JR Carbine - Gun, Ammo or Me? *BIG PICS*
- Thread starter geclark
- Start date
I have played around with mine for a while now.
Factory ammo of ANY type does not reliably feed! When the rifle fires, it feels like the bolt slams back too hard.
I took a box of factory and pulled all the bullets.
I wieghed the charges to come up with an average.
Took that weight and reduced it by 0.4 grains.
Reloaded the ammo with that slightly reduced charge.
After this modification, the rifle performed flawlessly!
I loaded up 200 rounds of ammo with the powder charges 0.2 grains above the mid point charge of three different powders.
The rifle fed everything perfectly!
The rifle simply isnt set up at the factory to shoot/function at factory ammo pressure levels! Pooooor QC!!!
Factory ammo of ANY type does not reliably feed! When the rifle fires, it feels like the bolt slams back too hard.
I took a box of factory and pulled all the bullets.
I wieghed the charges to come up with an average.
Took that weight and reduced it by 0.4 grains.
Reloaded the ammo with that slightly reduced charge.
After this modification, the rifle performed flawlessly!
I loaded up 200 rounds of ammo with the powder charges 0.2 grains above the mid point charge of three different powders.
The rifle fed everything perfectly!
The rifle simply isnt set up at the factory to shoot/function at factory ammo pressure levels! Pooooor QC!!!
Ar180shooter
CGN Ultra frequent flyer
- Location
- Ottawa, ON
On a more positive note, I took a 9mm JR Carbine to the range on Sunday to zero it, and it functioned great. There were a few FTE's at the beginning, but by the end of the first box of ammo, these had virtually stopped. Great little carbine.
Clobbersauras
CGN Ultra frequent flyer
- Location
- Waaay out west.
One thing to remember with blowback operated firearms is that they can be affected greatly by your stance and grip, similar to limp wristing a Glock or other pistol. You have to make sure you have the rifle firmly planted into your shoulder. It doesn't look like the problems addressed in this thread are caused by this but it can give a user FTF and FTE in some rifles.
I have the .40S&W version and have also found the above statements to be true. I've got a few ideas and some replacement parts on order. I'll update if everything works out. Fingers crossed.
I'm also kinda leaning towards this. I notice that my primers are all extruded (factory 180gr ammo) and the bolt is moving so fast it's catching the spent brass before it leaves the upper receiver, destroying it in addition to stripping a round from the mag and hammering into the crude, sharp feed-ramp-thing before the barrel.
So, need to address a way to slow the bolt down more (more weight? Stronger springs?)
I'm not giving up yet, but it is definitely disheartening.
The rifle feels good and is very accurate; I've owned a CX4 storm and the JR (when it shoots) is noticeably more accurate. Unfortunately the JR is nowhere near as reliable as the CX4 out of the box.
Luckily I've got time and nothing on the go, so I am determined to get this thing working right.
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Well, I got my replacement parts today in the mail.
I set out to do a mass part replacement approach in the hopes that I'd find multiple different parts and replace as necessary. Parts that were replaced: buffer, firing pin, extractor, rubber buffer and removable-feedramp.
Now, of all the items I received, only 2 were different.
-The *new* rubber buffer is .744" in length
-The *new* removable feed ramp is much more aggressive and lower (looks much nicer).
I think these will help, but, as DTHUNTER has posted, it would appear that the gun just can't handle the pressures in stock form; light loads and the guns runs fine. Normal loads and you run the risk of it choking.
So I am sitting here with all these parts and I am thinking what was so different about my .40S&W CX4 Storm. The one thing I distinctly remember from the CX4 was the MASSIVE bolt carrier group.
From memory when comparing the CX4 bolt carrier group to the JRCarbine, the JR's is tiny. It's like comparing a full-sized carrot to a baby carrot that's been cut in half.
I would now bet money that if we could add mass/resistance to the bolt it would solve a LOT of issues (also probably why the 9mm's are running fine, but the .40/.45 are the issue guns).
For starters, I now want to try replacing the buffer spring with a WOLFF eXtra-Power spring.
Does anyone know who'd carry these in Canada? I know I can order from WOLFF but I'd prefer to get the item before the end of the week in order to test on the weekend
The other part I want to swap is the buffer.What is the absolute HEAVIEST BUFFER on the market?
Thoughts?
I set out to do a mass part replacement approach in the hopes that I'd find multiple different parts and replace as necessary. Parts that were replaced: buffer, firing pin, extractor, rubber buffer and removable-feedramp.
Now, of all the items I received, only 2 were different.
-The *new* rubber buffer is .744" in length
-The *new* removable feed ramp is much more aggressive and lower (looks much nicer).
I think these will help, but, as DTHUNTER has posted, it would appear that the gun just can't handle the pressures in stock form; light loads and the guns runs fine. Normal loads and you run the risk of it choking.
So I am sitting here with all these parts and I am thinking what was so different about my .40S&W CX4 Storm. The one thing I distinctly remember from the CX4 was the MASSIVE bolt carrier group.
From memory when comparing the CX4 bolt carrier group to the JRCarbine, the JR's is tiny. It's like comparing a full-sized carrot to a baby carrot that's been cut in half.
I would now bet money that if we could add mass/resistance to the bolt it would solve a LOT of issues (also probably why the 9mm's are running fine, but the .40/.45 are the issue guns).
For starters, I now want to try replacing the buffer spring with a WOLFF eXtra-Power spring.
Does anyone know who'd carry these in Canada? I know I can order from WOLFF but I'd prefer to get the item before the end of the week in order to test on the weekend
The other part I want to swap is the buffer.What is the absolute HEAVIEST BUFFER on the market?
Thoughts?
True, but I am too far in.
I noticed that JR Carbine is now selling a 9.7oz buffer.
"Brass 9.7 ounce buffer for .45ACP models. Can also be used in 9mm and .40S&W models."
http: //shop.justrightcarbines.com/Buffer-For-45ACP-A0013BRASS.htm
I suspect that would do it. Because:
"Stainless 7.6 ounce buffer for 9mm and .40S&W models. Not for use in .45ACP models."
Looks like I was on the right track. I'll order the brass one and report back after a week or so
Cheers~
True, but I am too far in.
I noticed that JR Carbine is now selling a 9.7oz buffer.
"Brass 9.7 ounce buffer for .45ACP models. Can also be used in 9mm and .40S&W models."
http: //shop.justrightcarbines.com/Buffer-For-45ACP-A0013BRASS.htm
I suspect that would do it. Because:
"Stainless 7.6 ounce buffer for 9mm and .40S&W models. Not for use in .45ACP models."
Looks like I was on the right track. I'll order the brass one and report back after a week or so
Cheers~
Hope it works out for you, i wasted lot of time and ammo on the 45 acp.
!!!!!!!!
Mine too had this same issue, i figured the buffer deal out and trimmed mine, im telling you guys its mag related, i did the mag fix like jr says, and still stove pipes and jams on the 7th round cutting a hole in the brass, when i use my after market mag it works fine all ten rounds down range, i will swap mine over to a 1911 mag well first chance i get and itll be fine guaranteed, its the crap glock mag
Mine too had this same issue, i figured the buffer deal out and trimmed mine, im telling you guys its mag related, i did the mag fix like jr says, and still stove pipes and jams on the 7th round cutting a hole in the brass, when i use my after market mag it works fine all ten rounds down range, i will swap mine over to a 1911 mag well first chance i get and itll be fine guaranteed, its the crap glock mag
I sent mine back but kept the extra glock mag i ordered. I have put 300 rounds through my kriss superv with that mag with out any issues. The glock mag may have issues with the jrc but i dont think the glock mag is crap, i think the jrc design for the glock mag is crap.
After 300 rounds of cast 230's, not a single misfeed or damaged case! Whoohoo!
JR said that these rifles could/should not use cast bullets. Thats a load of malarky!
my bore chambered and shot the whole works as though it was jacketed!
I used Clays (3.8 Gr) and Trailboss.
The trailboss load (4.5),230 cast RN, Tumble lubed in Lee Liquid Allox.
Ave velocity is 830fps, and shoots about 3" or less at 75 yards.
This load was very soft shooting. It seemed to match the rifles setup/spring and buffer weight perfectly. When the rifle fired, the action came back, but never hit the full rearward point of the bolt travel. Sort of changed the way this rifle feels when shooting.
JR said that these rifles could/should not use cast bullets. Thats a load of malarky!
my bore chambered and shot the whole works as though it was jacketed!
I used Clays (3.8 Gr) and Trailboss.
The trailboss load (4.5),230 cast RN, Tumble lubed in Lee Liquid Allox.
Ave velocity is 830fps, and shoots about 3" or less at 75 yards.
This load was very soft shooting. It seemed to match the rifles setup/spring and buffer weight perfectly. When the rifle fired, the action came back, but never hit the full rearward point of the bolt travel. Sort of changed the way this rifle feels when shooting.
killer1963daddy
Regular
- Location
- peace river country B.C.
can we get a sticky on this thread? a lot of jr owners need this thread, or people thinking of buying one need to read this!
killer1963daddy
Regular
- Location
- peace river country B.C.
is there a date on this? i am pissed !
oops ment to quote the "new bolts being built" anouncement!
is jrc shipping parts free of charge?bolts, springs,buffers ,ramps???
how about free tools?
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killer1963daddy
Regular
- Location
- peace river country B.C.
ok, cooled off a bit, pulled gun apart, ran amo thru chamber in slow mo with just the bolt by hand, found the sharp edge and rough machining on the botttom of the bolt was indeed marking (and trying to drag forward)the casing still in the mag.
polished up the "stripper", and lightly polished the rest of the bolt with emery, untill it ran smooth in the striped reciever.
in addition the 10 round glock mag was only able to hold 9 rnds, so i removed coils from the bottom one at a time and re stretched the spring to oem lenth., i beleive i am at 3 coils (it was kinda late last night) and gave it a more agresive push to the back of the follower than shown on the jr website.i can now get 10 rnds in the mag, but it is too swollen to insert into the rifle! so i will try one more coil later.
as well, removing the coils and stretching the spring has lessend the upward force on the amo, lessening the damaged caused by the stripper on the bottom of the bolt.
the rifle would fire 3 0r 4 rounds before jamming as oposed to 2rnds max before, the brass showed a lot less stress as well
i then began reducing the load progressively, firing a single round,then checking the barrel/chamber before running the mag.
i am at 3.5 grains of hodgdon HP-38 with 230g fmj and just ran 9rnds in a row!.. so i guess i will make some low power rounds till i get some joy from jr(heavier buffer weight=more inertia)
also i have been playing with mag position (it flops around like a d!c in a shirt sleeve!) holding a little back presure on the mag seems to help, why it dosnt have a proper mag well is beyond me!?!?!?!?! i will experiment with this, and perhaps build a brace and or magwell extension.
gonna build some more rounds head to the range for some more testing later today or tomorow...will do an update
k69d
polished up the "stripper", and lightly polished the rest of the bolt with emery, untill it ran smooth in the striped reciever.
in addition the 10 round glock mag was only able to hold 9 rnds, so i removed coils from the bottom one at a time and re stretched the spring to oem lenth., i beleive i am at 3 coils (it was kinda late last night) and gave it a more agresive push to the back of the follower than shown on the jr website.i can now get 10 rnds in the mag, but it is too swollen to insert into the rifle! so i will try one more coil later.
as well, removing the coils and stretching the spring has lessend the upward force on the amo, lessening the damaged caused by the stripper on the bottom of the bolt.
the rifle would fire 3 0r 4 rounds before jamming as oposed to 2rnds max before, the brass showed a lot less stress as well
i then began reducing the load progressively, firing a single round,then checking the barrel/chamber before running the mag.
i am at 3.5 grains of hodgdon HP-38 with 230g fmj and just ran 9rnds in a row!..
so i guess i will make some low power rounds till i get some joy from jr(heavier buffer weight=more inertia)also i have been playing with mag position (it flops around like a d!c in a shirt sleeve!) holding a little back presure on the mag seems to help, why it dosnt have a proper mag well is beyond me!?!?!?!?! i will experiment with this, and perhaps build a brace and or magwell extension.
gonna build some more rounds head to the range for some more testing later today or tomorow...will do an update
k69d
Agreed! A local dealer has a .40 on display, but is hesitant to sell it because of the issues. He said the 9mm work flawlessly, the larger cal ones not so much. He cant get any 9mm right now. He figured if he could he would of been able to sell 20+ of the JR.
