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Posted: 4/28/2024 6:43:53 PM EDT
Alright so this is happening with my m&p15 sport 2. The ammo I'm currently using that this issue has occurred with is federal 55grain by fmj. The value pack of 100 rounds. So I've used 3 magazines. D&h, magpul gen 2's. In two other guns. These magazines work perfectly fine. Even the same ammo has ran fine on both. However with this ammunition in my m&p 15. While I'm shooting, I'll get a dead trigger. Notice the bolt is held open partially. The rounds are always stuck in the chamber. Sometimes the rounds have went off. And it's a spent case. But mostly it'll be a light primer strike, with a bent case still housing the bullet. Any idea what the can be?
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Originally Posted By Kgb2930: Alright so this is happening with my m&p15 sport 2. The ammo I'm currently using that this issue has occurred with is federal 55grain by fmj. The value pack of 100 rounds. So I've used 3 magazines. D&h, magpul gen 2's. In two other guns. These magazines work perfectly fine. Even the same ammo has ran fine on both. However with this ammunition in my m&p 15. While I'm shooting, I'll get a dead trigger. Notice the bolt is held open partially. The rounds are always stuck in the chamber. Sometimes the rounds have went off. And it's a spent case. But mostly it'll be a light primer strike, with a bent case still housing the bullet. Any idea what the can be? View Quote did you buy it new? is it lubed? new ar owner I met recently at the range was having similar issues. bolt and carrier were bone dry. I have a MagPul MIAD grip with the lube bottle, and most of the time I pull it out it's to help someone at the range. lubed it up, hand cycled it a couple times, no more problems. |
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The deuce you say.
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By the numbers,
Pull charging handle all the way back, and make sure face of bolt is forward of the ejection port back window edge by 1/16"~1/4", and lst inch of pull is no harder than middle of pull. Look the mag ejection button, and is the end of the catch thread section, flush with the face of the button. If no, then push button all the way in with pencil eraser, and thread catch one more wind in. If catch threaded section is either a wind in, or wind out, then unthread mag catch from button, rotate button in recess 1/2 turn, and reinstall the catch. Pull B/C from rifle, add CLP around the base of the key to top of carrier, hold the bolt in, and then use air compress to pressurized front of key 100lbs, and make sure not leaks between bottom of carrier key, to top of carrier. Now with a piece of tubing on the end of the gas tube, CLP at the end of tube to FSB, and around front and back of FSB to barrel, same with 100lbs of air down the gas tube, to verify no leaks of these three areas. Also, should have a good flow of air out the gas port to barrel bore, so listen for this as well, just in case gas block to barrel gas port is blocked, or the roll pin is missing that should be holding in the gas tube to FSB. Now pull bolt off carrier, and dry fit the carrier to the upper, and when the front of carrier is about 1"off back of barrel extension, gas tube should be entering the carrier key cleaning, not causing the tube to bind when it enters key. If tube is binding, then will need to pull front hard guards off barrel, so you can tweak the gas tube over the center of the barrel. When putting the clean B/C back together, make sure to use CLP to lube the carrier inside and out. Also, if mags have had some time to them, then pull then apart to CLP clean them inside and out. As for barrel, CLP with chamber brush to scrub the chamber to remove any storage grease that may still be in the bore, then run dry patches from the chamber to muzzle, to get out all the fouled CLP. Us Q-tip to clean the barrel extension area/lugs, and only lube the upper bearing surfices with CLP. Not, do not use Hoppes gun solvent to clean the bore, since leaves behind a protective coating, that just turns into a gooey mess with it mixes with CLP. So something like Sweets copper solvent to clean the bore with bore brush first, run patches until they no longer come out green, then CLP and chamber brush to clean chamber next, with the dry patched again from chamber to muzzle, to get the fouled CLP out. Also, sweets leaves no protective coating behind, but even with you think you have the bore and chamber dry, enough CLP left on both for short term protective coating. Simply, mag catch tight with threaded part to face of button, should hold the mags in well correctly to solve any low feed problems, and the rest is make sure rest of parts are clean/correct, and no gas leaks to cause short stroking problems. If you still have problems, then get S&W on the phone, to look at the rig under warrenty. Hence case being dented on loading, is caused by bolt over problems, with either the bolt not coming back far enough, or mag not recovering fast enough instead. As for cases being dented on ejection buy the upper receiver deflector, kind of normal, but velcro on defector will solve that denting problems. And again, face of bolt should not retract behind back of ejection window on full charging handle pull, since if it is, then spent cases will ding off inside lip of rear ejection window, which can cause spent case to be pivoted back into action. If you post a photo of the case dents, will tell of lot of how they are happening. |
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Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds... <---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind. |
Well I've had it for several years. And now I probably have about a thousand rounds through it. This just started happening within the past time range trips. It happened with pmc bronze 223, federal 223 and wolf gold 223. To simply it, I'll be shooting and then I get a dead trigger. Look to the chamber, notice the bolt is about half an inch from closing with a live round stuck on the chamber. It's typically dented or bent. Basically the rifle is short stroking I believe. Yes I cleaned it after the first incident throughly. Even ran a bore snake several times down the barrel. And I oiled the rifle. Keep in mind, this rifle has been 100% malfunction free until the last two range trips. With the same magazines and ammunition that I always use. My mcx and other ar15 both functioned flawlessly with this ammunition an magazines.
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https://i.postimg.cc/CLNFrd63/RDT-20240428-1902401867452312357165947.png
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Dude that website is trash when it comes to image quality. I can email it to you or text
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https://imgdump5.novarata.net/6d6act.png
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Is the gas key loose?
Is the buffer tube vent hole clear? |
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Keep your powder dry, and watch your back trail.
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I think we can eliminate it being a magazine problem. I've now tried 4 magazines. I just did a brand new d60 yesterday. And it ran 100%. The ammo was m855 556. See it doesn't do it every magazine. I can sometimes fire 30 or 40 rounds and everything works perfectly fine with the same ammo. And then dead trigger and bolt failing to go all the way home with a round dented and stuck in the chamber.
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So here's everything I've done. I pulled the bolt out of the carrier and checked alignment of the gas key with the gas tube. It went together like a knife through butter. I checked around the a2 front sight post for signs of carbon. Trying to see of its a gas leak or not. It's perfectly clean. I check to see if there was drag of the bolt and carrier in the receiver. And it didn't have any binding. Now my gas rings we're spaced apart a little. But not much, so I did just adjust those to make as far apart as they could be. After that, I checked my extractor spring. It's in tact and with a oring. I checked the head and where the cam pin goes for cracks. There are no visual cracks. I cleaned everything with clp and then lightly rubbed oil on the wear marks of the bolt and carrier. I cleaned the feed ramps. I inspected the feed ramps with that photo above I seen on another post already. And everything looked to align correctly from the naked eye. I checked the gas tube for play. It's on tight, the a2 sight doesn't have any pins walking out and isn't canted. Now my buffer spring and buffer are original from Smith and wesson. Yet there isn't quite a thousand rounds on it yet. Now why would it start giving me problems this low of a round count? Could be the culprit though. What I can tell you. Is the gun is way overgassed. My ejection pattern is almost 1 o'clock. It's ejecting so far forward from the video I took. It doesn't even come back and hit the shell deflector. Which is odd. I can see that when I slowed the video down. The bolt and carrier when pulled back with the charging handle sit right about a quarter or a inch from the opening of the chamber. Maybe a little less. Now in the middle of pulling back the charging handle. You do feel a little more tension. But that's likely from compressing the buffer spring.
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I've also check to see if the bolt would collapse on it's on weight. It doesn't, the gas key doesn't budge either. Now I can try running the bolt in another rifle and see if it does the same thing with 223 ammo. And then run one of my other other bolts in it. To see if it does it again. Because if the different rifle with the same bolt does it. We know it's related to the bolt and carrier. However if the problem persist with the different bolt in the same gun. We know it's something in the gas system or the buffer. This weekend I'll post an update on what happens. Thanks for your help btw.
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With those symptoms, it sounds a little anemic. Is it chambered for 5.56? If so have you run 5.56 for comparison?
I would closely inspect the gas tube to key fit, gas key, rings, bolt tail for wear and leak. Weigh your buffer. If your gas system is tight and your buffer is heavy, I'd drop buffer weight. There's a fair chance you've been on the edge of efficiency/ balance of gas vs buffer weight and normal wear has loosened things up enough that under gas symptoms are showing up. It could also be ported for 5.56 gas and .223 is making it struggle under these conditions. |
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Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds... <---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind. |
The rifle is not undergassed, it's quite over gassed. So much so that it's slinging spent cases at the 1 o'clock. An overgassed rifle can cause short stroking.
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Yeah it's chambered for 556. And yes it runs 556 fine. It seems to only malfunction when running 223 ammunition.
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What I can tell is the bolt every time was almost closed and behind the rim.
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Originally Posted By Kgb2930: What I can tell is the bolt every time was almost closed and behind the rim. View Quote But case bent, and not allowing the bolt to fully lock up? If yes, and not using the mag as either a by pod off the bench, or hand hold to cant the hell out of the mag in the well, then low feed out of the rig. Remove the mag catch from the rig, strip the problem child mag down to just mag body, and with bolt closed, insert the mag into the well until you have the body feed lips tight against the bottom of the carrier, then look at the bolt catch channel on the non ejection side, to see where the mags slot for the bolt catch is against the bottom slot of the receiver catch channel. Simply, mag locked in play, should have the mag lips about 1/8" below touching the mag, and if the mag is retained lower than this in the well, then going to have feed problem out of the mag with it sitting too low (or being able to rock too much fore and aft in the well during recoil). It could be a problem with either the lower receiver with mag catch slot too low, or could be a problem with the upper receiver, with the B/C channel in it too high, but if you have another rig, then swap the mag catches between the two, to see if the problem is following the mag catch with it too loose in the catch slot/ it top ledge too low to retain the mag high enough. Also, does not hurt to check a few mag slots against them selves, since on plastic mags, the top of slot for the catch to retain it, can peen over time. |
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Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds... <---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind. |
is this your only ar? can you swap a different lower onto it?
overgassed, or a weak buffer spring, should result in the same symptoms. buffer springs are cheap. like $4 plus shipping. |
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The deuce you say.
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Yes, actually thought of that too. And no it's not brand new. I've got maybe a thousand thousand through it now.
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Ok here's an update. Finally got another lot of ammo. I used IMI m193 556 this time. And the bolt still short stroked. But the other two bolts ran 100% i had. I bought a dozen brand new lancer mags. Took my other ar15. A Delton that runs 100% with a bcm bolt and carrier. I swapped the m&p bolt with the bcm from the Delton. The Delton suffered the same malfunction running the m&p bolt with the new lancer magazines. Basically short stroking. The round will hang up as it's clambering the next round. With the bcm bolt.. The m&p ran 30 rounds 100% with the lancer magazine. Yet if I put the gen 2 pmag in the Delton with the m&p bolt. It also runs 100%. And vice versa. So as you can see. This is confusing, is it a magazine issue? Or a bolt issue? When it first started happening. I didn't own the lancer mags. I used a d&h tactical magazine, and a m&p gen 2. Windowed. I also ran a psa premium bolt in the m&p. And it ran 100% with the lancer and m&p magazine. So we can rule out the lower received and upper receiver of the m&p. Now the m&p bolt will run good with some of my pmags. But then short stroke on the d&h magazine, lancer magazines and my windowed pmag. The lancer magazines are brand new. It will short stroke on both rifles. With the same magazines. But then I run those magazines with the psa and bcm bolt. And it runs 100% in both rifles.
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The gas key is tight, no wiggle. This particular bolt also looks staked correctly. I heard some m&ps made it out of the factory not being correctly staked.
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https://i.postimg.cc/Bndy2CHZ/20240610-013751.jpg
Ok so this is something I noticed after firing around 160 rounds through it. It looks like there may be some carbon building up in front of the gas key. And that could be my culprit there for the short stroking. |
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Symptomaticaly, it's acting like it's under gassed. I get that there's plenty of gas being supplied but it's not being used efficiently. Since you have narrowed it down to the BCG, it's a fair guess that something is either a grossly out of spec or blocked.
If you're confident that the rings are good, there's no obstruction in the gas key, and you don't have the tooling to measure the BCG to determine exactly how it's out of spec, I'd just replace the BCG. There's a chance you could get away with just replacing the bolt but, if the carrier is the problem you're not making any progress. |
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That's what I was thinking. Luckily I have two extra bcgs laying around. The staking looks identical to the bcm I have. To me, it looks good. The screws aren't loose. There actually tight as hell. Now it could be a alignment issue with the carrier. Just being a hair off since it has a little carbon on fromt of the key. When I get around to tearing into. And figure out what's the problem. I'll post an update.
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Here's a better image of the carbon build up in front of the carrier key.. https://i.postimg.cc/pdhLH96c/20240610-013751.jpg
https://i.postimg.cc/cLb8wtt0/20240610-013754.jpg The has rings are spaced evenly. They can't be worn out around a thousand rounds on them. I can't see any obstruction on the has key. But it could be way down in it. I'm just curious to why I have a carbon caking up in front of the key. It appears to me, to be a gas leak there. |
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Originally Posted By Kgb2930: Here's a better image of the carbon build up in front of the carrier key.. https://i.postimg.cc/pdhLH96c/20240610-013751.jpg https://i.postimg.cc/cLb8wtt0/20240610-013754.jpg The has rings are spaced evenly. They can't be worn out around a thousand rounds on them. I can't see any obstruction on the has key. But it could be way down in it. I'm just curious to why I have a carbon caking up in front of the key. It appears to me, to be a gas leak there. View Quote It may have little to do with screws being tight and more to do with the key not being flat. I would ignore the staking... it doesn't matter how it looks compared to anything, only that it's staked properly and preventing the screws from moving. The gas key could be removed and replaced with a new key or removed, lapped, and replaced. Even a new key could be lapped but should at least be checked for flat. The gamble is you want to know that the carrier body is not the part out of spec. If you have a precision straight edge you can check it. Seal with a thin coat of loctite, I prefer 620 for this. Reinstall with OCKS screws to 50-58 in-lbs and stake. The thing is, if you aren't already tooled up to do the job you'll outspend a new BCG fixing this one. Worth it if you see yourself doing more in the future, not so much for a one off. |
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