Twist rate & barrel length

W

will hunt 4 food

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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
 
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.
 
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.
 
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.
 
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.
 
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.
 
The way I read it is heavier than 140 needs 1 in 9.:confused: ! 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.
 
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.
 
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.
 
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.
 
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.
 
U.S. military sniper 308 barrels are done with a 1 in 11.25" twist, they shoot 175gr bullets.
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Even different cartridges in the same caliber sometimes require different twist rates to stabalize like bullets. You cannot compare a 30cal to a 7mm.

J.
 
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?
 
The original post was 9 years ago. He has probably made his choice by now.

I don't what the deal is with all the heavy bullet craze these days?
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Much better down range performance. I don't shoot 7-08, but have gone to 178/180 gr bullets in my 308. The 150 gr loads start out 200 fps faster, but the 178's hit harder at all ranges, are faster at 400 yards with only about 2" more drop.
 
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