Jump to content

Is my Sten ejector too far back?


Recommended Posts

Finally got around to trying to the kinks out of my Neal Smith Sten Mk II tube gun. I get 1 or 2 failures to eject per magazine, I notice if I push forward on the magazine I get 1 failure every couple of magazines. I replaced the extractor and extractor spring and there was no change. I shot some Slo-mo video and I see it extracts but instead of being tossed out the ejection port the case bounces forward and is caught between the bolt a breach face. Comparing my ejector placement to photos linked on another post. It looks like mine is at least 1/8 inch farther back than others. Can any Sten experts tell from these pics. Thanks

post-39665-0-63543900-1515264991_thumb.jpeg

post-39665-0-98750700-1515265025_thumb.jpeg

Link to comment
Share on other sites

Well, I went and looked at my C&R MK5 STEN, and the ejector in that looks like it extends about 1/16" into the Magazine port, so I would say yes you ejector is to far to the rear.Placement ofthe ejector can be hard to determine when building them if you dont have an example to go by. Fairly easy to fix. It does involve cutting grinding and welding.

 

I just went and read through the other string on STEN ejectors, and there is a nice link to the photos of correct position.

https://www.google.com/search?q=sten+ejector+position&rlz=1C1GIWA_enUS667US667&tbm=isch&source=iu&ictx=1&fir=_xM_dRq7JEL_nM%253A%252CLRgIaP0bp2h-AM%252C_&usg=__AKrXPtV5CpYd5gtU7y4xuoMSqxM%3D&sa=X&ved=0ahUKEwi-pbqP1r7YAhXBmuAKHTR1AzoQ9QEIMjAB#imgrc=9qlURwVpOmac4M:

 

Good info there nd clearly shows the problem you are having......

Edited by MG08
Link to comment
Share on other sites

I moved the ejector forward about 1/16”. No change. Might have to cut it out again and move it more.

Still not sure that is the issue, because it ejects perfectly 9 out of 10 Times.

Anything else I should try before cutting and rewelding the ejector again?

Thanks

Link to comment
Share on other sites

Here are some photos of the location of the ejector on a scrap tube. It sits flush with the back edge of the opening and the end bends forward so that the empty case is ejected in time. Ill get another photo with dimensions to check the positioning of the mag well and ejection opening in case they need adjustment. Its possible you may need to move the ejector forward quite a bit and also open up the rear edge of the ejection opening in the tube to match that of the mag well ejection opening. Hopefully all will become clear in the photos Ill post up next.

 

As a bit of an idea, if you have a Mk3 parts kit for spares (A good suggestion in one of Franks SAR articles) you could use the Mk3 ejector in place of the filler on the Mk2 mag housing and this would place the ejector in the correct position. You would need to weld the rivet hole and redrill then tap for a 2BA screw. Or use a Mk1 ejector from BRP which is a straight fit. Of course this means removing the Mk2 ejector unless it is so far back its out of the way. Does that make any sense?

post-1331-0-34069600-1515323205_thumb.jpeg

post-1331-0-54827500-1515323934_thumb.jpeg

Edited by m3bobby
Link to comment
Share on other sites

OK, Got some photos which I'll post below. I've got photos of a Mk2, 3 & 5 for comparison.

 

The photos of the ejection port show the guns upside down so that the numbers on the steel rule were the correct way up. On the Mk2 & 5 I rotated the mag well around to the opposite side to get clear photos of the mag port and ejector. The forward opening of the mag port is flush with the face of the breech which I've used a reference point in each photo with the steel rule

 

Mk2 first.

 

 

post-1331-0-59750300-1515331815_thumb.jpg

post-1331-0-52442500-1515332016_thumb.jpg

post-1331-0-43422300-1515332199_thumb.jpg

post-1331-0-66730300-1515332247_thumb.jpg

post-1331-0-57569000-1515332297_thumb.jpg

Link to comment
Share on other sites

Mk3

 

Hopefully the last photo may make things a little clearer. All marks of STEN have roughly the same dimensions between mag opening, ejection openings and ejector to breech face. So the breech face is flush with the forward opening of the mag port and the tip of the ejector should be approx. 40mm from the breech face. The Mk1 STEN ejector was a flat plate in the correct position, the Mk3 was a development of the Mk1 and is the same. The Mk2 ejector as you know is fixed to the casing or tube to allow the mag well housing to rotate into a dust cover and for compactness. The tip of the Mk2 ejector is machined to bend it to approx. 40mm from the breech face which when you look down the mag well should line up with the spacer in the back of the well ( which is the ejector in the Mk1 & 3).

 

 

post-1331-0-97865900-1515332415_thumb.jpg

post-1331-0-17462700-1515332448_thumb.jpg

post-1331-0-75670900-1515332503_thumb.jpg

post-1331-0-58101700-1515333105_thumb.jpg

post-1331-0-21196200-1515333131_thumb.jpg

Edited by m3bobby
Link to comment
Share on other sites

So to summarise the photos above:-

 

Mk2 fwd ejector tip is 39mm from breech face and rear of ejection opening is 58mm from breech face.

Mk3 fwd ejector tip is 40mm from breech face and rear of ejection opening is 58mm from breech face .

Mk5 fwd ejector tip is 38mm from breech face and rear of ejection opening is 58mm from breech face

 

Your Mk2 ejector tip I would guess to be about a good 45mm from the breech face and your rear ejection port opening appears to be about 3mm to close to the breech face (Assuming that the mag housing is in the correct position) so that to about 8mm (5/16") of error and will effect the timing of the gun. If you've already moved it 1/16" you may still need to move it another 1/4". Sounds an awful lot I know!

 

Using one of your photos I've highlighted some areas for you to look at. 'A' is the rear face of the ejection opening in the casing/tube. It should be flush with the rear face of the mag well housing (Provided that is in the correct place). B is the position of the ejector tip, it should be where the red line is, the 2 blue circles highlight where there is a gap that shouldn't be there. The ejector base should be welded in to those gaps. C shows that the breech face is not flush with the front face of the mag opening. There isn't much that can be done there without some serious cutting and rewelding to the barrel bushing/case(Although the original wasn't welded, they were riveted with 4 rivets and soft soldered into position).

post-1331-0-11945700-1515335043_thumb.jpeg

Edited by m3bobby
  • Upvote 1
Link to comment
Share on other sites

Thanks! Great detailed information. I really appreciate the time you took on this. Ill do some more measuring on mine and see if I can make the adjustments.
Link to comment
Share on other sites

I discovered one more variable, there is some forward to back play in the magwell, so these pictures are with it as far forward as it goes. This wont impact the critical dimensions of the ejection port and ejector, as we are measuring those from the breach face.

Breach face to back of ejection port is 58mm, so that looks good

The tip of the ejector is 44mm from the breach face(after I moved it yesterday), so that needs to move forward 5mm.

post-39665-0-06545700-1515348453_thumb.jpeg

post-39665-0-28868600-1515348486_thumb.jpeg

Link to comment
Share on other sites

Looks like were getting somewhere then. The mag well looks much better positioned in the photos youve posted above. We need to work out why there is so much FWD to Rear movement as it should be locked Fwd. Although with a mag inserted it will help keep the housing a little better positioned, its still not ideal. Have a check of the plunger and hole to see if there is any ware and if everything is true. The plungers and holes have been known to ware and bend.
Link to comment
Share on other sites

I moved the ejector forward so it is now 40mm from the breach face.

Not my prettiest job, but it seems to be in the right spot. Doesnt rub anywhere and gets the brass out of the extractor.

Still having the same issue at the same frequency, about 1 in 10 the brass does make it out of the ejection port.

This has all been with Walmart Winchester white box. I may try different ammo.

Also, perhaps the extractor is canted forward slightly an instead of the tip hitting the brass it is hitting further back on the extractor. I could put a spot of weld on the tip of the extractor and reshape it.

Also I think the magwell play is because of oblong hole, see pictures.

Any other ideas?

post-39665-0-38964400-1515357212_thumb.jpeg

post-39665-0-37967300-1515357320_thumb.jpg

post-39665-0-77016900-1515357400_thumb.jpeg

Link to comment
Share on other sites

4 mag dumps w/o a jam!

I built up the extractor with weld and reshaped with dremmel and files to about 0.010 tolerance from bolt, making sure the tip was the tallest part.

 

Still need to do cosmetic work, but not until I test some more. Range is closed today and I can only shoot so much in my barn before the neighbors get annoyed.

Thanks for all the help!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...