment: We have experienced a feeding problem in some 10-round .45ACP Glock magazines. Specifically, the last 1-3 rounds consistently stand straight up on the follower and do not feed into the chamber. We have traced the problem to the follower spring, where the top of the spring is formed in such a way that it applies most of its pressure on the front end of the follower and little, if any, on the back. In turn, the follower pushes upward unevenly on the cartridge – mostly on the forward half. When the bolt contacts the top round of ammunition and begins driving it forward, the unbalanced pressure on the front of the cartridge permits the cartridge to rotate upward as the cartridge case clears the magazine feed lips. We have developed a simple modification for your Glock magazine that will significantly improve the magazine's performance in both your JR Carbine and your Glock pistol. See our modification instructions here.


Overinserting the Magazine: Feeding problems are occasionally caused by shooters inserting the magazine too far up into the magazine well. This can interfere with the operation of the bolt and prevent proper ammunition feeding. Many shooters learned in the military to slap their M-16/M-4/AR-15 or pistol magazine up and into the magazine well to endure it is properly seated. In the AR-15 type rifle there is a magazine stop that prevents overinsertion. In most pistols there is a lip on the bottom of the magazine and/or an internal stop that serves the same purpose. The JR Carbine relies on the magazine catch to properly locate the magazine within the magazine well. There is no other internal or external stop. As per the Just Right Carbines Safety and Instruction Manual, the proper way to insert a magazine is to "insert a loaded magazine up into the magazine well until it clicks. Check to see that is is securely held in place by pulling down on the magazine; it should stay tightly in place." Avoid slapping the magazine into place - especially if you are loading with the bolt locked open to the rear - to prevent overinserting it.
Ammunition Issues:
Not all ammunition is created equal. Although all JR Carbines are manufactured and assembled to the same specifications and tolerances, any individual firearm is likely to tend to prefer one brand or type of ammunition over other, and the JR Carbine is no exception. In most cases the reason is variations in ammunition manufacture - even between lots of ammunition from the same manufacturer. If you are experiencing feeding difficulties unrelated to the magazine, consider trying different types and brands of ammunition to determine which performs best in your JR Carbine.just as with virtually all other firearms. Differences in bullet profile, case diameter, and bullet composition (cast lead bullets are not recommended) can significantly impact ammunition feeding.
 
Matt308 said:
hmm, the marks on the brass kinda look like the same shape as the feed ramp....maybe. I wouldnt think its mag related... does it bite a chunk out or every round? the first few from a fresh mag? I assume your using the glock model?
Click to expand...
Yes - I'm using the Glock model. It doesn't do this consistently, and it really only had failure to feed issues the first time I loaded a magazine with more than 1 round. I did 9 full magazines after that without a failure.

I'm away from the rifle until Friday, I'll yank of the buffer tube and take some pics then.
 
Thanks for this - I'm going to give this tweak a try.

I'll put 100 rounds of factory through it before I do to see if I have any further issues, and if I do I'll perform this magazine mod and try again.

slowpoke55 said:
I copied this info from JR's web site , I had a problem with my 9 mil bump firing , it turned out to be the steel case ammo . It was being feed buy the individual I had let shoot it.

Glock-45ACP Magazine Adjustment: We have experienced a feeding problem in some 10-round .45ACP Glock magazines. Specifically, the last 1-3 rounds consistently stand straight up on the follower and do not feed into the chamber. We have traced the problem to the follower spring, where the top of the spring is formed in such a way that it applies most of its pressure on the front end of the follower and little, if any, on the back. In turn, the follower pushes upward unevenly on the cartridge – mostly on the forward half. When the bolt contacts the top round of ammunition and begins driving it forward, the unbalanced pressure on the front of the cartridge permits the cartridge to rotate upward as the cartridge case clears the magazine feed lips. We have developed a simple modification for your Glock magazine that will significantly improve the magazine's performance in both your JR Carbine and your Glock pistol. See our modification instructions here.
Click to expand...
 
sounds like a plan man. Ever since my buffer upgrade mine has been hammering away without any issues. Im currently doing a test to see how long i can run it without a break down and clean. all im doing is putting a few drops of slip2000ewl on the bolt every now and then
 
Matt308 said:
how was the steel case causing a bump fire?
Click to expand...

I am not sure as to how the steel case ammo was casing it to bump fire .
But I phone EMF on a holiday Monday about the problem. They had thier gunsmith phone me back the next day.
I mentioned the type of ammo that was being feed to it and he was adamant , that was the problem.
I have always feed it brass and never had a bump fire , so I left it at that.

Sorry I do not have a more technical answer for you.
 
Buffer setup

Ok I got to the gun early, here's the buffer tube and guts.

JR-buffer-tube.JPG


As an aside, has anyone gotten the 'fixed' buttstock off the tube, or do people just replace it if going with an aftermarket buttstock.
 
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hmm, looks like it has the updated buffer. lets take a look at your feed ramp. pull the mag well and compare the marks on the rounds to the profile of the the feed ramp
 
Upon close inspection of my Carbine, there is a sharp edge just behind the feeding ramp.
The forked profile of the ramp allows my cases to slide up the ramp, and at the very bottom of the fork (behind the bolted in ramp) there is a sharp/square edged part of the action housing. I removed the bolt and hand fed a loaded case (slid the cartridge back and forth).

The very leading edge of the case (bottom, 6 O clock) was catching on this square edge. It would not catch every time. This edge would most certainly cause the case to buckle if the action was slamming forward under spring return force.

Mix this sharp edge with a magazine that delivers/feeds cartridges in a variable manner, and you have a Carbine that occasionally destroys brass. This is my theory anyhow.
I put a very "slight" radius on this edge to see if the rifle will feed more consistantly.

The bottom part of the bolt face that grabs the loaded round from the magazine was also very sharp. When I cycled the action slowly, I could see it digging into the brass case below the one the bolt face was feeding. I also gave this edge a small radius, and polished it up with crocus cloth. After this modification, I could see and feel the action feeding the rounds more smoothly.

Hopefully this has improved the function and dependability of the Carbine! I will give you guys a follow up report, after my next range trip.

I tried to get the bottom off my magazine, but it was being stubborn. Consequently, I will wait till I can obtain another magazine before I take this one apart. With my luck, I will probably break the bottom cover and have a Functionless/magazineless Carbine! I am not going to let that happen!

Talk to you gunnutz later!

Straight shootin, and keep it fun!
 
slowpoke55 said:
I am not sure as to how the steel case ammo was casing it to bump fire .
But I phone EMF on a holiday Monday about the problem. They had thier gunsmith phone me back the next day.
I mentioned the type of ammo that was being feed to it and he was adamant , that was the problem.
I have always feed it brass and never had a bump fire , so I left it at that.

Sorry I do not have a more technical answer for you.
Click to expand...

It specifically states in the JRC manual that you should never use steel or aluminum case ammunition and that doing so voids your warranty.
 
IShootHostages said:
It specifically states in the JRC manual that you should never use steel or aluminum case ammunition and that doing so voids your warranty.
Click to expand...

I spoke to the tech at JR about this some time ago......

Yes, as steel and aluminum do not expand uniformally in the chamber for a blow-back only rifle like the JR. Brass expands and seals better, (slowing down extraction) ensuring that chamber pressures are at a safe level before the bolt gets kicked open.

Steel and aluminum cases perform better, and are safer to use in locked-breech firearms.
 
The modifications I described in my earlier post has made a big difference in feeding dependability!
Not perfect, but I managed to run nearly three mags through before a failure to feed occurred. Shot #27 was the culprit.
After that, another full magazine was used and no malfunctions.
Not perfect, but HUGELY improved!

Hope this information can help someone.

Straight shootin, and keep it fun!
 
dthunter said:
I tried to get the bottom off my magazine, but it was being stubborn. Consequently, I will wait till I can obtain another magazine before I take this one apart. With my luck, I will probably break the bottom cover and have a Functionless/magazineless Carbine! I am not going to let that happen!

Talk to you gunnutz later!

Straight shootin, and keep it fun!
Click to expand...

Thanks for your efforts! Interestingly, in the manual, JR tells you how to determine if the Glock spring needs to be modified. Elsewhere in their manual it tells you all Glock mag springs have been inspected and modified at the factory!
I found the same problem with the mag plate coming off. I found that if I depressed the mag plate release button on the bottom of the mag and pushed against a wooden edge at the same time, the mag plate moves enough that you can then slide it off.
 
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