Haganah - TMT IV Sten markings

[browningautorifle]

on the sten bolt, why is there large hole at the rear

Do you mean the one from the side that holds the cocking handle or the one in the rear that allows it to be lighter?

[philb]

this..

[browningautorifle]

Like I said, to lighten the whole affair.

[Peter Laidler]

The weight of the bolt is the critical part of the safety feature in a blow-back weapon where the breech is 'secured' (it's not locked.....) only by the weight of the bolt and the spring.

[browningautorifle]

Advance Primer Ignition...which is still black magic by the way...witchcraft. A cartridge must stop to be fired...speaking in a strictly non-engineering viewpoint of course...

[Flying10uk]

Being a toolmaker by trade I would say that the U.K. and Canadian made trigger housing cover is made from a single piece of steel formed into shape using a power press. There would have been tooling to produce the profile/blanks followed by tooling to form the finished shape of the cover and both tools would have been reasonably hefty lumps of metal. The nicely flowing curve to the lower edge of the British and Canadian produced covers isn't so that the covers look nice and pretty when fitted to the gun. They are shaped like that with curves to help the metal form and flow in the form tool; if it was shaped like the cover which vincent has the metal would split and crack when being formed.

[Vincent]

If the spigot was solid it would add a lot of weight to the bolt. The added weight would slow the cyclic rate.

If you are interested in understanding how machine guns work, I highly recommend reading “The Machine Gun” by George M. Chinn. Blowback operation is in volume 4.

https://www.milsurps.com/content.php...eorge-M.-Chinn)

[Vincent]

Being a toolmaker by trade I would say that the U.K. and Canadian made trigger housing cover is made from a single piece of steel formed into shape using a power press. There would have been tooling to produce the profile/blanks followed by tooling to form the finished shape of the cover and both tools would have been reasonably hefty lumps of metal. The nicely flowing curve to the lower edge of the British and Canadian produced covers isn't so that the covers look nice and pretty when fitted to the gun. They are shaped like that with curves to help the metal form and flow in the form tool; if it was shaped like the cover which vincent has the metal would split and crack when being formed.

Is this also why the rear part of the English cover is welded?

[Vincent]

Advance Primer Ignition...which is still black magic by the way...witchcraft. A cartridge must stop to be fired...speaking in a strictly non-engineering viewpoint of course...

There are different kinds of API. The key is that the bolt/breech block is moving forward when the spent casing starts moving back and arrests the forward motion of the bolt/breech block.

In the Oerlikon cannon API is achieved by using a long chamber. The firing pin strikes the primer while the round is still moving forward in the chamber.

In blowback SMGs API is achieved by firing pin protrusion. The cartridge is stopped in the chamber when the firing pin ignites the charge, but the bolt/breech block is still moving forward when the spent case starts moving back and arrests the forward motion of the bolt/breech block. It’s just a gnat’s eyelash but that’s all it takes to get that Rolls Royce silky smoothness

[browningautorifle]

API

Yes, I was sort of kidding...we had to learn that and teach it during my first leadership course back about '78 or '79...for assessment and later to be used when teaching the weapons. It's just that the explanation in the book varies greatly with the actual facts. But then, it WAS written by Infantry Snr NCOs. The point of the whole argument we had here a couple years back was that the cartridge must be stopped to fire, or a long chamber(excessive headspace) wouldn't matter and the SMG would still work. I know this is important because I had a '28 Thompson once with a long chamber and it wasn't working until we reduced the chamber length. Anyway, I drag us off topic...again...