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New MPR Prep

This is a discussion on New MPR Prep within the Ruger Semi-Auto forums, part of the Rifle & Shotgun Forum category; Th other day I picked up my new AR-556 - the MPR version. Holy cow - it was dripping oil and goo right out of ...


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Old November 23rd, 2019, 04:57 PM   #1
 
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Question New MPR Prep

Th other day I picked up my new AR-556 - the MPR version. Holy cow - it was dripping oil and goo right out of the box. I thought I did a good job cleaning it and getting it ready, but apparently not. On the range, several times it would completely miss pulling a round off the top of the mag, a few times it would chamber a round but the bolt would not close all the way and it would get locked up, then I had to really mortar it to get the bolt and round disengaged. A few times when it didn't fire and I was able to pull the bolt back, I really had to give it a few whacks to shake the round out.

The guys at the range said it looks a little too wet and sloppy, and this could be the issue.

I am hoping that this is just because I just didn't do a good enough job cleaning it. I'm going to make a go at it with a chamber brush and do a really deep cleaning on it; and take down the whole BCG and really make sure all of the old machining oil & grease is really gone.

Based on your past experience, does this sound like it could be the issue?

Thanks in advance.



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Old November 23rd, 2019, 07:18 PM   #2
 
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I've never seen any AR, regardless of manufacturer, fail to run dripping wet, (after an initial cleaning of course). If you had to mortar it, your initial cleaning wasn't thorough enough or it wasn't wet enough when you reassembled it. Buy yourself a can of Ballistol and hose the BCG down next time, as in dripping. It will run better and clean up super easy. My son had the same issue with his AR556, turns out his idea of wet and mine weren't the same, needless to say it runs perfect now.
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Old November 23rd, 2019, 07:30 PM   #3
 
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Thanks! I think part of the problem is what it is actually wet with. I'll bet that there is stuff in the BCG that is actually gumming stuff up and not letting the cam pin slide properly - thinking more and more I'll bet my quick clean was less effective that I thought. I am going to do a much more thorough and complete cleaning.
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Old November 24th, 2019, 05:59 AM   #4
 
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After you get it back together, with the BCG in battery, shoot some Ballistol in the ejection port, (to much will not cause a problem) and work the BCG. That's my preferred way to get it good and wet.
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Old November 24th, 2019, 09:37 AM   #5
 
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When it comes to cleaning, I don't use any finesse. A spray can of Walmart carburetor and intake cleaner and spay it down good. Keep in mind if you have any varnished products like wood on the rifle take those off first as the carb cleaner will damage the finish.
I do collect the spray cleaner in a pan and store it in a bottle for future use (car parts) but it cuts cleaning time down to nothing. As for the bolt carrier group, it's at the bottom of the pan and it gets a good bath. Take it apart and make sure all of the old oil and carbon are gone. When you put it all back together use a good quality gun oil that is a lubricant and not so much a stick on preservative like comes from the factory.
Using the spray on cleaner gives you the opportunity to start from zero and do it your way with the products you want to use.

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Old November 24th, 2019, 11:33 AM   #6
 
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Thanks for everybody's advice!
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Old November 24th, 2019, 06:05 PM   #7
 
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A local gun store near me has conic cleaners larfe enough to clean an ar upper with an 18 inch barrel. I use that on most new ars.
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Old November 24th, 2019, 06:41 PM   #8
 
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Yes, my MPR came slopping wet with some kind of liquid. Not sure it's lubrication. I field stripped it completely including the BCG and wiped al that liquid off. Then applied lube liberally. It has not missed a lick in over 300 rounds. I clean it after every range trip which works out to about 100 rounds each trip.
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Old November 25th, 2019, 05:04 PM   #9
 
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I gave it a good cleaning and the rifle is performing better, but was still FTF'ing every few rounds. Thanks to a very helpful LGS employee, we might have found the real issue... I was running Federal .223 from a bulk box that I picked up. He thinks, based on the way it was FTF'ing, that it might be short stroking it a bit due to a heavy buffer and not getting a good grab on the next round.

I grabbed a box of hotter 5.56 Hornady ammo and it ran through all 20 rounds perfectly, split across two mags that were initially giving me some trouble.

I found somebody else online who also complained that his (unknown) AR was also not cycling right with Federal bulk .223; it liked the hotter stuff.

Time will tell. Thanks again for everybody's advice.
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Old November 26th, 2019, 06:35 AM   #10
 
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When I first took my MPR to the range after thoroughly cleaning and oiling it, I had consistent problems with failure to feed and failure to eject. I was running Federal 5.56 XM193, and managed to get 80-100 rounds through that day. There were frequent stoppages; maybe 10 rounds out of each 20-round magazine.

I was stumped as to why the rifle was performing so poorly. Different magazines didn't seem to improve performance. After this range trip, I did another light cleaning, but not anything more than I had done the first time. Next time out to the range, and ever since then, I have had zero malfunctions. Maybe 200-300 rounds through so far without a hiccup.

I'm still not sure exactly what the issue was. Maybe it just needed to get broken in a little... But, I'm super happy with the rifle now. It's really pleasant to shoot. The longer gas system and muzzle brake make for a very smooth-shooting rifle.

Below is a pic of some rounds that were jammed in the rifle. Most of the malfunctions involved the empty case being ejected and the next round being wedged under the bolt. The dimples in the case are from the lugs on the bolt digging into the brass. Occasionally, the spent case failed to eject as well.
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Old November 27th, 2019, 07:01 AM   #11
 
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Exactly - my "bad" rounds looked exactly the same as yours! I wound up dumping about 30 dinged up rounds on the floor of the range before I left. Hopefully, like yours, this will work itself out over time. When it does cycle properly, it is a great performing rifle.

Quote:
Originally Posted by LumberjackMac View Post
I'm still not sure exactly what the issue was. Maybe it just needed to get broken in a little... But, I'm super happy with the rifle now. It's really pleasant to shoot. The longer gas system and muzzle brake make for a very smooth-shooting rifle.

Below is a pic of some rounds that were jammed in the rifle. Most of the malfunctions involved the empty case being ejected and the next round being wedged under the bolt. The dimples in the case are from the lugs on the bolt digging into the brass. Occasionally, the spent case failed to eject as well.
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Old December 8th, 2019, 04:11 PM   #12
 
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dang dude i did the same think but the mpr i bought ran like a greased pig at the county fair shot hornady frontier 55gr and 75gr american eagle 55 62 grain even ordered some buffalo bore 77 gr fiocchi 69 grain federal gold medal 77 gr it ran everything great barrel doesnt like 55gr doesnt group well 62 does ok but 69 and 77 grain it loves it. just got a box of black hill 77 grain tmk gonna try some longer range with it been shooting 100 yds with 3x9x50 hunting scope its just under 1 inch groups with 69 and 77 bullets 55 it opens up to about 2-3 inch groups no problems so far
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Old December 13th, 2019, 06:57 PM   #13
 
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new mpr, jam-o-matic, tried different mags, ammo , bcg, buffer, spring, pulled handguard, gas block was loose , tightened set screw, runs great now
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Old December 16th, 2019, 06:26 AM   #14
 
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I used to run my AR15 pretty wet. I used Pro Shot one-step CLP, and I used to drip it in the holes in the bolt, and in the chamber after I cleaned it before putting it in my safe. I would just take it out and shoot it, never had an issue. Some people like Hickok45 prefer to run them wet vs dry as well.

I personally am a proponent of lube- just makes more sense to me than running something relatively dry. I switched to Lucas Oil Extreme duty gun oil, and it is like KY in a firearm. Not stripping a round off the top of the mag could be the mag, or light loads not shoving the bolt back hard enough... I had an issue with one where the person that built it put a longer barrel buffer spring in a carbine buffer tube- cause the bolt to not cycle fully...
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Old January 6th, 2020, 12:05 PM   #15
 
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My MPR came with a defective mag. I could put it in, then push on it and it would go in another half inch or so....since I threw it away and replaced it, the gun has run perfectly.
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