Bren Mk 2 Recoil Spring Issues

[djandj]

OK - here is what I have. (see what happens when you get a rifle w/o a manual). Just realized that I DO have a return spring in the stock as well as the striker spring. However - both seem very week as setting the gas port to anything but the lightest setting will cause the bolt group to SLAM into the stock. Plus I'm still crushing the striker spring. There was relatively little force as I unscrewed the cap at the end of the stock behind the return spring. Is this supposed to be a strong spring?

Take a look and tell me what you think

[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?

[Peter Laidler]

Taking into account what Bruce says in thread 22 above, it's little wonder that the breech block and piston/piston extension assembly (BB&PEA) opf your semi-auto hit the buffers like a run-away train! The actual gas operation of the gun still works as per the auto gun and as such still NEEDS the double return springs. This is JUST the reason why we put doubles in there in the first place. Jeeeees...., words fail me......... Each return springs should be 13.4" long (neutral) as on the rearward stroke they operate as a) buffers to cushion the violent rearwards action of the relatively heavy BB&PEA and B) store energy to act as the medium to retuyrn same to battery AND cock, feed, load and lock the gun.

Haven't got the EMER handy but bearing in mind sentence 2 in para 1 above, 'action weight' of the gun must still be as per original. That is (if I remember correctly so anyone with the EMER handy please feel free to correct me.....) 19 - 23 lbs weight that goes down to 16 - 23 at a unit level.

GET THE CORRECT SPRINGS PDQ and your prayers willo be answered!

[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

[Peter Laidler]

Any views of my comments in thread 23 Joe. Not knowing much about the mechanics of these semi Brens, you have to be a bit careful about what you say/comment on from afar

[Brit plumber]

djandj, did you pull the spring off the guide? It should be held together. As Peter said, just buy another Mk2 spring set.

I've also just noticed something which looks odd. Which spring have you got as the original return spring, and which is the striker spring? Looking at the setup of the striker on the slide in an earlier photo, it appears you have the longer and smaller diameter spring as the striker spring and the short fat spring as the return spring. Is that correct? If so, it's back to front.

[Brit plumber]

Disregard my last, I've just realised the earlier photo isn't of yours.

[Joe H]

Any views of my comments in thread 23 Joe. Not knowing much about the mechanics of these semi Brens, you have to be a bit careful about what you say/comment on from afar

Peter,

Your comments are correct. The semi bren works exactly like its full auto cousin. The difference is in fire control. The FA fires from an open bolt, the semi from a closed bolt. The sear catch is removed from the bolt carrier and a striker added behind the carrier. The striker has the sear catch. The piston post is ground back and slotted to allow for an extended firing pin. The FCG is modified to work in semi auto only. The return spring still has to return the bolt and carrier to in battery position. The gun is then fired with the trigger activating the striker. The gas system works identical to the original Bren.

Your comments are even more relevant when you realize that in order to use a 3/4" striker spring the original buffer has been removed on djandj and Wally's Bren's to make room for the striker spring. The design I used maintained the buffer and put the striker spring on the return rod. This limits the spring to max OD .35" and is more temperamental to get set up right.

Those return springs are definitely not the correct Bren springs!

Joe

[djandj]

OK Gang next question. As you can see, my Len Savage Bren came with the 3/4" striker spring located over the thin guide rod AND a mainspring which is located in the stock BEHIND the guide rod. NOW. I have received the new old stock MKII double springs (very small one inside a bit larger one (about 1/2 in diameter) SO.... I ASSUME I replace the 3/4 inch striker spring that the gun came with (right?) Do I leave the two new springs one inside the other as they came? and do I also replace the mainspring behind the guide rod in the stock?

Also, I wonder about changing to the real Bren springs now as it was pointed out above - the buffer block was drilled out to accept the 3/4 in spring Len originally sent with the gun. What happens when I change to the smaller 1/2 spring?

[Brit plumber]

The double spring goes in the butt and replaces your single return spring. Leave the striker spring as is for now.

The return springs should fit onto the guide so that you can hole the end of the spring and the guide will sit on the end as one complete item. I can't find a photo to show you.