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MkI and MkII bolt carrier assy
Is there any functional difference between a MkI bolt carrier and a MkII?
Or was it simply a production simplification?
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02-24-2010 12:14 PM
# ADS
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I dont think so, I've got some breech blocks from mk2s and there in Mk1s. The only point I can see is the Mk1 and 2 piston are slightly diffrent.
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Of the complete assemblies, it's only the piston that is a dedicated Mk2 part, being a cheaper variant. There are two types of breech block. One has a set of gas vent holes in the breech face.
The piston post plunger was lengthened and its recess in the piston post was deepened as a modification to prevent piston post springs breaking. It didn't really help very much so as a result, a new/replacement spring was always in the spare parts tin.
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Thank You to Peter Laidler For This Useful Post:
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Advisory Panel
Of the complete assemblies, it's only the piston that is a dedicated Mk2 part, being a cheaper variant. There are two types of breech block. One has a set of gas vent holes in the breech face.
The piston post plunger was lengthened and its recess in the piston post was deepened as a modification to prevent piston post springs breaking. It didn't really help very much so as a result, a new/replacement spring was always in the spare parts tin.
Is there any way of telling the difference w/o disassembly?
So a MkI and a MkII bolt carrier are funtionally identical and replaceable through the whole family from Bren MkI thru L4?
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Differences. You can tell the two pistons easily because the early Mk1 has a set of ribs between the front and rear piston ring halfway down the stem. These ribs were to close the Mk1 gun gas vent holes off. Early breech block - easy to see the gas vent/escape holes horizontally across the breech face. The piston assembly is interchangeable across the whole range from Mk1 to L4A9. Breeck block interchangeable throughout the whole .303" range but not with the L4's
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Advisory Panel
Differences. You can tell the two pistons easily because the early Mk1 has a set of ribs between the front and rear piston ring halfway down the stem. These ribs were to close the Mk1 gun gas vent holes off. Early breech block - easy to see the gas vent/escape holes horizontally across the breech face. The piston assembly is interchangeable across the whole range from Mk1 to L4A9. Breeck block interchangeable throughout the whole .303" range but not with the L4's
Ahh, so the fancy machining of the ribs has a purpose other than demonstrating design and machining ability!
A MkII piston with simply 2 rings machined to replace the ribbed block will function in an early MkI receiver?
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These flutes between the rings were a real problem because they were used to close off the gas vent holes, they had to be indexed to the threaded end AND to the slot for the retaining pin. There was a lot of wastage in spite of the spec being relaxed several times. They were made by the Bren Manufacturing Co in Gateshead, a wartime sub company of Sigmund Pulsometer Pumps (who are still in business).
Ah, yes...., where were we?
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PM
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