Question: Sterling Mk 4 SMG extractor spring plunger and the center spring plunger

[Steve762]

Questions on the Sterling Mk 4 SMG (L2A3):
--Is the extractor spring plunger the same part as the bolt's center spring plunger?
--Is the purpose of the center spring plunger at the rear of the bolt to retain the cocking handle in the center block?

Information

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[Peter Laidler]

Yes and sort of yes. The rear spring and plunger through is to prevent the cocking handle from rattling about. It is the slot in the casing that holds the cocking handle in the breech block. In the REAL mechanical world, the rear spring and plunger serves no real purpose. It was originally put there in order to use up existing early breech blocks that had a rear mounted striker.

[Vincent]

--Is the purpose of the center spring plunger at the rear of the bolt to retain the cocking handle in the center block?

If you’re looking at a “Stenling”, yes.

A “Stenling” is an American combination of registered Sten receiver tube and a Mk4 Sterling “parts kit.”

There was an abundance of fairly cheap registered Sten receiver tubes in the US. But US law prohibits narrowing the cocking slot. That meant they couldn’t be used to make Sterlings. But a very bright young man figured out if the block and cocking handle were drilled through, allowing the plunger to pass through, the widened cocking handle would be retained.