I just finished putting together a semi Sten MKVad am needing help getting it up and going. Anyone here with experience to share?
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I just finished putting together a semi Sten MKVad am needing help getting it up and going. Anyone here with experience to share?
What operating system are you using?
I'm using the kit from Indianapolis Ord.
The bolt has two springs and it has an AR firing pin.
The springs have to be balanced.
Both springs resist the recoil of the bolt assembly.
The bolt return spring must be strong enough to reliably close the bolt. It does this alone, because the striker spring is compressed, the striker being held cocked by the sear.
The striker spring must be strong enough to guarantee ignition.
You may find the cocking the action is difficult because the combined weight of the springs is excessive.
Make sure that the moving parts cycle freely and smoothly.
Ultimately, you are going to have to tune the springs by slightly shortening one or the other or both until you have obtained reliable functioning.
Trial and error.
thank you, I have ordered another set of springs as I didnt hit the sweet spot with these.
The IO system does have a good reputation, so it is just a matter of finding the correct balance.
any tips ?
Does it reliably feed dummy rounds when manually cycled? If it doesn't feed, dry fire, eject and recock when manually cycled, you aren't ready for live fire.
You can test ignition by chambering a primed case, and seeing if primers are reliably popped.
If it does, you are ready to move onto test firing.
Load one round. Does it fire, eject and recock?
If it doesn't, there may be too much resistance.
If it does eject and recock, does it close completely, successfully feeding a new round? If feeding isn't reliable, could be the recoil spring, could be magazine related, could be the geometry of your construction.
If it misfires, if there are light primer strikes, the striker spring may not have enough oomph.
If it functions with a single round, try two, try three.
It is a matter of experimentation.
You are just going to have to experiment.
Ammunition can be a factor as well.
thanks for all the info. Will regular blank rounds work for setup?
I suppose they could be used to check feed, ignition and extraction/ejection when hand cycled.
Are you having specific problems? If so, what are they? Please give precise details.
A number of specific and generic problems have been noted over time with the semi builds, including the IO parts. The IO parts are fine and will work well, but...
Building a semi Sten is like what we used to call on active duty a "magical operation." First you do A, then you do B, then a miracle is required to get the intended result.
I'm being only partly facetious; we've found several things that need to be done carefully during the build that are not widely discussed to avoid (or mitigate) feed, cycling, and firing problems. If we know precisely what problems you're having it will help the experts here step you through the solution(s).
Tiriaq gave you solid advice. Also check Peter Laider's many comments on Stens. He's provided a lot of detail about issues with the original FA guns that can show up in the semi builds as well.
Good luck!
As others mentioned, further info is needed on what problem(s) you might be having with the gun. Also, you should have several mags on hand for testing, to try and eliminate the bad ones.
And ... pictures! Always like to see some build pics. :D
Back in the good old days when we in the UK where trusted with such things, we could get Stens converted to semi automatic by simply welding the selector in the semi position.
I can see that these rather complex US semi builds are better than not having a Sten, but, it does seem these builds actually have little in common with the simple, solid machined breech block blowback brilliance, of the original cheap, selective fire Sten.
Mechanically, these semi auto Stens are very much like the Cooey Model 64 .22.
I have purchased three sets of springs so far. Problem I'm having now is that its not coming back to catch the sear to cock it. Everything was so easy until these dang springs...
---------- Post added at 02:21 PM ---------- Previous post was at 02:17 PM ----------
To clarify, its loading, firing and ejecting just not cocking back. When I get the striker spring short enough to cock back then it wont fire...
I would post pics if I could figure out how, it wants a url?
You may need a host like Google pics? I can post them if you send them to me...check your PMs for email.
Here's the pic OP was trying to post... Not sure it will provide the clarity these guys need though.
The method used in the semi-auto Uzi variants uses two springs. and an "axial" / linear striker.
Food for thought?
This will give you the concept
The sear in these semi-auto Uzis only acts on the linear striker, NOT the bolt, which is free to close after each shot. To "really" avoid "Rock 'n' Roll", carefully machine off the flange / collar from the side of the bolt-face that faces the magazine. This will mean that the case heads will slide across the bolt-face instead of "jumping back in" as the round chambers. IF something goes awry and the sear mech fails to rise into place, something interesting happens. Because the striker fully-forward, the head of a following round, stripped from the mag, will collide with the striker and the gun will stop.
Keep us posted.
anyone here have a build like this that's working that would measure your springs?
I got it going! Thanks for the help. I replaced the sear with a stamped one which is wider and easier to catch.