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MMR Issue

H

Hector

Copper BB
So I'm working on a buddy's MMR that has taken two trips back to Mossberg. The rifle has actually spent more time there than at his house. The problem has been jamming bullets. Both times the rifle has come back with grease on the feed ramps and no note or any indication of a problem. I took it apart and it looks like the upper receiver's feed ramps are way small and seems like the bullets are getting stuck there. Anyone have this issue? At this point, we are going to ditch the upper receiver with one with M4 feed ramps. I'm pretty sure that will fix it. Any help is appreciated as Mossberg has not been of help thus far.
Thanks
 
Welcome aboard @Hector .

Sorry to see you're having this issue. Not sure what we can do to help without being hands-on. Do you have any pics of the feed ramps, or lack thereof, you can share? I will say that Mossberg customer service can be hit or miss. Looks like your case is definitely chalked up in the miss column so far. Not sure who you've been dealing with at Mossberg, but we have a couple contacts that may be able to help...

Joe Zakher
jzakher@maverickarms.com

Norma Martinez
martinezn@mossberg.com

If you isolate the feed ramps as the problem, I would ask that Mossberg replace the upper receiver or even the entire upper. Either Joe or Ms. Norma should be able to help facilitate that. Good luck and keep us posted...
 
Something isn’t right but I doubt it’s the lack of M4 ramps because there are a lot of the same design upper that do not have the issue ……something might be out of spec in that area or somewhere else but the design seems sound or none of them would feed.

How many mags and what brands have you tried ?

Different ammo's do the same thing ?
 
That's the thing, we have tried:
1. Brass ammo- 3-4 brands
2. Steel cased ammo- 1 brand
3. Polymer Mag- P-Mags
4. Steel Mag- Mossberg
I shot it one time when it was having the issue and the rifle was really bad! The two times it came back from Mossberg it shot a full mag then went to jamming up every round. If I remember right, the bullet seemed to jam at the feed ramp. I'll get more info from my buddy. Joseph has contacted me as well so hopefully we can figure it out.
I have tried to find others with the same issue and have not, so hopefully this is an isolated case.
Thanks guys!
 
Have you checked the barrel nut or removed the barrel?

A loose barrel nut or improperly seated barrel could produce a downward cant to the muzzle end which would raise the feed ramps and cause loading issues. If the feeding issues are inconsistent this could point to something moving that isn't supposed to. You could try shooting the rifle with the end of the muzzle supported on a sand bag or a rest. If this reduces the number of failues the barrel nut or loose barrel might be the issue.

Another thing, have you checked to see if the mags are seating all the way up into position? If the mag is sitting too low relative to the feed ramps this could produce loading issues.

Hope you get it worked out...
 
I have disassembled the rifle and the barrel nut was nice and tight...
Mags seem to be seating properly as well.
I will try to shoot one of my uppers with the mossberg lower but all my uppers have the m4 ramps....
Thanks
 
Oh and I just confirmed with my buddy that to clear the jam he had to remove the magazine since the charging handle couldn't push the bullet through... This is what led me to the need ramps...
 
I took my Aero lower and compared it to the Mossberg. I don't think the lower is the problem. The bullet with the magazine in, rises to similar levels. The mag wells measure within a few thou of each other and dimensions look very close.
 
It'd be interesting to see if you can duplicate the failures with the Mossberg upper on your Aero lower...
 
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