STEN and mag go gauge

Hello All,

I'm a first time member. I live in the USA and just recently acquired my first STEN MK2. It was assembled by Fazakerley under their Dec 1941 contract according to Peter Laidler's book.

Trying to learn all I can. When doing a function check the first time on the gun, only one mag fed reliably. I just ordered a 10 pack of mags and am considering purchasing a STEN mag Go Gauge I've found but wondering if anyone knows how to use it?

I also have an armours mag repair tool that includes a mag insert and mandrel that goes over the feed lips. When using this tool, should I simply tap lightly on the end of the mandrel with a hammer?

Any help/advise would be greatly appreciated.

Thanks, Scott

Well your in the right place to ask Peter questions!

Sten magazines in relation to Sten guns were one-man-dogs. Just get yourself 10 magazines that operate/function correctly with YOUR gun and be done with it. We always accepted that the magazine lips should present the rounds at 8 degrees so that the bullet would hit the centre of the bore. And that the feed lips should be parallel. The big problem on Mk2 guns was droopy magazine housings . You don't say whether your is a bog standard auto fire gun, a re-work or a single shot version.

The gauge might have been useful when the guns were new’ish. Now the guns are worn and each one has taken on its own personality, I wouldn’t bother with the gauge.

Take your good mag and measure the presentation angle of the top round. Then adjust your other mags to the same angle.

The mag repair tool is good for getting dents out. I never could get it to form the feed lips correctly. The lips would always spring back. I even tried a hydraulic press and they sprang back after a few uses. A steel rod or punch in the vice and brass BFH make quick work of adjusting the lips. Some mags are just not going to work no matter what you do. There is so much variation in their manufacture.

I found the 19 round Indian converted mags the most reliable.

One last thing. NEVER, NEVER, NEVER hold the mag while firing the gun. Sooner or later you will have a round not go into the barrel chamber. If you’re lucky the round will not go off when the bolt hits it. If the round goes off….. the mag is not a good place for a hand to be.

Gentlemen,

Thank you for your posts, they were very helpful. I'm sorry for my tardy reply, work has a tendency to get in the way.

My Sten MkII is registered in the USA as a curio and relics gun so it is my understanding that this is not a rework or a tube gun. It is full auto and runs beautifully from one mag. I believe it is an original, unmodified gun with the exception of being re-blued and what appears to me to be a replacement barrel (as it is in pristine condition).

Following are more details concerning my experience with detailed observations of the mags. I suppose they may be irrelevant at this point since Peter suggests I simply find 10 mags that run with my gun as they seem to be particular to which mags they like.

But since I’ve done the research, I though I would post some pics in case anyone else should find it of interest. (And of course, I’m one of those technical guys who thinks there must be an answer to every problem. If it ain’t fixed yet, I just haven’t figured out what the problem is yet)

When doing a function check the first time, I only had one mag feed reliably. Problem with other mags was Failure to Feed. Interior of bad mags were clean and deburred, follower in good condition. Guessed it must be the presentation of the cartridge?

I have an armorer’s mag repair tool that includes a mag insert and mandrel and attempted to use this with the bad mags to no avail. The cartridges are presenting themselves at the correct 8 degree angle. Mr. Laidler's book mentiones the feed lips should be parallel but I found a measurement listed on another forum that states the feed lips should be 0.360 near the mouth of the case and only 0.330 at the rim of the cartridge in order for the cartridge to be presented at a 7-8 degree angle. Peter, I’m wondering if you would comment on that? Is that just misinformation floating around on the internet? (I’ve attached a picture which I hope helps explain better.) It does seem as if the lips need to be a little wider near the mouth of the cartridge if the round is to be at a higher angle than the feed lips. According to my measurements, my mag feed lips are at approximately a 2 degree angle. (I must be missing something here as I fully trust Peter's info to be the correct info?)

Attachment 78661

Additional info on the Failure to Feed issue. I've noticed when using the mag loading tool, that the magazine that feeds without errors also loads without errors. Every round is easily dropped in and pushed down. With all my bad mags, I experience issues loading the mags too. The problem is that when using the loader, some rounds (the base of the cartridge) fail to insert underneath the feed lips. When the happens, the round essentially ejects out the back side of the loader. I've attached two pics to demonstrate. One is a properly loaded error free mag with cartridge and the other demonstrates the problem mags not inserting under the feed lips. It doesn't happen on every round. But happens very frequently, perhaps every 2nd or 4th round?
Attachment 78659Attachment 78656


btw, I can manually load rounds in the bad mags so that all are under the feed lips but I still experience FTF problems when trying to run the gun. This occurs even if I only load 15-20 rounds per mag.

Lastly, with all mags, when cartridges are loaded, all 9mm rounds are presented at 7-8 degree angle.

I've also noticed that the top horizontal portion of the feed lips is longer on the mags that don't load or function consistently. Also, the concave line that runs along the back side of the mag is flatter on the malfunctioning mags. I've attached a picture and referred to the concave portion as dimpled and flat.

Attachment 78660

I would think that all the used mags I've purchased would have functioned properly at one time so it seems unlikely that I would need to file/grind material off the feed lips so guessing that length is not an issue. But maybe I need to re-dimple the back of the mags? Perhaps the cartridges are sitting too far back at the moment they are at the top of the mag? I suppose this point could wear out over time? I've attached a pic of the spots where the cartridges are polishing the back of the mag dimple. The malfunctioning mag is on the left with the longer polished point.

Attachment 78662

It's hard to tell by the picture but that polished point is actually flatter and presents more of an area for rubbing to occur.

I've also swapped the follower & spring from the functioning mag and put them in the malfunctioning mags and this did not correct the problem. And vise versa, the follower/spring out of the malfunctioning mags worked correctly in the mag that doesn't have FTF problems. So the issue appears to be something with the shell of the mag and not the follower, spring, etc.

When I experience a Failure to Feed, the same problem occurs each time. A round is actually stripped out of the mag but is not fed properly into the chamber. In every instance, the unfired cartridge ends up jamming between the bolt and the barrel. When this happens, it is done with enough force to push the bullet further into the casing. In some instances, it appears as if the nose of the bullet has been dented by hitting half way between the breech end of the barrel and the bore wall if that makes sense? See attached pictures.

Attachment 78657Attachment 78658

Regarding the magwell. It has very little play in it. When shooting, I hold on to either the barrel shroud or the trigger mechanism cover, never the magazine itself. With my one good mag, I can load it up to 32 rounds and do a full auto mag dump with no failures. I've done it several times so it wasn't just a one off.

So if you've read this post this far, I suppose you can image that I'm a little anally attentive to details. I live in Texas and guns are very common around here. My son and I do competitive pistol shooting and I reload about 50,000 rounds each year between our matches and practice. We tune our loads to different power factors for each gun. The ammo I'm running in my Sten is a 147 grain round nose running out of the barrel at about 1075 feet per second. (So it has a power factor of about 158 if your familiar with that metric. I don't usually run my ammo that hot but had been forewarned by my reading that I needed reasonably hot ammo to cycle the heavy bold in the Sten) I did a function check with lighter loads and it was not powerful enough to get the bolt to completely cycle. Essentially, the gun ran full auto even though it was in semi-auto mode. Thankfully, I had only loaded 3-4 rounds for the function check and was prepared for this potential problem.

I have read a post on another form that mentioned shaving off a little of the height on the feed lips but it's hard for me to imagine that a mag would need that kind of tuning. I'm guessing all my mags were functional at one time? Wondering if mags were ever issued that just didn't work from day one?

If anyone has additional comments or experience with tuning mags, your input is appreciated. In the mean time, I'll purchase as many mags as I can afford until I find 10 that run in my gun as Peter has suggested.

Once again, Peter and Vincent, I very much appreciate your expert advise.

The first pic with the cartridge showing has a cartridge that isn't being presented at the right angle, so that's why they're jamming into the barrel breech. They're going straight forward. They should be launching at an angle towards the chamber. Just about the way you suspect...

Like I said earlier. Like everyone else in the world who owns a Sten gun, you have a one man dog so just get 10 magazines the feed and function with YOUR gun!
Another thing is that YOUR gun was made to shoot UK Military standard 9mm round nose ammo. Just ike your MGB was made to run on super'X' octane petrol.
I don't have mags in front of me to compare BUT I don't think that the mag shown in photo 4(left) is from a Sten
As for those opinions about the mag opening measurements, well....... All I say is those immortal words '.......in my limited experience of these things....' and leave it there. There are real experts out there of course and I readily accept that.

I have seen Sterling magazines adapted for use in a Sten and they seemed to function perfectly. It has to be said that Harold Turpin was not happy with the magazine design from the word go, But he was told to use the Lanchester magazines that were already in production due to cost and time considerations*. Even then he (so said by his daughter who was Reginald Shepherds secretary.....) threw his teddy in the corner and came up with the shorter magazines. Not the answer but better than the long magazines he had to do his initial tests with.

Feeding a Sten........ Use 10 mags that work with your gun and use the ammo that it was made to use. Lips to be parallel with an angle of presentation of 8 degrees. This presents the tip of the nose INTO the chamber. If that happens, all is well

* don't forget, he only had £5 to spend to develop the gun.

Quote:

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Originally Posted by Peter Laidler

Lips to be parallel with an angle of presentation of 8 degrees.

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So, that takes them out of parallel with each other then...which seems to be where others stopped reading.

For ease of testing mags. It will save time & range facilities, to initially sort out suitably working Mags.
If you can 'dry fire' say 6 x drill rounds from each mag. that will be a potential purchase.

That will save you time & more importantly, Money. Before the final confirmation live fire test on the range.

just my 2 cents worth! :thup:

Quote:

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Originally Posted by Scott C

When I experience a Failure to Feed, the same problem occurs each time. A round is actually stripped out of the mag but is not fed properly into the chamber. In every instance, the unfired cartridge ends up jamming between the bolt and the barrel. When this happens, it is done with enough force to push the bullet further into the casing. In some instances, it appears as if the nose of the bullet has been dented by hitting half way between the breech end of the barrel and the bore wall if that makes sense? See attached pictures.

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After looking through sixty of my Sten mags I can’t find one that looks like your malfunctioning mag with the long lips. It’s possible that while it looks like a Sten mag, it could be for another gun.

The longer feed lips are probably the problem. The case must come free of the feed lips as the bullet nose goes into the chamber so the round can make the 8-degree change in direction. If the case is still being held by the feed lips at 8-degrees, the round cannot make the change of direction needed to align it with the chamber. The nose of the bullet pushes against the barrel but it can’t turn into the chamber and the force of the bolt keeps driving the case forward, pushing it over the stationary bullet.

Quote:

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Originally Posted by Scott C

I have an armorer’s mag repair tool that includes a mag insert and mandrel and attempted to use this with the bad mags to no avail. The cartridges are presenting themselves at the correct 8 degree angle. Mr. Laidler's book mentiones the feed lips should be parallel but I found a measurement listed on another forum that states the feed lips should be 0.360 near the mouth of the case and only 0.330 at the rim of the cartridge in order for the cartridge to be presented at a 7-8 degree angle. Peter, I’m wondering if you would comment on that? Is that just misinformation floating around on the internet? (I’ve attached a picture which I hope helps explain better.) It does seem as if the lips need to be a little wider near the mouth of the cartridge if the round is to be at a higher angle than the feed lips. According to my measurements, my mag feed lips are at approximately a 2 degree angle.

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All my Sten mags also have the feed lips at 2 degrees.

Those dimensions, 0.360 and 0.330 are the same as shown in a sketch on page 327 of Peter’s Sten book.

Quote:

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I have read a post on another form that mentioned shaving off a little of the height on the feed lips but it's hard for me to imagine that a mag would need that kind of tuning.

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The distance from the mag stop to the top of the feed lips is also shown in the diagram (2.595”) I have seen a few “F.H.D” marked mags that didn’t have the top of the feed lips and sheath cut. They were 2.800”ish. Probably never used and had not been tested when made.