View Full Version : Strange Issues - BCM even baffled
Been communicating back and forth with BCM the last couple days and even they are baffled.
Setup
BCM Blem Upper
BCM 14.5in Midlength barrel
BCM Mod 1 Comp
BCM BCG
BCM lo-pro gas block
BCM gas tube
Geissele SMR MK2 13in
BCM complete lower
BCM H buffer
BCM carbine spring
Problems -
Bolt Over Ride
"Partial Loading" - no double feeding but not completely loading the next round.
Its definitely a gas issue as it progressively gets worse. Today it is now a "bolt action" rifle as all it does is bolt over ride the fresh round.
It is extracting just fine but is not feeding the next round.
Yesterday I could get exactly 3 rounds off before it would either over ride or partial load the next round and jam.
Yes, I've tried 3 different BCM BCG's, 8 different magazines, 5 different types of ammo. All of the parts I swapped out work flawlessly on the 3 other rifles I use them in(11.5in BCM SBR, 16in BCM RECCE, 18in BCM 3gun Rifle).
That's what has all of us baffled. The fact I've tried so many different parts, mags and ammo(no handloads, only factory ammo including NATO pressure ammo).
Here is a picture of the "partial load" I'm taking about. There is not a round in the chamber.
http://i6.photobucket.com/albums/y201/paintballaddict/474f45e8-a0a7-4cc7-bc29-aeb70adfb67f_zps24951845.jpg (http://s6.photobucket.com/user/paintballaddict/media/474f45e8-a0a7-4cc7-bc29-aeb70adfb67f_zps24951845.jpg.html)
steyrman13
08-14-13, 17:53
Have you tried the upper on a different lower. Or different buffers?
You need to put the entire upper on to another lower and try it. I would also change the gas tube. I remember markm had an upper where the tube was worn near the lip where it meets the key and it was causing a progressive short stroking scenario.
JW, did you leave a gap between the gas block and the shoulder on the barrel?
Have you tried the upper on a different lower. Or different buffers?
Steyrman and IraqGunz -
Have tried different lowers(that had different buffers)
Just tried replacing the gas tube. It seemed to fix some of the problems. Now the NATO pressure stuff cycles fine but does not lock back on empty(4 different mags used to test) but the weaker 223 stuff, which I don't expect much from to begin with, still makes it a bolt action.
MT Dawg -
Barrel is dimpled, when you tighten the screw down into the dimple it self centers and leaves a gap.
Seems the gas tube was part of the problem. I can't even run water through it.....
Gas port is at .077, which seems slightly under sized. I think I read on here some where that 14.5 Mid gas ports are usually .080-.085?
jw,
The port size should be around .078 so you are good. I suspect that since we now know the tube was an issue you had a perfect storm of gas issues. See if you can locate a gas block that is tighter in the barrel.
Does the gas block fit tightly or is it easy to slide on?
Steyrman and IraqGunz -
Have tried different lowers(that had different buffers)
Just tried replacing the gas tube. It seemed to fix some of the problems. Now the NATO pressure stuff cycles fine but does not lock back on empty(4 different mags used to test) but the weaker 223 stuff, which I don't expect much from to begin with, still makes it a bolt action.
MT Dawg -
Barrel is dimpled, when you tighten the screw down into the dimple it self centers and leaves a gap.
Seems the gas tube was part of the problem. I can't even run water through it.....
Gas port is at .077, which seems slightly under sized. I think I read on here some where that 14.5 Mid gas ports are usually .080-.085?
Boba Fett v2
08-14-13, 18:27
Steyrman and IraqGunz -
Have tried different lowers(that had different buffers)
Just tried replacing the gas tube. It seemed to fix some of the problems. Now the NATO pressure stuff cycles fine but does not lock back on empty(4 different mags used to test) but the weaker 223 stuff, which I don't expect much from to begin with, still makes it a bolt action.
MT Dawg -
Barrel is dimpled, when you tighten the screw down into the dimple it self centers and leaves a gap.
Seems the gas tube was part of the problem. I can't even run water through it.....
Gas port is at .077, which seems slightly under sized. I think I read on here some where that 14.5 Mid gas ports are usually .080-.085?
I'm wondering if the gas port is properly aligned with the block. Think the dimple itself might be a little off?
Obstruction in the carrier key or loose carrier key?
You might want to pull the gas block and check the little ring o' carbon around the gas port. It will tell you right off if the gas block is aligned to a reasonable degree...
jw,
The port size should be around .078 so you are good. I suspect that since we now know the tube was an issue you had a perfect storm of gas issues. See if you can locate a gas block that is tighter in the barrel.
Does the gas block fit tightly or is it easy to slide on?
It fits tightly, doesn't slide on and off very easily. The weaker ammo like wolf and some federal 55gr frangible I'd like to use as a I have a ton of the wolf 55gr I got for the short range stages at 3gun's and for running drills so I don't have to worry about my brass. The frangible I like because we can run drills with steel targets really close and not have any thing coming back after us.
I'm going to order a different gas block and give it a try.
steyrman13
08-14-13, 18:48
Obstruction in the carrier key or loose carrier key?
He tried 3 different BCGs so not that.
Obstruction in the carrier key or loose carrier key?
You might want to pull the gas block and check the little ring o' carbon around the gas port. It will tell you right off if the gas block is aligned to a reasonable degree...
Its aligned properly. I would say loose carrier key..... but trying 3 separate carriers..... not the issue
He tried 3 different BCGs so not that.
10-4... Missed it.
Its aligned properly. I would say loose carrier key..... but trying 3 separate carriers..... not the issue
JW, the last couple of BCM barrels I've used had a flat milled dimple instead of the concave dimple. The flat dimple is a little bit larger than the head of the set screw and leaves a little bit of room to play. I'm just wondering if it is possibly covering the port slightly.
This is a coincidentally useful thread for me. I am having the exact same problem with an SBR with 11.5 BCM BFH. That rifle had over 5000 rounds of mostly PMC Bronze without a hiccup. Now, a few weeks after changing the handguard, it's unusable with the symptoms you describe. I've been through all the steps suggested here, just waiting for some time to replace the gas tube. It's gotta be the gas system...either the tube or VLTOR gas block.
JW, the last couple of BCM barrels I've used had a flat milled dimple instead of the concave dimple. The flat dimple is a little bit larger than the head of the set screw and leaves a little bit of room to play. I'm just wondering if it is possibly covering the port slightly.
Concave dimple.
steyrman13
08-14-13, 19:01
Obstruction in the carrier key or loose carrier key?
You might want to pull the gas block and check the little ring o' carbon around the gas port. It will tell you right off if the gas block is aligned to a reasonable degree...
JW, the last couple of BCM barrels I've used had a flat milled dimple instead of the concave dimple. The flat dimple is a little bit larger than the head of the set screw and leaves a little bit of room to play. I'm just wondering if it is possibly covering the port slightly.
Did you check to see if the ring of carbon as described above was bad?
If you look inside the gas block and check the gas port hole you will notice it is several times larger than the port itself. Unless it is grossly misaligned it shouldn't be an issue.
I believe that several 14.5 middy users have stated they needed to run some hotter ammo through the gun initially before using the crappy stuff. I have very little Wolf experience so its hard to know if that is true. Is it possible that you ammo is jacked? Bad lot maybe?
Most likely the GB is out of alignment or is not getting a good seal on the barrel. Next candidate would be gas key the is loose or gas rings that needs replaced.
C4
If you look inside the gas block and check the gas port hole you will notice it is several times larger than the port itself. Unless it is grossly misaligned it shouldn't be an issue.
I believe that several 14.5 middy users have stated they needed to run some hotter ammo through the gun initially before using the crappy stuff. I have very little Wolf experience so its hard to know if that is true. Is it possible that you ammo is jacked? Bad lot maybe?
very good possibility. I'm gonna run a couple hundred rounds of NATO pressure stuff thru it and see if it breaks it in a little.
Except he tried multiple BCGs already and same results. My guess is the its the Wolf ammo.
Most likely the GB is out of alignment or is not getting a good seal on the barrel. Next candidate would be gas key the is loose or gas rings that needs replaced.
C4
BravoCompanyUSA
08-14-13, 19:31
Jon,
Would you mind sending the entire rifle back to us? We can trouble shoot each component.
Paul
Jon,
Would you mind sending the entire rifle back to us? We can trouble shoot each component.
Paul
No problem. Just wanted to try and get it figured out to try and save on sending it back only for it to be something silly that I over looked.
Could there possibly be not enough back pressure with the BCM comp? I can swap to a BattleComp 1.5 possibly
RearwardAssist
08-15-13, 00:27
Have you tried different bcgs after you replaced the bad gas tube?
Anything is possible, but I don't think it's probable. FWIW- I am running a Colt 6920 barrel (.063 port) chopped and grinded with a Bravo Comp, Vltor A5 and -3 buffer and green Springco and it will shoot everything from Hornady Steel TAP (55gr./75gr.), M193, M855 (multiple types) and markm handloads and it runs 100%.
Could there possibly be not enough back pressure with the BCM comp? I can swap to a BattleComp 1.5 possibly
I have had the same exact issue with a rifle a few years ago. It drove me nuts and I spent way too much money on ammo trying to figure it out.
It turned out to be an out of spec gas block. I changed out the gas block and it has run 100% ever since.
Good Luck!
Robb Jensen
08-15-13, 06:07
Many 14.5" Midlengths won't run on sub-SAAMI pressure ammo like Wolf, Rem UMC etc. The weakest my BCM Midlength BFH runs on is PMC Bronze and it just barely does that.
Not locking back with 5.56mm ammo has me stumped. It should run, maybe the gas block replacement will fix it.
chasetopher
08-15-13, 08:27
Apologies if it has been tried and I missed it - have you tried to move down from the 'H' to a carbine buffer?
I have a 18" rifle gas BCM barrel that will cycle on 5.56 with an 'H' buffer beautifully but to run wolf without short stroking I need to step down to a carbine buffer.
Apologies if it has been tried and I missed it - have you tried to move down from the 'H' to a carbine buffer?
I have a 18" rifle gas BCM barrel that will cycle on 5.56 with an 'H' buffer beautifully but to run wolf without short stroking I need to step down to a carbine buffer.
My 18in BCM complete gun I use for 3gun I run a H3 and it cycles Wolf 55gr Classic perfectly, even locks back. Same with my 11.5in BCM upper using an H buffer cycles with anything I feed it. Thats why I'm super stumped with this rifle as its the first 14.5 middy I've ever had do this, I've built 6 others for friends/family and they all work. At least it happened to my build and not theirs.
Boba Fett v2
08-15-13, 12:12
Jon,
Would you mind sending the entire rifle back to us? We can trouble shoot each component.
Paul
Interested in hearing how this mystery is solved. No doubt BCM will make it right.
Shipping today. It's definitely a gas issue but where the problem lies is beyond me.
If you look at post#5 after he replaced the gas tube it ran the 5.56 stuff fine. The issue now is with the Wolf and I believe the frangible. I would never shoot frangible as it tears up the throat as I recall.
Not locking back with 5.56mm ammo has me stumped. It should run, maybe the gas block replacement will fix it.
If you look at post#5 after he replaced the gas tube it ran the 5.56 stuff fine. The issue now is with the Wolf and I believe the frangible. I would never shoot frangible as it tears up the throat as I recall.
I think he said 5.56mm wasn't locking back, but was cycling ok.
If you look at post#5 after he replaced the gas tube it ran the 5.56 stuff fine. The issue now is with the Wolf and I believe the frangible. I would never shoot frangible as it tears up the throat as I recall.
It's really hard on the whole operating system.
If you look at post#5 after he replaced the gas tube it ran the 5.56 stuff fine. The issue now is with the Wolf and I believe the frangible. I would never shoot frangible as it tears up the throat as I recall.
Even the 5.56 wouldn't lock the bolt back. Even with a Carbine buffer.
And I did not know that about frangible.... Sucks cause we got a shit load of it in for work training.
Even the 5.56 wouldn't lock the bolt back. Even with a Carbine buffer.
And I did not know that about frangible.... Sucks cause we got a shit load of it in for work training.
RHT ammunition is good for agencies who have the funds to replace worn out parts. The projectiles begin to disintegrated before they leave barrel and a lot of abrasive material gets pumped through your operating system. There are a couple of brands of frangible that have a jacket but I don't think they are considered a reduced hazard frangible round in the same sense the sintered variant is.
ETA: RHT is Reduced Hazard Training. They can be labeled different ways but usually involve some kind of lead free green theme.
attached is the image of the ammo we have that was causing the most problems in the 14.5 middy but functions in my 11.5.
17867
I must have missed that with all the back and forth.
I think he said 5.56mm wasn't locking back, but was cycling ok.
Let's not quote the ignorance.
Please explain
AE223
XM193
77smk handloads
All cycled fine.
Just a data point for comparison as I have a near identical spec rifle.
http://www.danpassaro.com/img/s10/v113/p1712497300-5.jpg
Talked to Troy at Bravo Co today. They got my rifle Friday and had it done today! The gas block was off center just enough and the tube was bent from that. I swear I adjusted that thing a couple times! His is why I let the pros look at it lol.
I can not applaud BCM's customer service enough!
steyrman13
08-19-13, 22:40
Talked to Troy at Bravo Co today. They got my rifle Friday and had it done today! The gas block was off center just enough and the tube was bent from that. I swear I adjusted that thing a couple times! His is why I let the pros look at it lol.
I can not applaud BCM's customer service enough!
I just looked back at my posts. I guess I deleted my response to IG instead of posting it earlier. I was thinking that since the barrel nut doesn't interfere with the tube like a normal barrel nut, the cocked gas block could cause the gas tube to be bent. I always like to check inside the receiver after a build and make sure the gas tube is centered inside the upper as well as slide the Bolt carrier without bolt in to make sure it glides in all the way smoothly without interference.
Glad they got you fixed up! Good to see great customer service!! The gun industry is one of the last industries with actually great customer service! Way to go BCM!
Interesting. I would have liked to have seen how far off it was. Was this caused by a defect in the barrel dimple location or something else?
When you were checking the upper did you run a stripped carrier into the upper receiver and check to see if the key was binding against the tube?
Talked to Troy at Bravo Co today. They got my rifle Friday and had it done today! The gas block was off center just enough and the tube was bent from that. I swear I adjusted that thing a couple times! His is why I let the pros look at it lol.
I can not applaud BCM's customer service enough!
Interesting. I would have liked to have seen how far off it was. Was this caused by a defect in the barrel dimple location or something else?
When you were checking the upper did you run a stripped carrier into the upper receiver and check to see if the key was binding against the tube?
I forgot to ask honestly.
Boba Fett v2
08-20-13, 07:49
Talked to Troy at Bravo Co today. They got my rifle Friday and had it done today! The gas block was off center just enough and the tube was bent from that. I swear I adjusted that thing a couple times! His is why I let the pros look at it lol.
I can not applaud BCM's customer service enough!
I was close in my assessment. I wouldn't have guessed bent gas tube though.
Most likely the GB is out of alignment or is not getting a good seal on the barrel. Next candidate would be gas key the is loose or gas rings that needs replaced.
C4
Grant for the win!
C4
Boba Fett v2
08-20-13, 07:52
Grant for the win!
C4
No way, man. I beat you to it!
;)
When you were checking the upper did you run a stripped carrier into the upper receiver and check to see if the key was binding against the tube?
This right here is a key test that I've started doing since I took IG's class and he showed it to us. It's helped catch at least two that were binding significantly...one was a factory-assembled upper.
PS, for what it's worth, my money was on the gas block as well ;)
Grant for the win!
C4
Whatever helps you sleep at night...
Who ever won, its something I looked at multiple times but some how evidently never got set correctly as it was up there on my list of probables as well.
If I talk to them again, I may ask if the dimple was off and causing that or what it was as this is the first in 30+ rifles I've built that I've had this happen.
Just like a Match DQ, its bound to happen to everyone at least once in their life. Guess it was my turn on the "way to go dumbass" train.
I've had at least a couple factory assembled uppers with the gas tube binding in the gas key, for various reasons including a misaligned gas block. Sure, you can 'tweak' the gas tube to get it kind of right, but I'd rather have everything lined up so that a straight gas tube works. I ended up sending an upper back to a very highly regarded mfg to correct their misaligned gas block, and it was for this reason. The gas port wasn't blocked at all but it put enough angle on the gas tube to cause some binding...not something I'm ok with.
No way, man. I beat you to it!
;)
Several people mentioned the GB alignment before I did. Was merely a joke. ;)
C4
FWIW- TM 9-1005-319-23&P allows for tweaking of the gas tube after installation into the upper by use of a flat tip screwdriver.
I've had at least a couple factory assembled uppers with the gas tube binding in the gas key, for various reasons including a misaligned gas block. Sure, you can 'tweak' the gas tube to get it kind of right, but I'd rather have everything lined up so that a straight gas tube works. I ended up sending an upper back to a very highly regarded mfg to correct their misaligned gas block, and it was for this reason. The gas port wasn't blocked at all but it put enough angle on the gas tube to cause some binding...not something I'm ok with.
Who ever won, its something I looked at multiple times but some how evidently never got set correctly as it was up there on my list of probables as well.
If I talk to them again, I may ask if the dimple was off and causing that or what it was as this is the first in 30+ rifles I've built that I've had this happen.
Just like a Match DQ, its bound to happen to everyone at least once in their life. Guess it was my turn on the "way to go dumbass" train.
I suspect the dimple was not off but the barrel was. that is if the dimple was drilled before the barrel was installed...
it's not unknown for BCM to have the front sight base canted a bit to the left from the factory. that's been discussed here and I've had one myself...
Mall_Ninja
08-23-13, 01:52
I always build mine so that the gas block to barrel alignment is as perfect as possible and never use the gas tube to determine gas block alignment. I use drill rod to make sure the barrel nut/upper receiver alignment is perfect as well. You can always tweak a tube afterwards (as IG brought up) using a stripped carrier as a guide. But what happens when the tube gets replaced? If you have a set screw block thats been "tuned/tweaked" to get the tube straight, or you have "adjusted" the barrel nut for better alignment, now you are back to square one...
No 2 gas tubes are alike...
This is why I scribe very small witness/timing lines on my barrel and gas blocks before installing. It's a good way to check dimple alignment, as well as port to port concentricity/alignment. A few measurements...even if closely eyeballing it, and you can put appropriate marks that will let you know if you're aligned or not before tightening with rockset or pinning.
As IG mentioned, the GB port is several times larger in size (probably 3-4 times) that the barrel port. So even rough measurements and scribes, or pencil marks, will get it right every time.
Aligning off of the tube isn't always a good idea to check port to port alignment, etc. a gas tube could be slightly tweaked, or even the tube hole could be drilled at a slight angle not perpendicular to the facing of the gas block.
Just my method...and I've never had any issue with dozen or so BCM middle builds. They shoot wolf, Tula, and light ass plinking handloads with nothing more than a standard carbine spring and H buffer. Thousands and thousands of rounds through many of the builds and never a hiccup!
Careful planning and attention to details pays off. Even if it takes you several hours to build an upper "perfectly".
Mall_Ninja
08-28-13, 02:07
I use a straight edge to put masking tape down straight over the center of the gas port to the tip of the barrel. I then take a Sharpie marker and draw a line on the edge of the tape giving me a straight center line from the hand guard "lip" to the muzzle. Then I slide the gas block on and use the line to make sure the block is plum. If the block requires dimpling or drilling then I verify alignment using light shined down the gas port (it will show a "spot" on the inside of the barrel. If the spot is symmetrical than you are GTG. A quicker easier check is a quick shot of brake cleaner. The Sharpie is easy to remove and leaves no marks...
johnnyrebel87
08-29-13, 09:35
Isn't it great having the internet.....if it were 1992, things would be a lot harder to fix.
Finally got home from Pro/Am 3gun and had a chance to go pick it up from my FFL(for some reason they required it to be shipped to FFL even though I sent it in for repairs). But I shot some of everything thru it and it functioned flawlessly with everything
That sucks, you would think they would know better, thats an amateur mistake. Did you have to pay the FFL a fee?
Nope, FFL I sent it to is the range I run 3gun matches for so I get transfers for free
Mall_Ninja
08-29-13, 13:24
Nope, FFL I sent it to is the range I run 3gun matches for so I get transfers for free
Did you have to fill out another 4473?
The issue has been solved so we can end this one.
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