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Discussion Starter #1
I’m having an issue with a JRA BM59, but being as it’s essentially the same function as a M14, I thought this would be a good place to start. The issue has to do with light primer strikes from the firing pin.

I locked the bolt back and inserted the magazine. I pulled the bolt all the way aft to release the bolt lock and allowed the bolt to travel forward chambering a round. The first round would fire properly. The rifle also seemed to cycle properly chambering another round from the magazine. However, the next trigger pull resulted in a light strike on the primer and a failure to fire. I manually extracted the round and allowed the bolt to travel forward, chambering the next round from the magazine. Again, this round fired properly and the bolt cycled. But again, the next round register a light strike on the primer and a failure to fire. I repeated this process a total of six times with the exact same result. The rifle functions properly after manually cycling the bolt, but does not fire on the next round after the bolt has cycled from a round being fired. I was using PPU 7.62x51mm M80 FMJ BT 145 gr.

Anyone ever hear of an issue like this? Only thing I can think of is some sort of issue with the gas operating system.
 

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Might be an ammo issue. Try some other ammo, like the Fed AE M1A load or Fed Match. Might be the PPU is not allowing full bolt closure. If it was a gas issue, it likely would not reset the trigger, or would short stroke and not pick up a round to chamber.
If the hammer is falling, but not hitting the primer hard enough, I suspect ammo.
You are sure the hammer is actually falling, getting a big CLICK when you pull the trigger?
 

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Discussion Starter #3
Might be an ammo issue. Try some other ammo, like the Fed AE M1A load or Fed Match. Might be the PPU is not allowing full bolt closure. If it was a gas issue, it likely would not reset the trigger, or would short stroke and not pick up a round to chamber.
If the hammer is falling, but not hitting the primer hard enough, I suspect ammo.
You are sure the hammer is actually falling, getting a big CLICK when you pull the trigger?
Yes the hammer is definitely falling and after ejecting the round there is a slight dimple in the primer. I would say ammo is the culprit, but the why does it fire every time the bolt is manually cycled?
 

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A bit more inertia perhaps allowing the bolt to fully close. If the bolt isnt fully locked, it wont fire. Try some other ammo. Could also be perhaps the firing pin is gunked up inside the bolt. Strip the bolt and clean it out.
 

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When you fire a round and the next one chambers, check to see if the bolt is fully locked by pushing down on the right lug. If the bolt turns a bit, try firing the round.
 

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Examine the leading edges of the hammer with a light and a magnifyer. There is an edge on the safety cam that swings close to the edge of the safety bridge in the receiver, and I've seen it that if it bumps slightly during the swing, it robs enough energy that you get light strikes. If it is hitting, it should leave a tiny silver mark on the hammer where there is contact. If you see it, just take a dremel and take a little material off the hammer.
 

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Discussion Starter #7
When you fire a round and the next one chambers, check to see if the bolt is fully locked by pushing down on the right lug. If the bolt turns a bit, try firing the round.
Didn’t think to check this unfortunately. Let’s say that is the case, what is the fix? Is it because the gas bleed pressure is not high enough on the op rod to fully retract the bolt, which then reduces the forward energy of the bolt due to the reduced spring compression?
 

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Discussion Starter #8
Examine the leading edges of the hammer with a light and a magnifyer. There is an edge on the safety cam that swings close to the edge of the safety bridge in the receiver, and I've seen it that if it bumps slightly during the swing, it robs enough energy that you get light strikes. If it is hitting, it should leave a tiny silver mark on the hammer where there is contact. If you see it, just take a dremel and take a little material off the hammer.
This I can check without going to the range. Will post results when I’m able to check.
 

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Didn’t think to check this unfortunately. Let’s say that is the case, what is the fix? Is it because the gas bleed pressure is not high enough on the op rod to fully retract the bolt, which then reduces the forward energy of the bolt due to the reduced spring compression?
If the bolt wasnt retracting far enough, it wouldnt strip another round off the top, or the trigger wouldnt reset. You may have a tight chamber and the PPU ammo may be a bit long on headspace.
 

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Didn’t think to check this unfortunately. Let’s say that is the case, what is the fix? Is it because the gas bleed pressure is not high enough on the op rod to fully retract the bolt, which then reduces the forward energy of the bolt due to the reduced spring compression?
Yes. You would be operating on that fine line. Either your operating system is slightly retarded or your ammunition is slightly underpowered.
 

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PPU had been known to cause issues. I would like to get a box of 20 to test but this the reason i never ordered it.
 
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PPU had been known to cause issues. I would like to get a box of 20 to test but this the reason i never ordered it.
PPU can be hard to chamber, requiring every bit of "oomph" that the operating system can generate. This can be rough on the extractor as well.

I always start with the ammo when diagnosing a malfunction. playpump, try some Federal to see if the same symptom occurs.
 

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Discussion Starter #14
It’ll be a little while before I can make it back out to the range to test a different M80 ammo. Would leave me with 200 rounds of PPU 7.62 I can’t use in the BM59, but I could always use it in my M1A. Any reason I shouldn’t use it in the M1A?
 

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Discussion Starter #16
JRA recommended Lake City and said PPU often has issues in the BM59. Unfortunately Lake City M80 ball is almost impossible to find right now unless you want to buy 500 rounds, which I don’t until I know if it functions properly. I contacted JRA to see if they would send me a box to test and they were gracious enough to oblige. They are also sending a new trigger housing to swap out as that can sometimes cause the issue as well. So far very pleased with their customer service and hopefully can get this thing running properly.
 

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JRA sent you a new trigger group and a box of ammo?
That’s fantastic.
Hip hip hooray for JRA!!
 

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Discussion Starter #18
They are. I have to return of of the trigger groups, but still pretty awesome that they are sending me a spare to test out.
 
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