Israeli Mauser 7.62 (.308) Twist rate and bullet weight

Discussion in 'Up To .375' started by Gert Odendaal, Jun 24, 2015.

  1. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    Hi Gert! I am still curious to get answers to these questions about your rifle. If you have the time please let us know. Thanks!
     

  2. Gert Odendaal

    Gert Odendaal AH Elite

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    Hallo Sesoppelman

    I will give feedback as soon as possible, I will be receiving bullets soon and start re-loading . My aim is to get one weight bullet that will group well in this barrel. I am curious as to which bullet weight will eventually group well in the 1:14 rifling twist...

    Regards

    Gert
     

  3. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    That's great, but I am more curious about the rifle itself.
     

  4. Gert Odendaal

    Gert Odendaal AH Elite

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    Update: I did not get good results with the 120-143 gn bullets....
    I am currently doing research to resolve this challenge :
    A few things I noticed:
    In a military step barrel boat tail bullet design seems not to be the answer, a flat base seems to be the better choice.
    1:14 twist rate means I need to shoot a choice bullet much , much faster to stabilise a hunting bullet with a flat base.
    Mistakes made :
    I confused very slow twist rate with light bullets shooting.
    I rather need to shoot bullets at high muzzle velocity to stabilise the bullet in a very slow twist rate military step barrel.
    I am now looking at bullets best shooting from a military step barrel with a very, very slow twist rate of 1:14 twist ..this barrel has an extremely long free bore as well.

    Now for the fun part members:
    Please give me suggestions regarding which bullet will shoot accurately in my Israeli Mauser with it`s 1:14 twist rate??
    Please correct my own assumptions about this scenario...I really would like to hear from all members regarding your own opinions /suggestions about how you would go about solving this riddle ????:LOL::LOL::LOL:(y)(y)(y)
     

  5. ZG47

    ZG47 AH Enthusiast

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    WIth a short bullet jump, any 144 gr target bullet should work BUT ... with that long bullet jump, the 152 gr flat-base M2 .30 cal bullet introduced in the late 1930s would be good. The Hornady #3031 150 gr flat-base spitzer would be a good choice for accuracy but a bit too hard for light game, given that it was designed for use in the .30-06 through to .300 Weatherby Magnum. The 150 gr Hornady round nose and the 130 gr Hornady spitzer could be good choices and a 150 gr Speer semi-spitzer Hotcor might be good but obviously a wee bit dearer.

    Step-barrel is irrelevant. The steps were machined because longitudinal barrel expansion due to combustion heat results in lateral pressure against the fore-end when the barrel is tapered toward the muzzle. Taper is great for muzzle-loading cannon that are supported on trunnions and at the base of the barrel BUT ... not so good for smallarm barrels!
     

  6. Gert Odendaal

    Gert Odendaal AH Elite

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    ZG47, thank you for the information, I will look at the Hornady #3031 150 gr flat-base spitzer , since our game here is RSA tends to be tuf and does not die so easily....
    The assumption that I need to reload for higher velocity to make optimum use of the 1:14 twist to stabilise the bullet in the very slow twist rate ..does it make sense??
     

  7. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    How was the twist rate determined? Its unusually slow for .30 cal.
     

  8. Gert Odendaal

    Gert Odendaal AH Elite

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    Members please be so kind as to provide a link to a bullet reloading calculator for a Sierra or Hornady bullet??
     

  9. Gert Odendaal

    Gert Odendaal AH Elite

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    Sest, I took a cleaning rod with a rotating handle , fit the end with a piece of 2"x4' push it into the barrel, make a mark and pull it back until I had a full rotation..I then did the calculations..did it various times to make sure about the twist..
     

  10. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    Ah, the cleaning rod method. Thanks.
     

  11. Gert Odendaal

    Gert Odendaal AH Elite

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    These Mausers were bought by Poland and secretly shipped to Israel where all the German marks were removed and some of them had gone through a re-barreling process...I think this is where the unusual slow twist rate originals from..or at least that is the story..(y)(y)
     

  12. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    With the exception that the Belgium FN rifles were purpose built as 7.62 NATO and not rebarrel rifles like the other makers. I asked earlier in this thread if yours was an FN and about its markings.
     

  13. Gert Odendaal

    Gert Odendaal AH Elite

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    I will be going to the gun smith shop on Monday and look at what kind of Mauser action it is..will give you feedback soon. I really hope to get this rifle shoot to it`s potential..I need something to shoot further out to 300-400 meters with good accuracy..this is why I think the 1:14 twist will be the answer ..
     

  14. ZG47

    ZG47 AH Enthusiast

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    Rotational velocity is the critical factor. If you send a bullet out of a 1-12” twist barrel at 2,400 feet per second, it will have a rotational velocity of 2,400 revolutions per second (this rotational velocity being maintained pretty much till the end of the bullet’s flight, according to Mitchell Maxberry, a much better rifleman and ballistician than I will ever be).
    With a 1-10” twist barrel, the conversion factor is 12/10, i.e. 1.2x; and with a 1-14” twist the factor is 12/14.
    Roy Dunlap writes about how, in the early days of 1903A1 rifle production, Springfield Armoury made a batch of barrels that were much more accurate than normal with the original 150 gr (WW1 era) ammunition. It turned out that the guide on one of the rifling machines had slipped and it was producing a twist rate close to 1-11.5”. That machine was reset to 1-10”.
    @sestoppelman you may already be aware of this, but Winchester Model 70 target rifles (chambered to .30-06) were available, to order, with an optional 1-14” twist, in order to provide best accuracy with the original 150gr flat-base projectile and the later M2 152gr flat-base projectile.
     

  15. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    I was not aware of that, but am aware that it was chosen for the Palma team to shoot the 155 Palma bullet.
     

  16. Gert Odendaal

    Gert Odendaal AH Elite

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    Am I then correct in my assumption that I need to shoot a 150 gn flat base bullet at least at 3200 f/s out this barrel with a 1:14 twist rate???? This will ensure the bullet to stabilise due to this extremely slow twist rate??
     

  17. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    You wont be able to get that velocity out of a .308 Win. within safe pressure limits. Be tough to do in a 30-06. But no you wont have to drive it that fast anyway. That weight is about ideal for that twist. You don't have to go crazy with speed with that combo. You may approach 3000 fps but it will be a max load.
     

  18. Gert Odendaal

    Gert Odendaal AH Elite

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    Sest , thank you..yes, it is much too fast..I will consult reloading manuals in this regards...your opinion on the flat based bullets in the military barrels like this Israeli Mauser? Why is it according to theory that the BT bullet do not work that great in this barrel?
     

  19. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    I don't know about that theory, but it sounds like baloney. The Palma bullet they shoot in 1-14 twist barrels are boat tails. The only way to know what kind of bullet a specific barrel likes is to shoot them and find out.
     

  20. Gert Odendaal

    Gert Odendaal AH Elite

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    Here is some guidelines I suppose.....
    Twist Rate Projectile Weight
    .224 / 5.56 (your .223 Ar)

    1:16 Up to 55 grains, 4300 fps or more
    1:15 Up to 55 grains, 4100 to 4300 fps
    1:14 Up to 55 grains, less than 4100 fps
    1:12 55-63 grains
    1:9 63-70 grains
    1:8 70 grains or more
    6.5mm
    1:9 Up to 130 grains
    1:8 130 grains or more
    .308
    1:15 up to 150 grains
    1:14 150 to 168 grains
    1:12 168 to 170 grains
    1:10 170 to 220 grains
    1:8 220 grains or more
    This is obviously just a quick list to give you an idea.
     

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