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If you built a rifle or just rebarreled a rifle what is ROT preference and why?
Wayne
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It has to do with what weight bullet you will be able to shoot our of your rifle. Usually the more twist is required to stabize a heavier bullet after it leaves the barrel down range.
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1~9 twist for me. It will work with virtually any bullet from 120grs to 175grs.
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Wayne, As Tonk says, it depends on what bullet weight you wish to shoot. Most 7x57's have a 1~9" or 1~9.25 and some have 1~9.5" My 1st 7x57 was a custom on a VZ-24... It had a 1~12" twist. I soon found out that any weight over 140 gr. was a waste of time. It wouldn't even shoot the 145 Speers... Personally, I am an advocate of heavier for caliber bullets. My preferred weight in the 7x57 is 154-160 gr. For that I prefer 1~8" or 1~8.5"... There is a chart in Speer Manual #8 that lists optimum twist by bullet length. If you could round up a copy, that might make your decision easier... Hope this helps... GH
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1~9 twist for me. It will work with virtually any bullet from 120grs to 175grs. In the half-dozen or so 7x57s I have owned, I have not been as fortunate as you. Most would shoot great with one or two bullet weights (150 - 175gr) and other weights so-so. One exception is a Ruger tang safety M77 with a 1-8.75 ROT that shoots respectable groups from 115gr to 175gr bullet range. My intent is to get a rifle to shoot MOA or less with the 140 gr TTSX. The M77 and two other rifles will not accomplish that. The ROT in those rifles are 1-8.75, 1-9 and 1-9.5.
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Wayne, As Tonk says, it depends on what bullet weight you wish to shoot. Most 7x57's have a 1~9" or 1~9.25 and some have 1~9.5" My 1st 7x57 was a custom on a VZ-24... It had a 1~12" twist. I soon found out that any weight over 140 gr. was a waste of time. It wouldn't even shoot the 145 Speers... Personally, I am an advocate of heavier for caliber bullets. My preferred weight in the 7x57 is 154-160 gr. For that I prefer 1~8" or 1~8.5"... There is a chart in Speer Manual #8 that lists optimum twist by bullet length. If you could round up a copy, that might make your decision easier... Hope this helps... GH Do not have the #8 Speer Manual. It would be appreciated if you would look up the twist for a Barnes TTSX bullet - 1.362" bullet length. Thanks - Wayne
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Early Ruger 77 had 1 in 9 1/2" twist... Newer 77 Mk II have 1 in 8" twist. Note the attached chart where somewhere in the middle, Ruger used 8 3/4" twist. Wonder which shoots best? with which bullet weight 7 x 57mm - 1 in 8" . . . . . . . . . . .Ruger (present) 7 x 57mm - 1 in 8 1/2" . . . . . . . .Winchester 70 (post 64) 7 x 57mm - 1 in 8.7" . . . . . . . . . .FN 7 x 57mm - 1 in 8 3/4" . . . . . . . .Winchester 54, 70 (pre �64); Ruger 77 7 x 57mm - 1 in 9" . . . . . . . . . . .Mannlicher-Schoenauer; Thompson/Center Rifle 7 x 57mm - 1 in 9 1/4" . . . . . . . .Remington 700 7 x 57mm - 1 in 9 1/2" . . . . . . . .Ruger 1, 77 (old); Savage 110 7 x 57mm - 1 in 10" . . . . . . . . . .Winchester 70 g
Last edited by GeoW; 06/03/11. Reason: add more stuff
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Well, I hate it when memory fails... The table I was thinking of is in Speer Manual #6 and it goes by weight. Can you tell me the approximate velocity that it will be going? I just arbitrarily guessed 2600 f.p.s. According to the chart, a 160 gr. @ 2600 would call for a 1~9.5 twist. (I'm thinking the 160 gr would likely be near the same length...) Whereas my unprofessional opinion would lean toward a faster twist. I'm thinking like 1~8", especially since you've already tried it in slower twists... Now that I think of it, these charts would likely NOT apply to mono-metal bullets anyway... Sorry for the bum steer... GH
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GH, a member PM'd me with this twist calculator. Have you tried it, if so do you believe it is valid? http://kwk.us/twist.html
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I have never seen that calculator... But after looking at it, that's as good a guide as any... And I believe that one cannot predict it EXACTLY . For some unknown reason, there are always exceptions to the rule... And as we should know, each rifle is a law unto itself! GH
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Wayne, as you know I used a 1-9 twist on my 7x57 and it shoots the 120gn GS Custom at 3235fps, the 160gn Woodleigh at 2700fps, and a 160gn cast at 2415fps all wirth very good accuracy. With the same scope setting on my 2-7 Leupold with LR retical the 120gn has a 250yd zero and the 160gn a 150yd zero. LR second bar gives the cast a 150yd zero. For me this twist works well and accuracy is certainly there for each intended purpose.
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Yep, I know, you are hitting on all cylinders with that rifle.
The end game for me is to get the 140 gr TTSX to give accuracy with velocity. This would be a good set up to hunt everything in North America except for big bear.
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Since those TXS bullets are longer than most, I would think that a faster twist barrel would be what you need to keep the bullet spinning on track and produce tight groups.
I have only shot a couple of 7 x 57 Mauser rifles, however it seems to me a 1 in 8 twist would be better for all those bullets above 140 grn upward.
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Completed another range test of the 140 gr Barnes TTSX yesterday and I am a happy camper. Previously, I had given up on the bullet and went back to CnC's and partitions. A couple weeks ago I resumed testing and was again disappointed with results using H414, IMR4350, H4350. My goal was to achieve 2,800 fps with MOA accuracy. What became clear was the closer I got to 2,800 fps the worse the accuracy became. Between 2,500 and 2,600 fps I was getting 2 inch five shot groups at 100 yds. Groups deteriorated with increased powder. The Campfire's Seafire has recommended a fast powder load of 40 grs IMR 3031 and I get 2,700 to 2,725 fps and 1.5" 5 shot goups with the 140 gr NP. With same powder load and the 140 gr TTSX I get about 2,750 fps with 1.6" 5 shot groups. This improvement with a faster burning powder got me to thinking about trying IMR 4320. Depending on the rifle, 44-45 grs produces 2,800 to 2,830 fps with five shot groups of .7 to 1" five shot groups. Happy Camper! They can put a ban on lead bullets now.
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ASSUME: 150gr eTip at 1.425" in length MV of 2600 fps Cool Arizona day
Don Miller's Twist Rule
Caliber 0.284 Inches
Bullet Weight 150 Grains
Bullet Length 1.425 Inches
Barrel Twist 9 Inches/turn
muzzle velocity 2600 fps
Temperature 80 degrees Fahrenheit (59 is standard)
Pressure 29.92 inches of mercury (29.92 is standard)
Sg = 1.51
Sg shouldn't be less than 1.4. If Sg is greater than about 2.0, you may
gain some accuracy by going to a slower twist barrel.
THEN: 1:9 Berger recommends a 1:9 for their 180 HVLD kwk.us recommends 8.9 (round up to 1:9)
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When doing a custom build I generally go w/ the fastest "standard" twist rate for the bore size I'm working with because I like heavy for caliber bullets, personally.
I'd strongly consider trying RL19 & RS-Hunter in the 7x57. I've had great results with those powders in that cartridge, although if you're going faster RL15 & RS-Big Game would be first stops for sure.
Good luck; I don't suppose there is anything you're likely to run across that'd stand up to a 140 TTSX at 2750 fps...
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Good luck; I don't suppose there is anything you're likely to run across that'd stand up to a 140 TTSX at 2750 fps...
Or 2800 to 2830 fps...
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Or a 160 TSX @ 2650 fps......
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HaYen, thanks for the chart and info. The recommendations come out to about where I am at now with twists. As noted previously, three rifles - 1-8.75, 1-9 and 1-9.5.
When I first tried to get the 140gr TTSX to perform to my goal I considered re-barreling a rifle with a 1-10 or 1-10.5 twist. I partially based that on a friends Win M70 with a 1-10 ROT. It shoots the 140 TTSX - lights out. I know rifles are different, but I was willing to follow it's example.
Now it turns out that by going to a faster burning powder I can obtain the results that I hoped for. You just never what will surprise you.
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Or a 160 TSX @ 2650 fps...... That would be going against the latest trend that I am trying to become part of - lightweight monolithic bullets with speed. I am a trendy kind of a guy.
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