Mike-Tornado Technologies Posted September 4, 2017 Report Share Posted September 4, 2017 I have an original STEN MkIII with an extremely tight chamber. Unlike our STEN MkII and every other 9mm SMG we have, a round will not seat fully in the chamber. You have to push it in to fully seat it, then it needs to be levered out.The chamber is clean and free from burrs. I get the feeling that it might have left the factory that way, as the gun is very clean and has seen little use.Testing with Dykem shows the chamber too small near the rifling. The above problem causes stovepipe jams. You can't get through a mag without dozens of jams. I was debating taking a 9mm chamber reamer and trying to fix the chamber, but as the barrel is fixed in the MKIII I'd have to go through the back and use a T-handle extension - and of course the ejector is in the way. In the MkIII it's riveted in place, so I'd have to remove that rivet. Rather not do that unless I have to. Suggestions anyone? Link to comment Share on other sites More sharing options...
jim c 351 Posted September 4, 2017 Report Share Posted September 4, 2017 When finish reaming the chamber on an M1 rifle, a long rod is inserted in the muzzle, the chamber reamer is fastened to the rod, and as the rod is turned the bolt is pressed down.Makes for perfect headspace.You need to locate a gunsmith that has such a combo for 9 M/M.Jim C Link to comment Share on other sites More sharing options...
Black River Militaria CII Posted September 4, 2017 Report Share Posted September 4, 2017 An open bolt SMG is not comparable to an M1 for "headspace", so all that needs to be done is to carefully ream the chamber preserving current depth with a 9 Para finish reamer to cut the chamber to a uniform diameter to the throat. A slightly loose chamber is fine in a Sten.This assumes that the ammo is not the problem. FWIW Link to comment Share on other sites More sharing options...
hawksnest Posted September 4, 2017 Report Share Posted September 4, 2017 Replace the barrel. Link to comment Share on other sites More sharing options...
jim c 351 Posted September 4, 2017 Report Share Posted September 4, 2017 Black river,My advise was not to enable Mike to get perfect headspace but to solve the problem of not being able to ream the chamber from the rear.Surprised an old hand like yourself didn't catch that.Jim C Link to comment Share on other sites More sharing options...
ron_brock Posted September 4, 2017 Report Share Posted September 4, 2017 Replace the barrel.This would be ok on a MKII but he's talking a MKIII. It's a little more involved due to the rivets. Ron Link to comment Share on other sites More sharing options...
Black River Militaria CII Posted September 4, 2017 Report Share Posted September 4, 2017 (edited) Easy to use an extension with a reamer from the rear of the receiver and have done that on quite a few occasions on other types of SMGs for various reasons. An extension is easily applcable in this situation and a rather obvious solution. I probably could have been more specific though to avoid confusion.Jim C: sorry to have misinterpreted what you were saying but it appeared to me to address a headspace issue and I was thinking about light reaming of the chamber with an extension. What you suggest would work fine, too, if one has the appropriate equipment for pulling a reamer from the muzzle end. Edited September 4, 2017 by Black River Militaria CII Link to comment Share on other sites More sharing options...
BillyDixon Posted September 5, 2017 Report Share Posted September 5, 2017 so knock out the rivit and remove the ejector. rivit is probaly copper, fhen you cad rework the chamber.. replace ejector with new rivit, really guys dont make such a big deal about it. Link to comment Share on other sites More sharing options...
Mike-Tornado Technologies Posted September 5, 2017 Author Report Share Posted September 5, 2017 so knock out the rivit and remove the ejector. rivit is probaly copper, fhen you cad rework the chamber.. replace ejector with new rivit, really guys dont make such a big deal about it. That's exactly what I proposed. It doesn't hurt When finish reaming the chamber on an M1 rifle, a long rod is inserted in the muzzle, the chamber reamer is fastened to the rod, and as the rod is turned the bolt is pressed down.Makes for perfect headspace.You need to locate a gunsmith that has such a combo for 9 M/M.Jim C Jim, We order customer reamers and gauges all the time, the problem with a custom 9mm pull style reamer is that it would be quite expensive and based on current items we have on order would take 3 months plus to get. Link to comment Share on other sites More sharing options...
Mike-Tornado Technologies Posted September 5, 2017 Author Report Share Posted September 5, 2017 An open bolt SMG is not comparable to an M1 for "headspace", so all that needs to be done is to carefully ream the chamber preserving current depth with a 9 Para finish reamer to cut the chamber to a uniform diameter to the throat. A slightly loose chamber is fine in a Sten.This assumes that the ammo is not the problem. FWIW That's exactly what I was thinking. We've done it before on other guns with damaged chambers and it's worked fine. I'm not seeing any damage to the chamber, so assuming it is a manufacturing defect. We tried Swiss Gecco, Federal 9mm and British MK2Z and none of them would chamber properly. A 9mm headspace gauge won't go in either so that's pretty conclusive. Link to comment Share on other sites More sharing options...
Mike-Tornado Technologies Posted September 5, 2017 Author Report Share Posted September 5, 2017 Replace the barrel. As another poser mentioned. The STEN MkIII receiver is built as an assembly, and the barrel is riveted in place with a number of rivets. Yes we can replace it, but I think it is easy to fix the chamber. Link to comment Share on other sites More sharing options...
Mike-Tornado Technologies Posted September 5, 2017 Author Report Share Posted September 5, 2017 so knock out the rivit and remove the ejector. rivit is probaly copper, fhen you cad rework the chamber.. replace ejector with new rivit, really guys dont make such a big deal about it. Billy, not a big deal. It doesn't hurt to bounce something off of folks before doing it. For all I knew there might have been some other solution that I hadn't thought of. Link to comment Share on other sites More sharing options...
BillyDixon Posted September 5, 2017 Report Share Posted September 5, 2017 while you have ejector out ot gun check for worn, burrs or bent, is your gun one of the mk iii imported from finland,, a lot of these had new finland made barrels installed, most of the mkiii from finland had a small hole drilled fhru the stick stock for a sling swivel Link to comment Share on other sites More sharing options...
Mike-Tornado Technologies Posted September 6, 2017 Author Report Share Posted September 6, 2017 while you have ejector out ot gun check for worn, burrs or bent, is your gun one of the mk iii imported from finland,, a lot of these had new finland made barrels installed, most of the mkiii from finland had a small hole drilled fhru the stick stock for a sling swivel No small hole on this one. It came with the standard T-stock. Interestingly, none of the loop stocks I have will fit, and would need material ground off of their locking lug in order to fit in place. Everything else on the gun look good - well as much as it can for a STEN MkIII. Link to comment Share on other sites More sharing options...
m3bobby Posted September 11, 2017 Report Share Posted September 11, 2017 Something is amiss here. An original mk3 would have been test fired on numerous occasions and faults fixed at the time. I suspect the barrel chamber is dirty/damaged or it is not an original barrel. Could it be an ex Indian gun? Link to comment Share on other sites More sharing options...
Mike-Tornado Technologies Posted September 12, 2017 Author Report Share Posted September 12, 2017 Something is amiss here. An original mk3 would have been test fired on numerous occasions and faults fixed at the time. I suspect the barrel chamber is dirty/damaged or it is not an original barrel. Could it be an ex Indian gun? All rivets appear to be original. Chamber is an clean as a whistle. We even checked with a borescope to make sure. Gun is English manufacture, no idea what country it was imported from. Might well have been India. Link to comment Share on other sites More sharing options...
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