I've got a quick question. My sten mkII will not hold in the semi position, being fired or racked after 10 cycles or so it will start going FA. It runs perfectly in semi if you press and hold the selector, if you put very little pressure on to the auto side of the button it will start going FA even though the selector is still in the semi position.

I've tried all 3 of my bolts, none of them make a difference with this issue.

I assume this is a issue with a worn trip lever? Any insite to the condition, id like the gun to run semi when wanted.

Factory ammo?
 

Ammo's not the issue, it does the same thing when your cycling it by hand.

Humm sounds like something is loose or out of spec.



Did you have a spare parts kit to swap out the sector?
 

lol no. I had about 7 kits a few years back but sold them when I got out of my "semi sten" stage. Never figured I'd need them

well that is irony





 

Get a new trip lever, milled sear, and sear spring.......

Got lucky and found a new trip lever and a milled sear last night. Gona swap them in later and see how that goes.

good,



funny thing with light loads my Laged Mac 10/9 has two settings full auto, and random burst ( could be 3-5- or 8 rounds)



 

Still doing it

I wonder if its the angle of my bullet trap (aiming the mg almost straight down) OR the ported silencer is bleeding to much of the power off the round to catch the sear?

The old trip lever was considerably worn compaired to the almost new one. The milled sear was a flop, somebody modified it......poorly........ probably for a semi build. The stamped sear is still in good shape so I'll stick with that for the time being.

It no longer pops from semi when I cycle it by hand so I'm begening to think that the silencer may be partly to blame, I think I was/am dealing with two problems. I'll know once I can get it to the range and play around with the factory non ported barrel.

If the silencers ports are to large I'll just send the can to a local guy who builds cans and have him install a non ported or less ported barrel and see how that works.

It's still acting up...

I shot it today with and with out the silencer, I'm 99% sure the silencer is not affecting the function. With or with out it the gun shoots the same using 115g GA ammo.

At first it was going full auto in the semi position, I took it apart and noted that the recoil spring was installed backwards and the trip lever was slipping to the left of the sear on occasion and not tripping. I bent the trip lever slightly and she ran better for a few mags, then it started running poorly again. This video was taken right after I put the slight bend in the trip lever.
http://www.youtube.com/watch?v=lTY8iTtmNaQ
http://www.youtube.com/watch?v=MSwVGr1w-U0

At the end of the day it really started to frusturate me because it started firing singles or doubles in the FA mode, basically no matter if it was in R or FA the gun acted the same. You MAY get 1-5 shots off at a time but no way of knowing what you were getting.
http://www.youtube.com/watch?v=6TRd_Kp_U00

I ordered a 2 new sears, another trip lever, a selector and 2 recoil springs

Anyone that has had any experiance with a sten and has any insight on this issue would be greatly appreacieated.

Could your selector be worn or moving under fire?  On my semi build my selector is stiff.  Very stiff.

I thought about that, there is a fair amount of side to side play with the trip lever, enough to let the lever slide next to the sear on occasion.