Starting a STEN Mk V SBR in the US

[17thairborne]

Great....thanks

[Peter Laidler]

I don't really understand all the geometry that you are talking about except that there is a problem with the breech block fouling the ejector when the cocking handle is rotated uo and forwards into the safety slot. Is this correct? Bear in mind that I am not familiar with the single shot conversions too!

If this is the case, and it is a small amount of metal that fouls, then why not just leave the casing and ejector full size and unaltered - as it is - And simply machine away a small section from the front/side face of the breech block where it is fouling the ejector. The part that is fouling will be the radius of the outer forward edge and nothing to do with the important feed horns.

Or am I missing something in the telling here?

[Brit plumber]

It sounds like the cocking handle slot is out of alignment with the mag port and ejection port by a few degrees. Does the sear align with the block OK (Or whatever it is with the semi conversion).

[17thairborne]

I don't really understand all the geometry that you are talking about except that there is a problem with the breech block fouling the ejector when the cocking handle is rotated uo and forwards into the safety slot. Is this correct? Bear in mind that I am not familiar with the single shot conversions too!

If this is the case, and it is a small amount of metal that fouls, then why not just leave the casing and ejector full size and unaltered - as it is - And simply machine away a small section from the front/side face of the breech block where it is fouling the ejector. The part that is fouling will be the radius of the outer forward edge and nothing to do with the important feed horns.

Or am I missing something in the telling here?

Peter,
It is such a large amount I was afraid it would alter the block in a very negative manner. That is why I elected to modify the ejector. I would have to take off a significant portion of the block where the feed horns are. In retrospect, the proper solution is to mill the safety grove farther aft of where the template renders it. On another note, if I use the selector switch with the below mentioned modifications, it will serve the same purpose as the upper bolt handle grove. It will, in essence, eliminate the need to use the upper grove. I could have just done nothing and not used the upper grove at all.

[17thairborne]

MODERATOR

Please delete two previous posts with wrong and duplicate photos. Moderator edit: 2 previous posts deleted as requested..

Sear aligns properly. Block aligns perfectly with the ejector during the loading, 'locking" and extraction phase. Is only when the block is rotated up and into the safety slot that the feeding groves foul with the ejector. That tells me the safety groove is milled too "high from the cycling grove. The problem with milling it at the proper angle is that the grooves would be too close together there would not be much metal from the tube between the two grooves. Too weak in my opinion. THis is why I conclude that milling the vertical grove more aft on the tube would solve this problem. You an see the thin line where I edited the image to show where I would mill the new upper grove. That will move the block aft enough to where it will not interfere with the ejector. You can also see if i milled the grove lower (closer to the long lower grove), there would not be enough metal between the two. Too thin I think.

[Vincent]

Will the bolt still clear the bar in the center of the spring retainer if the safety slot is cut that far back?

[17thairborne]

Sure will. The length of the center bar puts it just behind the aft of the lower grove, so that's well in front of the upper safety grove.

[Peter Laidler]

It seems from reading and avidly following this thread that the drawing sheets that you have for your conversion aren't quite right for your Mk5. Sort of LOOKS like they are sort-of Mk2 modified for Mk5 if you see what I mean. I could be wrong of course but surely if they'd actually done what the drawings are made to illustrate/represent, they'd have discovered these minor (?) errors.

If I were you I'd set about correcting their drawings and your project and then ask them if they'll contribute to your project for your efforts on their behalf.

I did something similar with a newish petrol mower after I found that to get to something for a bit of winter lay-up maintenance (as suggested in the user handbook no less......) was a real pain in the ***! All it needed to correct it was two readily commercially available slightly longer bolts with captive washers and the two bolt holes elongated and opened at the end. They collected my used 1year old mower, investigated what I'd done, incorporated it into future production and gave me a brand new one and a small cheque!

[Brit plumber]

I was forgetting you are using a new Breech block so could it be the Breech block machining that isn't the same as the original in the outside edge of the machining for the feed horns? How does it compare to the original block?

Looking at the photo of where the block interferes with the ejector, it looks to be about 1/2" long so would you not have to move the safety slot back the same amount for it to clear?

[17thairborne]

It seems from reading and avidly following this thread that the drawing sheets that you have for your conversion aren't quite right for your Mk5. Sort of LOOKS like they are sort-of Mk2 modified for Mk5 if you see what I mean. I could be wrong of course but surely if they'd actually done what the drawings are made to illustrate/represent, they'd have discovered these minor (?) errors.

If I were you I'd set about correcting their drawings and your project and then ask them if they'll contribute to your project for your efforts on their behalf.
!

I like your idea. IO sells the tube as a MK V template. I have not found anything on any forum where a builder encountered the same issue with the ejector. I did mention to Jason at IO about the template's rendition of the ejection port. On IO template, it is depicted to match the length of the opening on the Magazine well, a bit too large, whereas on an original MK V, the cut for the discharge port on the tube is smaller. It is also cut narrow at the front than the rear, and on the IO template is is a rectangle. I made that change on my tube to mirror the original tube. I should have paid more attention to the safety grove of the original MK V, but its hard to know how the new block and operating rods will be impacted when trying to use original dimensions. Well...now I know.