Doublefeeds

1361 Views 4 Replies 4 Participants Last post by John in AR, Aug 20, 2004

GBullet

Discussion Starter · Aug 19, 2004

One of the most frustrating maladies that can afflict auto and semiauto firearms is the doublefeed. When we usually speak of a doublefeed, we are refering to a failure to fully extract the fired case prior to stripping the fresh cartridge from the magazine.

Some thoughts on this problem come to mind:

1) During firing, pressure causes the case wall to grip the chamber. A rusty, pitted or irregular chamber surface can lead to a failure to fully extract.

2) A weak extractor spring, poor extractor design or a weak case rim can add to the likelyhood of troubles.

3) If the action of a locked breech firearm begins to open while the gas pressure is too high, the case will offer increased resistance to extraction. This assumes that the wall area times the coefficient of case/chamber friction will be greater than the area of the case head.

4) Shortening the barrel of an otherwise unchanged gas operated action will reduce the dwell time, during which gas is diverted to operate the action. This is why simply chopping the barrel of an AR15/M16/CAR to the front sight block is not a good idea, unless you move the gas port.

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Magnum88C

· #2 · Aug 19, 2004

How 'bout an interesting one one of the Colts I used to have pulled.

It'd extract the case, then feed the next round without ejecting the spent case. The spent casse would strip the next round out of the magazine and chamber it.

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RIKA

· #3 · Aug 19, 2004

Magnum88C said:
How 'bout an interesting one one of the Colts I used to have pulled.

It'd extract the case, then feed the next round without ejecting the spent case. The spent casse would strip the next round out of the magazine and chamber it.

Now thats an interesting thing to visualize. It would seem that the loaded round in the mag pushed the extracted - but not ejected case - up enough for the next round to chamber.

Assume that you have already fixed the problem. Am I correct to assume that there wasn't enough tension on the extractor and that there was a problem with the ejector?

A darn good reason to carry spare parts.

RIKA

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Magnum88C

· #4 · Aug 20, 2004

The extractor was way loose. Only thing I could figure was it was loose enough that the ejector just pushed the case instead of there being a "springing" action ejecting the round because of the extractor tension, so the round just got pushed aside a bit, but stayed in the extractor, then the next round in the magazine pushed the spent case back against the bolt face as the new round was being fed into the chamber.

Pretty f-ed up, never an extraction or feeding problem from the magazine. New extractor, properly tuned, fixed the problem.

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John in AR

· #5 · Aug 20, 2004

The things GBullet describes are exactly the problems I had with the Olympic 11.5" "shorty" I had several years ago.

When cold, it worked fine; when it got heated up, (within 7 or 8 rounds, if fired rapidly), it would fail to extract, but the bolt would cycle and try to feed a new round on top of the still-chambered empty case. Total of 5 go-arounds with 3 different gunsmiths (plus twice shipping it to the olympic factory) never did solve it.

No sign of damage to the brass rims or extractor, as if the extractor was having to pull too hard on the empty; and I could pry the empty out reasonably easily with a leatherman blade, small screwdriver, etc.

Had new extractor & extractor spring installed, had the chamber honed, even the gas port opened wider (that one made me nervous). Never, never made it functional when hot.

Of course, even though I TWICE explained to the factory that the problem didn't show up until the gun got hot, they were sticklers that their "policy" was to test-fire three rounds in a repair-shop gun. So twice they proclaimed it "fixed" & sent it back no different than they received it. The shame of it was that the gun was just amazingly accurate for such a short barrel, and if it could have been made reliable, I'd have kept it forever and been a walking referral for Olympic. But the service department's unwillingness to even attempt to re-create the problem as I explained it to them, cost them a customer forever.

I even offered to send a box of whatever factory ammo they preferrred along WITH the gun, the second time. They said there was no way around the "three-shot" function test, it was "Policy".

Finally traded it to one of the gunsmiths (who knew its problems) for the Bushmaster CAR that I still have.

In my limited experience, Olympic service sucks.

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