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#6503373 - 10/19/16 09:41 PM Best twist rate for 7mm-08 with a short barrel?
Burton Ranch Offline
Light Foot

Registered: 05/21/12
Posts: 37
I would like to build a 7mm-08 that can stabilize heavy bullets out of a 16" barrel. Does anyone have any experience with this? Thanks

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#6503415 - 10/19/16 09:58 PM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
TexFlip Online   content
THF Trophy Hunter

Registered: 08/18/12
Posts: 8633
Loc: Harris County
1:8.5" twist will work well with 168s. How heavy you wanna go?
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#6503422 - 10/19/16 10:04 PM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
ChadTRG42 Online   happy
THF Trophy Hunter

Registered: 09/16/09
Posts: 9398
Loc: Lewisville, TX
For the 162/168 grain, a 1:10" would be minimum and 1:9" would be best. For the 180 grain VLD's and Hybrid's, a 1:9" is minimum, and even a little faster would be better. For the new 195 EOL, a 1.83" is minimum, but a 1:8" is ideal.

http://www.bergerbullets.com/twist-rate-calculator/
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#6503427 - 10/19/16 10:06 PM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
Gone to Texas Offline
Veteran Tracker

Registered: 07/05/13
Posts: 2343
Loc: Hurst
popcorn
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#6503479 - 10/19/16 10:42 PM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
Burton Ranch Offline
Light Foot

Registered: 05/21/12
Posts: 37
Thanks, I was wondering if faster than 1:8 would be advisable? Is there such a thing as a twist that is too fast? 180 grn would prob be what I would be interested in. I would be running it with a can if that matters. A side question since you seem knowledgeable with the caliber. I have a ruger m77 hawkeye in 708. What would be the heaviest bullet you would push through it?

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#6503522 - 10/19/16 11:39 PM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
ChadTRG42 Online   happy
THF Trophy Hunter

Registered: 09/16/09
Posts: 9398
Loc: Lewisville, TX
If you look at the twist rate calculator link, you can run the numbers with the various twists and stability factors with various bullets. You want something over a 1.4 or a 1.5. For your Ruger, the 180's are a little long/heavy for a 9.5" twist. I'd stick with the 162/168 bullets as my max. Remember, bullet stability is based on bullet length, not the weight. So, the longer a bullet is, the more twist needed to stabilize it.

On your build, if you run a 1:8" twist with a 180 Hybrid at 2650 fps, you have a 1.8 stability factor. That's plenty for that bullet. The issue is getting this to feed in a short action, and getting enough speed for it to work well in a 16" barrel. I know shooters running a 180 grain in a 7-08, but they run long barrels (26"-31") to get the speeds up and seat the bullet out long. A 16" barrel pushing a 180 grain will be moving very slow. A 162 or 168 would be better off to get some speeds up. But it depends on what the goal of the rifle is. Knowing this, it will help.
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#6503641 - 10/20/16 07:25 AM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
Burton Ranch Offline
Light Foot

Registered: 05/21/12
Posts: 37
Thank you for all the good info. I would like something compact enough it could double as an everyday pickup gun, but also have hunting applications in west Texas (out to 400 yards). I also enjoy long range plinking, so with any gun I have built if it can hit steal at 1000 that would be a bonus.

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#6503670 - 10/20/16 07:47 AM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
FiremanJG Offline
THF Celebrity

Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
Mine will be a 1:9", which is a pretty standard twist. I'll work up loads with 154 gr, and 162 gr, then run them down the range. Which ever I like best will be what I stick with.

400 yards, and in will be no problem on coyotes, and hogs. Depending on energy delivery, it will probably be suitable for whitetail.
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#6503712 - 10/20/16 08:08 AM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
ChadTRG42 Online   happy
THF Trophy Hunter

Registered: 09/16/09
Posts: 9398
Loc: Lewisville, TX
The big debate on the 7mm bullets has always been- do you go lighter (162/168 grain) to get the higher speed for flatter shooting, but lower BC. Or do you run the higher BC (180 grain) at a much slower speed for more drop. There is a middle point somewhere around after 600-800 yards where the 180 grain will out perform the lighter bullets. If the rifle is planned to be used 90% of the time inside of 600-800 yards, then the answer is generally go with the lighter bullet to get your speeds up for the flatter shooting and good bullet expansion. Same principal for the 308 Win. I'll run a 155 or a 168 in my AR-10 to get the speeds up.
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#6503797 - 10/20/16 09:07 AM Re: Best twist rate for 7mm-08 with a short barrel? [Re: ChadTRG42]
FiremanJG Offline
THF Celebrity

Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
There comes a point of diminishing returns in any cartridge. Loading super high BC generally means a heavier bullet. And when the barrel is too short to get the high BC up to speed, it's not necessarily a better load. Same is true if your brass can't hold enough powder to get the bullet up to speed.

That was proven with my 7 Rem Mag. I've got a load pushing 180's 3030 fps MV. Chad experimented with the new Berger 195's in the same rifle. Significantly more BC, but the brass couldn't get it up to speed to out perform the 180's. I ran some numbers, and to equal the delivered energy of the 180's @ 3030, the 195's had to leave at 2800 fps MV. Pressure signs began before that velocity was achieved. Thus the 7-300 that is coming soon. More case capacity to push that 195 fast enough. The same holds true for short action chamberings. You won't do yourself any favors by loading a 230 gr in a .308 Win, at least not if you want performance at some distance.
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#6503806 - 10/20/16 09:12 AM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
ZK-315 Offline
Pro Tracker

Registered: 10/11/13
Posts: 1558
Loc: Temple...Hunt in Freestone Co.
Listening in on this one. Seems like a lot of good info I could potentially use in the next couple of years.

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#6503816 - 10/20/16 09:16 AM Re: Best twist rate for 7mm-08 with a short barrel? [Re: FiremanJG]
Gone to Texas Offline
Veteran Tracker

Registered: 07/05/13
Posts: 2343
Loc: Hurst
Originally Posted By: FiremanJG
Mine will be a 1:9", which is a pretty standard twist. I'll work up loads with 154 gr, and 162 gr, then run them down the range. Which ever I like best will be what I stick with.

400 yards, and in will be no problem on coyotes, and hogs. Depending on energy delivery, it will probably be suitable for whitetail.


Would a suppressor on a 16" barrel increase velocity?

Also, how much energy is recommended to hunt whitetail?
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#6503824 - 10/20/16 09:22 AM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Gone to Texas]
FiremanJG Offline
THF Celebrity

Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
Allegedly it does, though I've never chronographed the same load with and without suppressor. Suppressor length, and type and number of baffles, is certainly a factor.

Round here the ft/lbs I've seen mentioned for whitetail is 1000 or more.
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#6503833 - 10/20/16 09:27 AM Re: Best twist rate for 7mm-08 with a short barrel? [Re: FiremanJG]
Gone to Texas Offline
Veteran Tracker

Registered: 07/05/13
Posts: 2343
Loc: Hurst
Thanks!
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#6503852 - 10/20/16 09:44 AM Re: Best twist rate for 7mm-08 with a short barrel? [Re: Burton Ranch]
Korean Redneck Offline


Registered: 06/24/09
Posts: 2274
Loc: Houston
Originally Posted By: Burton Ranch
Is there such a thing as a twist that is too fast?


That's a good question I never thought of. The few times I've had an exact choice of twist, I just got the fastest I could assuming it could never be fast enough.

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