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http://www.fieldandstream.com/bl ... -feed-and-push-feed
A blogger of my acquaintance asked me to explain the difference between controlled-feed bolt-actions and push-feed bolt actions, and the importance thereof to shooters.
Controlled feed refers to the system developed by Peter Paul Mauser for his Model 98 bolt-action. When the bolt is cycled, a cartridge rises up from the magazine and the extractor—that long, flat piece of metal that rides alongside the bolt—snaps onto the rim of the cartridge and holds it in a death grip on its trip into the chamber. When the round is fired, it pulls the case clear until it is kicked out of action by the ejector, a small, unattractive piece of steel that is fixed in place behind the follower and rides through a slot in the bolt face. So, controlled feed: Each round is held in place throughout the firing cycle.
Push feed was introduced by Remington in 1949 in the Model 721 (which eventually became the Model 700). Here, as a cartridge rose up out of the magazine, the bolt simply pushed it forward into the chamber without holding on to it. As the case chambers, a small unattractive clip snaps onto the rim, and pulls the case out when the round is fired. The shell is kicked clear by a spring-loaded plunger in the bolt face.
The advantages to push feed are that it’s cheaper to manufacture than controlled feed, and that the bolt face can be made to completely enclose the case head, so that if the case ruptures, you won’t be blown up as badly.
Controlled-feed fanatics snort and fart and claim that push-feed is unreliable; that without firm guidance, rounds will not find their way into the chamber consistently. The truth is that push-feed is just fine if the magazine rails fit the case correctly. Trouble comes when manufacturers try to make guns on the cheap and the rails fit poorly.
They further claim that the big extractors on controlled-feed bolts pull stuck cases better than the small extractors on push-feed bolts. Again, not so. A full-length extractor can slip off a case rim given enough force, and a push-feed extractor can either shear through the case rim or break.
In a properly-made rifle, either system works fine, and there are better things to worry about. |
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发表于 2013-5-24 14:18
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