Unusual? malfunction w/Bushy AR please help

[beta]

I had a strange occurence at the range today with my Bushmaster AR A2.

After shooting about 150 rounds, I had an FTF (I thought). The bolt was not fully forward and giving the forward assist a good smack resulted in no movement, I was also unable to retract the bolt and eject the round, the charging handle would only move back about 3/8".

After I got home I discovered after pushing out the takedown pins that the buffer tube is pushing the bolt forward, It must have either broken the detent or rotated past the detent and is (under spring tension) pushing the bolt forward, but not fully chambering the round..

I am unable to seperate the upper and lower, both pins can be pushed out to their stops, but the front of the lower can only be rotated down less than half an inch and the rear is being pushed forward about a quarter of an inch but because of the buffer assembly can't be seperated from the upper.

Any suggesstions on how to get them apart?

Warmest regards,

beta

 

[Hkmp5sd]

You can remove the stock and unscrew the buffer tube or use something like a butter knife and insert it between the upper and lower to hold the buffer back (if it is the buffer that is sticking too far forward).

If the bolt carrier is partially inserted into the buffer tube, you'll have to remove the stock & buffer tube. You should then be able to pull the bolt carrier back enough to get the chamber open and access the cartridge or at least separate the upper and lower.

BTW, there is a reason Eugene Stoner didn't design the original AR with a forward assist.

 

[beta]

Thanks for the help HKmp5sd,

Yeah, I tried to pry the buffer tube back with a thin bladed screwdriver wrapped in electrical tape (very gently) but did not have enough clearance to move it back far enough.

I did take the stock off and remove the buffer tube housing, I thought that would do it but, no joy.

Finally took a wooden dowel and hammer and carefully tapped the bolt back, discovered the buffer tube detent spring pinched between the upper and lower, the detent itself fell out when the bolt was pulled out.

Everything re-assembled as normal, seems the buffer itself must have rotated and allowed the detent/spring to float freely (hmmmm, not very confidence inspiring), any suggestions from all you AR experts\armorers out there to prevent this from happening again?

Again, appreciate the input HK,

Warmest regards

beta

 

[Badger Arms]

Two conditions could have caused this. One is that the buffer tube itself is not significantly long in the threaded portion which threads into the receiver. If this is the case, a longer buffer tube will be required. The other problem might be that the receiver was not properly machined.

Before I get into that, was this one of those 'fixed' collapsable stocks? If so, the tube might just need to be rotated one more time and perhaps trimmed a bit up front for it to fully engage the buffer stop and keep it in it's hole where it belongs. If it's a standard A2 stock, there is no adjustment and you can only screw it in till it stops.

Gene Stoner never thought about this in his design. If the bolt's not fully into battery, it's nigh onto impossible to clear a malfunction without tools.

 

[Hkmp5sd]

Even with the forward assist, this malfunction required tools. I've always been of the opinion that if you get a FTF, its better to yank the charging handle and eject the round than trying to force the bolt closed.

But then, I've never carried an AR/M16 in combat either.

 

[beta]

Thanks for the input HK and Badger.

I think in hindsight that I may have incorrectly assembled my rifle.

I have the standard A2 stock, and have never removed the buffer tube or the stock, but have removed the buffer and spring to grease them, perhaps I didn't have the buffer installed with enough tension to stay in contact with the detent.

This is disturbing, as my confidence in the weapon has been compromised, as I was unable to perform a field expedient repair (without tools).

I love this rifle, I have taught sheople who have never fired a gun before to hit 6 inch steel targets at 200 yards every time.

Again, thanks for the positive input,

Warmest regards,

beta

 

[Badger Arms]

Hmmmm, maybe I'm not understanding something. The buffer itself is that long falic looking thingy with the rubber bumper on the end. If you have a bolt carrier in the gun, the bolt carrier rests against the buffer face when the gun is fully in battery. It's not possible for the buffer to telescope into the upper receiver UNLESS you have improperly assembled the bolt carrier without a bolt? maybe or completely left the bolt carrier out of the upper. In addition, you'd have to have the detent and spring missing so that the buffer were allowed to telescope into the receiver.

 

[beta]

Hi Badger,

I think what happened is that the detent/spring somehow came out, I think that the detent or spring was jamming the bolt carrier from being fully in battery and also not allowing me to retract the bolt.

The buffer was telescopeed into the upper about a half inch which may have happened when I pulled the takedown pins to see what was wrong, this was why I couldn't get the upper and lower apart.

All is well now, maybe I should try one of those pneumatic or hydraulic buffers though.

Thanks again for the help,

Warmest regards,

beta

 

[mark mcj]

Hey beta, Badger Arms hit this one easy. You'll have this up and going in no time.

The buffer has no function in holding the buffer retaining detent in it's proper postion. If you carefully look at the buffer detent, you will notice it has a shoulder that holds the extention at the proper height to retain the recoil buffer.
The buffer tube, regardless if it is an A2 type or a "fixed collapsable" keeps the buffer retaining pin captive.
I've had to fit buffer tubes on two different builds. Both shortening and thinning to get a strong positive engagament.
As already noted above, a failure here and it's bad juju.
In my humble opinon, this malifunction points to improper assemble. Good luck and have fun.

 

[Tupperware]

What was the cause of the FTF? Bad ammo? You may have NO problems with your rifle at all. Your detent probably got out of place when you removed the buffer tube housing.
I've seen rounds stuck the way you describe that would not allow the charging handle to retract. Usually all that is required is to apply rearward force to the charging handle while banging the buttstock against the ground. Not pretty, I know, but effective for removing an oversize round. As usual, pay attention to keeping your muzzle pointed in a safe direction while performing this drill.

 

[beta]

Hi Tupperware, thanks for the response.

I have had a couple of weeks to mull this over and have come to the conclussion that I had two different things happen, let me pick your brain here.

I noticed that the buffer end itself is not completely round, it has a couple of "flats" when installed in the buffer tube, there is not a lot of the detent holding it back with the flat part at the bottom, when rotated slightly, there is more contact between the detent and the end of the buffer.

I think you are right that the detent and spring came loose when I removed the buffer tube. When the buffer tube was re-installed and snugged up into the lower, there was plenty of overlap to trap the detent "shoulder" and spring in the hole.

Since I could see the buffer extending into the upper after pushing out the rear pin, I can only conclude that I had the "flat" part of the buffer end down, and that the buffer managed to get past it's detent pin somehow, but, I now wonder why the round didn't chamber successfully.

I did give the rifle a couple of good taps on the bench on the end of the stock while holding back the charging handle ( muzzle safely pointed up), but no joy.

I was shooting my own re-loads, they have been very reliable and the removed shell is within spec dimensionally. There are however some pretty good scratches on the bullet itself but I don't know if they are from an FTF or from the attempts to extract it.

The weapon was not particularly clean, It probably had ~500 rounds through it since it was last cleaned and lubricated. Do you think there where two random failures here?

One final note, as I previously mentioned, when I finally got the upper and lower apart, the detent fell free, but the spring appeared to be pinched between the back of the bolt carrier and the upper. Also, this is a factory built rifle not home built, and has functioned flawlessly since.

WHEW!!!, sorry for such a long post, so, Badger, HK, Mark, and of course Tupperware, any further analysis?

Warmest regards,

beta

 

[mark mcj]

Without actually seeing your rifle it's hard to really be 100% sure about anything, and when you do get to see one in person sometimes fixing it can still be a 50/50 thing.
I reread your previous posts and didn’t see any mention about a failure until your first failure. With your bolt forward but not chambering a round. Then you took it home and couldn’t separate the upper from the lower.
When you removed your buffer tube it would have let the buffer tube detent go for sure and the rear pin spring and detent. Also, you have noticed there is very little tolerance in regards to the buffer detent and buffer. With these two facts I would say the buffer detent managed to release from its position and jam your rifle.
With the demand for AR’s I can see where this item could be passed by.
I seem to recall two or three different threads in the past that had pretty much the same issue.
I have attached a picture that I hope will convey my standard for the correct retention of the buffer detent.
The last couple of AR’s I built I spent more time getting a good fit for the buffer detent than torquing the barrel. I hope the picture is clear enough. In the photo, hopefully, you’ll notice the buffer tube was shortened and flattened on the bottom to get a good and strong retention of the detent.
As you have noticed, a failure with the retention of this detent will put an AR down for the fight.

 

[mark mcj]

Sorry for the back to back post.....
The photo really doesn't show where I shortened the tube but the thinning of the tube on the bottom shows o.k. but the wear of the buffer shows the positive engagement of the detent very well.

 

[Tupperware]

beta,
From your description it appears that you have adequate retention of the buffer. I'm more concerned with your description of the buffer "extending into the upper". In a rifle that is in spec this would not be possible. You were probably looking at the side of the bolt carrier. Check for yourself by cracking your rifle open and looking to see that the bolt carrier is flush with the rear of the upper receiver. If it is not call Bushmaster and set up a warranty repair. If it is flush, write this off to bad ammunition. How did you determine that the cartridge was "in spec"? Did you use a case gauge or a caliper or both?
Finally; should you encounter a round that doesn't want to chamber easily, extract that round and try another. There is a reason it didn't go the first time. 500 rounds probably isn't enough filth to cause problems unless the ammo in question is especially dirty.

 

[beta]

Hey Mark and Tupperware,

Thanks for the rapid response.

The photo uploaded by Mark shows the "flat" on the end of the buffer tube, Tupperware, I think that is where the initial problem lies.

After all the analysis, it seems that one of my reloaded rounds "hung up" during the chambering phase, and the buffer "jumped" over the detent, due to me not rotating the buffer during re-assembly to have more purchase of the buffer/detent.

I did open up my rifle and it seems that the bolt carrier is as flush with the upper as expected.

I checked with a caliper, the OAL, the length of the brass, and the case mouth dimensions, and they are all within spec. I do have the Stony Point chamber gauge and know my chamber dimensions. After all is said and done, the rifle is performing as expected.

I will now use my reloads only as range ammo, and factory stuff for when it may really count.

Thank you guys, Badger, Mark, Tupperware, and HK for your input, you live and learn everyday, and folk like you make it easier, Thank You.

Warmest regards,

beta