Sten full auto to semi auto bolt converter

stencollector said:
But won't the tripping lever trip, and the sear close, before the second bent goes over? Would you have to pull the trigger twice to effect normal firing?
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If you pull back the bolt carefully and slowly on an open bolt sten the tripping lever will trip the sear before the bolt is held back, as soon as it trips let the bolt move forward again, then bring it fully back. This is what will happen with two bents. ( is bent really the right word ? ) There is no problem, it works fine.

I will be ordering three of these bolt extensions due to the minimum $25 order charge. If anyone wants one let me know and you can have it for what it cost me.
 
tiriaq said:
Conventional open bolt has been accepted here for a few designs, so I don't think there is any reason to pursue this design concept.
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The reason as far as I am concerned is that it makes me sleep easy knowing that it can not be made to fire full auto with low powered ammo. With the original bolt with a semi auto only bent and the extension it will function the same as a standard sten in semi auto mode. I can see no downside.
 
Try letting the bolt close slowly, see where the second bent would be when the tripping lever is activated, and the sear pops back up.
I am not convinced that there is a reason though to really pursue this modification. Use of low powered ammunition doesn't produce predictable auto fire, but rather upredictable bursts. It is an ammunition malfunction.
 
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tiriaq said:
Try letting the bolt close slowly, see where the second bent would be when the tripping lever is activated, and the sear pops back up.
I am not convinced that there is a reason though to really pursue this modification.
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By letting the bolt move forward slowly I can see that the extension bent would be caught by the sear as is supposed to happen. What I have in effect duplicated is what would happen with an underpowered round. With a normal powered round the bolt would go right the way back and the sear would catch on the bolt's original bent. The second one will come into effect only when low powered ammo is used.
 
spencer IF the rcmp wants to see your gun you WILL be submitting it

it would have to be built EXACTLY as a sas3 or its not a sas 3 and therefore NO FRT#

to obtain an FRT # the rcmp techs need to approve it. a CFC employee and your local verifiyer has NO real power there

the rcmp guys are ok to work with and the guys i delt with really knew thier #### but at the end of the day they follow the laws and personally I dont think they or thier masters really want this type of stuff approved

they are not fast at one point i was told dec NO word till JUNE of that year.....

My project will be resubmitted soon If I can get the gunsmith to hurry up
 
With this convertor installed on the bolt, the second bent will be just shy of 2" to the rear of the original.
From the engagement face of the sear, to the rearward edge of the tip of the tripping lever is about 1".
As soon as the original bent contacts the tripping lever, the sear will be disconnected, and the sear will pop back up.
The sear is going to catch the new bent, as Stencollector suggested. It will take two trigger pulls to fire the gun. Pull, clunk, pull, bang.
The bolt extension will only work if the original bent is removed from the bolt, per the US instructions.
Its no wonder the supplier has lots of these pieces for sale - they are of no use.
 
tiriaq said:
With this convertor installed on the bolt, the second bent will be just shy of 2" to the rear of the original.
From the engagement face of the sear, to the rearward edge of the tip of the tripping lever is about 1".
As soon as the original bent contacts the tripping lever, the sear will be disconnected, and the sear will pop back up.
The sear is going to catch the new bent, as Stencollector suggested. It will take two trigger pulls to fire the gun. Pull, clunk, pull, bang.
The bolt extension will only work if the original bent is removed from the bolt, per the US instructions.
Its no wonder the supplier has lots of these pieces for sale - they are of no use.
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Having to pull the trigger twice wouldn't be any goofier than trying to load a magazine through the ejection port. :rolleyes:

This would also effect the momentum of the bolt in relation to picking up a round, and the effort the advanced primer system would (not) have to overcome. Also, if there is a bit of a hangup on the pickup of the round, whatever you do, don't aid the cycle by pushing the bolt handle forward. It would be hard on your thumb when the round finally does detonate.

I have seen the bolt add-ons listed on gunbroker for years. Never could figure out why anyone in the US would buy one. As Tiraq mentions, an open bolt gun won't fly there in the first place, so why would one think that they could build one with this modification and get away with it.
 
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stencollector said:
...This would also effect the momentum of the bolt in relation to picking up a round, and the effort the advanced primer system would (not) have to overcome. Also, if there is a bit of a hangup on the pickup of the round, whatever you do, don't aid the cycle by pushing the bolt handle forward. It would be hard on your thumb when the round finally does detonate...
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That, of course, is another consideration. The bolt won't move much before contacting the top round, its foreward inertia will be less, which will affect feeding, and the API cycle.
The Sten was designed the way it was, by folks who knew what they were doing, and who thoroughly understood what was involved.
 
tiriaq said:
That, of course, is another consideration. The bolt won't move much before contacting the top round, its foreward inertia will be less, which will affect feeding, and the API cycle.
The Sten was designed the way it was, by folks who knew what they were doing, and who thoroughly understood what was involved.
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Yes, but that was as a primarily fully automatic SMG. Our criteria is different...semi only, and hard to make it malfunction, and fully legal under our firearms system.
A whole different set of requirements from original.

Even with the issues raised about Spencer's weld on extension, it would still probably make it more foolproof as an open bolt semi...weld it such that the bolt is captive and who knows? Personally I'd rather own that than an SAS3.
 
I would rather own an open bolt sten as well. I may give it a whirl further down the road. But along with legal, one must also worry about safe. It was engineers that designed the sten; there was some degree of science and physics involved. When you change part of the equation, the final product will not likely be the same.

In the meantime, my open bolt sterling will continue to fill my need for an open bolt SMG.
 
contact148 said:
spencer IF the rcmp wants to see your gun you WILL be submitting it

it would have to be built EXACTLY as a sas3 or its not a sas 3 and therefore NO FRT#

to obtain an FRT # the rcmp techs need to approve it. a CFC employee and your local verifiyer has NO real power there

the rcmp guys are ok to work with and the guys i delt with really knew thier s**t but at the end of the day they follow the laws and personally I dont think they or thier masters really want this type of stuff approved

they are not fast at one point i was told dec NO word till JUNE of that year.....

My project will be resubmitted soon If I can get the gunsmith to hurry up
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Not the MKIII for reasons that I have stated over and over. I would however expect and be happy to send in the MKII
 
tiriaq said:
With this convertor installed on the bolt, the second bent will be just shy of 2" to the rear of the original.
From the engagement face of the sear, to the rearward edge of the tip of the tripping lever is about 1".
As soon as the original bent contacts the tripping lever, the sear will be disconnected, and the sear will pop back up.
The sear is going to catch the new bent, as Stencollector suggested. It will take two trigger pulls to fire the gun. Pull, clunk, pull, bang.
The bolt extension will only work if the original bent is removed from the bolt, per the US instructions.
Its no wonder the supplier has lots of these pieces for sale - they are of no use.
Click to expand...

From experiments I did today, it looks that with the extension and the standard spring the original bent will not go back far enough to trip the lever. I don't think it matters whether the original bent is removed or not. I will know for sure soon, but either way it's only a technicallity.
 
stencollector said:
I would rather own an open bolt sten as well. I may give it a whirl further down the road. But along with legal, one must also worry about safe. It was engineers that designed the sten; there was some degree of science and physics involved. When you change part of the equation, the final product will not likely be the same.
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I can think of no gun that is less safe than a sten.

stencollector said:
In the meantime, my open bolt sterling will continue to fill my need for an open bolt SMG.
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What are the differences between a sterling police carbine and a full auto sterling ? As there is already a fart number for the police version surely it would be a straightforward matter to make one and get it registered ??
 
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cantom said:
Even with the issues raised about Spencer's weld on extension, it would still probably make it more foolproof as an open bolt semi...weld it such that the bolt is captive and who knows? Personally I'd rather own that than an SAS3.
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But do you absolutely know that that is necessary ? I don't know it !

I hear from quite a few people here that if you can easily swap the modified bolt for an original one,then this would automatically make it fail to meet the criteria. Does anyone actually KNOW this ??

Let's take this one step further. If an FRT can be refused because it is possible to exchange a major part, surely an FRT can be refused because it is possible to exchange the entire gun :confused:
 
Spencer said:
From experiments I did today, it looks that with the extension and the standard spring the original bent will not go back far enough to trip the lever. I don't think it matters whether the original bent is removed or not. I will know for sure soon, but either way it's only a technicallity.
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When the convertor is installed on the bolt, there is only a vestigal spigot for guiding the spring. This change is going to affect the rearward action. Remember, this conversion was a deadend in the US because of BATFE rejection. Only a limited number of guns were made before they were ruled to be NFA firearms. Have you found any reports of guns with this conversion actually being testfired? Because BATFE has ruled that any gun in the US using this system is subject to the NFA, would the part be considered a machinegun part for the purposes of export from the US? The drawing for the convertor is in the public domain; why not just turn one up on your lathe if you want to experiment. Pretty simple turning, would only take a few minutes. Epoxy the thing to your bolt, try it, easy enough to remove if it doesn't work, you will not have spoiled an original bolt by welding.


The disconnector is tripped as the bolt goes foreward, in addition to being hit when the bolt comes back.
 
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