skippyjohnson Posted January 2, 2016 Report Share Posted January 2, 2016 I've got a Sten Mark II that I've been playing with for a couple years now. I'm sure I lose points in the historical category and purists will hate me for it, but I've put together a collection of parts and pieces for my Sten. I've gone with a gray cerakote on the pieces that stay with it most often. Here's a picture of my custom case - work in process. Not all the parts fit in the case. https://www.amazon.com/clouddrive/share/ofYxSvru4OJ2bCAySMRfKfUjp3WIxoBDHIDcdNCMTtD?v=grid&ref_=cd_ph_share_link_copy The function has been rather spotty with FTEs and FTFs several times in a mag. I have a mix of 20 round modified mags and original British mags. The 20 rounders using the new Winchester forged ammo with steel cases seems to function the best. Top speed on this thing has been between 5 and 6 rounds per second. I've got several different parts kits I pull from. I have one bolt that's been reworked to reduce weight to speed things up. Here's where we get to my question. I went shooting today and I had trouble taking the Mark V stock off. When I got it home and played with it a little, I realized that the metal was getting hammered out when the cocking handle on the bolt is coming back and slamming into the back of the receiver. That made it difficult to push in the button on the back to remove the stock. See the pictures looking in from the back and in from the side. Side viewhttps://www.amazon.com/clouddrive/share/BGyIO3ooiPQ5X2VhKy0KoxlldMjFpBf9AzzTd7fcmIp?v=grid&ref_=cd_ph_share_link_copy Rear viewhttps://www.amazon.com/clouddrive/share/cLPYrsAmvwWrMvfxtfEMFxkNaPweXjyUZfECSmU0PQ3?v=grid&ref_=cd_ph_share_link_copy The material is hammered almost twice the width it should be. It seems like it wouldn't be difficult to hit it with a Dremel or something and knock it down, but my concern is that this is wear and tear to the tube (receiver). Almost all the value of the Sten is in the scarcity of the papered receiver. That's the most important thing to protect. Is this damage normal? I haven't seen it mentioned in the books i have. Maybe a reference to how Stens are fired much more by collectors than they ever were in WWII. The spring was a new one I purchased. I wouldn't think the spring is the problem, but that seems a possibility. Springs are cheap. I could order another. Any ideas on how to prevent this type of damage? How concerned should I be about it? Would be a shame to turn this Sten into a safe queen. Link to comment Share on other sites More sharing options...
RoscoeTurner Posted January 2, 2016 Report Share Posted January 2, 2016 Using modified parts to speed the rate of fire is causing the problem. Link to comment Share on other sites More sharing options...
skippyjohnson Posted January 2, 2016 Author Report Share Posted January 2, 2016 Thank you for responding. Help me understand something. The rate of fire is supposed to be about 550 rounds per minute. That equals about 9 rounds per second. Right now, I'm getting less than 6 rounds per second. So, I'm only hitting about 360 rounds per minute. Shouldn't the design of the Sten be able to handle that speed without a problem? Link to comment Share on other sites More sharing options...
dalbert Posted January 2, 2016 Report Share Posted January 2, 2016 I've never seen a Sten run as slow as 360 RPM. What are you using to measure the RPM? David Albertdalbert@sturmgewehr.com Link to comment Share on other sites More sharing options...
skippyjohnson Posted January 2, 2016 Author Report Share Posted January 2, 2016 I'm using an IPSC Shot Timer on my Android phone. Link to comment Share on other sites More sharing options...
RoscoeTurner Posted January 2, 2016 Report Share Posted January 2, 2016 "I have one bolt that's been reworked to reduce weight to speed things up." This you should either use as a paperweight or throw away. Are you shooting standard ammunition? No Plus P or anything similar?That IPSC shot timer is not recording the round count accurately. To do this correctly you need a timer with a specific ROF function such as this one - http://www.cedhk.com/shop/products/CED8000-Timer.html Link to comment Share on other sites More sharing options...
dalbert Posted January 2, 2016 Report Share Posted January 2, 2016 skippyjohnson, Since you're using a phone for RPM, perhaps you've recorded the Sten in action? Do you have any video of it firing? David Albertdalbert@sturmgewehr.com Link to comment Share on other sites More sharing options...
skippyjohnson Posted January 2, 2016 Author Report Share Posted January 2, 2016 Not a lot of rounds fired, but here's a recent test. https://youtu.be/eBqZs-VSXVY Link to comment Share on other sites More sharing options...
skippyjohnson Posted January 2, 2016 Author Report Share Posted January 2, 2016 Not using +P. I've put a lot of rounds through it using Tula steel. Those consistently run poorly. The best results have been just recently with this ammo. http://www.shootingsportsretailer.com/2015/09/29/winchester-offer-steel-cased-pistol-ammo/ I've also seen reasonable results with this stuff.http://www.cabelas.com/product/shooting/ammunition/handgun-ammunition%7C/pc/104792580/c/104691780/sc/104372280/herter-s-reg-select-grade-tnj-handgun-ammunition/1261880.uts?destination=%2Fcatalog%2Fbrowse%2Fhandgun-ammunition%2F_%2FN-1100189%2FNs-CATEGORY_SEQ_104372280 Idea for reducing weight came from page 82 of "The British Sten: Manual for Shooters and Collectors." Suggestion was to drill holes. This was machined down - can post pictures of just the bolt later today. Link to comment Share on other sites More sharing options...
skippyjohnson Posted January 2, 2016 Author Report Share Posted January 2, 2016 Thank you for the responses thus far. Here's the bolt from a few different angles. Not the best pictures, but you get the idea. Sounds like the bolt is bad news and I need to discontinue using that. Will using the original bolt prevent future damage? Will the existing damage get worse? Link to comment Share on other sites More sharing options...
RoscoeTurner Posted January 2, 2016 Report Share Posted January 2, 2016 Not using that lightened bolt would be the first place to start to sort out your problem. Never had a problem shooting Tula or any other brand of standard pressure 9mm rounds in either of my Stens. Shoot the same in an Uzi and MP40. Thank you for the responses thus far. Here's the bolt from a few different angles. Not the best pictures, but you get the idea. IMG_20160102_155221815.jpg IMG_20160102_155202389.jpg IMG_20160102_155141338.jpg Sounds like the bolt is bad news and I need to discontinue using that. Will using the original bolt prevent future damage? Will the existing damage get worse? Link to comment Share on other sites More sharing options...
Grasshopper Posted January 3, 2016 Report Share Posted January 3, 2016 Hi Skippy, To my ear the video is well in excess of 500 RPM. The android is indicating something in the range of 320 RPM. ? The reduced weight Sten bolts are great for running a suppressed Sten, 115gr ammo, and a ported barrel with the port about 2 - 3" forward of the breach. This was common years back as 147 or 158gr 9mm ammo was not available in the War. The ported barrel gave the shooter subsonic ammo with a light bullet and less push on the bolt. Likely not the best idea for non-ported barrel use. Set-up correctly, the Sten can be very smooth. The bolt should not hit the rear of the receiver and the cocking handle should not hit the rear of the cocking slot. I've not got a Sten handy (but I may edit this post later). I'll try to get the distance from the back of the collar at the rear of the receiver to the end of the slot. The tube may not be quite to dimension. HTH, Grasshopper Link to comment Share on other sites More sharing options...
dalbert Posted January 3, 2016 Report Share Posted January 3, 2016 Hi Skippy, To my ear the video is well in excess of 500 RPM. The android is indicating something in the range of 320 RPM. ? The reduced weight Sten bolts are great for running a suppressed Sten, 115gr ammo, and a ported barrel with the port about 2 - 3" forward of the breach. This was common years back as 147 or 158gr 9mm ammo was not available in the War. The ported barrel gave the shooter subsonic ammo with a light bullet and less push on the bolt. Likely not the best idea for non-ported barrel use. Set-up correctly, the Sten can be very smooth. The bolt should not hit the rear of the receiver and the cocking handle should not hit the rear of the cocking slot. I've not got a Sten handy (but I may edit this post later). I'll try to get the distance from the back of the collar at the rear of the receiver to the end of the slot. The tube may not be quite to dimension. HTH, Grasshopper I was just thinking what Grasshopper already posted, both in the rate of fire demonstrated in the video, and with the measurement of the slot cut. I also wonder if a bad recoil spring could be at issue, but I think you should check the slot cut measurement first. I assume you are not the first owner of this Sten, and that it has been fired a lot previously? The Sten should run like a sewing machine. I don't recall ever hearing of an issue like this, so it will be interesting to see if it is truly due to trying to overclock it, or another issue. Who was the manufacturer of your tube? David Albertdalbert@sturmgewehr.com Link to comment Share on other sites More sharing options...
skippyjohnson Posted January 3, 2016 Author Report Share Posted January 3, 2016 Hey Grasshopper and Dalbert, I'll try to get some exact measurements of the slot cut tomorrow. The tube was manufactured by Wilson Arms. Any feedback on them? The books I have don't call Wilson out specifically. I've seen discussions online that sound positive. Information is under the trigger housing on this one. I bought from a local collector. I know it was not a total safe queen but do not know much it was fired before I got it. I was told it ran flawlessly for them. Never has for me. I've tried a lot of different things and had a couple trips recently that went pretty well. By that, I mean that half the time I could get through a mag without a FTE or FTF. Trying a lot of different mags, different ammo, and even spent some time polishing the 'feed ramp' on the barrel. The android using a shot clock app for IPSC (image above) is how I came up with the RPM. That plus some math (not a skill I'm strong at, but I think my math is good on this one). RoscoeTurner suggested a different timer. I may have access to something like that I can use to check again, but I want to make sure I'm not causing additional damage before I shoot this more. The modified bolt will go on the shelf as suggested. Skippy Link to comment Share on other sites More sharing options...
RoscoeTurner Posted January 3, 2016 Report Share Posted January 3, 2016 One of mine is a Wilson, I can check the slot length measurement for you for comparison. The other is an Erb. Link to comment Share on other sites More sharing options...
DINK Posted January 3, 2016 Report Share Posted January 3, 2016 In your video it appears that the bolt is slamming into the rear of the cocking slot and the Sten is recoiling much more vigorously than it should. The Sten is normally a pussycat to shoot. If the bolt is coming back too far and too fast, there are several possibilities, some of which have been addressed; The recoil spring is too weak, the bolt is too light, or the ammo is too hot. The Sten is designed to have the bolt come to the rear, run out of energy without actually smashing into anything, then return forward. If the gun has been altered so that the bolt is actually damaging the cocking slot, it will eventually destroy the back end of the gun, so I suggest you get rid of the altered bolt, buy a new recoil spring, and enjoy the Sten for what it is. If you want something that cycles faster, buy a MAC. Wilson was a very well-regarded manufacturer of tubes that were turned into Stens, Stirlings, Swedish Ks, and MP40s, among others. The problem is that you have no way of knowing who actually built the gun. All you know is that a Wilson tube was used. 1 Link to comment Share on other sites More sharing options...
skippyjohnson Posted January 4, 2016 Author Report Share Posted January 4, 2016 Measurements of the slot cut and wall thickness. Link to comment Share on other sites More sharing options...
RoscoeTurner Posted January 5, 2016 Report Share Posted January 5, 2016 Length on the slot of my Wilson tube was 5.86.I spoke with a timer manufacturer today that produces timers for USPSA and IPSC use and was told that you have to have a timer with a RPM specific function. This unit does have a RPM function for MGs - http://pact.com/products/shooting-timers/mkiv-xp/ Link to comment Share on other sites More sharing options...
dalbert Posted January 5, 2016 Report Share Posted January 5, 2016 Could the slot be the correct length, but cut in the wrong place on the tube? Seems like we need a tube measurement, and a measurement from the end of the tube to the beginning of the slot. David Albertdalbert@sturmgewehr.com Link to comment Share on other sites More sharing options...
RoscoeTurner Posted January 5, 2016 Report Share Posted January 5, 2016 Did you do anything to try to speed up the rate of fire to increase the rate shown on your phone? Link to comment Share on other sites More sharing options...
warren Posted January 7, 2016 Report Share Posted January 7, 2016 Get rid of the lightweight breech block and get yourself a new main spring!!!!! Get a spring cup and a retainer cup while you are at it.Check the retainer cup for battering and also the lugs on the spring cup as well.You need the engineered recoiling mass for 9mm and playing with the bolt and spring is a recipe for disaster!!!!!I have seen the spring cup and retainer cup broken from hardening under the constant pounding with a soft spring by guys removing a coil or two trying to speed up a STEN. Link to comment Share on other sites More sharing options...
skippyjohnson Posted January 7, 2016 Author Report Share Posted January 7, 2016 Could the slot be the correct length, but cut in the wrong place on the tube? Seems like we need a tube measurement, and a measurement from the end of the tube to the beginning of the slot. David Albertdalbert@sturmgewehr.com Sorry, not sure I understand what measurement you're looking for. Can you clarify? Link to comment Share on other sites More sharing options...
skippyjohnson Posted January 7, 2016 Author Report Share Posted January 7, 2016 Did you do anything to try to speed up the rate of fire to increase the rate shown on your phone? No. The video was captured using the modified bolt. Link to comment Share on other sites More sharing options...
RoscoeTurner Posted January 7, 2016 Report Share Posted January 7, 2016 Did you do anything to try to speed up the rate of fire to increase the rate shown on your phone? No. The video was captured using the modified bolt. That modified bolt would qualify as trying to speed up the rate of fire. Link to comment Share on other sites More sharing options...
eMGunslinger Posted February 2, 2016 Report Share Posted February 2, 2016 (edited) Destroke the gun a little, make a buffer for the gun really pretty easy to do.I've had to do it to a few transferable Sterlings running around that the cocking handle would jump out of the slot.Really though trying to run a sten fast is a bad idea, new mainspring and don't run lightened parts. A correcrtly running Sten the bolt shouldn't bottom out at any point. Edited February 2, 2016 by eMGunslinger Link to comment Share on other sites More sharing options...
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