SAS bolt also fouls the ejector. Even prevents the bolt from going all the way into battery. Easiest to just alter the ejector to clear the bolt.
Found this out on my first project, had to alter the ejector after it was welded in place. Much easier to do before welding.
The safety cut in the main casing is sort of awkward to use - to rotate the bolt handle up and into the slot, the guide rods et al also have to rotate. The whole thing has to be dragged around.
There are ways to alter the selector into a rotating or crossbolt safety.
Okay...thanks for that comment. I think I will alter the ejector by filing the aft portion somewhat as well as the thickness and work with it until the bolt clears.
The IO instructions indicate a method of modifying the disconnect lever by cutting a semi-circular notch in the arm to accommodate the selector pin. THere is a requirement to weld a piece of metal with a grove to prevent the disconnect lever from moving side to side. These two steps apparently allow you to use the selector pin to put the weapon on safe.
I have fully assembled the STEN, minus the barrel, firing pin and I still need to modify the ejector. When I cock the weapon and let the bolt ride forward, the hammer is visible aft of the block (normal operations for the closed block system). As I pull the trigger, the sear lowers and releases the hammer which is propelled by the tensioned spring behind the hammer causing the hammer to slam forward against the pin. (Still normal operation here).
I simulate the aft forces on the block of a live round by manually pulling the block aft as in recoil. I notice that if I keep rearward pressure on the trigger (simulating a slow release of the trigger) the sear remains in the downward position and does not lock the hammer back. Given the fast block movement under live fire conditions it seems this scenario would result in a block forward, a round in the chamber and an un-cocked hammer. In order to get the hammer to cock, I must release the trigger BEFORE the block moves aft of the sear. Normally the rearward movement of the block would allow the tripping lever and sear to move upward, catching the notch of the hammer and the trigger would (click) once I relaxed rearward pressure on the trigger to fire the next round.
I assumed the rearward movement of the block would allow the vertical arm of the tripping lever to move into the small recess of the block causing the sear to move upward thus catching the notch on the back of the hammer.
If I release the trigger before I move the block aft, it functions normally.
What could be causing this malfunction?
Is the vertical arm missing the grove in the block? Perhaps the narrow slot at the bottom of the receiver tube through which the tripping lever arm passes is off to the felt or right and the arm is not aligned with the grove in the bottom of the block?
Last edited by 17thairborne; 04-13-2014 at 10:47 AM.
I don't know anything about these single shot closed bnolt guns but you are clearly on the right lines. I cannot see the usual relieved section for the nose of the tripping lever on your special breech block and so presume that you don't have it because your gun will ONLY work in the semi-auto role. The TRIPPING LEVER is tripped by the breech block on the forward pass of the breech block. If you trip that lever, even if you trip it with your finger to show a class of students, it WILL release the sear upwards, under the tension of the trigger spring (via the pawl of course). If your bolt isn't tripping the tripping lever then something is misaligned. Check this. Occasionally we'd get this with service guns with a slightly bent tripping lever that would foul the edge of the underside of the casing. Occasionally you'd get a knackered change lever slot that might push the lever too far....., or not far enough.
If you are going to bend the lever, be aware that they are bloody hard and springy and occasionally, the buggers would just snap! The nose that contacts the breech block is also hardened and the Mk5 gun lever should have a chamfer on the rear that the bolt face can cam against.
Hope that this has answered the Q's. But if not, it will be a simple alignment question - hopefully.
A question for you........... Can I assume that because your breech block is totally different to the standard ones I'm used to working with, can I assume that you cannot have the Mk5 safety 'push-through-to-lock' cocking handle?
It would seem that the bolt assembly is not contacting the tip of the tripping lever enough to depress it, and allow the sear to catch the hammer as it comes forward. If you had a full length firing pin, the gun might fire bursts. As is, it would not recock, and would wind up hammer down with a round chambered.
Make sure that the tripping lever is not being fouled by the sides of its slot in the casing, isn't being twisted to one side, etc. Strip out the bolt assembly, and see the sear will disconnect if you poke the tip of the tripping lever with a rod. It should react positively, with a noticeable click.
Also, the tripping lever was designed to work with a main casing with rather thin walls. Your casing is made with, what, .093" thick walled tube?
It may be that the tripping lever's tip is simply not projecting far enough into the casing to be activated by the passage of the moving parts.
If this is the case, either the tip of the tripping lever needs to be built up, or its notch which engages the sear needs to be deepened, allowing the tip to rise further into the casing.
Here is a video of what's happening. I think i've described the problem using correct terminology. I think I will need to file down the base of the tripping lever so that it protrudes farther into the receiver tube to allow the bolt to push it back down.
I think you've both hit upon the problem and provided some help for me. The thicker tube is preventing contact between the rearward moving breech block and the tripping lever (TL). The TL is staying in the grove, its just not touching the breech. As peter stated I have the Mk V modified TL that has been ground slightly at the rear of the rounded arm. I thought I had some Johnny's Garage modification there until you mentioned it, but I think it's good.
I think my best solution is to modify the tripping lever by filing the base where the notch is. This will allow the arm of the TL to sit deeper into the receiver tube and make contact with the block. I will have to file down the TL both in front of and behind the notch or I will defeat the purpose.
I had thought of filing down the ramp of the sear where the TL sits, but that will change the movement moment from the pin around which the sear rotates.
The ideal solution would be to have a TL that has an arm that is slightly longer and protrudes farther into the receiver tube.
The current state would prohibit FA because the hammer stays in the breech block and would simply ride forward together with the firing pin and spring with insufficient inertia to detonate the primer. I think. That thought had crossed my mind, but there just isn't sufficient force on the firing pin without a fully cocked hammer spring releasing that heavy hammer against the firing pin and its spring. I doubt the primer would even get a dimple. Even if one filed down the TL to create this situation, you still would not have FA. You would have to install a fixed firing pin, which I'm assuming would be illegal.
Last edited by 17thairborne; 04-13-2014 at 02:56 PM.
---------- Post added at 02:20 PM ---------- Previous post was at 02:12 PM ----------
Gents,
Thanks so much for your comments....we have success. The tripping lever now protrudes sufficiently into the tube to allow the breech to move it down enough upon recoil to allow the sear to return to battery and snag the hammer in the cocked position.
Just checked with ATF, the Form 1 is "pending" which means received, logged in and awaiting an agent to review the application. Still looking at 10 months total time. They have hired a few new agents to fill retirements and such, but they are not anticipating any reduction in the processing time as of yet.
Originally Posted by tiriaq
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