Sterling Mk5

[Peter Laidler]

I wonder how a long barreled Mk6 would function using a blowback/API L2A3/Mk4?

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[Vincent]

That’s an interesting question, Peter.

Doubling the barrel length would require a considerably heavier breech block.

The Mk6 barrel has a deeper chamber than the Mk4 barrel. Would it still have API in an open bolt system?

I don’t understand how API works with a fixed firing pin on the breech block. I know it does work because I can see and feel it. But how is the primer ignited while the round is still traveling forward?

I understand how API works in the long chambered Oerlikon cannon. But I have never seen an explanation of how it works with a fixed firing pin.

[browningautorifle]

I still think that's just theory. I think the cartridge has actually stopped and the breechblock is still moving, that I'll buy. I know, I've taught the classes on the Sub Machine Gun C1, mechanism...still...

[Vincent]

So the firing pin protrusion ignites the cartridge and in a fraction of a second the cartridge case starts to move back while the breech block is still moving forward?

[Peter Laidler]

I wrote an article about API on the forum and basically it's as BAR has said but API as a stand alone feature is not of itself special. It is simply an incidental feature of having a fixed firing pin. Maybe someone wot is comu'a literate can bring the article up. Anyone........?

[browningautorifle]

The primer's ignition depends on the firing pin protrusion and the hardness of the primer. The cartridge firing cushions the bolt's forward movement which is the most important feature, I still don't like slamming those heavy breech blocks against the breech faces dry. Yes, the theory is the bolt is still moving forward when the cartridge goes off...but if the cartridge is too, then why do we get out of battery firing early when you have a gritty chamber. The cartridge is in fact as far forward as it is going when it fires, no matter what. It's not still going forward. That's a theory on paper.