AR15.Com Archives
 Bolt closes but does not pick up next round after firing.
ASNixon  [Team Member]
12/29/2003 4:15:42 PM
I have a problem with my AR15. I have read the listed FAQs, especially about short stroking, but could not find the problem I am experiencing. Maybe I am experiencing multiple problems? My AR is a Fulton Armory M4A3 type 16" carbine (called a Guardian) that I purchased a year ago. It has the shorty buttstock with the adjustable buttpad. I have put ~600-700 rounds total through it so far and it operated great until this weekend.

The rifle was clean and lubed before I started to shoot it. It shot great for about 80 rounds and then all of a sudden stopped picking up the next round with 3 left in the mag the first time. I was using the DPMS 10rnd plastic mag when this happened. I tried it again with 20 rounds in an Okay 30rnd mag and ended up having to manually charge the rifle after each round - all 20 rounds. But each time, the bolt would fully close. I did have 3 random rounds that tried to load with the 30rnd mag, but ended up 45 degrees starting into the chamber with the bolt hitting it midlength. The bolt did lock back on the last round each time and extracted/ejected properly. This happened with both Federal XM193 and S&B M193.

I have checked the fit/finish of the parts:

1. carrier key is tight and carrier/bolt closes and locks effortlessly when droped at the 45 degree angle. Bolt is sort of tight when installing into the carrier, but has always functioned properly.

2. checked the carrier key and gas tube for wear to make sure they mated properly - looks good with no wear marks on either or in the upper channel for the charging handle.

3. looked for signs that the hammer was dragging? There is a thin metalic exposed line down the center of the hammer where the finish has rubbed off. The firing pin looked normal though?

4. completely cleaned the rifle again after the problem and tried it again. This time it started after only 20 rnds - same problem. Used three different mags this time to troubleshoot with.

[cut from sample]
I have had the rifle for one year and this is the only problem I have experienced. Please help me, I really really love my AR and I've been told you guys are the best.


Thanks in advance.
A rookie really out of his league.
[/cut from sample]

I know there is a lot of knowledge on this board, so thanks in advance for the help.


Paid Advertisement
--
Ky_Bob  [Team Member]
12/29/2003 5:16:14 PM
Broken or missing gas rings? Loose stuff in the buffer tube causing drag? Part of pipe cleamer broken off or left in gas tube? (You should never have to clean the gas tube) Dinged upper receiver causing drag? Loose gas tube? Weak buffer spring? Hell I'm just guessing as it looks like you have covered all the bases. Good luck, Bob
ASNixon  [Team Member]
12/29/2003 6:12:36 PM
[quote]Originally Posted By KY-Bob: Broken or missing gas rings? [/quote] No - in good working order [quote] Loose stuff in the buffer tube causing drag? [/quote] No - pulled out the buffer/spring - looked good to me. Buffer face facing the carrier has scratches? Wouldn't that be normal? [quote] Part of pipe cleamer broken off or left in gas tube? (You should never have to clean the gas tube) [/quote] I never clean the gas tube other than the outside portion exposed inside the upper receiver just to makre sure mating with key is good. [quote] Dinged upper receiver causing drag? [/quote] Nope - carrier and charging hande operate without a problem. Also, the bolt lugs (hope I got that right) are ok - none broken. But if they where, the round wouldn't load in the first place when charged. [quote] Loose gas tube? [/quote] Seems tight - no wear that I can see other than power residue. [quote] Weak buffer spring? [/quote] Might be? How can I check without having a peice of equipment that does this? [quote] Hell I'm just guessing as it looks like you have covered all the bases. Good luck, Bob [/quote] Thanks - ALL help is appreciated. More than one brain on this is better. Thanks.
Ky_Bob  [Team Member]
12/29/2003 7:28:23 PM
Have you been using a .22 rimfire converter kit? I have heard of lead building up in the gas port in the barrel. Bob
ASNixon  [Team Member]
12/29/2003 7:43:20 PM
No - .223 / 5.56 only.
Dano523  [Team Member]
12/29/2003 8:35:19 PM
[quote]Originally Posted By ASNixon: The rifle was clean and lubed before I started to shoot it. It shot great for about 80 rounds and then all of a sudden stopped picking up the next round with 3 left in the mag the first time. 4. completely cleaned the rifle again after the problem and tried it again. This time it started after only 20 rnds - same problem. Used three different mags this time to troubleshoot with. [/quote] Some times I think you guys make these up just to give me a break from racking by brain. This one is way too easy to fix/correct. When a rifle will run fine clean, then start acting up as it fouls, it just means that the chamber surface has started to foul and the rough fouled chamber is casing the problem. To get the rifle to fire 20 rounds before jamming, clean the rifle as you have been. To get the rifle to fire 80 rounds before jamming, use a 30 cal cotton mop on a few rods and spin the CLP soaked mop in the chamber in a in/out motion to get the fouling at the last of chamber (last step just before the throat) that is causing the rifle's ammo to act as if the round is overpowered, and causing the round to bind. To completely solve the problem, polish out the chamber to be as smooth as a baby’s ass. The problem is that the chamber is rough/tight, and as the fouling builds up, it causes the cases to bind. With the chamber shinny smooth, the fouling does not have areas to allow build up (read rough surfaces). ----------------------------------------------------------- To polish, you can use the 30 cal cotton mop with bore bright (takes a few minutes, and the thickness of the 30 cal mop will prevent you from pushing the jig into the throat of the rifling), or a 22 LR “Nylon” brush with brass wool built up on the jig (takes about 10 seconds). When using the brass wool, build up the wad to be just a tad bigger than the chamber. Then spin the wad/jig in the chamber one full depth, and then pull it back out. The wad will be the shape of the chamber. Using a spent case, check the wad against the spent case. While looking at the shoulder of the case/wad, remove all the brass wool from the wad that would be forward of the end of the spent case (where the bullet would be). This will insure that when your moving the wad in and out of the chamber, you are not pushing the wad into the throat of the rifling, and only polishing the chamber walls. Once you have the wad/jig formed then while spinning the jig, spin the jig in and out of the chamber a few times and look at the chamber walls. If needed, add a little more wool (careful not to build up the wad so it will polish/mar the throat of the rifling) and run the jig/wad a few more times. Whenever the wad is inserted, keep it spinning and in a constant in/out motion. Just remember, your just going for smooth and shinny, not trying to oversize the chamber. Note: you can use very fine steel wool, but until you get the feel polishing out a chamber, stay with the fine brass wool. It works a little slower, and allows you to get a feel of how to polish. Also, never use a brass/steel wire brush for the base jig. The brass/steel bristles can stick out past the wad, and the bristles will groove the chamber walls, hence the reason that you never drill-spin a wire bristle in a chamber. And, don’t even thing about using a spent case with lapping compound as the jig, nor sand paper, both will destroy a chamber by grooving it. The jig/wad need to be able to contort to the chamber as it moves back and forth over the chamber walls.
Boog  [Member]
12/29/2003 9:59:42 PM
Also get a heavy duty extractor spring with the black insert. It helped solve my early extraction problems I was experiencing in a new 16" upper that I had put on an older lower. Dano, " hence the reason that you never drill-spin a wire bristle in a chamber" when I clean I will take one of those chamber brushes with the larger diameter part to clean out the area around the lugs and use my cordless drill to spin this in the chamber/lug area for a few seconds to scrub it out before I clean it up with a mop. bad idea?????
ASNixon  [Team Member]
12/29/2003 10:27:51 PM
Thanks Dano523. Not to dispute what you say, but please educate this newbie for a second. How does the chamber being fouled cause the bolt not to strip the next round out of the mag on the way forward after firing? I have no ejection problems at all - the round just never makes it to the chamber. Let me know if I am close here: The round is loaded when manualy charging everytime. The round is tight in the chamber because of fouling. After the round is fired, because the expended case is tight, the bolt has to exert extra force to pull the fired case out. This causes the bolt to loose some momentum backwards and in turn exhibits the symptoms of short stroking? If this is the case, this is where I get totally lost. Wouldn't the bolt still try to load a round and just not make it - maybe the round starts but only makes it half way or stops all together? I mean the bolt completely closes and locks here without loading a round in the chamber at all. Could you clear this up for me? Again, not trying to dispute what you say, and I will definately take your recommendations and clean it tonight, but I am confused with the recommendation since the problem results after one round is ejected and the bolt is on its way forward. I really do appreciate the help - please do not take this as an insult - take this as a question from an uneducated AR newbie.
Dano523  [Team Member]
12/29/2003 11:18:58 PM
[quote]Originally Posted By Boog: Dano, " hence the reason that you never drill-spin a wire bristle in a chamber" when I clean I will take one of those chamber brushes with the larger diameter part to clean out the area around the lugs and use my cordless drill to spin this in the chamber/lug area for a few seconds to scrub it out before I clean it up with a mop. bad idea?????[/quote] Very, very bad!!!! The chamber tool is to be used by hand. Spinning the brush is going to groove the chamber, and this will cause the fired case to expands into the grooves, and you will get either the ejector stripped off the case rim, or the action short cycling as the energy of the bolt unlocking is wasted as it tries to pry the grooved bound case off the chamber walls. Plus, you don't even want to know what your doing to the throat of the rifling.
Boog  [Member]
12/30/2003 12:05:18 AM
ok. I have only done it 3 times now. I have also been very careful not to press it too far into the throat. I will discontinue using it in this way.
Dano523  [Team Member]
12/30/2003 12:09:48 AM
I thought that someone covered this, but you have check the carrier key allen head screws to make sure that they are still tight. As the carrier heats up, the loose screws can stretch and cause the key to leak gas, hence short stroking. Before you do anything else, check the carrier key screws to make sure that they are still tight. When I first posted regarding the chamber, I thought the rifle was new, but since you have over 600 rounds threw the rifle, the chamber has self-polished, and shouldn’t need to be polished, unless you have been using the ammo with dirt coated ammo, or in a dirty/sandy environment. [quote]Originally Posted By ASNixon: The round is loaded when manually charging every time. The round is tight in the chamber because of fouling. After the round is fired, because the expended case is tight, the bolt has to exert extra force to pull the fired case out. This causes the bolt to loose some momentum backwards and in turn exhibits the symptoms of short stroking? If this is the case, this is where I get totally lost. Wouldn't the bolt still try to load a round and just not make it - maybe the round starts but only makes it half way or stops all together? I mean the bolt completely closes and locks here without loading a round in the chamber at all. Could you clear this up for me?[/quote] You have the correct idea, and will further explain what happens, but this can all be mute is the carrier key is loose on the carrier. On a clean chamber, the case is pulled out of the chamber cleanly and the B/C- buffer makes a full run to the back of the receiver extension. Once all three have made their full rearward travel, the buffer stalls the forward return stroke of the parts and the spent case is impact thrown/pivoted from the bolt face via the ejector on the bolt face. The ejection path of the spent case is around the 4:00 position and the spent case is thrown around 10 to 15 feet away, since the spent case is pressure bound to the bolt face until the end of travel. Also, when the buffer strikes the back of the receiver extension, the jolt will assist any mag on getting the top round into position (on a questionable mag). Once the rough/new chamber fouls, the energy of the gas/action is wasted on getting the pressure bound case off the chamber walls (both due to binding and the fouling causing the round to act as if it was loaded too hot), and the action short strokes. Since your rifle is not picking up a new round, then chances are that the bolt is never clearing the back of the rim of the top round in the mag. And, since the ejector on the bolt face is spring loaded, once the spent case clears the chamber on chamber withdraw, the case is pushed from the bolt face. But, since the B/C, buffer did not make it to the rear of the receiver extension, the spent case is dribble out (1 to 2 feet) of the rifle, and chances are that it is thrown forward. Also, since the buffer did not make contact with the receiver extension, there is no jarring to assist a questionable mag on getting the top round back up. Remember, as the carrier moves back, the top round is pushed/held down in the mag, and unless the bolt moves behind the rim, with enough time to allow the round to pop back up, the bolt just slides back over the top. The dead giveaway to see if the rifle is running correctly is to watch the ejection path of the spent case. If all is normal, then you get a clean 15 feet ejection of the spent case, but as things start to gum up, or the chamber starts to fouls and cause the ammo to show signs of high pressure, the ejection path changes due to the buffer not making full contact with the back of the receiver extension, and you loose buffer stalling and the distance and the ejection path of the round changes to a forward/dribbled out path. [quote]I did have 3 random rounds that tried to load with the 30rnd mag, but ended up 45 degrees starting into the chamber with the bolt hitting it midlength[/quote] If the bolt comes to rest on the middle of the case, then the bolt never cleared the case rim, and the bolt grabbed the top of the round forward of the rim, stripped the round with the bullet tip in the chamber, and the bolt wedged on top.
ASNixon  [Team Member]
12/30/2003 12:04:24 PM
Most excellent explaination Dano523. I will start with cleaning the chamber and inspecting to ensure it is "polished". Come to think of it, isn't the Federal XM193 a little hotter then the S&B M193 stuff? I originally was using all Federal stuff until it started and then switched to S&B. I guess the damage was already done by that time. Again, thanks much for the help - it is greatly appreciated. Paid my membership last night - seems it has already paid for itself in knowledge and was well worth it. [Edited] - BTW, what would be the best way to check the carrier key bolt tightness since the bolts are staked?
Ky_Bob  [Team Member]
12/30/2003 1:39:47 PM
If you can tighten them, they were loose. If you cannot, then they are fine. Bob [quote]Originally Posted By ASNixon: BTW, what would be the best way to check the carrier key bolt tightness since the bolts are staked? [/quote]
Dano523  [Team Member]
12/30/2003 4:42:48 PM
Set up a torque wrench to 35lbs, if the allen screw moves before the wrench click, then pull the screws, clean the key and carrier mating surfaces and use blue loctite to create a thin gasket between the two. Remembering to re-torque the screws to 35-38 LBS and re-stake. Note: You have the option of replacing the screws to new ones. If you have to pull the key a third time, change them out to new onces, or you stand a good chance of snapping them.
ar-wrench  [Member]
12/30/2003 5:02:04 PM
Torque for screws is usually expressed in Inch pounds. Torque for bolts is ususlly expressed in foot pounds. Don't mean to be a grammer nazi, but there is a big difference. BTW, Bushmaster started having loose carrier keys AFTER they required their techs to use torque wrenches on all the key screws. It seems the "ugh torque" worked better...
Dano523  [Team Member]
12/30/2003 8:20:07 PM
Ar-wrench, No worries!!!!! Armalite spec them to 40. The idea is that the rifle should be service every so often, and parts like a worn key should be replaced every so often. The problem is that the key screws can be torque well past the 40 before they snap. But by just tighten until your fingers hurt, gives you no idea of how tight the screws are, and how much you have stretched them. My thoughts are unless the screws are from COLT or FN and are triple checked for defects before I receive them, I would hesitate to man-up on the screws supplied by some of the suppliers. Also, I find it better to check the Allen head screws periodically to see if the screws (NON Mil-spec) have stretched and needs to be replaced. God knows that half the crap/parts that you receive in some of the kits are a joke, (incorrectly hardened, or not at all) so why would you think that the Allen head screws are going to be any different. P.S. Don’t mind me if I go off on a supplier or two over the next few months. I am currently waiting on a few parts that are being sent/replaced due to defectives parts sent in a kit that should never have left their shop in the first place. The pisser is that I will be out of town until late summer, so unless the parts show up by Friday, I won’t finish the rifle until then.
FiveO  [Team Member]
1/5/2004 8:01:10 AM
ASNixon has described the EXACT problem I was having Saturday. I came here to post and see if I could find a fix... I'll get my chamber clean as a whistle! If that does nt work, I'll be back begging for help! YOU GUYS ROCK!!! Dano is the MAN!!! [hail2]
ASNixon  [Team Member]
1/5/2004 1:24:51 PM
Finally decided to send the rilfe back to Fulton instead. Clint said he would warranty the problem. He seemed to think it might actually be the FSB. After talking to him, I finally noticed the FSB to be adjustable - go figure. He thought it might have wandered to far forward and started closing over the port. Will let you know. Thanks for the support!
Ky_Bob  [Team Member]
1/5/2004 1:45:12 PM
[quote]Originally Posted By ASNixon: Finally decided to send the rilfe back to Fulton instead. Clint said he would warranty the problem. He seemed to think it might actually be the FSB. After talking to him, I finally noticed the FSB to be adjustable - go figure. He thought it might have wandered to far forward and started closing over the port. Will let you know. Thanks for the support! [/quote] There is the missing bit of info. An adjustable FSB. It never occurred to me that it would be adjustable. Bob [/quote]
ASNixon  [Team Member]
1/5/2004 8:15:36 PM
That makes two of us...sorry.
Dano523  [Team Member]
1/5/2004 11:44:49 PM
Only one question, since the M-4 rig is used as a combat/ service rifle, what the fuck is an adjustable sight doing on the unit. Granted that I have adjustable front sights on my target/ DCM rigs, I would never consider putting one on a combat/ working service rig. Hell, It would never survive a drop test much less the FBI Frisbee test (snap off, much less hold it's zero). My advice is to have the adjustable sight tower pulled, and replaced with a Forged fixed unit. That way, if you do every take a combat shooting course, the rifle/sight will at least survive the plane flight down and a few prone drops before you have to check the zero (three point sling with the rifle strapped to your chest). ------------------------ For all you guys that strap way too much crap or non proven items on you rifle. Strap/3 point sling the rifle up on your chest, then do a 3 foot dive for cover, then do a belly crawl for another 20 feet threw the rocks and high grass. Anything that is not still attached to the rifle or working correctly, really doesn’t belong on the weapon. You may think that you have a fancy range queen, but at least now you know why we shake our heads and roll our eyes every time you guys show up at the range. Or better yet, how do you find the new guy on the combat course during training, just follow the trail of crap that has fallen off his rig.
ASNixon  [Team Member]
1/6/2004 10:19:42 PM
[quote]Originally Posted By Dano523: For all you guys that strap way too much crap or non proven items on you rifle. Strap/3 point sling the rifle up on your chest, then do a 3 foot dive for cover, then do a belly crawl for another 20 feet threw the rocks and high grass. Anything that is not still attached to the rifle or working correctly, really doesn’t belong on the weapon. You may think that you have a fancy range queen, but at least now you know why we shake our heads and roll our eyes every time you guys show up at the range. Or better yet, how do you find the new guy on the combat course during training, just follow the trail of crap that has fallen off his rig. [/quote] Don't know whether this was necessary or what brought it on - but I do appreciate the advice. Didn't mean to offend you with a rifle I paid for. I also have an M1 Garand Battle Rifle, but really have no intentions of building a 600yrd range to really use it. Haven't hit a combat course and in al honesty have no interest in really doing so. I just enjoy collecting military rifles and shooting them. But thanks all the same. But as I said above, didn't really notice the FSB was adjustable. Sent the rifle back to Fulton Monday, so he should get it by tomorrow. I will call him to see if he will swap it out. Thanks
Ky_Bob  [Team Member]
1/6/2004 10:57:29 PM
[quote]Originally Posted By ASNixon: [quote]Originally Posted By Dano523: For all you guys that strap way too much crap or non proven items on you rifle. Strap/3 point sling the rifle up on your chest, then do a 3 foot dive for cover, then do a belly crawl for another 20 feet threw the rocks and high grass. Anything that is not still attached to the rifle or working correctly, really doesn’t belong on the weapon. You may think that you have a fancy range queen, but at least now you know why we shake our heads and roll our eyes every time you guys show up at the range. Or better yet, how do you find the new guy on the combat course during training, just follow the trail of crap that has fallen off his rig. [/quote] Don't know whether this was necessary or what brought it on - but I do appreciate the advice. Didn't mean to offend you with a rifle I paid for. I also have an M1 Garand Battle Rifle, but really have no intentions of building a 600yrd range to really use it. Haven't hit a combat course and in al honesty have no interest in really doing so. I just enjoy collecting military rifles and shooting them. But thanks all the same. But as I said above, didn't really notice the FSB was adjustable. Sent the rifle back to Fulton Monday, so he should get it by tomorrow. I will call him to see if he will swap it out. Thanks [/quote] Some guys love it by living it. Some guys live it by loving it. I think there are two different objectives here. YMMV Bob
Dano523  [Team Member]
1/6/2004 11:23:02 PM
ASNixon, I wasn't pointing a fingers at you directly, more at the idea of someone offering an adjustable target front sight tower on a M-4 is a little more than off. As for my tangent, it was late, and I tend to think in the "Keep It Simple Stupid" (KISS) way. Currently, it seems that every time someone post a photo of his or her new rifle, it has more crap tacked on it then a Lincoln town car. Somehow, the "have to have" items to add to the rifle has went off the deep, and the entire idea of keeping the rifle combat ready and proven, has taken a back seat to what someone can tack onto the rifle/or offer to sell, is just to make the rifle look more cool. My thoughts on the rifle had never changed, and that is function over fashion. Also, funny you bring up the Garand. My next project is an H&R DCMP rack grade rifle and NM it, Hence a 600 yard rig. Once I get it built, you can poke fun at me for having a rifle that the front hand guard is free floated-glued in place and never to be touch, much less handled (only for show), more glass in the stock then the front fender of a Corvette, and a barrel so short throated that factory ammo/surplus ammo can’t be using in the rifle.
ASNixon  [Team Member]
1/7/2004 3:59:35 PM
[quote]Originally Posted By Dano523: Also, funny you bring up the Garand. My next project is an H&R DCMP rack grade rifle and NM it, Hence a 600 yard rig. Once I get it built, you can poke fun at me for having a rifle that the front hand guard is free floated-glued in place and never to be touch, much less handled (only for show), more glass in the stock then the front fender of a Corvette, and a barrel so short throated that factory ammo/surplus ammo can’t be using in the rifle. [/quote] I'll go ahead and poke fun anyway...[:)] One word for this - BLASPHAMY!! H&Rs and Winchesters are getting to be pretty rare now days. It took me a while to find a decent stock to make this Sept 44 M1 whole. The only non-period part is the barrel SA-9-50. As for the FSB, I don't really disagree with you putting one on an M4 style rifle or concerning the equipment issue. I do have a rail system for it, but I am planning on nothing more than a light just because of the hassle of holding one while handling the rifle. A semi-auto with a foregrip is well...you answer that. So, glass bedding but no lug? Kreiger or Douglas or ???
Dano523  [Team Member]
1/7/2004 11:21:29 PM
A stainless Steel Douglas 4 1-10 if I can find one. Don't really know if I can find one in SS, but may have to spend the Extra $200 for a Krieger to get a SS barrel. And Yes, on the rear lug. Can't really see going to all the effort of spending three days on glassing in an action if the rear end of the receiver can still move/walk around. The up side is that I won't get to the rifle/project until early summer due to being on the road, so this gives me time to order/receive all the parts, and be able to just knock it out in a week when I get back. Figure I can fit all the parts in a few days if every thing gauges right; park'g will take a long day, then the slow process of glassing. My last one went this fast, but until I get my hands on the odcmp rifle (still debating if I'm going to order rack or service grade), I really won't know for sure what needs to go, or can be saved. P.S. Hopefully, I can finish this rifle while I'm on holiday this summer, unlike the current AR-15 project that is sitting on my bench in pieces, waiting for replacement parts to arrive.
Paid Advertisement
--