AR jam

[Jynx]

Went shooting today. Got through one magazine of PMC 223 ammo, and on the second shot of the same ammo in a different magazine it jammed. The shell casing got cought between the bcg and the end of the charging handle. Tried a third magazine and got the same result after the first shot. Was going to disassemble and clean. But want to know if I have a bigger problem and what to look for when it is apart.

Thanks
Jynx

 

[RamRoddoc]

Inspect the bolt closely, check the bolt ejection spring and gas rings. Inspect the BCG and insure it's properly staked and not loose. Inspect the chamber with light and check the gas tube for alignment and air flow.

Carbon expectedly builds up on these rifles. I use a pick to get the BCG/bolt/firing pin carbon off.

For adjustable gas blocks that are not pinned in, insure it has not moved forward. If so clean the set screw, red locktite it and torque it down within spec.

Edit:

Insure it's properly lubed. The bolt/BCG lightly oiled, the charging handle lightly oiled as well.

 

[jcountry]

Also-

The gaps in the gas piston rings should not be aligned with one another. Can let a lot of gas blow by.

One should be at 360 degrees, one at 120, and one at 240. Just like the points on a Mercedes emblem

 

[Jynx]

Ok I will check all of these out in the am when I clean it.


Thank you.

 

[cmshoot]

......or switch the 3 individual gas rings for a McFarland-style coil gas ring.

 

[00formula6spd]

I may be wrong, but was there a time folks said to load 30rd mags at only 28-29 because of this? Its late ....who knows.

 

[righter13]

I may be wrong, but was there a time folks said to load 30rd mags at only 28-29 because of this? Its late ....who knows.

I've heard this before too but to me every round counts.

 

[jcountry]

I may be wrong, but was there a time folks said to load 30rd mags at only 28-29 because of this? Its late ....who knows.

28.

Ensures that the mag will seat in the gun properly if you change mags on a closed bolt.

(Nothing more embarrassing in a firefight than to yell "take this mother****er" and go bang once with your mag falling and hitting your foot because it wasn't seated. Poor form.) Slightly less embarrassing in front of your buddies at the range.

 

[RamRoddoc]

Doubtful it's a magazine issue since it occurred with other magazines. Modern magazines or accurately modern followers should not have issues if loaded to capacity.

Back in the 1980's or early 1990's as a 101'st unit Armorer we had to swap out magazines due to issues with the followers. Older G.I. magazines can be updated and the follower changed out.

Troy hits the history pretty good (about a 1/4 downFAQ). His reply is below. Below that he discusses overloading 20 round magazines that created jamming issues:

http://www.ar15.com/content/page.html?id=331

The original plastic follower design has a long center post, designed to prevent spring over-compression, and a short anti-tilt leg in the rear. It does not have any anti-tilt leg in the front, which means that the rear of the follower can tilt down and fail to push the rounds up to the feed lips. This results in both bullet-feed misalignments (jams) and in "bolt-over-bullet" fails to feed. The latter is especially common on the last couple of rounds in the mag, when spring pressure on the follower is the lowest. This happens whether or not mags are loaded to capacity or underloaded, and is completely independant of the ammo type used. It is simply a result of poor follower design.

This problem had been an issue with the 30-round mags ever since they had been adopted. In the mid-80s, it was noticed that the problem seemed to happen more frequently with Sanchez-brand magazines, and so an investigation was started to try to determine the cause. It was assumed that the investigation would determine that Sanchez mags were not in-spec. This turned out not to be the case, and the final recommendation was to correct the design of the follower. Thus, new followers with a front anti-tilt leg were created, which used green plastic to make them easy to identify, and were shipped with new Sanchez mags starting in 1988 for field trials. The trial ran through 1990, and proved to be successful at eliminating the feed problems associated with the original followers, resulting in formal adoption of the new design in 1991. All USGI-contract 30-round AR mags were required to have the anti-tilt followers as of late '91. Existing black-follower mags were not upgraded.

...

You have to decide for yourself how reliable you expect your mags to be. While millions of BF mags exist and have been used, there have been lots of feed problems that are directly attributable to the design of the BFs. GFs are known to significantly reduce or eliminate these problems. Upgrading costs $1.00-1.50 per mag, depending on quanity. Is it worth it? That's a question only you can answer for yourself.

All of my USGI 30s have GFs.

-Troy

His next reply to overloading 20 rounders.

By '68 or so, most units were correctly filling their 20 round mags with 20 rounds, and not having any problems. But some units, who were trained the "old" way and/or who believed all of the myths and mistruths that were spread about the M16, would still train the "18 in a 20" method. Some folks STILL underload their mags to this day, and there is NO reason to do so.

Well, okay, there is ONE reason that makes sense:

Underloading your mags by ONE (1) round will make it easier to to a "tactical reload", which is where you remove a half-empty mag and replace it with a full mag during a lull in the fighting. When you do this, your bolt will be forward on a loaded chamber, and if your mags are full, you have to give the mag a FIRM smack on the bottom in order to compress the spring enough to allow the mag to lock into place. If you fail to do this well enough, the mag will often fall out of the gun on the next shot. Underloading the mag will leave more slack in the spring, and make reloading with the bolt forward a bit easier.

I still prefer to load to capacity. As long as you understand the big picture, this is no problem.

-Troy