Twist Rate Insights

[Tallest]

Good morning, folks! I'm looking for some opinions and educated experience here....

I have a friend who is helping me get started on a little reloading, letting me use his press while I supply dies and supplies to reload for my 7mm-08. I've been looking at different bullets, and since I've always had pretty decent luck with middle weight bullets. My .223 likes 55 grain and 62 Grain bullets best, my 300 WM likes 180s the best, and my 270 likes 130 a lot. So I think I'm subconsciously conditioned to like middle weight bullets.

Most 7mm-08 loads run 120 or 140 grain bullets. But Speer makes a 7mm bullet in 130 grain. It's a soft point boat tail, also a favorite configuration. But it's kind of unique, which makes me wonder if it would actually be right for a pretty generic hunting rifle.

The rifle is a Ruger American, so it's 1:9.5 twist rate. I know that on paper, that's an acceptable match-up for the bullet and barrel. But I'm wondering, from those of you who have a lot more experience, if going this way is straying from the path of wisdom.

Please feel free to weigh in. The more knowledge I have, the less money I'll waste and the better off I'll be! Thanks!

[jmr40]

Don't over think this. The trend today for newer rifles is toward faster twists so they CAN shoot heavier bullets. Within reason lighter bullets still shoot fine in the faster twists. If you were going to the far extreme on either end of the spectrum then it may be a concern.

[Jim Watson]

I have no experience in the caliber but a 130 gr 7mm will surely be stabilized by any usual rifling twist, no need to overstudy that part of it.

How well it shoots gets you into what you have already mentioned, does your barrel "like" it?

By the way, there is also such a thing as a 140 gr .270, "splitting the difference" between the long time standards of 130 and 150. Hornady, I think.

[BBarn]

I have done a little work with the 7-08. I'm looking at bullets in the 139gr to 150gr range for deer. Too early to tell yet which bullets mine may prefer.

[Tallest]

Gentlemen, I appreciate the input so far. I have been known to over think myself into an unnecessary quandary.

I guess as much as anything, I'm wondering why 130 grain is so rare for 7mm-08, or the 7mm bullet at all.

[hdwhit]

jmr40 wrote:
The trend today for newer rifles is toward faster twists so they CAN shoot heavier bullets.

The trend is indeed towards faster twist rates. But the faster twist rate is needed to stabilize "longer" bullets, not necessarily "heavier" bullets. If we are talking conventional gilding metal jacketed lead core bullets, then for any particular diameter, a longer bullet will be heavier so longer and heavier are synonymous.

But, as we see greater use of copper, frangible composites and lead-polymer hybrids the distinction between length and weigh should be noted as in 7mm (0.284) a composite bullet as long as Hornady's #28405 162gr BTHP might only weigh in at 90 or 95 grains. Such a bullet, even though lighter than most 7mm bullets, would require a faster twist rate to stabilize because of its length.

[hdwhit]

Tallest wrote:
My .223 likes 55 grain and 62 Grain bullets best,...

And each gun is likely to have its own sweet spot for the bullet weight it "likes".

A few things to keep in mind when working with barrel twist rates:

• "Faster" twist rates are needed to keep longer bullets stabilized in flight over long distances.
• The twist rate determines how fast the bullet rotates in flight. For most high velocity cartridges, the bullet will leave the muzzle rotating at between 200,000 and 300,000 rpm.
• The larger the bullet's diameter, the faster the outer edge of the bullet is moving (since it has to cover a longer distance with each rotation).
• Such fast rotation produces enormous mechanical stresses within the bullet. Often these stresses are considered by the bullet designers in how the bullet will perform when it strikes the target.
• But faster twist rates have a down-side; spin a bullet too fast and the mechanical stresses will tear the bullet apart inflight. When this happens you will see what looks like a whisp of smoke about 50 to 75 yards downrange (and there will be no hole in the target).

My Mini-14 with a 1:12 twist rate will turn Hornady 50 grain SX bullets (current catalog number #2240) into vapor above about 3,000 fps. So, investigate what range of bullet lengths (often given in weight assuming that you will be shooting conventional gilding metal jacketed lead bullets) the bullet you want to use can work in and then work up a load in the usual manner, beginning at the starting load and working your way up incrementally.

[Scorch]

I'm wondering why 130 grain is so rare for 7mm-08, or the 7mm bullet at all.

Because you have to draw a line somewhere, and most people shooting 7mms prefer relatively heavy bullets. Hornady (just to pick one manufacturer) makes 120, 139, 150, 154, 162, 175 and 180 gr bullets. They used to make a 100 gr bullet for varminting, but apparently not many people used their 7mms for varminting.. Since most people use larger calibers to hunt game animals, and 7mm is a relatively common hunting rifle caliber, they make a good selection of 7mm bullets in a broad spectrum of weights that people would likely use for game animals. A 130 gr would add little other than to expand the number of production machine changeovers they would need to do.

For deer- to elk-sized game, bullets around 140-150 gr seem ideal. I have hunted with 139, 140, 150, 154 and 162 gr bullets and chose 140s for a long time.

[NHSHOOTER]

Hello Tallest, Funny you should ask about speer 130 BT, I just picked some up on sale at my LGS. Loaded 10 with varget, 10 with IMR 4064, 1/2 groups with the varget @ 100 yds, just over a inch with the 4064. Rifle is a Vanguard S2. Just to add, leaving on a deer hunting trip on Friday, will post results with the 130's when I return in a week.

[Tallest]

NHSHOOTER - I look forward to it.

And I thank you all. Once hunting season ends here in VA, I hope to work up some loads and see how it goes. I'll post some results once I have them.

[Don Fischer]

Generally I don't care what the twist rate is, I'm a hunter. In my old varmint 22's I used mostly 50 gr SX Hrnady. In my 243's now, one get's 87gr Hornady's and the other 75 gr V-Max and 70gr SMK's . The twist in all of them are fine. Why would I want to shoot a 70 or 75 gr bullet requiring a fast twist in a 22 cal when I can fire the same weight bullet with a standard twist in a 243?

[T. O'Heir]

"...newer rifles is toward faster twists..." Nothing really new about it. Commercial hunting rifles chambered in .243 Win have been rifled for deer bullets since before.
Changing the bullet weight is a tried and true method of reducing felt recoil too.
"...bullet for varminting..." Hornady's 120 is a V-Max. That is a varmint bullets. Not suitable as a "Do anything" bullet. Their 130's and up are deer sized game bullets. However, absolutely nowhere is it written that "Thou Shalt Use Varmint Bullets For Varmints and Deer Bullets for Deer." Ain't nothin' that's better shooting practice for deer season than shooting varmints with your deer load.
Anyway, the velocity differences between a 130, 139 and 140 are negligible. Pick one and work up a load.

[michaelcj]

I have no experience with the 7-08..... However my 7x57 has a Douglas Bbl with a 1:9.5 twist rate.
I have not loaded anything lighter than the 139/140.

The rifle shoots MOA or better with 140, 150, 160 grain bullets. I suspect yours will be equally happy with most weights associated with the 7mm.