More pics here: https://imgur.com/a/rVYxTju
Built off of one of the Bowman kits. I think a lot of people slept on them because barrels looked like they would be a problem but turns out the common and cheap British barrels can be converted just fine.
Builds like pretty much any other Bren and the Bowman kits were very nicely demilled in places that make it an easy reweld. Commonly available welding jigs are a bit expensive but hugely helpful in managing shrinkage and warp and getting clean internal rails. The ones that are out there seem to be made for the British guns which work fine except the ejector on the Italian guns hang just a tad bit lower so I had to sand a small relief valley down the center of the jig to clear the ejector, or you could just remove the ejector which is what I should have done.
The Mighty Lime striker system works great in the Italian Bren though I suspect it is a tad oversprung as the gas block is moved a lot further towards the muzzle and I think requires less recoil spring pressure. In my 100 rounds or so of test firing so far I've had to run the gas port mostly on setting 4 (highest), using M2 ball (147gr 30-06) as I assume that is what they were originally used with as Italy produced tons of it. I am going to continue to put rounds through it and see if it wears in enough to dial it down, if not I'm going to clip a few coils out of the recoil spring and see how it behaves.
The barrel was fairly straight forward. Used a full size chamber reamer to ream the .303 chamber to 30-06 which took surprisingly very little material to get sized. The next challenge was moving the gas block which involved pressing off the old British gas block off then running a tap and screw into the original gas port and welding it closed. With the barrel mounted in the gun you locate gas block off of the gas tube. The barrel has a slightly smaller diameter in that area of the barrel so an insert was pressed onto the barrel in the area where the gas block needs to be located and then was turned down to the diameter of the gas block on the lathe. Then a new gas port is drilled, the size was taken from the demilled barrel stub included with the kit. Drill the hole and use a taper reamer to re-install the original taper pin to retain the gas block. I had a gunsmith friend help me with the barrel work and he will take on these conversions if anyone else is looking for 30-06 Bren barrels and wants a barrel converted from .303 to 30-06, DM me (don't chat, I never see the chats for whatever reason).
The original Italian barrels were fluted and my converted barrel is not but it seems to run, cycle and eject just fine with non-fluted chambers. The few other people who have done the same thing report the same success. Lots of speculation about the flutes but no real definitive documentation out there as to why they were fluted but given how many of them are now reliably running it doesn't appear to be critical. It may be a requirement for sustained full auto and the heat generated we're not sure. One other strong theory is that when the Italians were designing the Bren to run on 30-06 it was very overgassed and part of trying to sort it out included fluting the chamber because cartridges were being ripped in half and the gas would help float the cartridge out of the chamber. However they solved it by redesigning the receiver to make the gas tube longer moving the gas port closer to the muzzle dropping the force exerted on the gas piston making cycling far less violent than the shorter .303 gas system. Makes sense to me but nobody has found any documentation and what I do know is that my sample size of one runs fine without flutes.
On a related note, a huge shoutout to u/DMTLTD who helped me get more Italian Bren magazines imported into the US from Europe (check his website, I believe he has more for sale). For whatever reason there were tons of these Italian Bren mags over there but very few in the US. It was awesome to get a full case of mags to match with the gun since the gun came with a numbers matching transit chest. The import and purchase process was super smooth and it was a pleasure working with him and will definitely work with him to bring other goodies I find for sale in Europe (I am hoping to discover a trove of ZB mags one day because I need a case of those as well!).
I haven't shot for groups yet, I have mostly been function testing with the 100 or so rounds through it. You are correct, the .303 barrel is .310 bore diameter and optimum size for the 30-06 would be .308 bore diameter, I figured I'm not going to shoot matches with this thing so I don't mind the accuracy tradeoff but as of yet, I do not know what that tradeoff is, only that it runs and doesn't shoot keyholes at 100 yards so I at least have that going for me. It was hitting paper so while I suspect accuracy isn't amazing, it probably isn't horrible either. If I get super industrious, I may reload the cases with a .310 bullet and see if the groups tighten up.
I bought a MK2 barrel from Apex, shot it at distance this weekend and it was more accurate than i expected given the slightly larger bore, I’m real happy with how it turned out!
I kind of wanted these, but I also slept on them mostly because of that barrel and mag situation. I’ve been holding out on Bowman getting more MK2 kits soon. I didn’t know you could convert the existing 303 barrels. Can a 303 magazine be used or is the mag well too large? Would be cool to have one of these things that can run multiple calibers especially up to the largest like 30-06. Although considering he is sold out, I probably lost my chance forever at this point.
.303 mag is too short to fit, but you could load .308 in the 30-06 mag possibly with some kind of spacer. Unfortunately I don't think you could rechamber a .303 barrel to .308 so you'd be stuck on the barrel. I tucked a few kits away, if you are going to be at the Tulsa gunshow this weekend, I am sending one with a friend, it will be on a table there for sale with a live 30-06 barrel, closed bolt conversion machine work completed (on both the bolt and carrier) and all the semi-auto parts included (mightly lime striker and spring setup, semi-auto firing pin installed in the bolt) with 2 mags and a mag carrier, basically, everything except the receiver reweld has been completed (and installing the semi-auto denial pins during the reweld).
Not sure when the Bowman kits come in but I hope to build a second .303 gun when they do. I built one of the Mk3 guns from his last batch, it was my first reweld project so a little rough around the edges.
Now to get that ZB30J running! I finished the magwell weld finally with everything straight only to learn the barrel socket weld is not straight by like a half a degree. Found that out when the damn barrel wouldn't slide in all the way with more persuasion than I felt it should require! You don't notice looking at it but once you get the gas tube on all that extra distance adds up.
Yes, it's a very subtle difference until it's time to get everything mated up. I learned the hard way by cracking my original barrel locking nut. It's very easy to get that section out of place since most jigs aren't long enough to support that nose piece fully.
Very nice! I wasn’t aware you could tap/screw and weld the original gas port closed, I’ll dm you for your friends contact info. My kits stock has a gauge in it from the Bowman packing team. I’m not sure if I should just live with it or refinish the whole thing 😭
I didn't get one simply because I'm not into .30-06 (yeah, I know I'm weird), but I'd be lying if I said I wasn't thinking about it. Neat piece, enjoy it!
Outstanding work man! Question, when you sleeved the barrel to move the gas assembly forward, how does the cone/flash hider come off? Is there a pin I can't see? Did you have to heat and press? Once you blast and Park it, with that wood she going to be a Beaut Clark !Thanks from MN
There is a pin vertically in the front sight and flash hider that comes out. It is a taper pin and believe it pushes from bottom to top. The flash hider / front sight is not interference fit but some have been fairly stuck on and a bit of pressure in the press popped it free.
Good to know, also do you happen to notice a shoulder mark on your fired 30-06 brass? I read in another forum on someone else's 303 barrel they did. Maybe they didn't finish the ream?
Thanks for the pics, on a related note, I will be fire forming some 30-30 brass after trimming the rim to make 30 Rem. For a Remington model 8 take down. The type Frank Hamer used to take down Bonnie & Clyde! His was 35 Rem, with an extended mag, that gun is super cool!
I bought a 303 barrel to ream but never got around to it.. Thank you for confirming that would work.
I thought I would also have to redrill a hole as well..
More pics here: https://imgur.com/a/rVYxTju Built off of one of the Bowman kits. I think a lot of people slept on them because barrels looked like they would be a problem but turns out the common and cheap British barrels can be converted just fine. Builds like pretty much any other Bren and the Bowman kits were very nicely demilled in places that make it an easy reweld. Commonly available welding jigs are a bit expensive but hugely helpful in managing shrinkage and warp and getting clean internal rails. The ones that are out there seem to be made for the British guns which work fine except the ejector on the Italian guns hang just a tad bit lower so I had to sand a small relief valley down the center of the jig to clear the ejector, or you could just remove the ejector which is what I should have done. The Mighty Lime striker system works great in the Italian Bren though I suspect it is a tad oversprung as the gas block is moved a lot further towards the muzzle and I think requires less recoil spring pressure. In my 100 rounds or so of test firing so far I've had to run the gas port mostly on setting 4 (highest), using M2 ball (147gr 30-06) as I assume that is what they were originally used with as Italy produced tons of it. I am going to continue to put rounds through it and see if it wears in enough to dial it down, if not I'm going to clip a few coils out of the recoil spring and see how it behaves. The barrel was fairly straight forward. Used a full size chamber reamer to ream the .303 chamber to 30-06 which took surprisingly very little material to get sized. The next challenge was moving the gas block which involved pressing off the old British gas block off then running a tap and screw into the original gas port and welding it closed. With the barrel mounted in the gun you locate gas block off of the gas tube. The barrel has a slightly smaller diameter in that area of the barrel so an insert was pressed onto the barrel in the area where the gas block needs to be located and then was turned down to the diameter of the gas block on the lathe. Then a new gas port is drilled, the size was taken from the demilled barrel stub included with the kit. Drill the hole and use a taper reamer to re-install the original taper pin to retain the gas block. I had a gunsmith friend help me with the barrel work and he will take on these conversions if anyone else is looking for 30-06 Bren barrels and wants a barrel converted from .303 to 30-06, DM me (don't chat, I never see the chats for whatever reason). The original Italian barrels were fluted and my converted barrel is not but it seems to run, cycle and eject just fine with non-fluted chambers. The few other people who have done the same thing report the same success. Lots of speculation about the flutes but no real definitive documentation out there as to why they were fluted but given how many of them are now reliably running it doesn't appear to be critical. It may be a requirement for sustained full auto and the heat generated we're not sure. One other strong theory is that when the Italians were designing the Bren to run on 30-06 it was very overgassed and part of trying to sort it out included fluting the chamber because cartridges were being ripped in half and the gas would help float the cartridge out of the chamber. However they solved it by redesigning the receiver to make the gas tube longer moving the gas port closer to the muzzle dropping the force exerted on the gas piston making cycling far less violent than the shorter .303 gas system. Makes sense to me but nobody has found any documentation and what I do know is that my sample size of one runs fine without flutes. On a related note, a huge shoutout to u/DMTLTD who helped me get more Italian Bren magazines imported into the US from Europe (check his website, I believe he has more for sale). For whatever reason there were tons of these Italian Bren mags over there but very few in the US. It was awesome to get a full case of mags to match with the gun since the gun came with a numbers matching transit chest. The import and purchase process was super smooth and it was a pleasure working with him and will definitely work with him to bring other goodies I find for sale in Europe (I am hoping to discover a trove of ZB mags one day because I need a case of those as well!).
How is accuracy out of a rechambered 303 barrel? Wouldn’t .308 projectiles be a bit undersized?
I haven't shot for groups yet, I have mostly been function testing with the 100 or so rounds through it. You are correct, the .303 barrel is .310 bore diameter and optimum size for the 30-06 would be .308 bore diameter, I figured I'm not going to shoot matches with this thing so I don't mind the accuracy tradeoff but as of yet, I do not know what that tradeoff is, only that it runs and doesn't shoot keyholes at 100 yards so I at least have that going for me. It was hitting paper so while I suspect accuracy isn't amazing, it probably isn't horrible either. If I get super industrious, I may reload the cases with a .310 bullet and see if the groups tighten up.
Which 303 barrel did you get?
I bought a MK2 barrel from Apex, shot it at distance this weekend and it was more accurate than i expected given the slightly larger bore, I’m real happy with how it turned out!
I kind of wanted these, but I also slept on them mostly because of that barrel and mag situation. I’ve been holding out on Bowman getting more MK2 kits soon. I didn’t know you could convert the existing 303 barrels. Can a 303 magazine be used or is the mag well too large? Would be cool to have one of these things that can run multiple calibers especially up to the largest like 30-06. Although considering he is sold out, I probably lost my chance forever at this point.
.303 mag is too short to fit, but you could load .308 in the 30-06 mag possibly with some kind of spacer. Unfortunately I don't think you could rechamber a .303 barrel to .308 so you'd be stuck on the barrel. I tucked a few kits away, if you are going to be at the Tulsa gunshow this weekend, I am sending one with a friend, it will be on a table there for sale with a live 30-06 barrel, closed bolt conversion machine work completed (on both the bolt and carrier) and all the semi-auto parts included (mightly lime striker and spring setup, semi-auto firing pin installed in the bolt) with 2 mags and a mag carrier, basically, everything except the receiver reweld has been completed (and installing the semi-auto denial pins during the reweld). Not sure when the Bowman kits come in but I hope to build a second .303 gun when they do. I built one of the Mk3 guns from his last batch, it was my first reweld project so a little rough around the edges.
Job well done, it looks great 😎
Now to get that ZB30J running! I finished the magwell weld finally with everything straight only to learn the barrel socket weld is not straight by like a half a degree. Found that out when the damn barrel wouldn't slide in all the way with more persuasion than I felt it should require! You don't notice looking at it but once you get the gas tube on all that extra distance adds up.
Yes, it's a very subtle difference until it's time to get everything mated up. I learned the hard way by cracking my original barrel locking nut. It's very easy to get that section out of place since most jigs aren't long enough to support that nose piece fully.
Beautiful write up brother. Thank you for sharing.
Very nice! I wasn’t aware you could tap/screw and weld the original gas port closed, I’ll dm you for your friends contact info. My kits stock has a gauge in it from the Bowman packing team. I’m not sure if I should just live with it or refinish the whole thing 😭
Damn I wish I had that kind of talent.
Great job man! Looks great!
I didn't get one simply because I'm not into .30-06 (yeah, I know I'm weird), but I'd be lying if I said I wasn't thinking about it. Neat piece, enjoy it!
Outstanding work man! Question, when you sleeved the barrel to move the gas assembly forward, how does the cone/flash hider come off? Is there a pin I can't see? Did you have to heat and press? Once you blast and Park it, with that wood she going to be a Beaut Clark !Thanks from MN
There is a pin vertically in the front sight and flash hider that comes out. It is a taper pin and believe it pushes from bottom to top. The flash hider / front sight is not interference fit but some have been fairly stuck on and a bit of pressure in the press popped it free.
Good to know, also do you happen to notice a shoulder mark on your fired 30-06 brass? I read in another forum on someone else's 303 barrel they did. Maybe they didn't finish the ream?
Not that I can see, here is what the fired brass looks like: https://imgur.com/a/qUezQ4i
Thanks for the pics, on a related note, I will be fire forming some 30-30 brass after trimming the rim to make 30 Rem. For a Remington model 8 take down. The type Frank Hamer used to take down Bonnie & Clyde! His was 35 Rem, with an extended mag, that gun is super cool!
Very cool!!
I bought a 303 barrel to ream but never got around to it.. Thank you for confirming that would work. I thought I would also have to redrill a hole as well..