What is up with this?

K

Kodiac

New member
This weekend my beloved Bushmaster did something strange - 3 times with two different mags... The rifle miss fed three rounds at different times, the rounds came part way out of the mags, with the bolt bending the rounds in the middle - like the bolt is hitting the case in the middle of the length. This was all with the same ammo - ammo I had no faults with before - factory reloads... Ultra Max stuff. Any Ideas? Bad lot of ammo and not getting the pressure to push the carrier all the way back? Any one else have a jam like this? I had to strike the butt of the AR on a stump while pulling the charging handle at the same time to get the bolt unstuck...
I usually end up getting rid of guns that start jamming up on me - like a faulty employee - they get "fired". I would hate to fire this Bushmaster... Its done good - freakyly accurate - nailed a crow on the wing at about 100 yards (God's Truth).
And the guns Hygien is impecable - gets cleaned more often than my blue jeans...
Maybe it is a magazine issue? These are relativly new mags - with fresh springs too.



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"I got a bad feeling about this..."
 
I don't mean to start a flame here, but I can't stand it anymore.
I'm sorry Bulldog, but you're working from old and inaccurate information.
The USMC did an EXHAUSTIVE study concerning the importance of "Gas Ring Alignment." and determined that it makes absolutely NO difference to the function of the M16/AR15 rifle system. I know, I'm tipping sacred cows here and a LOT pf people are going to tell me I don't know squat about hunkering, but the FACT remains, it's an old myth that refuses to die. Believe me, I'm in a position to know, I took part in the study. Wish I could find a copy of it laying around.
If you don't believe me, give it a try yourself. Start with a clean weapon and line the rings up so that all the gaps are in a row. Fire for effect and see what happens.

Kodiac
Probably bad magazines or possibly you need a little lube on your ejector. It can be clean but dry. One drop will do it.

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Your mind is your primary weapon.
 
Ken and Bulldog,

I always like to make sure my guns are going to work right and I wonder if you could tell me where the gas rings are in an AR-15, so I can make sure they are lined up properly.
 
The gas rings are on the bolt, about 3/4" from the back. They're in that first bulge from the back, about 1/2" from the keyhole.
 
Kodiac, you might check to see if you're getting case separations. The difficulty you described in getting the thing unstuck is almost identical to the times I had case heads separate and eject, leaving front half of the case in the chamber. The next round goes partway in and resulting mess is very difficult to clear. This has happened to me most often with reloads and Israeli surplus.
 
Kodiac,

If I understand you correctly, the cases are Bent in the center.. more specifically could this be a "dent", cased by the boltface?

I have seen this type of malfucntion several times. It seems that the round begins to come up into the chamber and then stops, but the bolt keeps going forward.. "running into" the round which is angled up, denting the case below the neck.

A little lubrication to the bolt and a "dust off" of the feed ramps has always cured the problem... though I am not sure of what originally caused the malfunction.. like I said, I've seen it happen with several guns and several types of ammo.



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-Essayons
 
Kodiac:

Oil on the bolt is a good idea like Rob says. For the rest of my suggestions I will assume the rifle is clean, including inside the receiver where the bolt carrier rails ride.

Try loading the mags (NOT to maximum) and smartly slap the side of the mag HARD. If the mag vomits the top cartridge, the lips are messed up. I don't know of a way to fix this other than junk the faulty mags.

How much mileage is on the rifle? This is a long shot but if the problem happens with ALL mags then maybe a new recoil buffer spring will help. An even slimmer chance of a problem is if the gas tube is cracked or something and you're losing gas pressure. I don't see how this would cause the problem you are seeing, but while we're here, might as well get the AR as good as new, right?

I hope the mags are not Ram-Line. I never got one of their 30s to feed well and had the "cartridge stuck halfway" problem with every mag somewhere along the line.

Of course, if this is a pre-ban then maybe you really ought to get rid of it. I'll take it off your hands. :D

Edmund
 
Hmmm...
All good suggestions...
But my chambers are flawless - sanitized, sterilized, scrutinized, and slickerized...
Oil the Ejector? Hmmm - I'll give that a shot. I am one to keey those parts clean and dry... Maybe some lube there wont hurt.

The mags - no problems there - I have isolated one suspect mag... but there is no visible faults or anything. Lips are just fine.

Maybe I'll have the check those gas rings... I dont care what the Marines say - My Drill Sergents always told us magots to stager those gaps!

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"Fear will keep the local systems in line..."
 
OK, I was going around a bit on the gas rings as I always called them bolt rings, which I think is what Colt calls them...I was in the Army in the M1 days, so not up on latest "do it my way..". The only purpose of those rings is to direct the exhausted gas out the escape holes in the side of the bolt carrier instead of letting it get into the forward part of the carrier and get things dirty (or dirtier). By the time they come into play, the gas has done about all it is going to do in regard to operating the carrier.

The trouble with the bent rounds could be weak ammo, but could also be very hot ammo, and the results look the same. In the case of weak ammo, the cause is obvious. But in hot ammo, the bolt comes back hard enough to bounce and comes forward before the top round in the mag can rise into position. Weak mag springs, especially in 30 rd mags, can also cause this with good ammo; the problem is weight of the ammo column.

Try some factory (preferably GI) ammo and known good 20 rd mags, and see what happens.

Lubing things will help and if that is the fix, it is a cheap one. There are other possibilities (clogged or bent gas tube, for example), but let's stick to the simple first.
 
Kodiac,

Your problem is indicative that one of two, or possibly both situations may exist in your firearm. The end result is that the bolt, instead of striking the base of the case and driving it forward into the chamber, is instead striking the wall of the case and "dragging" it forward while forcing the base downwards as it clears the magazine. The two most common situations that are potential causes of mis-feeds of this type are:

1. The magazine spring is weak (you indicated that these are new so they are much less suspect), or the follower/cartridge column has undue friction which does not allow the top cartridge to "pop-up" before the bolt returns from its rearmost position in recoil. I've seen this caused by oxidation, dust and burrs on the inner walls of the magazine or on the follower, and improperly assembled spring/followers. I've also seen the condition caused by reloads that exceeded the OAL of the M193 Ball cartridge causing the points to drag the forward wall of the magazine. Similarly, I've seen soft-pointed spitzer factory loads that were not pushed all the way back to the rear magazine wall, thereby allowing the exposed lead tips to drag the forward wall (tap bottom and back of mag to properly seat the cartridge column).

2. The bolt cycling velocity has changed. If the weapon is dirty (including a partially clogged gas port or gas tube) the bolt may not have sufficient velocity to pass behind the magazine, thereby not allowing proper "pick-up" of the top cartridge. Conversely, changing the weight (mass) of the bolt carrier assembly, buffer group assembly, or changing the recoil spring tension all may alter the bolt velocity. However, if your internal firearm componets are still stock from QP/BFI, then this latter is unlikely.

Should the above not help resolve the problem, then:
a) inspect the carrier rails and their tracks on the inner wall of the upper receiver for any burrs or indication of excess friction.
b) inspect the underside of the carrier and the "ride-over" surface of the hammer to ensure there are no obvious indications of undue friction or difficult in the hammer being forced down by the bolt carrier.

If none of the above indicate a correctable condition that would cause the problem, then take the firearm, the magazines, and some of the ammo that you used to a competent gunsmith or armorer that is familiar with the AR-series firearms.
 
Mykl and Kodiac,

You are right about problems caused by bolt velocity change, but the velocity change could be the other way, too fast. Kodiac said he is using hot loads. Under high pressure, the bolt can bounce back so fast that the cartridge doesn't have time to rise. Remember all the trouble Colt had with getting the cyclic rate down to spec, and all the jams they had before they were able to work out the right buffer?

The buffer could also be a problem, in combination with hot ammo. Could be some folks are using the old buffers (cheap).
 
I was looking really hard at the mags and found some burrs on the follower that may cause the magazine to get sluggish in the firing cycle... A little DREMEL work and they seem to be fine... but could stand some good lube of the dryish kind... not like a wet oil or grease -
Hey - Thats a good thread topic - LUBES and CLEANERS... General section?

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"There is no Spoon"
 
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