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Thread: .300wm twist rate

  1. #1

    .300wm twist rate

    Suggestions on ideal twist rate for a .300wm please? Will be shooting 165-190gr bullets.

  2. #2
    Usual twist is 1:10
    (The Unspeakable In Pursuit Of The Uneatable.) " If I can help, I will help!." Former S.A.C.S. member!

  3. #3
    Normal is 1:10, but 1:12 will work well, too, because the .300 Win Mag has so much forward speed on the bullet.

    Just look at the .308 Win, which can shoot 175 and 190 grain bullets quite accurately, although being rather anemic compared to the .300 Win Mag.

    I have a dozen .30-06s, most with 1:10. One of then, a Browning B78, has a 26-inch barrel that is 1:12. I have not tried many loads in it, as it is a hunting rifle, but it shoots 155-gr Palma bullets very well, 180-gr hunting loads sub MOA, and I am going to try some 190-gr SMK and 208-gr Amax in it this week, maybe out to 600 yards or further.

  4. #4
    I have a. 308 with 1:9 and shoots 150gr very accurately. Would a. 300wm with 1:9 shoot the lighter 150-165gr well still and be OK for the heavier stuff. Most the info I read says 1:10 pretty standard, is there much if a difference between 1:9 and 1:10 in your opinion

  5. #5
    The U.S. Army pretty much developed the .30 caliber cartridges we have today. The 1:10 twist was just a holdover from the .30-40 Krag. The .30-03 used a heavy, 220-gr RN bullet, like the .30-40 Krag had before it. When the 8x57IS was changed from a heavy 196-gr to 220-gr bullet to faster 154 and 150 gr bullets, the .30-06 was changed to match it. The 8x57IS remained at 8.66 rate of twist in most rifles, and the .30-06 remained at 1:10. Both rifles shot the 150-gr bullets ( or 154 or 147 ) very well.

    When the US Army was looking to replace the M1 Garand and 1903A3 Springfield, they tested the 7.62x51mm cartridge developed by Winchester with a wide range of bullet weights, because they were using 163 AP, 173, 174 and 175 grain bullets in the sniper and match .30-06. They found the .308 Winchester, released prior to the adoption of the 7.62x51, could shoot 125 to 180 grain bullets quite well with 1:12 twist. The M-14 rifle was set to 1:12.

    Palma rifles in .308 are mostly 1:12 and some slower, and some of the long range target rifles in .30-06 were 1:12. I had one, a Winchester Model 70, made for 600 to 1,000 yard work.

    Back to your question, I would not want a .300 Win Mag in 1:9 rate of twist. It just raises pressures and wears out the barrel faster. A 1:12 would work in the .300 WM ( and has, in competition rifles for it and the .300 H&H). The .300 WM really outdoes the .30-06 and .308 with 190, 200 and 208-gr bullets, at ranges like 600 yards. A 150-gr bullet is too fast for shooting most game closer than 250 yards without a lot of damage. Beyond 400 yards, the heavier bullets outperform the 150s ballistics, in drop and in energy.

  6. #6
    Quote Originally Posted by Southern View Post
    The U.S. Army pretty much developed the .30 caliber cartridges we have today. The 1:10 twist was just a holdover from the .30-40 Krag. The .30-03 used a heavy, 220-gr RN bullet, like the .30-40 Krag had before it. When the 8x57IS was changed from a heavy 196-gr to 220-gr bullet to faster 154 and 150 gr bullets, the .30-06 was changed to match it. The 8x57IS remained at 8.66 rate of twist in most rifles, and the .30-06 remained at 1:10. Both rifles shot the 150-gr bullets ( or 154 or 147 ) very well.

    When the US Army was looking to replace the M1 Garand and 1903A3 Springfield, they tested the 7.62x51mm cartridge developed by Winchester with a wide range of bullet weights, because they were using 163 AP, 173, 174 and 175 grain bullets in the sniper and match .30-06. They found the .308 Winchester, released prior to the adoption of the 7.62x51, could shoot 125 to 180 grain bullets quite well with 1:12 twist. The M-14 rifle was set to 1:12.

    Palma rifles in .308 are mostly 1:12 and some slower, and some of the long range target rifles in .30-06 were 1:12. I had one, a Winchester Model 70, made for 600 to 1,000 yard work.

    Back to your question, I would not want a .300 Win Mag in 1:9 rate of twist. It just raises pressures and wears out the barrel faster. A 1:12 would work in the .300 WM ( and has, in competition rifles for it and the .300 H&H). The .300 WM really outdoes the .30-06 and .308 with 190, 200 and 208-gr bullets, at ranges like 600 yards. A 150-gr bullet is too fast for shooting most game closer than 250 yards without a lot of damage. Beyond 400 yards, the heavier bullets outperform the 150s ballistics, in drop and in energy.
    Thanks for the detailed explanation. It will help me in my choice I'm sure.

  7. #7
    Quote Originally Posted by Southern View Post
    The U.S. Army pretty much developed the .30 caliber cartridges we have today. The 1:10 twist was just a holdover from the .30-40 Krag. The .30-03 used a heavy, 220-gr RN bullet, like the .30-40 Krag had before it. When the 8x57IS was changed from a heavy 196-gr to 220-gr bullet to faster 154 and 150 gr bullets, the .30-06 was changed to match it. The 8x57IS remained at 8.66 rate of twist in most rifles, and the .30-06 remained at 1:10. Both rifles shot the 150-gr bullets ( or 154 or 147 ) very well.

    When the US Army was looking to replace the M1 Garand and 1903A3 Springfield, they tested the 7.62x51mm cartridge developed by Winchester with a wide range of bullet weights, because they were using 163 AP, 173, 174 and 175 grain bullets in the sniper and match .30-06. They found the .308 Winchester, released prior to the adoption of the 7.62x51, could shoot 125 to 180 grain bullets quite well with 1:12 twist. The M-14 rifle was set to 1:12.

    Palma rifles in .308 are mostly 1:12 and some slower, and some of the long range target rifles in .30-06 were 1:12. I had one, a Winchester Model 70, made for 600 to 1,000 yard work.

    Back to your question, I would not want a .300 Win Mag in 1:9 rate of twist. It just raises pressures and wears out the barrel faster. A 1:12 would work in the .300 WM ( and has, in competition rifles for it and the .300 H&H). The .300 WM really outdoes the .30-06 and .308 with 190, 200 and 208-gr bullets, at ranges like 600 yards. A 150-gr bullet is too fast for shooting most game closer than 250 yards without a lot of damage. Beyond 400 yards, the heavier bullets outperform the 150s ballistics, in drop and in energy.
    Intresting. I had never considered velocity as a factor for determine the twist rate. I thought only bullet weight was important. Is there any intresting reading about that ?

  8. #8
    SD Regular Greener Jim's Avatar
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    Google the Greenhill and Miller formulae and go from there.

    The usual Wikipedia link: https://en.m.wikipedia.org/wiki/Miller_twist_rule
    Any Questions Feel Free to PM me

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