What Causes Double Feeds?

Check your extractor and spring

I ran into it this morning in a 9mm 1911 using a MecGar mag. In the past, its been an empty case with a live round driven into it. Today, it was a live round in the chamber with a live round driven into it, which is something new.

Im in the process of getting it figured out, and I do believe the main culprit is the extractor, as 1KPerDay said, as Ive had some improvement there with some tuning of the extractor, but Im also starting to think some of it may be the mags as well.

Fun malfunction to work through, isnt it?

The problem would have to happen more then 1 time, for me to do anything, other then a good extractor flushing with WD40. (Please, no debate on WD40 ty)

The fired case is not ejected, remains in the chamber. Clean the extractor. If that doesn't fix it, the extractor can be bent in a few thousandths to better grab the case rim. Did it with my 1911 45acp.

D.B. Cooper said:

new magazine

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May cause problems. Number each magazine, see if only 1 does it.

Hotter ammo changes the slide timing. Another thing to consider.



Always feed rounds from the magazine. If the round is put directly into the chamber, the extractor has to bounce over the rim, when closing the action. . Hard on the extractors on many guns.

The same problem also happened to me and a friend of mine with the Sellier & Bellot cartridges: same morning at the range, same ammunition, two different pistols (I had the SIG-Sauer P226 AL SO and he had the Tanfoglio P21L), same problem by FTE on the first round chambered from the magazine. Both pistols were clean an lubricate. Considering that it happened to you with a Beretta 92FS which I understand to be in excellent condition and with the same brand of ammunition, I'm not sure I can blame the pistols and not the ammunition.

the only time I've had or seen a double feed, is for whatever reason the magazine fails to hold the round under the one being stripped correctly, so - it pops two rounds up out of the mag and the gun jams the bolt does not close and no round makes it into the chamber. This was a Remington 760 in 30-06 it was my father's deer rifle and I had purchased a couple Remington mags as the one that was with it had the spring broken and did not function. I got two mags, both did the same thing - if I worked the action overly slowly sometimes it would work. I could get it to work correctly if I only loaded 2 rounds in the magazine, worked fine. I never figured out why and once I came up with a fix I stopped trying to figure it out, since I don't use the firearm much and don't need more than one magazine. Eventually I just pulled the spring out of one of the aftermarket mags and put it in the kind of rusty 40 year old mag after I cleaned it up, and that one works perfectly. I probably could have eventually figured out how to modify the feed lips on the aftermarket magazines, but - once I had a working magazine I wasn't motivated to take time to mess with it further.

To your original question, about the only way to cause a “double feed” is to have a bad extractor and to rack the slide with the first round chambered. It seems more likely that you had a failure to extract and the expended casing was still in the breech. That’s still an extractor issue, but not with two live rounds.

243winxb said:

Always feed rounds from the magazine. If the round is put directly into the chamber, the extractor has to bounce over the rim, when closing the action. . Hard on the extractors on many guns.

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Excellent advice…I hate seeing people just drop a round into the breech!!

I suppose if you got a lot of out of spec brass and the rims werent correct, it could be an issue. If the extractor doesnt get a proper grip on the rim, it will be trouble. I see that on a fairly regular basis with my reloads that are worn out and nearing the end of their life and their rims are pretty torn up from the constant extraction.

At first with the 1911(Tisas), I was assuming it was a mag issue, as that's what it tends to be when there's trouble, but I have another 9mm 1911(Colt), and use the same mags in it, and no problems there. So Im pretty sure its the gun that's the issue.

When I picked up the Tisas, I immediately started having feeding issues from the first round in the mag, when I released the slide with the slide stop. The rounds nose dive into the ramp. It was a little better when I slingshotted the gun.

The more I shot the gun, the more I started having double feeds with it, about every other mag, with it until I tweaked the extractor a little bit, and that seemed to do the trick, until yesterday. That also seemed to help the first round feeding issue a bit as well, although its still there.

Im thinking it might be a little bit of a couple of different things going on here now. The extractor, the ramped barrel of the Tisas (its not a Colt type barrel), and the mags. I still think the extractor is the main culprit though.

The double "live" round feed is a bit of a puzzle though, as they round the chamber in the past has always been an empty case. Im wondering if that one wasnt due to the mag.

The Internet Double Feed is really a failure to extract, leaving you with a round coming up behind an empty case.

A Real Double Feed with a live round started into the chamber and another live round hung up behind it is very uncommon but can happen. The usual recommendation is a fresh magazine spring to hold the top round against the magazine lips until forcibly stripped out in its proper time.

D.B. Cooper said:

The only way that happens is when someone manually places a live round in the chamber, then inserts a magazine, and then releases the slide. Actually, there is another way. First round is a fail to fire, shooter immediately does the tap rack drill, followed by a FTE. That would do it, too.

Now that I've talked that through, that could have been what happened to me. I remember doing the tap, rack drill and then still having nothing and thinking to myself: "what the crap." when I finally tipped the muzzle up (on my first run at the tap, rack, I don't think I even looked at the gun-I just did it) is when I saw the malfunction I had. Either way, my double feed just about has to be connected to an extractor and a FTE.

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I didnt load a round first and drop the slide. It happened in the middle of the mag while I was shooting. Im suspecting the mag must have let two go, as the MecGar's often let a round pop while you're loading them. I assumed the round in the chamber was a spent case, until the live round dropped out when I was clearing it. All the others have been spent cases, this was a first. It was also the only one of the day too. The nose dives have slowed down, but are still there. Slingshot is still better than slide stop too. Things are still better, but not quite there.

Jim Watson said:

The Internet Double Feed is really a failure to extract, leaving you with a round coming up behind an empty case.

A Real Double Feed with a live round started into the chamber and another live round hung up behind it is very uncommon but can happen. The usual recommendation is a fresh magazine spring to hold the top round against the magazine lips until forcibly stripped out in its proper time.

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The failure to extract is what I was running into early on. That seems to have quit since I tweaked the extractor.

This live round double feed is something new, and Im hoping it was just one of those things and not something new.

The MecGar 1911 mag's I have are OK for the most part. The 45acp mags seem to be better than the 9mm mags though.

Im still not convinced its the mags in this case, as I said before, the same mags usually give me no trouble in my Colt. Ive only had these problems in the Tisas. If it were the mags, Id expect the same or similar issues in the Colt.

D.B. Cooper said:

Thanks for the info. I'm not really a fan of "cheap" ammo. Well, I mean, I like ammo to be cheap, but not "cheap ammo." I got this stuff from a friend who was moving out of state and couldn't take it with him. There isn't that much of it, so I'll stop running it in competition and go back to my usual Blazer Brass (which, BTW, is cheap ammo that isn't cheap ammo) and see what happens. Or, hopefully, doesn't happen.

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Cheaper Sellier & Bellot can also have steel brass plated cases. If the ammo box was white then they were 99% steel cased rounds.

Jim Watson said:

A Real Double Feed with a live round started into the chamber and another live round hung up behind it is very uncommon but can happen.

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I agree with Jim. Here's what happens.

Let's say there are 4 rounds in the magazine numbered 1 to 4 in ascending order where #1 is the top most round and #4 is the last round in the mag.

• #1 chambers and fires normally.
• As the slide cycles #2 slips out of the magazine (inertia feed caused by weak spring, oil on the feed lips, too wide feed lips) and noses into the chamber
• #3 is engaged by the slide and pushed forward out of the mag
• #3 gets stuck under #2

So, in addition to it being caused by a poorly fit extractor (inadequate hook to breechface distance, excessive tension, poor hook geometry) you can add inertia feed to the list of possible causes.