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December 18, 2008, 11:19 AM | #1 |
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Twist rate & barrel length
What would be the optimum twist rate fore 120 to 145gr bullets from a 7-08? What length barrel would give the best performance up to 28"?
Thanks, Will Hunt |
December 18, 2008, 12:16 PM | #2 |
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Depends on the powders you are using if you reload, but the 308 length cartridges typically do well with a 22" barrel. Twist rate should be between 1:9" and 1:10". 1:10" works well for 140 gr but I prefer a little tighter twist.
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December 18, 2008, 12:35 PM | #3 |
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I'm too lazy to look it up, but I get sub-MOA from my 700 Ti in 7mm08, whatever twist that is. 22" barrel. The loading handbook says I should be getting around 2,800 ft/sec with a 140-grain bullet.
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December 18, 2008, 12:36 PM | #4 |
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Factory loaded 7mm-08 rounds use a fairly fast powder. They generate something like 95% of maximum terminal velocity in the first 16 inches of barrel travel. That is why Ruger can get away with their Frontier models with 16" barrels - they don't loose very much velocity. A slow burning caliber (like a 30-06 for instance) could never get away with that.
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December 22, 2008, 12:01 PM | #5 |
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The barrel maker and shilen are recommending 1 in 11". Does this seem a little slow?
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December 22, 2008, 12:03 PM | #6 |
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Seems slow to me. Isn't a 1 in 9 standard for a 7mm-08?
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December 22, 2008, 12:19 PM | #7 |
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1:10" twist is almost a standard for 7mm, but for a 7mm achieving lower velocities (like the 7-08 and 7X57), a 1:9.5" is a good bet. Heck, European 7X57s often come with a 1:8.7" twist, and my Ruger 77 has a 1:9" twist from the factory. 1:11" would be absolute minimum twist to stabilize a 145 gr bullet, and could cause a few issues if you opt for BTHP or VLD bullets. I build rifles, and I would never build a 7mm rifle with a 1:11" twist unless the customer specified it.
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December 22, 2008, 12:19 PM | #8 |
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That is what EA Brown, Rem, Savage, Browning use. 1 in 9" or 9.5".
Last edited by will hunt 4 food; December 22, 2008 at 12:51 PM. |
December 22, 2008, 01:14 PM | #9 |
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Re-read Shilen's recommendations here. 1:11" twist is for bullets up to 140 gr, meaning it will just barely stabilize a 140 gr bullet. For 140 and heavier, they recommend a 1:9" twist barrel.
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December 22, 2008, 01:32 PM | #10 |
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The way I read it is heavier than 140 needs 1 in 9. ! in 10" seems like a good compromise. Am I wrong? I stated up to 145gr but aren't mant bullets between 140 & 160.
7mm/.284 - 8" for all bullets-customer discretion 180 gr. VLD - 9" for bullets heavier than 140gr. - 11" for bullets up to 140gr. |
December 22, 2008, 01:47 PM | #11 |
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Scorch I'm not trying to argue, just getting a lot of conflicting info. Berger also says 1 in 11". http://www.bergerbullets.com/
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December 22, 2008, 01:53 PM | #12 |
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Are you building a rifle?
Well I dont like anything less than a 1 in 9" for my 7's. I like to shoot everything from 120's to 175's and the 1 in 9" does that well. I would not build a 7 with anything slower than a 1 in 9", it would just limit your bullet selection too much. I do not shoot VLD's in any of my 7's or I may opt for something faster than a 1 in 9". J. |
December 22, 2008, 01:59 PM | #13 |
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It is better to err on the faster side rather than the slower side. You will not see any ill affects going with a faster twist barrel but you may if you go slower.
J. |
December 22, 2008, 02:01 PM | #14 |
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I've got a mod 7 in 7-08(1 in 9.25")and those 2 weight bullets are all I have come to shoot. The 140's shoot much better in it, or I might shoot 120's more. I'm getting this barrel made for another rifle.
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December 22, 2008, 02:06 PM | #15 |
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U.S. military sniper 308 barrels are done with a 1 in 11.25" twist, they shoot 175gr bullets.
My 700 5R has the same barrel and is sub moa, as long as I am.
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December 22, 2008, 02:15 PM | #16 | |
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Quote:
J. |
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September 25, 2017, 05:04 AM | #17 |
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I would probably specify it if it were me Lol. I don't what the deal is with all the heavy bullet craze these days? A 130-140 grain bullet is all I would ever want in a 7mm08. That would cover everything up to and including black bear. Of course my weatherby with a 1 in 9.5 twist doesn't shoot 139 grainers good at all and with 162 grain I can get almost a 1" group at 100 yards. Of course I don't know if the twist rate or just because it's a weatherby that it don't want to shoot good? Should have got a Mossberg Patriot I guess?
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September 25, 2017, 05:45 AM | #18 | |
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The original post was 9 years ago. He has probably made his choice by now.
Quote:
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September 25, 2017, 10:54 AM | #19 |
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Ah, necrothreadia!
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