Problems with my Sten - many stovepipes

[Riss]

Anyone have one that has had similar problems ? It will fire anywhere from 1 to 3 shots before one of the rounds stovepipes. A new round is chanbered but the fired case failes to clear the face of the bolt and gets smashed. Is this from not enough extractor spring pressure or too much? Need info from an actual owner as I have already gone through ALL of the other possibles. Extractor, bolt, dirt, extractor spring, ammo, recoil spring etc.

 

[Jim K]

Have you checked the ejector? It sounds like the case is not being ejected as it should be. Also, what ammo are you using? The STEN requires pretty hot ammo and the US stuff has a reputation for not being hot enough.

(In WWII, ammo made to US specs was marked on the box by the British "Not for STEN" because it wouldn't blow the bolt back far enough for the sear to catch and the gun wouldn't quit firing until the magazine was empty.)

Jim

 

[Riss]

have tried all kinds of ammo

Tried everything ammo wise. Tried 4 types of 115 gr. some 124 gr, and 147 gr and at most got 7 shots off before it started jamming. I have another bolt to try, possibly tomorrow. Slightly different extractor, and smaller extractor spring. If it is a matter of not enough tension on the extractor it is easy enough to fit another spring into the bolt. Both extractors look good. Almost no wear or no wear at all. And the hooks are sharp and clean.

 

[kirbythegunsmith]

Details

Is this a STEN of original mfg., a kit gun from past legal times, a pieced frame, or what? We are talking MG, not semi, right?

I believe that the extractor is superfluous for the initial phase of bolt movement, but needs to hold tightly enough for the ejector to make a brisk impact kick for proper fling- just had a similar situation on a High Standard .22, needed to add a stiffer extractor spring for sufficient ejector action.

Chamber crud, rust of even minute levels, cartridge case varnish (WOLF crappage type, for example) can all add to the retarding of case velocity, and that is all there is to make that inertia bolt get moving against the spring.

Try putting a piece of tape over the bolt handle slot to gauge the travel amount, since the STEN is designed for overrun past the sear engagement travel point. Put a mark where that point is on the slot, and start with the tape to the rear of there, and move forward until regular contact marks the tape edge. Use this method to verify and compare various loads for operating power, but always hold the gun tightly and the same during such comparisons for the best and consistent results, since the gun has to buck against you as a part of the mechanism's designed condition of operation.

If you can fit a fired case carefully into the chamber and not get a sticky case condition, close the bolt on the case, and then activate the bolt handle manually, and see if the ejection happens as normal. Almost any gun can have a manual test of ejection, and only some are balky at feeding tests manually, like some Rem. 1100 types, for instance. Get enough bolt velocity by hand, the shell will fly free of the port.

Improper tip position, face angle, or other situation can occasionally cause an interference of the case against the lip of the ejection port, but not likely. I would rim the inside lip area with a magic marker to see if any strikes wipe off the ink.

Did you read the rim edge of the fired cases to see if any heavy scrape marks are present from difficulty freeing from the bolt face pocket during ejection? This is not likely to cause as much grief if any burr edges may be present on the extractor side, as on the ejector side.

Some ideas that may give you a "leg up", so hope that they help.

See my previous posts for some gunsmith perspective.

[email protected]

 

[Cosmoline]

Have you tried it with different magazines? Also--if you're holding the mag while shooting, try not doing that.

I wish I had a Sten to have problems with

 

[Mtdew]

Is this a new problem or a (new to you) sten

As allready stated try a different mag if you havent allready, though they usually only cause FTFeed's

It sounds like a weak extractor spring, but if you have a spare bolt swap it and see if it runs

 

[Riss]

It is actually a Lanchester, built on a Sten tube. Uses a Sten bolt and yes it is not a semi. I got another Sten bolt out and polished it up on the lathe. I know for a fact that this other bolt runs and runs good so I should be able to narrow down the problem a little. IF YOU KNOW, I need to be able to gauge how much extractor tension is needed. Both Sten bolts have little pressure from the spring. The springs are original and starting to show a little rust, and lots of gunk. It would not be hard at all to fit another spring from something else if it needs more pressure on the extractor.

 

[Riss]

Unknown When The Problem Is From

Is on a gun that I just purchased, so I cannot say for sure where the problem lies. The gun is barely broken in, and at this rate it may take a while.