First off I will say I am new on this forum and glad I found this. Start off bought a M&P 15 Sport 2 about month ago. Put maybe 200 rounds through it. Well today went to go shoot and was working perfect for about 5 shots. Then either wouldn't eject the fired case or it would and the bolt would not fully seat the new round. Two rounds the bullet is not straight with the case like its a tad bit when the new round was trying to go into the chamber. I've disassembled the rifle and everything looked to be good. Still would do the same thing. Anyone have any ideas or some solutions to look into? Kinda sucks this happened on a Saturday so most places are closed.

Lube your BCG with a GOOD QUALITY lubricant! And while you're at it, you might as well do the inside of the upper receiver, charging handle, inside the buffer tube, buffer and buffer spring. A PROPERLY lubricated AR is a HAPPY AR!

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SIC SEMPER TYRANNIS

Yeah I went ahead and lubed the BCG again seemed to not be as lubed, have to try and shoot it tomorrow

I have a friend who had similar problems with a Bushmaster XM-15. About every third round, it would fail to extract or fail to feed another round from the magazine. He asked me to take a look at it. When I disassembled the rifle, I found the BCG, buffer and buffer spring dry as a bone. Additionally the gas rings were unusually worn. I replaced the extractor, extractor spring and o-ring as precaution and also replaced all three gas rings. I lubed the BCG with ALG Go-juice per the manual. I sprayed Ballistol on the buffer and buffer spring, wiped the excess off and reinstalled. I took it to the range and put two 10-round and one 20-round magazine through the rifle and it fired without any malfunction. You shouldn't have to do all that to a new rifle, but just proper lube should make it run smoother. If it continues to have extraction problems, start looking at the BCG and the extractor.

The last time I bought an AR, I went straight to the range, gave the gun a quick once-over, loaded 'er up, and started shooting -- or tried to. The rifle choked every 2-3 rounds through the first magazine. I rummaged around in the truck, found a can of WD40 with a few squirts left in it, and spritzed the BCG. Next 100 rounds went smoothly, and a few thousand rounds later it has yet to stumble again. WD is not what I would necessarily recommend, but my point is --- it needs lube, and it really doesn't matter what you use.

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Pisgah

Oh wow wasn't expecting the rings to go that fast with out lube. Yeah when I bought the rifle I dissembled and lubed everything up. Gonna go and shoot it later with a update but I have a feeling last time I cleaned the rifle I didn't lube it enough.

Well after shooting was still having problems. Was using rangemaster line 5.56. Switched to Winchester 5.56 and had the fist couple either not pick up a new round or chamber the round but after those shot two 30 rd mags without any problems.

A: It'll take several thousands of rounds before the bolt gas rings wear enough to cause issues. And even then...maybe.

B: Keep your AR lubed. Not dripping wet with lubricant, just adequately lubed.

C: Check your mag to make sure they aren't damaged in some way (usually deformed mag lips). Bad/damaged magazines are one of the main causes of malfunctions.

D: Unless there's some issue with the gas system (ie: misaligned gas block, worn/broken gas ring(s), loose carrier key, etc., with the proper buffering system it should function perfectly.

Keep it lubed, check your mags and keep shooting!

All my AR's run like Swiss watches.

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SIC SEMPER TYRANNIS

A couple things to check while you're at it. Is the gas key tight and properly staked? Are the gas rings clean and the gaps properly off-set? What magazines are you running? If you're bending bullets, something isn't allowing it to feed correctly, in addition to everything mentioned before, out of spec ammo could be an issue to consider. Good luck.

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SFC, US Army, Retired

Don't care what anyone tells you but I have shot a fair amount of NRA/CMP across the course and seen hundreds of AR's on the line. When one hangs up during a match a couple of sprays of a decent CLP will most always get them running. They don't run well dry. They can run full of crud but not dry.
The rifle is short stroking. Usual cause is:
1. Gas ring gaps not opposed. Check them, they are good for 3,000+ rounds. If you can extend the bolt and it will support the weight of the bolt carrier stood on the bolt face the rings are good.

2. Carrier key loose

3. Mag spring weak or follower hanging in the mag. Clean & dry lube the mag. The followers can be troublesome but most newer mags are good to go. I assume you are using a Mil Spec or better.
4. Most NATO spec rifles don't run well with less than full power loads unless you go to a weaker buffer spring which "I" don't advise.
5. Way less likely but possible is a bad buffer spring or poorly cut A4 feed ramps.

I was using range finder 5.56 55grain ran prolly 4 mags since I bought it until yesterday when started acting up. Switched to Winchester 5.56 and didn’t fail to fully seat maybe 4 times. Emptied that mag and put a 30rd mag in with only 28 rounds in it and fired alright till last three bullets. I have a feeling was prolly the ammo and possibly didn’t have it oiled enough. I have two Pmags one is gen2 and gen3.

If the gun is 100% factory, then I'll check with s&w for issues? I've had the gas tube binding against the gas key causing drag. What you can check is by separating the upper and lower, using hand only work the bcg in and out of battery. If it's smooth then it's good to go. Some 5.56 might be under powered where only a few make it cycle (hit and miss on enough pressure or volume of gas). When it ejects does it eject around the 3-4 o'clock? If so, the ammo should be ok. If it ejects 1-3 or 4-5 then there's other issues. The chamber could be a little tight is what has happened with 2 of my 6.5grendels, but loosened up after a 100 rounds or so. Try (while the upper and lower is separated) removing the bcg, point the muzzle down, drop in a round and see if it plunks. Then slowly turn the muzzle up and see if the round falls freely. That checks ammo and chamber, but doesn't mean if it doesn't fall freely that both are bad?

The bulk of all problems you’re likely to experience with a brand new AR of reputable make (which the Sport II is), are going to be as follows:

* improper, and/or insufficient lubrication
* a damaged or faulty magazine
* poor quality ammunition

I would estimate that in 20 years of shooting AR’s, with most of those years spent at a job that issued them to me along with a little over a hundred coworkers, those three things account for a solid 80% of problems I’ve personally witnessed with an AR. The good news is that lube is an easy fix, magazines are cheap and abundant, and there really isn’t that big of a cost difference between good ammo and junk, so you might as well be using decent stuff.

If all of those possible sources are eliminated as your cause, I’d look to things like the buffer and buffer spring, and extractor. And while the occasional lemon does make it through the doors of every manufacturer, the AR is a design that lends itself well to the manufacturing and assembly process, making it less likely than a lot of other designs to exhibit problems right out of the gate.

Buy yourself a handful of good quality magazines, and a few boxes of something like Winchester XM193 5.56 ammo. Field strip the rifle, and lube it up using something like a decent CLP product making sure to put a light coat of oil on the inside of the upper receiver where the bolt carrier and charging handle ride. Also, disassemble the bolt and be sure to lube the individual components of it before reassembling. Finally, make sure that the buffer and buffer spring get a light coat of oil as well.

If you need help with field stripping or reassembly, there are tons of online tutorials, or just ask here. I have probably fired no less than 10,000 rounds through various AR’s, and I can count on my hands how many stoppages I have personally experienced in that time. The AR is a very reliable rifle, and Smith & Wesson makes a good one. Properly cared for, that rifle should give you a lifetime of trouble free service.

Despite what has been written and repeated innumerable times on the internet, the interior of the receiver extension/buffer tube benefits greatly from being LIGHTLY lubed. I have heard buffer springs loudly dragging, scraping and screeching when being slowly cycled. I have also seen the interiors of more than a few buffer tubes that were incredibly poorly machined and left extremely rough, they should be smooth. New AR rifles can definitely benefit from being run a little wet during break-in.

Two mags is hardly enough (I have hundreds of them, I like to load up at home and spend my time at the Range shooting). You need to buy more magazines and number/mark them. When one is less than reliable it goes in the garbage.

Just giving a update, sent the rifle to Smith and Wesson and after three weeks got the rifle back and the bolt was out of spec. I guess there were a set of them made that the bolts were not within spec and I happen to bought one of them. Haven’t had the chance yet to fire it but just by charging the weapon it’s a lot smoother.