450M conversions.
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  1. #1
    Deadeye
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    450M conversions.

    I've posted this everywhere but here so I thought I would see what everyone here thinks. Jackfish, Jayco, Nanook 450, Gunjunkie, everyone that can give me their opinion on this idea.

    I'm trying to determine if it would be safe and possible to build a wildcat on the Marlin 1895M action that will push a 7 mm, 130/140gr bullet to 28-3000fps, on about a 22-24 inch barrel. I have modified the 450M case down to 7mm using a software program but that doesn't tell all. Pressure I feel like is the big issue. I will included the specs for the case that I have drawn up and would like some people that have wildcatted in the past for their advice. Negative or positive, I don't care as long as it's constructive enough that I can learn where I am going wrong or right. I can play with the dimensions of the case to possibly reduce pressure or other mods that might need to be made.


    Here are the dimensions for my case.
    280M
    Case cap. = 60.6grs of water
    ID = .284
    OD1 = .309
    OD2 = .510
    OD3 = .512
    L1 = 1.9
    L2 = 1.6
    L3 = 1.5
    T1 = .025
    T2 = .025
    Web = .244


    Ok I can't post a picture cause www.gunpix.com is under construction. But here is a link to another post that has a picture of it.

    http://shootersforum.com/showthread.htm?t=17881

    JDW

  2. #2
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    450M conversions.

    Changing the dimensions of the case won't affect pressure. The relative burning rate of the powder and the amount of the powder used affect pressure. However, a case with more capacity will generally exhibit less pressure with the same powder charge. But by adding to the charge in the case with more capacity one can bring the pressure up to the level that the smaller case exhibited with the initial charge. So, reducing the size of the case does not necessarily reduce the pressure and would actually increase it if the same charge were used.

    I can't tell you if you will be able to achieve 2800-3000 fps with a 130/140 grain bullet. But, with a guess I would say it would be more like a 130 grain bullet at 2800 fps than a 140 grain bullet at 3000 fps. The 280 Remington is a cartridge with more capacity, operating at higher pressures which achieves about 3000 fps with a 140 grain bullet. So I don't see this wildcat getting too close to that.

  3. #3
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    450M conversions.


    I think it looks like it will perform OK as is. But, to operate with a 2.55" or so COAL bullets will have to seated relatively deep diminishing any advantage the short neck might have yielded in case capacity. So, it probably wouldn't hurt to lengthen the neck. It appears it would have more capacity than the 7mm Shooting Times Easterner which is based on the 307 Winchester case. That cartridge yields 2915 fps with 120 grain bullets and 2710 fps with 139 grain bullets.

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  5. #4
    Nanook 450
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    450M conversions.

    I shoot a 450 and I shoot a 7 mag - I ain't no Jackfish, I don't make ammo, much less wildcat - whatever Jackfish says . . . he's the Master.

    Respectfully,

    Ken

  6. #5
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    450M conversions.

    Bullet supply would be very limited. Check out what is being done for the now defunct 7mm lever action cartridge made from a 30-30 case.(7-30 Waters)? Most of the owners of that gun either bought up a bunch of bullets, or use cast now.

  7. #6
    Deadeye
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    450M conversions.

    Thanks Jackfish that's what I'm looking for. I had orginally thought that I did need to reduce case size to reduce pressure. So if I leave the case length up around the 2 or 2.1 inch mark and use a slow burning powder I may be able to run at a little lower pressure. I've since went back and modified my case to a longer length. Also the base thickness(T1) is too low, I think it should be around .04. Maybe I'm dreaming to big. I had hoped to reproduce velocities a tad better, if not equal to that offered by the 7STE(7/07) or get close to the 7/08. With Winchester big bore getting harder and harder to find I hope to use a platform that is more readily available, like the 1895M. I know others have converted the 444 marlin down to 7mm for the Contender (7mmBellm( but I don't know the pressures on such a conversion. This is all new to me.

    JDW

  8. #7
    Deadeye
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    450M conversions.

    Dr. A

    If I have to I'll make up a jig that I can use to make my own flatnosed bullets. I can use boattails is what to then. Speer just came out with a 130grfn and 120grfn is still available as well. Or last time I checked.

    JDW

  9. #8
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    450M conversions.

    Speer no longer lists the 130 grain flat point designed for the 7mm-30 Waters, but Midway has them on sale right now so perhaps if this is the route you are going you might want to pick up a couple thousand.
    http://www.midwayusa.com/rewriteaproduct/220936

    Beartooth Bullets has a 140 grain hard cast.
    http://www.beartoothbullets.com/bull...hp?catagory=31

    This cartridge will likely exceed the performance of the 7mm STE in the Marlin lever gun. It is also likely that it will equal the 7mm-08 performance.

  10. #9
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    450M conversions.

    Quote Originally Posted by jackfish
    Changing the dimensions of the case won't affect pressure. The relative burning rate of the powder and the amount of the powder used affect pressure. However, a case with more capacity will generally exhibit less pressure with the same powder charge. But by adding to the charge in the case with more capacity one can bring the pressure up to the level that the smaller case exhibited with the initial charge. So, reducing the size of the case does not necessarily reduce the pressure and would actually increase it if the same charge were used.

    I can't tell you if you will be able to achieve 2800-3000 fps with a 130/140 grain bullet. But, with a guess I would say it would be more like a 130 grain bullet at 2800 fps than a 140 grain bullet at 3000 fps. The 280 Remington is a cartridge with more capacity, operating at higher pressures which achieves about 3000 fps with a 140 grain bullet. So I don't see this wildcat getting too close to that.
    If you change case demensions you sure will change pressure if you don'r alter the powder charge. When you change the demensions you change case volume.

  11. #10
    Deadeye
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    450M conversions.

    Quote Originally Posted by jackfish
    So, reducing the size of the case does not necessarily reduce the pressure and would actually increase it if the same charge were used.
    Bear 45/70,

    I think the above is what jackfish was getting at. Regardless the more case capacity I can create might be a step in lower pressure, which is what I need in a leveraction.

    JDW


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