AR guys: can bad ammo cause double feeds/failures to extract?

[1KPerDay]

Trying to diagnose a buddy's AR woes... he has reported lots of jams in the past. Bushmaster, heavy fluted barrel, A2 stock with carbine gas. BCG is unmarked that I can see, but dull chrome finished (I think). Buffer appears to be standard rifle.

With Okay industries mag and new Cproducts teflon no-tilt I got repeated double-feeds and failures to extract shooting Grace Ammo copper sintered stuff.

Just out of curiosity I shot 40 rounds of Wolf Gold through both mags with zero malfunctions.

Not really statistically significant, but enough to make me wonder.

The grace ammo runs perfectly in all my ARs and my SCAR 16s.

 

[Comrade Mike]

Absolutely. Gas systems are susceptible to what is generating the gas.

 

[Slamfire]

One of the greatest sources of unreliability, if not the greatest source, is the magazine. At the time these issues were being fought out, post WW2, the Infantry was used to its Garand, wanted stripper clips instead of magazines. Garand ammunition was on an eight round clip. There is a Memo from the user in the Black Rifle (or the M14?) complaining about the cost of magazines, the weight, etc. The User does not like change. The Army likes what it has, wants something better but only a little different, and totally rejects complete change. Going from a clip fed rifle to a magazine fed rifle was just one of those things that made the milk sour for baby, and baby tried to puke magazines out from the next rifle development. If you notice, the M14 has a stripper clip guide on the top. Stupid. If it were left up to the Infantry, they would still be using M1861 Muskets.

Stoner gave the Infantry what they wanted, a cheap, lightweight magazine. They also got something they did not expect: unreliable feed. The feedlips on the M16 magazine spread and cause misfeeds and double feeds.

That, along with over pressure rounds, could be your bud's problem.

 

[TJohn]

Sounds like you solved your problem with the ammo switch. Could just be a bad batch/lot # of ammo, every manufacturer lets bad rounds out their door at times.

I see that you say your rifle does fine with Grace ammo,however, are you talking from past use or did you shoot some rounds from the same box your friend was using, in your rifle?

Has your friend tinkered with the rifle, i.e., changed out the buffer or changed or modified the gas system in any way?

 

[ColoradoShooter77]

I've had failures to extract with reloads that are on the low end of the charge scale.

I've upped the charges to near max and it runs like a clock.

I use P-mags and have never had a problem.

Sounds like faulty ammo to me.

I also had (2) FTE's in a box of Aguila 62 grain FMJ ammo. I'm not buying that stuff anymore. Although the brass is pretty good!

 

[Sunray]

Bad ammo can do that in any rifle. Not just an AR.
"...The Army likes what it has..." Yep. Same thing went on when the U.S. adopted the M1 Rifle. The M1 Rifle originally had a 20 round box mag that the Army said no to in 1920ish. At least then, they actually wanted the thing. They got the M-14 because it was invented Stateside.

 

[offthepaper]

Bad ammo or faulty gas system would be my guess.

 

[NWcityguy2]

Ammo can cause both of your problems and sometimes a failure to eject can look like a double feed. This can also be caused by ammunition that is both under-powered and over-powered, and I've seen it happen both ways. I'm inclined to say that since the gun is having two problems at once, it is not the magazine.

When I went to the police academy, we were all issued Bushmaster carbines. Almost immediately a significant portion of us began having both extraction problems and what appeared to be double feeds. Since the academy was a semi-military environment, when someones rifle had a jam, it was that persons job to immediately clear it and keep shooting. Since the guns were almost new but the magazines (D&H) were hand-me-downs, a bunch of people rushed out to Academy sports and bought themselves P-mags to solve the problem.

The thing was though, the new magazines didn't solve any problems and even the instructors noticed this. When someone next to me had another double feed, I stopped him from clearing the jam and watched him as he did. When he locked the bolt to the rear, out came both a new round and an expended round. From the outside it looked like a double feed because two cartridges were trying to force their way into the chamber at the same time. But what had happened was the extractor couldn't hold on to the fired casing. Without the extractor holding on, the ejector couldn't swing the casing out. Pressure from the barrel pushed the casing back with the bolt, the bolt picked up a new round from the magazine, and then both casing were pushed forward into the chamber.

When we took apart our bolts, we saw that Bushmaster had used a blue rifle insert and what I assume to be an under-powered extractor spring. Once they were replaced with a black insert and a 5-coil spring, all problems went away.

From your description of the problems, and how they went away with a different choice in ammo (which it won't do if the magazine is truly giving double feeds), he needs to upgrade his extractor spring and insert, possibly the extractor, or just replace the bolt.

 

[1KPerDay]

Sounds like you solved your problem with the ammo switch. Could just be a bad batch/lot # of ammo, every manufacturer lets bad rounds out their door at times.

I see that you say your rifle does fine with Grace ammo,however, are you talking from past use or did you shoot some rounds from the same box your friend was using, in your rifle?

Has your friend tinkered with the rifle, i.e., changed out the buffer or changed or modified the gas system in any way?

Rifles were fired back to back same mags same ammo. Dunno if he's messed with it. I don't think so but he didn't build it (bought it used). I lubed the BCG well to see if it helped. It didn't.

I've shot 1K rounds of the Grace stuff through various ARs all from the same "bulk" box. No malfuntions in 4 ARs and a SCAR. But his chokes on it apparently.

Could it be some weirdness with carbine gas and rifle buffer? They're supposed to be compatible, right?

 

[NWcityguy2]

Could it be some weirdness with carbine gas and rifle buffer? They're supposed to be compatible, right?

Yes. All things being equal (IE the rifle doesn't already have a problem), using a rifle stock on a carbine and a carbine stock on a rifle is perfectly fine.

 

[1KPerDay]

Ammo can cause both of your problems and sometimes a failure to eject can look like a double feed. This can also be caused by ammunition that is both under-powered and over-powered, and I've seen it happen both ways. I'm inclined to say that since the gun is having two problems at once, it is not the magazine.

When I went to the police academy, we were all issued Bushmaster carbines. Almost immediately a significant portion of us began having both extraction problems and what appeared to be double feeds. Since the academy was a semi-military environment, when someones rifle had a jam, it was that persons job to immediately clear it and keep shooting. Since the guns were almost new but the magazines (D&H) were hand-me-downs, a bunch of people rushed out to Academy sports and bought themselves P-mags to solve the problem.

The thing was though, the new magazines didn't solve any problems and even the instructors noticed this. When someone next to me had another double feed, I stopped him from clearing the jam and watched him as he did. When he locked the bolt to the rear, out came both a new round and an expended round. From the outside it looked like a double feed because two cartridges were trying to force their way into the chamber at the same time. But what had happened was the extractor couldn't hold on to the fired casing. Without the extractor holding on, the ejector couldn't swing the casing out. Pressure from the barrel pushed the casing back with the bolt, the bolt picked up a new round from the magazine, and then both casing were pushed forward into the chamber.

When we took apart our bolts, we saw that Bushmaster had used a blue rifle insert and what I assume to be an under-powered extractor spring. Once they were replaced with a black insert and a 5-coil spring, all problems went away.

From your description of the problems, and how they went away with a different choice in ammo (which it won't do if the magazine is truly giving double feeds), he needs to upgrade his extractor spring and insert, possibly the extractor, or just replace the bolt.

Yeah, that's what I suspected... if one is left in the chamber (which it definitely was on at least 2 occasions) the next round can't chamber, and it looks like a DF. Or if the fired case partially ejects, etc.

That's exactly what's happening. I believe your diagnosis is correct. I'll order a new extractor spring and insert or whatever.

thanks guys!

 

[NWcityguy2]

Since shipping is expensive and the parts are cheap, I would recommend ordering a new extractor as well. If the hook on his old extractor is worn, the new spring and insert won't help all the much. It's much cheaper than buying twice and paying for shipping twice.

 

[1KPerDay]

Good idear. thanks!

 

[NWcityguy2]

If I ever want to shoot substantially slower, I'll follow your advice too.

 

[ifit]

Had same issues after one of my builds, took a while to figure it out....process of elimination found out that I had a worn out extractor. Since replaced never had anymore issues. You might want to give that a try

 

[1KPerDay]

ok thanks!

 

[TJohn]

Based on what others have said about possible extractor issues, you could probably drop your bolt into his rifle and fire off a few rounds to see if the problem persists

 

[offthepaper]

Based on what others have said about possible extractor issues, you could probably drop your bolt into his rifle and fire off a few rounds to see if the problem persists

Good idea.

 

[d2wing]

While the extractor is likely an issue, I had a similar problem with an AR, turned out it needed a heavier buffer to slow down extraction. I used an H2. Solved the problem. This is common on carbine actions. Also switching to a BCM extractor and better spring, and maybe a O ring will help as well.