Savage 7mm-08 and 1:11.5" twist


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New User
November 10, 2009, 05:12 PM
I was thinking about ordering a new Savage in 7mm-08, but I saw that the barrel is 1:11.5" twist, which I do not think will stabilize the heavier bullets I want to use. I am pretty knew to paying attention to barrel twist and bullet weights, so I am wondering:

1. Does anyone have any experience with the 7mm-08 and a 1:11.5 twist?
2. What bullets would be ideal for a 7mm-08 with a 1:11.5 twist?

Thanks for your help.

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rbernie
November 10, 2009, 07:27 PM
The Greenhills formula is [T=150(d/r)], where T is the twist rate, d is the bullet/bore diameter, and r is the ratio of bullet length to diameter. If the expected bullet velocity will exceed 2800fps, increase the constant from 150 to 180. (The constant really should track more linearly against velocity, but 150 and 180 are the accepted 'close enough' numbers...)

A 7mm bullet has a diameter of .284 inches. Whipping out a caliper and measuring some samples from the loading bench shows me that a Winchester PSP 150gr 7mm bullet is 1.19" long and that (at the other end of the spectrum) a Sierra 100gr HP is .885" long. That means that the Winchester 150gr would optimally require a 1:10" twist, according to the formula, while the little 100gr Sierra would want something closer to a 1:16" twist.

You'll notice that this formula depends upon bullet LENGTH and not weight. It also makes a bunch of assumptions about bullet density (the bullet is assumed to be made of lead) and bullet speed. Now, it's reasonable to assume that a heavier bullet must be longer, and the examples above proved that point clearly, but there are variances. Round nose bullets are short for their weight, for example, and will often stabilize where a really low-drag design might not. A boattail bullet will want fractionally more twist than would a flat base bullet. A bullet that is all copper will be very long for its weight and will likely require a faster twist than would a lead jacketed bullet of equal weight. A barrel that is longer will create more velocity, which will spin the bullet faster.

All other things being equal, I would expect the Savage barrel to be useful across the range of factory 7mm08 loadings, which usually start at 100gr and top out at around 140gr. It will probably show a sweet spot in the 140gr range. If you handload, you can possibly use 150gr or above if you keep the velocities close to max and/or use bullets that are relatively short for their weight. I would not expect the barrel to shoot the 175gr bullet well at all, but those bullets are constructed for 7mmMag velocities anyway and will likely prove unsatisfying for use on game at 7mm08 velocities...

Lone Star
November 10, 2009, 07:59 PM
I prefer a faster twist in a 7mm. Euro twists run around 1-9 or even tighter, probably to stabliize the 175 grain bullets at 7X57 velocities.

I have a Howa 1500 7mm/08. Does anyone know the twist rate? Got it in a trade with my son, so didn't check. Does Howa have a Website?

Thanks,


Lone Star

Lone Star
November 10, 2009, 08:18 PM
Just found the answer on the Legacy site. Twist in the 20" bbl. is 1:9.5. Sounds okay.

This link http://www.legacysports.com/products/howa/howa_youth2n1.html shows my Youth rifle.

Howa appears to offer 7mm/08 only in this rifle. Pity: it's a good cartridge, if limited in factory bullet weight ammo.

But a 140 grain Core-Lokt bullet will knock off most game. Like to see it with Nosler Partition bullets, too. Does any factory load those in this caliber?

Lone Star

Runningman
November 10, 2009, 08:36 PM
That is interesting. I would not be surprised if Savage did some testing and found a 1 in 11.5 twist was optimum with most of all of the factory 140 grain loads (bullet length) available from the factory in the 7mm-08. Sounds like Savage was thinking outside the box. It makes perfect sense to me if your using factory 120 - 140 grain loads. Not many people even handload with bullets heaver than 140 in the 7mm-08.

I've played with 160s in the 7mm -08 and they shoot well but velocity was not acceptable to me in my 20" 7mm -08 model 7.

The usual 7mm barrels have twist rates around 1 in 9 - 1 in 9 .5 and in most cases will shoot the longer 160 and 175 grain bullets the best. I have a 7mm STW that I had a 1 in 10 twist barrel put on it and it still shoots the longer 160 grain bullets much better than 140s.

The pre Japan Weatherby Mark Vs German made (before 1972 or 1973) 7mm Weatherbys actually used a 1 in 12 Twist barrel. A friend of mine ended up with one of these in 7mm Weatherby with a 1 in 12 twist. Helped him develop hand loads for it in the early 90s. It shoots the 140 Grain Sierra , 140 grain Nosler Partition real well.


but I saw that the barrel is 1:11.5" twist, which I do not think will stabilize the heavier bullets I want to use.
Having said all of that if you are planing on handloading longer 7mm bullets than a typical 7mm 140 this may not be the rifle for you.

rbernie
November 10, 2009, 09:20 PM
The 7mm08 does not fare well in the heavier bullets, due to its limited case capacity. Also, the heavier bullets are constructed to withstand the higher impact velocities of the bigger 7mm chamberings, and will likely prove too slow to open up on light thin-skinned game.

I would not be surprised if Savage did some testing and found a 1 in 11.5 twist was optimum with most of all of the factory 140 grain loads (bullet length) available from the factory in the 7mm-08. Sounds like Savage was thinking outside the box. Keep in mind that velocity is lost as twist rate is increased. There is little profit in an overly-fast twist rate for the intended use of the rifle. Since 7mm08 is, from a case capacity perspective, best for 100gr-140gr projectiles, it makes sense to provide a twist rate that hits that sweet spot and doesn't try to overspin the bullets and lose some incremental velocity as a result.

New User
November 10, 2009, 10:27 PM
Rbernie,

Thank you for your post. Your post seems to make the most sense to me. Just because I can buy and load heavier 7mm bullets for the 7mm-08, it does not mean that I should. I really just want a gun for poking mulies and blacktails in Oregon, and Savage's twist plus 140 grainers seems to be a good match.

Uncle Mike
November 10, 2009, 10:53 PM
Talk about a phart in church! I guess there is more than a few people besides themselves over this deal!

I was on the 'Savage Shooters' website the other day, and some of those guys were to say the least...puzzled.
We had a customer come in spittin' nails over it, said his 16 wouldn't shoot 140's for poo...
He hasn't brought it back in for us to evaluate...we did ask him to, but nothing yet.

I called Savage myself and put the, 'What the %#@!' question to them but only received the generic answer...'our engineering department conducted research that showed this twist(1/11.5") to be optimum for the caliber and the vast majority of commercially loaded ammo' answer!

The older Savages' had the 1/9.5" twist, why the change... who knows.

I have not shot a 1/11.5" 7mm-08 yet to see for myself. It is odd that the rest of the modern world has chosen to use the 1/9.25" twist, as far as production hunting rifles go.

There are several sandbagers using the 1/11.5" in bench competition but I would think they are using the 120's...?
Maybe check out 6mmBR.com for a clue. I am going to call several barrel manufacturers and put the question to them.

All my 7mm-08's have the 1/9.25" twist and do very well with 120-140 grainers.

rbernie
November 11, 2009, 08:11 AM
I am going to call several barrel manufacturers and put the question to them.
From Shilen's web site: 7mm/.284
- 8" for all bullets-customer discretion 180 gr. VLD
- 9" for bullets heavier than 140gr.
- 11" for bullets up to 140gr.

SSN Vet
January 20, 2010, 03:26 PM
Does anyone know when Savage switched to the 1/11.5" twist on their 7mm-08 chambered rifles?

Uncle Mike
January 20, 2010, 06:46 PM
Less than a year ago.

SSN Vet
January 21, 2010, 12:01 PM
Boy did I luck out...

I purchased a model 14 in November, but it had been on the dealers shelf for two years....

Thanks UM for this detail....

If your rifle has the bolt release/cocking indicator on the right, rear side of the receiver, then you have a 1/9.250" twist

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