Questions from an AR virgin.

OK, yesterday was the first trip to the range with the new AR platform. Overall, I'm pretty pleased with the Mossberg MMR Hunter, I got groups of just over an inch despite the miserable factory trigger with its gravel road feel and 2.3 miles of creep. A new trigger is already on order...

I got her on paper with some economy handloads, but I had two observations/issues.

1. There is a pronounced kaa-pooinggggg after I fire each round. Obviously this is the buffer/recoil spring, but the vibration after each round fired can be felt/heard through the stock for a couple of seconds after the round is fired.

Is this normal for the viberations to be this pronounced and to continue for this long? Is there a fix for this?

2. The range session was abruptly ended by a round that didn't fire and remained stuck in the chamber. And, of course, my cleaning rod didn't make it back in the range kit. I tried lowering the bolt serveral more times including letting it slam home quite forcefully. It wouldn't fire.

After removing it easily with a cleaning rod back at the ranch, I noticed the primer was not even dented. I was expecting a slightly dented primer, or one that was fully struck and just didn't go off. The primer is properly seated, nothing out of the ordinary.

I stripped the rifle down and fully cleaned it, inspecting the firing pin. Everything is functioning fine. I confirmed it by firing two primed cases.

What gives?

Many thanks.

Grouse
 
dunno abou 1, you do hear the spring but I can't say I ever noticed it lingering.

2 is what happens when the bolt fails to go into battery, usually a sign that it needs cleaning. The hammer drops but it doesn't fire.

In order to fire that round, the hammer has to be cocked again. If you can pull the BGC back far enough, that will cock it. If you can't but you can get the bolt fully in battery, you can remove the rear take down pin, crack it open & manually cock the hammer back. Close it up & fire the round.

Then stop & clean the rifle
wink.gif
 
Your chamber could be a little on the tight side. A tight chamber will prevent some rounds from chambering completely, resulting in the bolt being a bit out of battery. When the bolt is out of battery, the firing pin cannot contact the primer.

It could be that there is some preservative or something in the chamber which gives the same results, so you should clean it thoroughly with solvent. It could also be that the round in question is out of spec. However, there are certain AR makers that tend to put out the occasional tight chamber and you may have gotten one
 
Could of been the brass wasnt sized all the way. It takes a lot of shooting to dirty up a chamber to not close on a round. And yes if the bolt isnt all the way into battery it wont go bang. Was the brass different headstamps? I agree with some chambers being tighter than others. Reamers wear out especially reaming production barrels.
 
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The sproing of the action spring is normal, but is worse if the inside of the receiver extension is a bit rough. Getting an RE with a smooth inside will go a long way to making it quieter and sometimes the sproing will get quieter as the rifle is shot more. Some will lightly coat their springs with grease but that has the potential of introducing other problems
 
I had it happen once with factory ammo. New rifle, prolly enough rounds fired -with no problems- that it needed to be cleaned.
 
RE 1: It is normal. Few options in addition to above: get a heavier buffer, get adjustable gas block, get JP Enterprise's captured buffer.


Going the JP route is a surefire way to eliminate that twang.
 
Originally Posted By: Stu Farishdunno abou 1, you do hear the spring but I can't say I ever noticed it lingering.

2 is what happens when the bolt fails to go into battery, usually a sign that it needs cleaning. The hammer drops but it doesn't fire.

Then stop & clean the rifle
wink.gif



This would appear to describe what happened. I wasn't aware of it, but is it true that UNLIKE a bolt action, the AR hammer will drop with the gun out of battery?

I think that's what threw me. The hammer was dropping, I had that solid clunk after the trigger was pulled, but no dented primer.

So the round might not have gotten sized propely or I have a tight chamber? I'm pretty sure it wasn't a dirty gun as at the point of the stuck round, I had fired 39 rounds.

That leads to another question. Should this happen again, is there any trick that would extract the round WITHOUT a cleaning rod?

BTW, thanks for the feedback for those that addressed the "kapoing" question. Just wanted to make sure that wasn't out of the ordinary.

Grouse
 
Originally Posted By: The Famous GrouseOriginally Posted By: Stu Farishdunno abou 1, you do hear the spring but I can't say I ever noticed it lingering.

2 is what happens when the bolt fails to go into battery, usually a sign that it needs cleaning. The hammer drops but it doesn't fire.

Then stop & clean the rifle
wink.gif



This would appear to describe what happened. I wasn't aware of it, but is it true that UNLIKE a bolt action, the AR hammer will drop with the gun out of battery?

I think that's what threw me. The hammer was dropping, I had that solid clunk after the trigger was pulled, but no dented primer.

So the round might not have gotten sized propely or I have a tight chamber? I'm pretty sure it wasn't a dirty gun as at the point of the stuck round, I had fired 39 rounds.

That leads to another question. Should this happen again, is there any trick that would extract the round WITHOUT a cleaning rod?

BTW, thanks for the feedback for those that addressed the "kapoing" question. Just wanted to make sure that wasn't out of the ordinary.

Grouse




Yes, the hammer will drop even when the bolt isn't fully into battery. However the floating firing pin prevents the round from ingnighting. The pin never makes it.

When charging the rifle, your hands should be nowhere ne'er the charging handle. Lock it to the rear, then hit the release. Or, bring the charging handle fully to the rear, and let go. This is how the rifle is designed to work, it hurts nothing. (This is just to cover basis, I am not saying you're not charging the weapon in this way...just covering the topic) If the rifle does not go into battery when properly charged, then there is one of two issues...round or the firearm. Since there were many others that fired, I would suspect the round.

And for future reference, colapse the stock, and strike the butt of the rifle on the bench, while pulling back the charging handle. This will clear any bolt/round issues. And it is perfectly safe for the forearm...just maintain proper muzzle control and clearance.
 
I have yet to have the vibration/spring noise effect as you mentioned.
One thing I did w/both my MMRs was to pull the buffer (its rifle length)take the plastic top off and added my own rubber washers I made due to the fact the inside parts are not snug, that may stop some of the spring/vibes. I just put them on top to fill the space under the plastic top.
I can say buy a replacement buffer top as the very hard plastic one in the MMR will actually separate sooner than later.
I had both the tops split on mine and Mossberg WILL NOT replace them, they want the whole gun back or tell you since you took it apart to find the problem it voided the warrantte....BS on their part so they don't have to replace a $6 item.
 
Originally Posted By: 5spdOne thing I did w/both my MMRs was to pull the buffer (its rifle length)take the plastic top off and added my own rubber washers I made due to the fact the inside parts are not snug

The weights inside the buffer are supposed to float around. They are to act as a shock absorber to reduce carrier bounce
 
Originally Posted By: MistWolfOriginally Posted By: 5spdOne thing I did w/both my MMRs was to pull the buffer (its rifle length)take the plastic top off and added my own rubber washers I made due to the fact the inside parts are not snug

The weights inside the buffer are supposed to float around. They are to act as a shock absorber to reduce carrier bounce

Yep...similar to how a dead blow hammer works.
 
The spring noise drove me crazy in the beginning. If you put a very light coating of axle grease on the spring it will stop the noise. Just coat the whole thing lightly.

I have read this "can" be bad as it could collect dust or leak when it gets hit or whatever but I have never had an issue with this on any of my rifles. We have a lot of dust and heat....
 
As stated, your spring noise can be abated a little by a very light (and I emphasize light) application of a heavy grease that has been wiped off but you will need to inspect is routinely for dirt/debris build up...Or, you can spend a few bucks and obtain a David Tubbs Flat Wound Action Spring and that will also reduce the noise without any negative effects...Since I normally shoot with hearing protection, I guess my brain has eliminated the sound from my consciousness, as I am not aware of it while shooting anymore...

Your failure to seat or hard extraction is likely caused by gunk that was left over from the barrel manufacture that normal cleaning seldom removes...Take a section of your kit cleaning rod and install your chamber brush...Chuck the rod into a cordless drill motor, apply a couple of drops of lubricant to the brush and spin the brush in the chamber for 20-30 seconds and then wipe it out with a clean patch wrapped around the brush..I've had the same problem in the past with most ARs and I now make that part of my normal cleaning routine...

You're not seeing any primer strikes on the primer, as the firing pin should not even free float to make contact if the bolt is not fully closed and if it's not fully closed, even though the hammer is activated, the geometry angle will not allow it to contact the rear of the firing pin unless the bolt is fully engaged and locked...Just a safety factor that is built into the design...
 
I appreciate all the advice. A couple of updates.

The ka-poingggggggg of the buffer/spring was mainly a question of "Is this normal?". Some of the old recoil-driven semi-auto shotguns like the Browning A-5 have a similar sound/feel, but with the MMR, it's not so much that I can hear it as I can feel the vibration in the stock for 5 seconds or more after the last round.

I may try to dampen it with grease, but here in the arctic tundra that might not be the best move in the winter. I think I will shelve this issue until spring.

Regarding the stuck round, I have now cleaned the rifle thoroughly a second time including the chamber. I had already given it the "factory de-gunk" cleaning treatment before I shot it the first time, as I do with all new rifles. They all seem to come with MUCH more grease, gunk, oil, goo, etc on them than I would ever use. The Mossberg was no exception, it was leaking oil like the Exxon Valdez from being overlubed at the factory.

So hopefully with the latest cleaning, I've eliminated manufacturing leftovers as the cause or a possible cause. Since it happened after I had fired over 25 rounds, I have to think that somehow that round that stuck was just a little tight. But I'll be bringing a cleaning rod and kit with me next time to the range, that's for sure.

Grouse
 
As Mr. Old Turtle suggested, I would immediately replace the spring with a Tubb spring. Do that and the need to grease the spring, etc is gone.

http://www.midwayusa.com/product/693755/...-chrome-silicon

I have these in my rifles and they are WAY better than the customary factory springs. The rifle locks up more solidly and the noise is 98% gone.

A good fix (in my opinion, but some will argue) is the RR National Match 2-stage trigger. It's not benchrest material, but for a great hunting trigger it is well worth the money. I have bought a few from a guy on eBay. You can't beat the price and he ships quickly.

http://www.ebay.com/itm/Rock-River-Arms-...=item2c92542cf4

Just my thoughts.
 
I'm not going to argue with Hidalgo, I put the RRA trigger in my M&P15 and am very happy with it. I found it at a local shop for 120 and saw it online for about 99 so with free shipping that is a really good price.
 
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