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Thread: trenches' Bren build

  1. #41
    Senior Veteran sdk1968's Avatar
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    im kinda chasing GG there ^^ my Bren IS set up in 54r and 303 both so you can look at some of my pix if you want ...

    made acouple of small changes to get it to all work right cause most of my 54r is the light ball stuff.

    drilled out the gas port even bigger in the regulator and the barrel holes... so i have one port for 303 and one for 54r.. ( could have just got 2 regualtors i guess.)

    then used the zb39 mags with no issue at all.

    did have to do a little work to get the headspace right as im using 2 different bolts on the same carrier.. took some playing but it runs fine.

    the 54r does not feel as smooth as the lower powered 303 and its not as accurate either.. but i can afford to shoot it.

    Trenches and me send pm's to each other all the time so im sure he doesnt mind me putting this post in his thread. if he does, i'll take ti out.

    sdk
    say what you mean & mean what you say!

  2. #42
    Veteran kevin's Avatar
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    one problem i have is the front of the mag is very tight. i filed it some to make it fit looser and it helped. Even with 10 rounds the bullet nose dives into the front of the mag. I can load 1 at a time in the chamber by hand and its fine. I cant seem to find the right kind or size of spring to put in the magazine. I think the chamber may be a little tight as well. I need to have some help to get the extractor enlarged enough to grab the 54r round. Right now its still set for 303

  3. #43
    Senior Veteran Global Gunsmithing's Avatar
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    Quote Originally Posted by kevin View Post
    one problem i have is the front of the mag is very tight. i filed it some to make it fit looser and it helped. Even with 10 rounds the bullet nose dives into the front of the mag. I can load 1 at a time in the chamber by hand and its fine. I cant seem to find the right kind or size of spring to put in the magazine. I think the chamber may be a little tight as well. I need to have some help to get the extractor enlarged enough to grab the 54r round. Right now its still set for 303
    might be a mag issue, have you tried different mags?, I`m using the 303 extractor with no issues, eats and ejects everything I feed it, my 2 cents, I doubt the chamber is too tight, you could try polishing it, or a good cleaning with wire brush set up on a drill, are the case necks of the 54r doubling or deformed?
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  4. #44
    Veteran kevin's Avatar
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    there is a double neck on the cartridge after firing. I was trying bulgarian 54r light ball brass cased. I tried multiple mags. Because the extractor hasnt been modified its like it wants to not completely chamber and lock the bolt and then after firing you have to have a 2x4 to hit the bolt handle to get it to eject

  5. #45
    Senior Veteran sdk1968's Avatar
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    if you hd your bolt opened up and your barrel to match then it should come right out of there...

    yes you'll still get the double neck deal but a good chamber job they wont stick..

    lots of "experts" will say it doesnt help this part.... but thats one of the reasons i gave the 54r even more gas port than the 303.... so that the bolt carrier had PLENTY of power/speed on its way back to make the bolt YANK the round out.

    on a side note: im gonna ask you a question here... if its not ejecting all the time does the bolt seem like its hanging?

    Kevin,
    what you mentioned in that last post there above is from the head space not being exactly right and the timing gets thrown off...

    heres why... as the round lights and takes off the BOLT is starting backwards BEFORE the carrier.

    NOT supposed to work that way. the delay is the all important part. we're talking nano seconds here, but its all it takes.

    the bolt is jamming between your lcking shoulder and the carrier. THIS WILL GET WORSE if its doing it now. it took me some playing around to figure out if the shoulder was too small or the carrier just not moving fast enough.

    i balanced mine out by letting more gas thru the port/barrel/regulator to move the carrier with more force AND then i had to change the locking shoulder to one that was just a shade tighter..

    so that the bolt hits the locking shoulder and stops UNTIL the carrier is going back and grabs the bolt and pulls it down away from the shoulder.

    im trying to make this sound right but if that didnt ring thru just say so and i'll look for another way to tell it.

    soon as i fixed this problem mine ran as you see it in the vids here.

    ive made NO changes to the zb mags and run 20 rnds all the time in them with no problems. try another one.

    hope this helps

    sdk
    say what you mean & mean what you say!

  6. #46
    Senior Veteran Global Gunsmithing's Avatar
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    like sdk1968 said, i`d be looking at headspace
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  7. #47
    Veteran kevin's Avatar
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    in 303 it runs absolutely perfect if you put a weaker firing pin spring in it will even fire surplus. Maybe i need to send a gas regulator to someone to have it opened up a little. I checked my headspace with feeler gauges on the back of the bolt against the locking shoulder to get the 303 and 54r the same. all my mags make the bullets nose dive into the front of the mag. I just cant find a spring at any of the harware etc stores.

    how do you know if too much pressure will go through the gas port? I dont want to send it back with too much force

  8. #48
    Senior Veteran Global Gunsmithing's Avatar
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    i gota split right now, but when I get back i`ll check the size of the opening on the regulator, might be .070, I drill the same for the 303 and 54r, only thing I changed was the mag and barrel, everything else is the same
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  9. #49
    Senior Veteran sdk1968's Avatar
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    .070? lmao

    my opening is .1875 = 3/16" for the 54R and the gas port in the regulator is matched to that..

    my 303 is .15625 = 5/32"

    yes the head space may measure the same on the 54r.. but it is too much for that cartridge in this gun if its jamming up like that.... OR as mentioned its just not getting that bolt carrier past it to pull it down.. its forcing it back into the shoulder instead.

    gotta remember the 54r is a good bit hotter than the 303 and the delay still needs to be the same... so the bolt HAS to stay in battery long enough for the carrier to do the job.

    you may only need a K or two... we're talking baby steps here. it could also be that you jsut need the carrier to hold the bolt up in a fraction tighter for the 54r

    measure your two bolts and see if they are exactly the same height at the back from the slide section to the par that hits the shoulder.
    say what you mean & mean what you say!

  10. #50
    Senior Veteran weasel_master's Avatar
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    For mine in .303 is .172"
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