Bren Mk 2 Recoil Spring Issues

[Bruce_in_Oz]

Just wondering:

When folk convert Brens to 7,62 x 54R, what (if anything) is done to allow for the significant difference in operating pressure?

The Russian cartridge is very close to the .30-06 in capacity and performance, thus, if an "original" barrel is simply reamed out for it, the port pressure will be higher than for the original .303. Let's also not forget that the .303 shoulder sits further forward than the 7.62.

So, what is the arrangement with your Bren?

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Joe H]

Just wondering:

When folk convert Brens to 7,62 x 54R, what (if anything) is done to allow for the significant difference in operating pressure?

The Russian cartridge is very close to the .30-06 in capacity and performance, thus, if an "original" barrel is simply reamed out for it, the port pressure will be higher than for the original .303. Let's also not forget that the .303 shoulder sits further forward than the 7.62.

So, what is the arrangement with your Bren?

Bruce,

Pressure doesn't seem to be a problem. The Bren is capable of handling much larger cartridges than the .303. Originally designed for 8mm and I think some may have been built in 30-06. The semi-auto striker version of the semi Bren has more recoiling parts (striker) and an additional spring so the additional pressure from the 7.62x54r is a welcome advantage of the conversion.

The typical conversion consists of running a 7.62x54R reamer in the barrel and opening up the bolt face for the larger rim. Barrel ID for 54R is the same as the .303 british .311/.312". As you noted the cases come out fire formed with a double shoulder. There are no reports of extraction problems but the cases are useless. That is not a problem as the military cases are steel and berdan primed.

I did my own conversion work. I drove a short sleeve into the chamber with a mandrel before using the reamer. The sleeve provided material to correct for the void. Cases come out without the double shoulder.

It is a very popular conversion in the USA mainly because of the cheap price of mil surplus ammo.


Joe