View Full Version : FTF with New Gun (Pics) *Update on p.3*
I brought my new AR to the range today and put 69 rounds through it. 30 HSM 5.56 75gr, 12 BHBB 75gr, and 27 Guatemalan M193 surplus. The reason that I only shot 27 of the Guat instead of all 30 in the box is that three of them failed to feed. The tip of the bullet ended up pointing above the chamber, and the bolt ended up closing on the side of the brass case. I don't find it easy to fault the ammo, since it's been fine in my other rifles. This AR is a 14.5" w/carbine gas system, and an H-buffer. Brand new. Bought the upper and lower, each fully assembled. The gas key is staked, and solid. What appears to have happened is that after firing a round, the bolt, on returning to battery, is catching on top of the brass, just forward of the case head. I had it happen while using a used steel magazine, and also with a brand new Pmag. Can anyone help explain this one? See below.
http://dl.dropbox.com/u/9266193/FTF%20%281%29.jpg
http://dl.dropbox.com/u/9266193/FTF%20%282%29.jpg
http://dl.dropbox.com/u/9266193/FTF%20%283%29.jpg
What make and model is this weapon?
BCM upper
BCM "BCM4" lower
Ok. Now that we know what we are dealing with you need to isolate the problem. I would use a different magazine and fire the Guat M193 by itself and see what happens.
What other AR's have you fired this ammo in without problems?
It sounds as if it may be really hot ammo. Do you have any USGI aluminum magazines?
BCM upper
BCM "BCM4" lower
ForTehNguyen
12-10-11, 18:02
have you tried it with other mags?
Were you using the same magazine for the entire outing, or did the 30 rounds of Guatemalan M193 have their own magazine?
My initial thought on this was a defective magazine. I got a TangoDown ARC magazine when they first came out, and had these types of failures about every five rounds with it.
I'd remove the magazine you used with the Guatemalan M193 from the equation and see what happens.
Folks he stated it happened with both a steel mag and a P mag. That being the case I agree that you should try some different ammo and see what happens. A total of 69 rounds is not telling you all of what you need to know.
Not saying you should expect nor accept such an issue with a BCM no matter how hot the rounds are, just dictating the logical next step.
Is it me, or do the rounds in the picture above look like they are crimped really hard?
Particularly the top one in the 2nd photo.
Is it me, or do the rounds in the picture above look like they are crimped really hard?
Not seeing it, but even if it was crimped too hard it would not cause feeding issues.
OP just keep shooting the weapon, but try longer sessions with each type of ammo. That's the best way to narrow down whether or not it is intolerant to that specific Guatemalan M193.
Hi folks, thanks for the input. I feel kind of stupid for leaving this fact out (I may have posted before taking the time to add two and two). But during that first shooting session, I had failures of the bolt to lock back after the last round in the mag. For whatever reason, I didn't consider that two different malfunctions would be symptoms of the same problem. Now I'm fairly certain that this only happened with the Guat, but am not 100%. That's why I'm going back out today with 100 rounds each of the BHBB, and the HSM, and 120 rounds of Guat. I will narrow this down. I really don't think it's the mags. It seems, now that I think about it, to be a classic short stroking problem, with the 'bolt over' being the symptom. If it happens even once, with ammo other than the Guat, I suppose it could indicate either gas leakage, or an out of spec gas port drilled in the barrel. We'll see what happens.
Well, unfortunately the problem doesn't seem to be the ammo. I had several more malfunctions. With the Guat, they were mostly failures to chamber a round. It wasn't even bolt-overs this time, it was the bolt closing on an empty chamber, with rounds still in the inserted magazine. The top round in the magazine ended up looking like this:
http://dl.dropbox.com/u/9266193/2011-12-11%2008.55.41%20%282%29.jpg
Judging from the linear mark on top of the case, it doesn't even look like the bolt travelled far enough back to clear the case lip. Unless I'm reading that mark the wrong way.
With the HSM and Black Hills ammo, there was no problem chambering any of them after firing one off, but I had failures of the bolt to lock back several times with three different magazines- all in good working condition (two of them brand new Pmags). Roughly 30% of the time, the bolt would not lock back with an empty mag.
So now, it looks like I'll have to go through the proper channels to get this taken care of.
Well, that's unfortunate.
Look forward to seeing where this goes- this could potentially be the first I've heard of a BCM having a factory defect. I guess it had to happen eventually.
I would be curious to know what would happen with a standard carbine buffer? In any case I am sure you will be takenb care of.
I had considered dropping in a standard carbine buffer just to see. Actually, my other 2 ARs are 'builds', both 16", with mid-length gas systems, and both have standard buffers. With the same ammo and with that same steel magazine, neither have had similar problems.
I figure that something is still wrong though, because an H-buffer should work fine with a 14.5" carbine. I wouldn't be comfortable thinking that my carbine is the exception in a world where so many others successfully run the same system.
You don't have a Magpul BAD lever (or any similar contraption on your gun do you)?
Can we see a pic of the gun in question?
C4
No BAD lever or similar contraptions. Here are some photos (haven't cleaned it yet):
http://dl.dropbox.com/u/9266193/2011-12-11%2013.13.14.jpg
http://dl.dropbox.com/u/9266193/2011-12-11%2013.17.20.jpg
http://dl.dropbox.com/u/9266193/2011-12-11%2013.15.59.jpg
http://dl.dropbox.com/u/9266193/2011-12-11%2013.15.20.jpg
Can't really tell from the pic, but is that rail free floating and or did you do any work on the gun (remove parts, add parts, etc)?
C4
That's a Knight's M4 RAS, which I installed. Everything I've done since getting the gun has been of a bolt-on nature except for the installation of the MOE grip. Otherwise, the BCG, the upper, and the complete lower are as-received.
eternal24k
12-11-11, 15:02
what happens when you shoot several mags of the ammo with only 1 round loaded? Lock back?
With three different known-functioning mags, I did the one round test several times. It locked back on most of them, and came back to battery on the empty mag around 30% of the time. Mostly with the year 2000 headstamped Guat M193, but also with the newer HSM 5.56 and the BHBB .223 .
Did you purchase the lower complete or build it up?
Complete lower. All I did was slip a stock onto it.
TheGhostRider
12-11-11, 17:21
I've never had a bad BCM BCG... but, did you check your gas key?
Sound's like it's under gassed.
Recoil spring length?
A2 spring in a carbine extension?
LUBE? Wet and ready to party? or Dry and ready for a nap?
Bad Hammer
12-11-11, 17:45
I've never had a bad BCM BCG... but, did you check your gas key?
Good point. Unless I'm mistaken there was another thread here, or on TOS, where a BCM carrier had a broken bolt on the carrier key.
BCM resolved the problem quickly.
It happens.;)
I've never had a bad BCM BCG... but, did you check your gas key?
Sound's like it's under gassed.
Recoil spring length?
A2 spring in a carbine extension?
LUBE? Wet and ready to party? or Dry and ready for a nap?
gas key = staked, solid, screws intact
recoil spring = carbine
lube = party time ;)
Well, unfortunately the problem doesn't seem to be the ammo. I had several more malfunctions. With the Guat, they were mostly failures to chamber a round. It wasn't even bolt-overs this time, it was the bolt closing on an empty chamber, with rounds still in the inserted magazine. The top round in the magazine ended up looking like this:
http://dl.dropbox.com/u/9266193/2011-12-11%2008.55.41%20%282%29.jpg
Unless my eyes are deceiving me, the left side feed lips on that magazine look mighty funky. The small portion at the front appears to be bent up, and the long portion at the rear seems to be bent in, and probably down, at the front. If it's not a optical illusion, seems like those two defects could make for some interesting feed problems.
Good catch, also it looks like the round on the right is not parallel to the chamber. Looks like the tip is pointing up and not sure where it will end up oriented when it's next in line. Also the BCG doesn't look wet enough but it could just be the picture.
The same mag:
http://db.tt/gQPrJvAf
http://db.tt/35a73isl
Also worth noting is that all rounds chambered upon pulling back the CH and releasing, and that the same malfunctions occurred with brand new magazines, which I have eyeballed, and are in good condition. Looking at the steel magazine right now, the feed lips look fine. :confused:
I have never shot the ammo you are using but it looks like the bolt is traveling too slow at the end of it's retraction so it could be under powered based on the design intent for xxx type of round. Think of the mag spring starting to push the round while the blot is still at the rim of the casing. If it were me the first thing I would do is check the spring length and trade out the buffer to a standard weight. This will allow faster travel time closer to the end of the BCG's retract. Keep us posted .
One last thing you could look at is the magazine catch. Make sure it’s installed properly. If it’s not turned in far enough it can cause feeding issues. The end of the catch should be flush with the button.
Again guys, thanks for the comments on this problem. I'm becoming more convinced that this is a problem with the speed of the bolt traveling rearwards. The ammo should not be a factor since the malfunctions occurred with 'name brand', American made ammo as well as the Guatemalan surplus, and the magazines are out due to the variation of the three mags, and the fact that the one that seems to be in question has worked perfectly in 2 other ARs. Take a look at this photo of the underside of the BCG. Does that amount of brass residue seem odd to you?
http://db.tt/mSgpwOho
Have fired many crates of the Guatemalan surplus (both the plastic camo battle packs and the black).
It's dirty but it runs in everything. I would be really surprised if it's the ammo.
Here is what I would do. Get some Federal M193 or similar not reloads or surplus and see what happens. If you have the same issue you can CONCLUSIVELY rule out the ammo.
If possible try some different buffers. I am not saying that you should buy any but if you know others that may be able to swap around with you that would be great.
Otherwise I think you should contact BCM and explain the issue and ask about sending it back for examination.
OP: you mentioned you installed the Knight rail yourself, is it possible you might have messed up the gas tube in the process, restricting the gas flow just enough to get these malfunctions? I've seen a number of gas tubes crushed by joe installing PEQ boxes and other stuff on A2s, I know I almost did just that my first time mounting the old PAQ-2.
I don't see how installing a KAC rail or a PEQ would cause any of these issues. That makes no sense whatsoever.
OP: you mentioned you installed the Knight rail yourself, is it possible you might have messed up the gas tube in the process, restricting the gas flow just enough to get these malfunctions? I've seen a number of gas tubes crushed by joe installing PEQ boxes and other stuff on A2s, I know I almost did just that my first time mounting the old PAQ-2.
TacMedic556
12-12-11, 23:15
:confused:
Iraqgunz: its been a good long time, so I'm probably confused on the matter, but I seem to recall mounting something onto my A2 back when we still had them that involved putting bolts through the handguard and attaching to the barrel or something like that, up by the front sight post, and that if done incorrectly it could pinch off the gas tube causing all sorts of issues. Then again, I could be completely mistaken and or we just went about installing stuff wrong.
Now granted I don't see how installing a KAC rail would cause a situation like that, just tossing out something else to look into to, just to cover all the bases, not trying to imply the OP is incompetent or anything, weird stuff happens from time to time, thats all.
TacMedic556
12-13-11, 00:10
The same mag:
http://db.tt/gQPrJvAf
http://db.tt/35a73isl
Might be camera angle but the mag does look just a slight bit "whacky" up at the feed lips. They aren't bent at all?
With three different known-functioning mags, I did the one round test several times. It locked back on most of them, and came back to battery on the empty mag around 30% of the time.
So 30% of the time the bolt failed to lock open on a empty magazine?
Fire one round while pushing in on the bolt catch, hold the rifle as loosely as possible.
Did you put a wrench to the carrier key bolts?
I'm sure I'll get scolded for this... but you are holding the rifle firmly against your shoulder, right?
Hello again.
So 30% of the time the bolt failed to lock open on a empty magazine?
That's correct. To answer your other question, I haven't done anything to the carrier key bolts.
Unfortunately, I didn't get to try your bolt catch test (too late - see below), but will keep it in mind just in case.
Might be camera angle but the mag does look just a slight bit "whacky" up at the feed lips. They aren't bent at all?
I know- looking at the photo, it does look weird. But no, I swear to you, eyeballing them, they look fine.
rero360, I did install the M4 RAS myself, but properly installed, I don't believe the little clamp that engages the barrel nut could really do any damage. I did look at that area of the gas tube, but it's fine.
So BCM agreed to take a look at the upper. They'll get it on the 19th. I am glad of this, because they would be able to determine conclusively anything about the gas system, whereas I would not. And one way or another, what I hear from them will either confirm my suspicions, or simplify any further troubleshooting.
I'll update the thread when I hear something.
I had the EXACT same thing happen to me with my BCM upper. When I installed my rail I didn't do it exactly right so the delta nut wasn't flush and the bottom of the top half of the nut was resting on the gas tube (if that makes sense, if it doesn't...the rubber part that would be near the gas tube was in contact with it). That probably bent the gas tube which prevented the bolt from cycling all the way back. I sent it back to BCM and they fixed my oops and they had it back to me as fast as shipping would allow.
bfk4lyfe, thanks for the input, but I don't believe our problems were the same. If my gas tube were out of alignment to the carrier key, the bolt would have problems going to battery. My problem now is that it goes to battery just fine, but without a cartridge in front of it.
A further thought on this problem. At first, the factory new bolt was picking up cartridges from the side of the case, and causing them to go nose-up into the chamber, with the bolt wedged against the cartridge case. Considering all the brass buildup on the surface of the lower bolt teeth and carrier, does it not seem like the brass has in effect lubricated the metal surfaces of the bolt teeth? That would explain why on my second outing, I didn't have any bolt-overs with the cartridge being partially stripped off the mag. I only had the bolt slipping right over the top round in the mag without stripping it out. Again, this would indicate that the rearward travelling bolt isn't clearing past the case lip. Only, that when there was enough friction between the bolt surface and the top round, the round was able to be partially stripped out, and subsequently misfed (see the marks on the brass in the first pictures I posted on page 1). Ergo, undergassed.
Also, why more failures with the M193 than the two 75gr loads? Because the heavier, slower bullet allows more dwell time for the gas before it leaves the muzzle. Another reason to suspect it's a gas issue. That's my thinking, anyway.
Hello again.
That's correct. To answer your other question, I haven't done anything to the carrier key bolts.
Unfortunately, I didn't get to try your bolt catch test (too late - see below), but will keep it in mind just in case.
I know- looking at the photo, it does look weird. But no, I swear to you, eyeballing them, they look fine.
rero360, I did install the M4 RAS myself, but properly installed, I don't believe the little clamp that engages the barrel nut could really do any damage. I did look at that area of the gas tube, but it's fine.
So BCM agreed to take a look at the upper. They'll get it on the 19th. I am glad of this, because they would be able to determine conclusively anything about the gas system, whereas I would not. And one way or another, what I hear from them will either confirm my suspicions, or simplify any further troubleshooting.
I'll update the thread when I hear something.
No worries, I've installed a set or two myself, they do seem to be just about joe proof. Definitely wasn't a knock against your abilities, just trying to present alternative possible sources of problems. It is intriguing though, please let us know what BCM finds out, curious minds and all that.
I received my upper back on January 5th. Looks to be a completely new upper, as I didn’t see all the brass marks that were left on the bolt carrier assembly and the shell deflector from last time.
I put the upper back on my lower, and took it to the range for some testing. The only two types of ammo I have right now are the same HSM 75gr 5.56, and the Guat M193. I started with a bunch of the old Guat M193. Filled two 30-round Pmags with it. Everything cycled fine while firing, but still noticed the bolt failed to lock back after the last round of one of the mags. So the rest of what I did for that range session was to check on bolt lockback by loading rounds both one and two at a time for each magazine.
Out of 50 rounds of the HSM 75gr, loaded one at a time, the bolt locked back every single time.
Out of 30 rounds of Guat, loaded two rounds in the mag each time (15 chances to observe the bolt locking back), the bolt failed to lock back on an empty mag 4 times.
I switched to a standard carbine buffer, and did the same test with 30 more rounds of the Guat. Two at a time. Another 4 failures to lock back out of 15 chances.
Well, there were no bolt-overs at all this time. That’s great. Also, the only times the bolt didn’t lock back on an empty mag were with the Guat ammo.
Bolt lockback failure:
Guat: 27% (30 tries)
HSM: 0% (50 tries)
So I will still have to try different loads going forward, but that seems like good news. Hopefully I can blame the ammo. I just ordered some IMI M855, and have several different types of 5.56 stashed elsewhere (long drive), so I’ll have to look forward to that.
BCM was prompt and responsive, and I couldn’t have asked for more from them on the customer service side.
Heavy Metal
01-15-12, 17:12
My past experience with the Guat surplus is that is is good, stout, true 5.56 spec ammo and suprisingly accurate.
What buffer are you using now?
I received my upper back on January 5th. Looks to be a completely new upper, as I didn’t see all the brass marks that were left on the bolt carrier assembly and the shell deflector from last time.
I put the upper back on my lower, and took it to the range for some testing. The only two types of ammo I have right now are the same HSM 75gr 5.56, and the Guat M193. I started with a bunch of the old Guat M193. Filled two 30-round Pmags with it. Everything cycled fine while firing, but still noticed the bolt failed to lock back after the last round of one of the mags. So the rest of what I did for that range session was to check on bolt lockback by loading rounds both one and two at a time for each magazine.
Out of 50 rounds of the HSM 75gr, loaded one at a time, the bolt locked back every single time.
Out of 30 rounds of Guat, loaded two rounds in the mag each time (15 chances to observe the bolt locking back), the bolt failed to lock back on an empty mag 4 times.
I switched to a standard carbine buffer, and did the same test with 30 more rounds of the Guat. Two at a time. Another 4 failures to lock back out of 15 chances.
Well, there were no bolt-overs at all this time. That’s great. Also, the only times the bolt didn’t lock back on an empty mag were with the Guat ammo.
Bolt lockback failure:
Guat: 27% (30 tries)
HSM: 0% (50 tries)
So I will still have to try different loads going forward, but that seems like good news. Hopefully I can blame the ammo. I just ordered some IMI M855, and have several different types of 5.56 stashed elsewhere (long drive), so I’ll have to look forward to that.
BCM was prompt and responsive, and I couldn’t have asked for more from them on the customer service side.
Right now, I'm using the H2 buffer that came with the lower.
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