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New MPR jamming

This is a discussion on New MPR jamming within the Ruger Semi-Auto forums, part of the Rifle & Shotgun Forum category; Hello been a ruger fan for many years, had an SR556 that has worked flawless for years. Got a great deal on a new MPR, ...


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Old September 17th, 2018, 04:20 PM   #1
 
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New MPR jamming

Hello been a ruger fan for many years, had an SR556 that has worked flawless for years.

Got a great deal on a new MPR, cleaned it real good to get the factory gunk out of her like I do on all my firearms, ran a clip of federal ammo through it and it worked flawless, about half way through the second mag it started to jam every other shot, a couple into the 3rd mag it jammed with the bolt in the closed position with a round in the chamber, trigger would not depress, charging handle would not open the bolt to eject the round.

I had to disassemble the gun to pry open the bolt to remove the round, after putting it back together it can now be charged again, but have not shot it since.

Any thought on to whats going on with this brand new rifle?



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Old September 17th, 2018, 06:09 PM   #2
 
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Sounds like you had a bullet setback from a jam and had an over pressure round. I had the same happen with Tula ammo. Bullet setback is when the bullet gets pushed back into the case due to a missfeed when chambering. This causes the pressure to increase to the point where you get a stuck case. Your trigger wouldn't work because it wasn't reset.

As to the base issue, MPR's tend to be ammo sensitive due to the bolt carrier design and stiff recoil spring. The easiest, but not cheapest way, to fix this is replace the bolt carrier with one with a full auto profile. Otherwise the gun just needs to be broken in. Let us, and Ruger, know if it happens again.
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Old September 20th, 2018, 03:09 PM   #3
 
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Quote:
Originally Posted by csuengr View Post
Sounds like you had a bullet setback from a jam and had an over pressure round. I had the same happen with Tula ammo. Bullet setback is when the bullet gets pushed back into the case due to a missfeed when chambering. This causes the pressure to increase to the point where you get a stuck case. Your trigger wouldn't work because it wasn't reset.

As to the base issue, MPR's tend to be ammo sensitive due to the bolt carrier design and stiff recoil spring. The easiest, but not cheapest way, to fix this is replace the bolt carrier with one with a full auto profile. Otherwise the gun just needs to be broken in. Let us, and Ruger, know if it happens again.
excuse my ignorance, my last ruger was piston gun so the bolt was different, so with that being said what is the issue with this bolt and why does it not work the way it should, is there a better replacement you can recommend?
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Old October 11th, 2018, 05:33 AM   #4
 
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Update

So I bought some new cleaner and gun lube and gave her another work over. loaded up 15rds into a magpul g3 mag and the gun continued to no cycle the next rd, then i loaded up 15rds into the magpul g2 mag that came through it and they all cycled fine. Then I tried another g3 mag and it was doing the same as the first.

At this point I was thinking this gun had an issue with the G3 version, so I continued to put lead down range with the G2, after about six of these mags going through the gun without failure I tried another G3 mag, to my surprise all cycled without issue, so i tried severals others and they all have been good since.

I dont know what the issue was with the G3 mags as first but the issue has seemed to clear.

I did see at the end of range day that the mlok hand guard had started to back away from the upper.

Has this been common with the MPR?
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Old October 11th, 2018, 07:47 AM   #5
 
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The Ruger DI (Direct Impingement) guns use a unique bolt carrier profile (on the bottom at the rear of the firing pin) that creates extra effort to push the bolt back. This causes some short cycling, along with the fore mentioned recoil spring. Both of mine took a couple hundred rounds before they would feed from a Magpul D60. Neither will run Tula still.

Both my hand guards started to back off. They have a lousy attachment. That is part of how Ruger kept the price low. I took my hand guards off, wiped the oil from them and the barrel nut, put them back on and put BLUE lock tite on the screws and cranked them down. The hand guards haven't moved since.
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Old October 11th, 2018, 09:11 AM   #6
 
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seems like setback to me.
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Old March 11th, 2020, 10:04 AM   #7
 
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MPR Rifle. I am having a fail to feed issue and fail to lock back on empty issue. It can happen anytime after about 10 rds are fired in a string and especially after 50 to 60 rds are fired. This is a duty gun and our strings of practice fire can be fired pretty rapidly leading to heat build up. There is a polished ring on the bolt carrier next to the extractor pin (not sure what its called). The fit is very tight between the bolt carrier and this ring.
When I swapped out bolt carrier groups the gun functioned flawlessly. The gun has between 600 and 800 rds down the barrel. Is this a break-in issue?
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Old March 11th, 2020, 12:33 PM   #8
 
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Quote:
Originally Posted by stryker6040 View Post
Update

So I bought some new cleaner and gun lube and gave her another work over. loaded up 15rds into a magpul g3 mag and the gun continued to no cycle the next rd, then i loaded up 15rds into the magpul g2 mag that came through it and they all cycled fine. Then I tried another g3 mag and it was doing the same as the first.

At this point I was thinking this gun had an issue with the G3 version, so I continued to put lead down range with the G2, after about six of these mags going through the gun without failure I tried another G3 mag, to my surprise all cycled without issue, so i tried severals others and they all have been good since.

I dont know what the issue was with the G3 mags as first but the issue has seemed to clear.

I did see at the end of range day that the mlok hand guard had started to back away from the upper.

Has this been common with the MPR?
Don't know how well you lubed your bolt carrier assembly but most AR's run well with very liberal lube on them to the point it is almost dripping off especially when you are breaking it in. After break in you can back off the lube a little. AR's will run dirty and wet but not so much dirty and dry.
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