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Thread: Interesting project.

  1. #1
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    Interesting project.

    I'm a big fan of the Browning B78 single shot rifles. More particularly, the ones with the varmint weight round barrels. I've had four over the years....two being unfired NIB ones that were just too nice to do anything with but sell them to collectors. So, for a few years I've been looking for one that's in 'shooter condition'.

    Some weeks back, I bought one with an interesting history. It was originally a 6MM Remington but the barrel had been set back and rechambered to the 6MM Jet which is the 307 Winchester (308W with a rim) necked to 6MM. It came from an estate and the gentleman that owned it was a big fan of rimmed cases, evidently. The shop that did the work is out of business but was pretty well known for their work on these high walls. Part of the mods included shortening the extractor to catch the rim. So essentially...it's a rimmed 243 Winchester. It also has a rare Canjar set trigger on it.

    I'm a bit torn on what to do. On one hand, the 307W cases are hell for stout. But on the other hand, that's a non issue as the pressures are going to be kept reasonable in this high wall action. Necking the 307W cases down basically makes it into a short neck 243W.

    I'm leaning toward sourcing a new extractor for a .473 case head (not as easy as it sounds) and just using some 243W brass with the necks shortened .030. The chamber looks good. It came with one formed case that I'll fire soon and get some real dimensions to work from.

    Thoughts?
    Last edited by Al Nyhus; 08-06-2020 at 10:14 AM.

  2. #2
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    What are you planning to use it for?
    My 6MM Rem. Ruger #1B became my favorite hunting rifle over the years and somewhat close to the same. On another note I knew a B78 collector out my way who owned at least one of the various chamberings that were produced.

  3. #3
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    Al,

    I remember reading years ago...I don't remember where or who wrote it...that single shots such as Hi-Walls, Low-Walls, etc., were designed to fire rimmed cartridges and worked there best when doing so. Maybe that was the reason for the original owner converting it to 6mm.

    Those 78's have beautiful lines. I can see your attraction to them. Put a Super Targetspot or a Unertl on it, and it doesn't get more classic than that.

    Justin

  4. #4
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    That'll never work! Bring it down, and we'll convert into something that has a chance . . . He's back from the dead - again! Been babbling, non-stop, about a 6mm WASP . . . and Wilson Arrow - ya know, HE doesn't care for the, "commynist" calibers, so, the Arrow may win out! RG

  5. #5
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    Quote Originally Posted by R.G. Robinett View Post
    That'll never work! Bring it down, and we'll convert into something that has a chance . . . He's back from the dead - again! Been babbling, non-stop, about a 6mm WASP . . . and Wilson Arrow - ya know, HE doesn't care for the, "commynist" calibers, so, the Arrow may win out! RG

  6. #6
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    Quote Originally Posted by R.G. Robinett View Post
    That'll never work! Bring it down, and we'll convert into something that has a chance . . . He's back from the dead - again! Been babbling, non-stop, about a 6mm WASP . . . and Wilson Arrow - ya know, HE doesn't care for the, "commynist" calibers, so, the Arrow may win out! RG
    Good Lord! The last I knew, He was partially entombed in Memory Valley, Iowa with the remaining pieces in the Wyoming landscape between the Stacked Stone Tower and the Three Triceratops area! The ancient Druids also employed a similar practice whereby the remains of persons thought to be less than.....errrr....'stable' were divided up and seperated so they could never reconstitute and come back to bother the normal population.

    But I like the idea of Him being around. A little chaos is a good thing.

    That's it, then. I'm going to used the rimmed 307W case and not take the easy way out. Now I just have to puzzle out the best way to neck the 307W case to 6MM while keeping the necks fairly straight. A pass through a 7-08 fl die, then a 260, and finally a 243W would likely work. I've got a .165 short 308W Carstensen die that sizes all the way to the neck/shoulder junction as well. With a few bushings and that might work. Inside bore the necks, anneal and there we'd have it.

    It'll never work....
    Last edited by Al Nyhus; 07-28-2020 at 06:30 PM.

  7. #7
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    [QUOTE=
    That's it, then. I'm going to used the rimmed 307W case and not take the easy way out. Now I just have to puzzle out the best way to neck the 307W case to 6MM while keeping the necks fairly straight. A pass through a 7-08 fl die, then a 260, and finally a 243W would likely work. I've got a .165 short 308W Carstensen die that sizes all the way to the neck/shoulder junction as well. With a few bushings and that might work. Inside bore the necks, anneal and there we'd have it.

    It'll never work....[/QUOTE]

    Your scheme to make 6MM Jet cases should work just fine. A very long, long time ago in a Galaxy far away I shot a 14" SSK Contender barrel chambered in 7JDJ#2 in 500 meter pistol competition. ( The 7JDJ#2, a J D Jones creation is basically a 7-08, 40 Degree Shoulder, Rimmed cartridge. ) I grew so disgusted with the quality of .307 Winchester brass that I decided to try to make cases starting with Remington .444 Marlin brass. I started by necking down with full length .358 Win, .308 Win and 7JDJ#2 dies in succession, then cut off the excess length with a tubing cutter, trimmed to length and fire formed to final form. Finished product turned out great, much better than the factory Winchester stuff. Didn"t even need to neck turn for my chamber. Accuracy was so much better that I didn't mind all the extra work. Necking down from .307 to .243 shouldn't be much of a stretch by comparison. Good luck with your project!

  8. #8
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    307W case (left), formed 6MM Jet case with Sierra 85 seated (center), std. 243 Winchester (rt.)

    I'm going to stress relieve the shoulder area before whappin' it with some pressure. I'll check the fired case neck diameter and compare it to my plug gauge measurement and section the fired case to see how the case thickness looks along the length of the shoulder. If it looks in the ball park, I'll make another test mule case, stress relieve it and fire it 6-8 times and see how the shoulder area acts when being sized. If need be, it wouldn't be a big deal to do a thinning cut along the length of the shoulder to make it behave.

    The 307W case necks are surprisingly thin. I'm sure the neck I.D. will need some attention, also.

    Swapping the extractor and using 243W cases is starting to look better! Just a .030 push on the shoulder and we'd be there.

    Last edited by Al Nyhus; 07-28-2020 at 06:31 PM.

  9. #9
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    Quote Originally Posted by vlcakc View Post
    Your scheme to make 6MM Jet cases should work just fine. A very long, long time ago in a Galaxy far away I shot a 14" SSK Contender barrel chambered in 7JDJ#2 in 500 meter pistol competition. ( The 7JDJ#2, a J D Jones creation is basically a 7-08, 40 Degree Shoulder, Rimmed cartridge. ) I grew so disgusted with the quality of .307 Winchester brass that I decided to try to make cases starting with Remington .444 Marlin brass. I started by necking down with full length .358 Win, .308 Win and 7JDJ#2 dies in succession, then cut off the excess length with a tubing cutter, trimmed to length and fire formed to final form. Finished product turned out great, much better than the factory Winchester stuff. Didn"t even need to neck turn for my chamber. Accuracy was so much better that I didn't mind all the extra work. Necking down from .307 to .243 shouldn't be much of a stretch by comparison. Good luck with your project!
    Thanks! Some good food for thought. -Al

  10. #10
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    Surprise, surprise, surprise!

    Iinteresting thing about a gun like this....sketchy details, minimal history, no dies, no chamber print and an obscure wildcat chamber. What could possibly happen?

    Yesterday was fire forming day. The gun came with one formed case so I decided to use that as my test case. I pulled the bullet that was seated in that and did a fairly aggressive stress relieving on the case shoulder/neck area. Since it's basically a rimmed 243 Winchester, or so I thought, I tossed in a mid weight charge of RL17 and a old Hornady 75 gr. flat based bullet seated .005 short of the lands.

    To my surprise, out came this cute little 40 degree case that looked for all the world like a 243W Ackley. Having had a 243 Ackley in the past, I headed home and compared the fired cases. While it's not exactly a rimmed version of the 243 Ackley, it ends up being a .065 short version of it when measured from case head to the neck/shoulder and body/shoulder junction.

    Now that I've got a fired case, the next step is to neck down some 307W cases so they just fit the chamber. For dies, I'm hopeful that a shortened 243 Ackley die will work for sizing.

    307W (l), 6MM Jet (c), 243W Ackley 40 degree (rt)


  11. #11
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    Cool

    Quote Originally Posted by al nyhus View Post
    iinteresting thing about a gun like this....sketchy details, minimal history, no dies, no chamber print and an obscure wildcat chamber. What could possibly happen?

    Yesterday was fire forming day. The gun came with one formed case so i decided to use that as my test case. I pulled the bullet that was seated in that and did a fairly aggressive stress relieving on the case shoulder/neck area. Since it's basically a rimmed 243 winchester, or so i thought, i tossed in a mid weight charge of rl17 and a old hornady 75 gr. Flat based bullet seated .005 short of the lands.

    To my surprise, out came this cute little 40 degree case that looked for all the world like a 243w ackley. Having had a 243 ackley in the past, i headed home and compared the fired cases. While it's not exactly a rimmed version of the 243 ackley, it ends up being a .065 short version of it when measured from case head to the neck/shoulder and body/shoulder junction.

    Now that i've got a fired case, the next step is to neck down some 307w cases so they just fit the chamber. For dies, i'm hopeful that a shortened 243 ackley die will work for sizing.

    307w (l), 6mm jet (c), 243w ackley 40 degree (rt)

    make die withchamber reamer lap with bushing and shoulder bump forthe -press i made 3 for my 25 bms

  12. #12
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    Quote Originally Posted by BillBrawand View Post
    make die withchamber reamer lap with bushing and shoulder bump forthe -press i made 3 for my 25 bms
    Unfortunately, the gun came from an estate sale...no dies or reamer.

    And the shop that did the 'smithing has closed. Checking with three reamer makers has met with zero results with a reamer that fits the fired case dimensions. The reamer was likely a one-off and the sizing dies a full length 243 Ackley shortened .065.

    I'll fire form a few more to get a better idea on dimensions. -Al
    Last edited by Al Nyhus; 08-06-2020 at 07:17 AM.

  13. #13
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    Started with 50 new WW 307W cases. After some culling and case loss as the necking down process was tweaked, I ended up with 30 cases ready to f-form. To neck down, I used a 308W body die that I had on hand from my early HBR days shooting the .30 WareWolf (a .165 short case based on Lapua 308). Jim Carstenson had shortened a Redding Body Die and converted it to hold a neck bushing which sized all the way to the bottom of the neck. I used a succession of bushings, .335, .325, .321, .290, .280 and finally a .275. I'll use a .268 bushing to size the necks for f-forming. A loaded round measures .272 and the neck on a fired case measures .276.

    After the neck down, it was time to relieve a little stress.

    In 1/2" of water to act as a heat sink:





    After the correct amount of time, tip the case over as the ring comes off to cool the cases:



    All done:



    Scrub in hot water and Dawn. Get in the case with a Nylon brush to remove any goo:



    After rinsing with hot water, I soak 'em in acetone for a few minutes to get 'em squeaky clean:



    Set 'em outside my sod hut for the South Dakota sun to finish the drying.

    Last edited by Al Nyhus; 08-06-2020 at 10:20 AM.

  14. #14
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    Project BFD78

    If the showers hold off this morning, more cases will be f-formed. It's hard to say how many years this poor thing languished after being left for dead. It's good to get guns like these up and running again, if only for our own enjoyment. If it shoots honest 1/2" 3 shot groups, I'll be a happy rifle tinkerer.

    It's now tagged as the 'BFD78' project (Back From the Dead).


  15. #15
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    Quote Originally Posted by Al Nyhus View Post
    If the showers hold off this morning, more cases will be f-formed. It's hard to say how many years this poor thing languished after being left for dead. It's good to get guns like these up and running again, if only for our own enjoyment. If it shoots honest 1/2" 3 shot groups, I'll be a happy rifle tinkerer.

    It's now tagged as the 'BFD78' project (Back From the Dead).


    He's LIKING this! . . . mumbling around the shop - once in a while, a distinct, "ded cyoot pik 'd top it off" . . . comes out . RG

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