Archived Posts » 59,609,787
FIXED (B.A.D. lever issue): Bolt sometimes does not lock rearward after last round
3/12/2012 3:25:06 PM
Before i get the usual rant about me not looking around in this section, I'd like to note that I've checked, and all the similar named threads actually seems to be different problems, hence me setting up a different thread for this.
To the problem. I have second hand ar15, DPMS kit lower, panther arms upper, 14,5" barrel, A2 gas blcok, Miculek compensator. The thing is that the rifle doesn't lock the bolt back on the last round when I shoot it from hand about 90% of the cases. When shot from beanbag rest or bipod mounted to the handguard is locks the bolt successfully about 95% of the cases.
The original configuration of the rifle was commercial spec. reciever extension tube, and I guess milspec spring with standart carbine buffer. The buffer is little less then 2.9oz (and it's still in place). I didn't notice this when I bought the rifle, since I shot it only from some no name bipod mounted to the quadrail UTG handguard. But even in this configuration it never really worked realibly when shot from hand without support.
Then I went over the following :
replaced the reciever extension to UTG milspec tube and just to be safe, replaced the buffer spring (it's milspec now, matching the tube)
I wanted to replace the A2 gas block, and had suspission that it's somewhat misaligned anyway, so it's now some aloy one, railed. The gas block isn't likely the issue, as I have the same problem with the new one.
The handguard is now furnitured with Magpul MVG stubby grip. The handguard is tight in place, no racking or anything. It's not freefload handguard.
While I've replaced the A2 gas block I've inspected the gas tube (seems okay, no bents and dents) and the pipe cleaner showed down the tube came out clean
The gas key is very tight in place, the bolts are properly staked. The gas rings seems okay as well.
There are no obvious issues with the bolt travel path, it goes smoothly.
The rilfe locks the bolt in the rearward posistion when racked by the charging handle. I've tested about 5 pmags and one gmag, all confirmed working okay with other rifle. Suffice to say, all of my 6 mags lock the bolt in the rear when the rifle is shot supported by the bean bag under the handguard.
Here we shoot pretty much only Barnaul ammo (3 rounds a buck!) but I've plunged to go for brass Sellier&Bellot .223 (less than one round a dollar!!!) and the behaviour was quite the same as noted above, irrelevant of the amunnition tested. The brass ammo is ejected from the rifle at roughly 3 o'clock, while the Barnaul steel cased is ejected somewhere between 4 and 5 o'clock. I didnt' notice any unuasual dents on the spent cases bottom.
Now, I'd happily take the rifle to a gunsmith, but in my country, there is exactly none understanding the ar15 (more than I do anyway:).
My next course of action would be to replace the buffer for something heavier. Due to the fact that the rifle seems to be working okay while shot supported under the handguard, I'm thinking along the lines that the recoil is rather different. I'm thinking that the rifle is maybe over-gassed, hence heavier buffer.
There isn't many people around here I could go by asking to borrow me lowers or the buffers, so I'm pretty much left on my own. Due to the shipping charges I don't want to end up with bunch of buffers that I don't use afterall, so should I go overboard with 5.5oz, or just an oz at a time?
At last, the rifle is still fun to shoot, and during the troubleshooting process I've learned a great deal of knowledge about this family of weapons, so all in all I'm still somewhat okay with the rfile:)
To the problem. I have second hand ar15, DPMS kit lower, panther arms upper, 14,5" barrel, A2 gas blcok, Miculek compensator. The thing is that the rifle doesn't lock the bolt back on the last round when I shoot it from hand about 90% of the cases. When shot from beanbag rest or bipod mounted to the handguard is locks the bolt successfully about 95% of the cases.
The original configuration of the rifle was commercial spec. reciever extension tube, and I guess milspec spring with standart carbine buffer. The buffer is little less then 2.9oz (and it's still in place). I didn't notice this when I bought the rifle, since I shot it only from some no name bipod mounted to the quadrail UTG handguard. But even in this configuration it never really worked realibly when shot from hand without support.
Then I went over the following :
replaced the reciever extension to UTG milspec tube and just to be safe, replaced the buffer spring (it's milspec now, matching the tube)
I wanted to replace the A2 gas block, and had suspission that it's somewhat misaligned anyway, so it's now some aloy one, railed. The gas block isn't likely the issue, as I have the same problem with the new one.
The handguard is now furnitured with Magpul MVG stubby grip. The handguard is tight in place, no racking or anything. It's not freefload handguard.
While I've replaced the A2 gas block I've inspected the gas tube (seems okay, no bents and dents) and the pipe cleaner showed down the tube came out clean
The gas key is very tight in place, the bolts are properly staked. The gas rings seems okay as well.
There are no obvious issues with the bolt travel path, it goes smoothly.
The rilfe locks the bolt in the rearward posistion when racked by the charging handle. I've tested about 5 pmags and one gmag, all confirmed working okay with other rifle. Suffice to say, all of my 6 mags lock the bolt in the rear when the rifle is shot supported by the bean bag under the handguard.
Here we shoot pretty much only Barnaul ammo (3 rounds a buck!) but I've plunged to go for brass Sellier&Bellot .223 (less than one round a dollar!!!) and the behaviour was quite the same as noted above, irrelevant of the amunnition tested. The brass ammo is ejected from the rifle at roughly 3 o'clock, while the Barnaul steel cased is ejected somewhere between 4 and 5 o'clock. I didnt' notice any unuasual dents on the spent cases bottom.
Now, I'd happily take the rifle to a gunsmith, but in my country, there is exactly none understanding the ar15 (more than I do anyway:).
My next course of action would be to replace the buffer for something heavier. Due to the fact that the rifle seems to be working okay while shot supported under the handguard, I'm thinking along the lines that the recoil is rather different. I'm thinking that the rifle is maybe over-gassed, hence heavier buffer.
There isn't many people around here I could go by asking to borrow me lowers or the buffers, so I'm pretty much left on my own. Due to the shipping charges I don't want to end up with bunch of buffers that I don't use afterall, so should I go overboard with 5.5oz, or just an oz at a time?
At last, the rifle is still fun to shoot, and during the troubleshooting process I've learned a great deal of knowledge about this family of weapons, so all in all I'm still somewhat okay with the rfile:)
3/12/2012 5:51:48 PM
First thing that came to mind is that you may have the wrong recoil spring. If you put a rifle type recoil spring in a carbine setup, the spring will not let the bolt retract far enough to the rear for the bolt catch to work correctly.
I guess before we go too much further you should try a simple test.
With rifle unloaded and empty magazine in, pull the charging handle all the way to the rear and hold it there. Look in the ejection port to see how much space there is between the rear of the bolt catch and the bolt face. You should have 5mm or so distance. If there is less distance, you probably have a rifle spring, or else the buffer tube is too short or something else that is incorrect in the configuration.
By alloy I presume you mean aluminum for the replacement gas block, those are a bad idea as they loosen up rapidly from heat when firing, and will leak gas and sometimes lose alignment.
Bolt catch not activating can be caused by "short stroking", which is a lack of gas (energy) from the operating cycle. The alloy gas block concerns me here, along with your description of the difference between shooting by hand and off the bench.
In rare cases, a rifle with excessive energy from the gas system will have the bolt carrier moving so fast that it "bounces" from the back of the buffer tube and back forward so rapidly that the bolt catch doesn't have time to work. From your description it does not sound like this is the problem though.
Check the distance first via the test I mentioned above and let us know, and we'll go from there.
I guess before we go too much further you should try a simple test.
With rifle unloaded and empty magazine in, pull the charging handle all the way to the rear and hold it there. Look in the ejection port to see how much space there is between the rear of the bolt catch and the bolt face. You should have 5mm or so distance. If there is less distance, you probably have a rifle spring, or else the buffer tube is too short or something else that is incorrect in the configuration.
By alloy I presume you mean aluminum for the replacement gas block, those are a bad idea as they loosen up rapidly from heat when firing, and will leak gas and sometimes lose alignment.
Bolt catch not activating can be caused by "short stroking", which is a lack of gas (energy) from the operating cycle. The alloy gas block concerns me here, along with your description of the difference between shooting by hand and off the bench.
In rare cases, a rifle with excessive energy from the gas system will have the bolt carrier moving so fast that it "bounces" from the back of the buffer tube and back forward so rapidly that the bolt catch doesn't have time to work. From your description it does not sound like this is the problem though.
Check the distance first via the test I mentioned above and let us know, and we'll go from there.
3/12/2012 6:17:06 PM
It never really occured to me that the recoil spring might be rifle instead of carbine one, as I have specifically purchased it to be carbine and milspec. From here my assumption that the original spring was milspec/carbine in comercial tube, as the new one I ordered as milspec had the same size and number of colis (in other words I was assuming, that the new spring is milspec/carbine without checking). Perhaps both are rifle.
When it comes to the spring dimensions, is there somewhere a definitive guide of the correct leghts? I suppose the armorers manual published somewhere around here? Or what should I google for?
As for the gas block, I'm not 100% positive it's aluminium, but I'd guess so due to the oddly low weight compared to the A2. I'm thinking this wasn't the best idea either, so this one will likely go. However, as I said before, this isn't the culprit, as the stock A2 gas block demostrated the very same behaviour. Anyway, good to know that aluminium gas block isn't a good idea.
Thanks for the advice so far. I'll post once I'll get back home.
When it comes to the spring dimensions, is there somewhere a definitive guide of the correct leghts? I suppose the armorers manual published somewhere around here? Or what should I google for?
As for the gas block, I'm not 100% positive it's aluminium, but I'd guess so due to the oddly low weight compared to the A2. I'm thinking this wasn't the best idea either, so this one will likely go. However, as I said before, this isn't the culprit, as the stock A2 gas block demostrated the very same behaviour. Anyway, good to know that aluminium gas block isn't a good idea.
Thanks for the advice so far. I'll post once I'll get back home.
3/12/2012 6:21:42 PM
There is no "commercial" or "milspec" springs as far as size.
The difference in "commercial" and "milspec" with regards to carbine buffer tubes is the exterior diameter, the interior dimensions are (should be) the same.
The difference in "commercial" and "milspec" with regards to carbine buffer tubes is the exterior diameter, the interior dimensions are (should be) the same.
3/12/2012 9:58:50 PM
Okay, home now. Checked the clearance between the bolt and bolt catch when the bolt is displaced all the way to the rear with the charging handle and I'd say it's little over 5mm. While I was at it, I've noticed slight scratchmark/dent on the bolt catch teeth (the image attached). Furhtermore, I forgot to mention before, that there is Magpul BAD installed on the bolt catch, so I guess I should start by removing that piece.
The recoil spring is 27,7cm (10.9 in) long, which according to this seems to be within the limits. While I was at it, I've also showed a gauge down the buffer extension tube and it's inner depth is 17.7cm (6.96in), which also indicates correct lenght of the milspec tube.
I'm not particulary in favor of shortening springs that are meant to be this long, but since I have two buffer springs I could sacrifice one for the sake of some testing.
The recoil spring is 27,7cm (10.9 in) long, which according to this seems to be within the limits. While I was at it, I've also showed a gauge down the buffer extension tube and it's inner depth is 17.7cm (6.96in), which also indicates correct lenght of the milspec tube.
I'm not particulary in favor of shortening springs that are meant to be this long, but since I have two buffer springs I could sacrifice one for the sake of some testing.
3/13/2012 12:51:49 AM
A, Make sure that the bolt catch is moving freely in the upper receiver slot with no binding (just light spring tension pulling it back down).
B, Insert all your empty mags into the lower with the upper shotgun opened, and make sure that all take the bolt catch all the way up with authority. If the mags are new/USGI models, and the bolt catch coming up is questionable, then could be that the spring/detent channel for the catch in the receiver was not cleaned correctly before the parts where install, the channel not milled deep enough, or the wrong/too long bolt catch spring in play. Here, you just need to pull the bolt catch via the roll pin, then take a drill bit to clean up the bolt catch spring channel before reinstalling the parts.
C, With the rifle back together, pull all the way back on the charging handle. The face of the bolt should max back about 1/4" to 3/8" in front of the back of ejection ports, and when you are pulling back on the charging handle, the last few inch pull of the handle should be no stronger in tension that the middle pull. If the charging handle pull is loading up, then double check for hammer wedging (will have white lines, dents on the back of the trigger and disco tails.
D, ejection of the spent cases should be around 15' out, or slightly shorter if the spent brass is hitting the upper receiver deflector. If you are getting much less distance of the spent brass that this, then you have problems else where, with the bolt not stroking hard enough for the mag to recover fast enough to get the catch up before the bolt starts moving back forward.
B, Insert all your empty mags into the lower with the upper shotgun opened, and make sure that all take the bolt catch all the way up with authority. If the mags are new/USGI models, and the bolt catch coming up is questionable, then could be that the spring/detent channel for the catch in the receiver was not cleaned correctly before the parts where install, the channel not milled deep enough, or the wrong/too long bolt catch spring in play. Here, you just need to pull the bolt catch via the roll pin, then take a drill bit to clean up the bolt catch spring channel before reinstalling the parts.
C, With the rifle back together, pull all the way back on the charging handle. The face of the bolt should max back about 1/4" to 3/8" in front of the back of ejection ports, and when you are pulling back on the charging handle, the last few inch pull of the handle should be no stronger in tension that the middle pull. If the charging handle pull is loading up, then double check for hammer wedging (will have white lines, dents on the back of the trigger and disco tails.
D, ejection of the spent cases should be around 15' out, or slightly shorter if the spent brass is hitting the upper receiver deflector. If you are getting much less distance of the spent brass that this, then you have problems else where, with the bolt not stroking hard enough for the mag to recover fast enough to get the catch up before the bolt starts moving back forward.
3/14/2012 1:03:31 PM
A) yep, moving okay. although it's wigling little front to back.
B) the mags take the catch all the way up, only that the teeth that comes in touch with the follower is having solid contact over then 1mm, but I've tried to wiggle the magazine and the catch and I didn't manage disengage the bolt catch.
C) I'm not sure what you call bolt face (is it the part where the bottom of the case touches the bolt, or the frontmost point of the bolt?). Anyway, when the bolt is pulled all the way back by the charging handle, the frontmost part of the bolt is flush/level with the rear of the ejection port. When the bolt is on the bolt catch, it sticking past the rear edge of the ejection port by roughly 5mm. The pull is rouhly the same all the way of the bolt travel. (what are the disco trails? Which part is the "back of the trigger" please?)
D) 15' reffers to 15 feet right? It would be about right distance I'm getting. If you reffering to the clock position where the brass is landing, it's roughly 3 o'clock for quiality brass and roughly 4-5 o'clock with the steel casings. The deflector doesn't have any scratch marks or anything that would indicate the brass is hitting it.
In the meantime, friend of mine offered high speed cammera, so you guys have any idea what should I look for? I was thinking to take a shot of the bolt travel and see where it goes. That would rule out over/under gas of the rifle, but what else?
Thanks
B) the mags take the catch all the way up, only that the teeth that comes in touch with the follower is having solid contact over then 1mm, but I've tried to wiggle the magazine and the catch and I didn't manage disengage the bolt catch.
C) I'm not sure what you call bolt face (is it the part where the bottom of the case touches the bolt, or the frontmost point of the bolt?). Anyway, when the bolt is pulled all the way back by the charging handle, the frontmost part of the bolt is flush/level with the rear of the ejection port. When the bolt is on the bolt catch, it sticking past the rear edge of the ejection port by roughly 5mm. The pull is rouhly the same all the way of the bolt travel. (what are the disco trails? Which part is the "back of the trigger" please?)
D) 15' reffers to 15 feet right? It would be about right distance I'm getting. If you reffering to the clock position where the brass is landing, it's roughly 3 o'clock for quiality brass and roughly 4-5 o'clock with the steel casings. The deflector doesn't have any scratch marks or anything that would indicate the brass is hitting it.
In the meantime, friend of mine offered high speed cammera, so you guys have any idea what should I look for? I was thinking to take a shot of the bolt travel and see where it goes. That would rule out over/under gas of the rifle, but what else?
Thanks
3/16/2012 1:19:19 AM
Does it lock back without the BAD on it?
3/16/2012 5:52:35 AM
I'm at work over the weekend, so I can't take it out to range, but will remove it next week and take it to range on tue.
If it does lock reliably without the BAD, what is the remedy for that? I mean I like the BAD, so I'd like rather get this fixed so that the BAD can stay...
If it does lock reliably without the BAD, what is the remedy for that? I mean I like the BAD, so I'd like rather get this fixed so that the BAD can stay...
3/16/2012 9:17:58 AM
OP,
I had the same problem with my 20" and Barnaul some years ago. With the Wolff XP recoil spring in, it was intermittent with Barnaul and fine with SA from a battle pack. With the standard spring in, it was fine with both. In my case is just seemed to be a combination of a strong spring and weaker ammo causing the failure to lock back consistently.
FWIW
YMMV
I had the same problem with my 20" and Barnaul some years ago. With the Wolff XP recoil spring in, it was intermittent with Barnaul and fine with SA from a battle pack. With the standard spring in, it was fine with both. In my case is just seemed to be a combination of a strong spring and weaker ammo causing the failure to lock back consistently.
FWIW
YMMV
3/16/2012 12:27:14 PM
Originally Posted By taboracek:
I'm at work over the weekend, so I can't take it out to range, but will remove it next week and take it to range on tue.
If it does lock reliably without the BAD, what is the remedy for that? I mean I like the BAD, so I'd like rather get this fixed so that the BAD can stay...
I'm at work over the weekend, so I can't take it out to range, but will remove it next week and take it to range on tue.
If it does lock reliably without the BAD, what is the remedy for that? I mean I like the BAD, so I'd like rather get this fixed so that the BAD can stay...
If it works without the BAD there are a few things that can be done, but some rifles will just not work with a BAD installed.
Read through this train wreck of a thread:
http://www.ar15.com/forums/t_3_118/564759_Magpul_B_A_D__Lever_Issue.html
3/16/2012 2:25:09 PM
Next tue I'll go to the range, remove the BAD and see. Anyone see a point in destroing one of the recoil springs by removing a coil or two, to check whether it's not too stiff? I'm not in favor of running parts modified like that, but this is fun rifle and I'd only test if it starts to work with lighter spring, then go order some other new spring.
Since we're around recoil management here, is there any benefit in fitting the heavier buffer? I'm going to US next month, so I could bring one back for rather reasonable price. I guess I could shove in a spare buffer spring too, so what would be your typical spring manufacturer of choice?
Unfortunately the PMAGs (and bunch of other gear) goes under ITAR:(
Since we're around recoil management here, is there any benefit in fitting the heavier buffer? I'm going to US next month, so I could bring one back for rather reasonable price. I guess I could shove in a spare buffer spring too, so what would be your typical spring manufacturer of choice?
Unfortunately the PMAGs (and bunch of other gear) goes under ITAR:(
3/17/2012 10:24:16 AM
I semi see a 9mm mod'd bolt catch in your future for the p mags.
But in the mean time, borrow a aluminum USGI mag to see of that will lock the bolt back correctly on the last round out.
But in the mean time, borrow a aluminum USGI mag to see of that will lock the bolt back correctly on the last round out.
3/20/2012 7:00:13 AM
Okay, so the culprit is the BAD lever. This is somewhat good news in terms that I know of what is wrong and somewhat bad as the lever is really a helpfull tool. Tried drilling some malfunctions clearing on the range today without it, and I have to say that I feel almost like I don't know how to do it:(
Anyway, thanks for the advice from everyone.
Anyway, thanks for the advice from everyone.
3/21/2012 1:24:40 PM
Originally Posted By taboracek:
Okay, so the culprit is the BAD lever. This is somewhat good news in terms that I know of what is wrong and somewhat bad as the lever is really a helpfull tool. Tried drilling some malfunctions clearing on the range today without it, and I have to say that I feel almost like I don't know how to do it:(
Anyway, thanks for the advice from everyone.
Okay, so the culprit is the BAD lever. This is somewhat good news in terms that I know of what is wrong and somewhat bad as the lever is really a helpfull tool. Tried drilling some malfunctions clearing on the range today without it, and I have to say that I feel almost like I don't know how to do it:(
Anyway, thanks for the advice from everyone.
There is ways to modify your rifle to make a BAD lever possibly work.
Some of the solutions are covered in the thread I linked to above.
But some rifles do not like to work with a BAD lever on them.
If ITAR applies where are you located? Your location says USA.
Originally Posted By taboracek:
Next tue I'll go to the range, remove the BAD and see. Anyone see a point in destroing one of the recoil springs by removing a coil or two, to check whether it's not too stiff? I'm not in favor of running parts modified like that, but this is fun rifle and I'd only test if it starts to work with lighter spring, then go order some other new spring.
Since we're around recoil management here, is there any benefit in fitting the heavier buffer? I'm going to US next month, so I could bring one back for rather reasonable price. I guess I could shove in a spare buffer spring too, so what would be your typical spring manufacturer of choice?
Unfortunately the PMAGs (and bunch of other gear) goes under ITAR:(
Next tue I'll go to the range, remove the BAD and see. Anyone see a point in destroing one of the recoil springs by removing a coil or two, to check whether it's not too stiff? I'm not in favor of running parts modified like that, but this is fun rifle and I'd only test if it starts to work with lighter spring, then go order some other new spring.
Since we're around recoil management here, is there any benefit in fitting the heavier buffer? I'm going to US next month, so I could bring one back for rather reasonable price. I guess I could shove in a spare buffer spring too, so what would be your typical spring manufacturer of choice?
Unfortunately the PMAGs (and bunch of other gear) goes under ITAR:(
3/21/2012 3:24:20 PM
Sorry, didn't figure out the profile thing while registering, should be updated now, however the historical posts still show US.
As for the ITAR, it's not entirely impossible to do, but it's not an insignificant money and helluva lot of paperwork to process. There are P-MAGs available around here (I guess they're somewhat smuggled here and there) for roughly 40USD each (!). Interestingly enough, G-MAGs (afaik made in germany) are for the very same price and it's not uncommon to pay even more than that. So it would be possible to do for say bushmaster rifle (still it would be like half the price it is here:) but I just don't have the nerves to go through the paperwork.
Don't get me wrong, we're probably the most liberal country in europe when it comes to gun laws (check the wiki article) but AR15 is not the most common platform around here. Generaly we're rather short on gunsmiths and there is exactly none (good anyway) in the capital. So troubleshooting something we don't have much local knowledge and experience here and hard to procure spare parts is rather complicated (btw, when you advised to try the metal USGI mags, I found exactly one local company some 100Km away from me that had them in stock, used for 8 bucks each - used), so pardon my seemingly moron questions throughout the process:)
As for the ITAR, it's not entirely impossible to do, but it's not an insignificant money and helluva lot of paperwork to process. There are P-MAGs available around here (I guess they're somewhat smuggled here and there) for roughly 40USD each (!). Interestingly enough, G-MAGs (afaik made in germany) are for the very same price and it's not uncommon to pay even more than that. So it would be possible to do for say bushmaster rifle (still it would be like half the price it is here:) but I just don't have the nerves to go through the paperwork.
Don't get me wrong, we're probably the most liberal country in europe when it comes to gun laws (check the wiki article) but AR15 is not the most common platform around here. Generaly we're rather short on gunsmiths and there is exactly none (good anyway) in the capital. So troubleshooting something we don't have much local knowledge and experience here and hard to procure spare parts is rather complicated (btw, when you advised to try the metal USGI mags, I found exactly one local company some 100Km away from me that had them in stock, used for 8 bucks each - used), so pardon my seemingly moron questions throughout the process:)
