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View Full Version : Semi Auto Rifle w/ Controlled Feed, Primary Extraction


tophatjones
05-23-2009, 4:48 PM
Do they exist?

KAVEMAN762
05-23-2009, 6:03 PM
Semi Auto Rifle w/ Controlled Feed, Primary Extraction ---what the he** does that mean? Can you explain your theory? Is this a trick question? :)
Im curious......

nrakid88
05-23-2009, 6:09 PM
I want to know too!, first what hes talking about and second if they exist.... also where can i get 130 gigawatt phase blasters?

Arteel
05-23-2009, 6:10 PM
:shrug:

Futurecollector
05-23-2009, 6:21 PM
What? im confused :confused:

Jpach
05-23-2009, 6:27 PM
Is this Boo?

elSquid
05-23-2009, 7:35 PM
GZZphk6JWfQ

As for a semi auto, no idea.

-- Michael

tophatjones
05-23-2009, 7:49 PM
Thanks ElSquid, I was just about to post that vid. As I understand it, primary extraction is some quality in the design that allows the bolt to loosen a cartridge from the chamber after the round has been fired. When the cartridge is hot and expanded, it is sealed to the chamber. Most guns are OK with just providing some delay time between firing and extracting, to allow time for the cartridge to cool and separate easier. A weapon with primary extraction will add an extra action to the cartridge to loosen it from the chamber. One example is a bolt that turns before it starts backward travel. The turning adds torque to the cartridge/chamber seal and helps break that seal. IIRC, the Ak has some kind of rotating primary extraction, but I could be wrong.

Fjold
05-23-2009, 8:31 PM
Controlled round feed is when the cartridge is fed under the extractor when the bolt first starts to strip the cartridge fom the magazine. The extractor holds the cartridge rim as it pushes the cartridge into the chamber.

This is different from a pushfeed which is how most (if not all) semi-autos work.

A pushfeed bolt pushes the next cartridge out of the magazine and the cartridge is loose in the feeding area until it gets completely into the chamber when the extractor snaps over the rim as the bolt moves forward at the last part of the bolt's forward travel.

Vtec44
05-23-2009, 8:45 PM
So under controlled round feed, the round is under "tension" all the time? Interesting, what are the pros and cons?

Quiet
05-23-2009, 8:48 PM
AFAIK (not 100% sure), the Walther WA-2000 is semi-auto and uses a controlled feed with a rotating bolt.

Too bad only 176 were ever made and out of those only 15 were ever imported into the USA. Current selling price for one is $75,000.

bohoki
05-23-2009, 8:50 PM
a 1911 with 16 inch barrel and stock?

Fjold
05-23-2009, 9:05 PM
So under controlled round feed, the round is under "tension" all the time? Interesting, what are the pros and cons?


Some of the differences are that:

With CRF you can cycle the rifle on its side (loading port down) and the cartridge won't fall out of the loading port while it's being loaded.

On a pushfeed bolt action rifle as you pull the bolt back the empty case will eject (spring loaded plunger type extractor) the instant that the empty case clears the front of the ejection port. If you don't continue to pull the bolt back the rest of the way and just push it forward again, the bolt will not pick the next loaded round out of the magazine and you will be shutting the bolt on an empty chamber. This is called "short stroking". With a CRF rifle the empty case will not eject until the bolt hits the standing blade ejector at it's compete rearmost position. It cannot "short stroke"

CRF (or claw) extractors are larger and don't rely on small spring loaded plungers for ejection (fewer small parts).

Disadvantages to CRF are that more of the bolt face has to be cut away for the larger blade type ejectors and claw extractors and they don't handle leaking gas as well from cartridge failures and require large bolt baffles and gas vents.

KAVEMAN762
05-23-2009, 9:44 PM
Cool thanks for the explanations. I know what you guys are talking about now, didnt know the terminology. I can hold my AR upside down and it still feeds the round into the chamber without falling out. Probably because it cyles so fast, and maybe I need to try more than 4 rounds to induce a malfunction? Cool concept for semi auto, but its probably not needed.

tophatjones
05-24-2009, 2:48 PM
The AR is push fed. Try cycling upside down slowly, the round will fall loose. The SKS, OTOH, seems to be some kind of controlled feed. It probably doesn't matter whether or not a design has these features, I'm just curious. Any semi autos besides the AK with good primary extraction?

nrakid88
05-24-2009, 3:10 PM
Wow... I wonder how the range master will feel when I am firing my ar upside down?

zaitcev
05-24-2009, 5:18 PM
Cool thanks for the explanations. I know what you guys are talking about now, didnt know the terminology. I can hold my AR upside down and it still feeds the round into the chamber without falling out.

Although AR is a push-feed in theory, the feed path is reasonably controlled by the magazine. By the time the round's rim clears the front edge of lips, it's about 1/3 into the chamber already.

To have a controlled feed on a double-stack magazine, you must have a magazine that narrows on the top, like on many pistols. Neither AR, AK, or Mini have this feature.

The last selective fire gun with controlled feed that I know of was PK. It uses a two-stage extraction from its belt. The claws jump the cartridge while it's in the belt like they would do on a push-feed gun, then extract it to the rear. A lever on top directs it into the chamber. Between shots, the cartridge is hanging in the controlled feed fixture while the gun is being knocked around. The ultimate in the controlled feed!

Kel-Tec RFB uses a push feed, but the claws do not jump the cartridge (to the best of my knowledge). Instead, they slide from the top when the bolt tips. This action also releases the spent case. But I'm not certain about the details of RFB's action.

-- Pete

KAVEMAN762
05-24-2009, 5:32 PM
I like the RFB, just havent shot one yet. Thats probably the only keltec Id spend money buying.