Ammo for Sten MKII

[flgunguy]

So for a few weeks I have been testing my Sten and it did not do well at all. Constant failure to eject, so I bought two other bolts to try, but I would get the same issues. I tried different mags, different bolts, and different ammo.

Then I tried S&B 115gr ammo and it ran perfectly. This led me to learning that there are stark differences in velocity between some ammo brands. PPU was the worst for me, Aguila was pretty bad, and PMC Bronze was bad as well. I used all of those in 124gr. 

Now I want to try S&B in 124gr. Would I have the same problems? S&B in 115gr makes my sten run perfectly, I am emptying mags with no issues. My Uzi does well with mostly everything, and the bolt seems heavier so I am not sure why the Sten would have more issues than the Uzi.

[b_san]

C&R or tube, some tube guns can have different specs that may cause issues, also have you changed out your recoil spring? I've never had any issues running any S&B, Am Eagle, Blazer, PMC or WWB 124gr through any of my MGs, Sten included.

[flgunguy]

I do have two other recoil springs. I can try them with my existing setup that I know works with S&B. It didn't feel heavy at all to me. One of the springs is a bit shorter even, I can try that with the PPU and Aguila ammo that didn't work before. 

[OA/DAW]

Newton's third of motion states for every action there is an equal, but opposite reaction.  Your Sten does not have enough "Poop" to cycle the action.  The Brits experienced this also in their Sten silenced 9mm.  The solved it by cutting 4 coils off of the recoil spring.  That balanced the equation for them.

We use Israeli 9mm+P+ ammo that we acquired ears ago at Knob Creek.  This also solves the equation.  We have some extra if you wish to experiment.  If you get some, please don't shoot it in your polymer pistol.  The results could be catastrophic.

 

Don Wagenknecht

Ozark Armory

Lincoln, MO

660-547-3068

dawandoa@earthlink.net

[flgunguy]

I will try the shorter recoil spring I have then, that would make sense.

[eMGunslinger]

Is it a failure to eject because the ejector geometry is messed up, or because the bolt isn't cycling far enough back to contact the ejector?
Load one round in it and shoot it on semi, see if the bolt stays back. If it does the ammo is not your issue.

[flgunguy]

I am fairly certain the bolt wasn't cycling far back enough. It emptied mags with no issues using S&B 115gr. 

I have a slightly cut down spring and will try it with the ammo that wasn't cycling well soon. Can't remember well but I think I tried on semi and it would not go back far enough. 

[eMGunslinger]

That is very odd especially if you bolt moves freely in the tube without the recoil spring in. If thats the case I would be interested to know the condition of your barrel. It is highly possible that the barrel is shot out and not making enough chamber pressure to correctly cycle your bolt.

Edited December 17, 2020 by eMGunslinger

[flgunguy]

Barrel is like new, I actually used 3 during testing. Only 1 brand of ammo worked. Bolt slides right in easily, and I tried other bolts. 

After reading more I do think it may be that the spring is too stiff, I just can't try my shorter spring until a week or so.

[BrettBaker]

Could be a mag issue, too. I have only 1 mag that likes Blazer aluminum 115-grain; the rest will get at least one, and often multiple jams per mag. I've had good luck with steel case ammo and most brass case ammo.

At least you have an ammo your gun likes, so guys had to rebuild guns to get them to work I'm told.

[flgunguy]

The shorter spring did help and some ammo that didn't cycle before did it this time. 

I have a suspicion that the quality control at ammo factories has gone down. I feel like I am getting more bad rounds per box than usual.