January 27, 2020, 11:38 PM | #1 |
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.243 twist rate
I'm looking at buying a Ruger #1 in .243 26" barrel. It comes with a 1:7.7" twist and I'm trying to find out if that's too much spin. I shoot Buffalo Bore 85 grain TSX. Twist calculators call for 1:10" twist. I know I can't go slower, but can I accurately shoot 1:7.7" using this bullet?
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January 28, 2020, 03:09 AM | #2 |
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Hmmm.... Interesting...
Typically the lighter the bullet the shorter the bullet/bearing surface, the slower the twist you can get away with. There is video of 7mm Rem Mag experiencing bullet blow up at 20 yards with a 162gr ELDM. But being a solid, you needn't worry about that. What you may experience is called torque. The spin of the bullet traveling down the barrel has an equal opposite reaction. Hence trying to twist the gun while shooting. Not sure how severe it's gonna be with an 85gr bullet, but a possability. With that twist rate, you would probably be better off with a heavier bullet. Seems awfully fast for a 243. From what i could find, Ruger #1 in 243 listed as 1:10 from the factory.
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January 28, 2020, 08:01 AM | #3 |
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This is what the website is showing. I thought it seemed really fast also.
https://ruger.com/products/no1/specSheets/21300.html |
January 28, 2020, 08:25 AM | #4 |
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A 1:10 twist used to be standard, but lots of people wanting to shoot high BC bullets now so manufacturers are responding. I'm betting you'll be fine.
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January 28, 2020, 09:39 AM | #5 |
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I shoot 75s from my 1:7.7 twist without any issues. That is as light as I have shot out of that barrel.
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January 28, 2020, 11:46 AM | #6 |
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Andy1,
From an accuracy standpoint, there are four issues with too much spin: 1.) A bullet with any tilt in the bore that offsets its center of mass (CM) from the bore line will have that CM eccentrically orbit the bore line traveling down the barrel. When that eccentrically spinning CM clears the muzzle, it is like letting go of a weight spinning around on a string, throwing the bullet tangent to the side of the bore closest to the CM when it exists. That throw imposes lateral drift away from the intended trajectory path that stays with the bullet all the way to the target (because it is too slow for drag to slow it down appreciably during the time of flight of the bullet). The faster the spin, the higher that drift velocity is, so the more it opens the group by displacing point of impact. Short bearing surface bullets tilt in the bore more easily than long bearing surface bullets, making them more vulnerable to this phenomenon, and therefore more sensitive to excess spin.If you are using solids with no soft lead core to expand, you don't have to worry about 3.) or 4.). Manufacturing by bullet specialty companies has become more precise over time so the mass asymmetry issue in 2.) is a smaller problem than it was thirty years ago, especially with match bullets. You can still get Service Rifle match accuracy out of 168-grain MatchKings, for example, even with gyroscopic stability numbers between 2 and 3. Most surplus military bullets and some cheap brands are not going to do well at high spin rates, but they won't be great even at an optimal 1.5, anyway. The only thing you want to watch out for with your solids is because of 1.), a bullet being spun too fast will benefit from taking extra care to load it straight. That means minimizing cartridge runout (search for any of the several existing threads on the board that addresses this issue). Investing in a runout gauge will let you segregate the most accurate commercial rounds out of a box. You can even bend them straight by drilling a bullet-size hole in a piece of plastic (like a cutting board) or hardwood and putting the bullet in and pushing the case to the side until the gauge tells you the runout is within a thousandth of an inch or so.
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January 28, 2020, 02:02 PM | #7 |
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My .243, not a Ruger No.1, is 1 in 9.125". That'd the standard before the 1 in 10. It likes heavy bullets. Most commercial .243's, even Varmint rifles, are rifled for deer weight bullets, 85 grains and up vs varmint bullets.
The part that's most important is to use the right bullet for the game. As in no light varmint bullets(most of those under 85 grains) for deer sized game. And there ain't nothing like varmint hunting with your deer load as practice for deer season. The 1 in 7.7 is a Talo Distributor Special. A TSX is a solid copper bullet. Don't think that matters though. There are custom barrels, like Lilja's, that start at 1 in 7. Shilen says their 1 in 7 or 8 barrels are for 100 grain plus bullets. 1 in 10 for up to 95 grains. Twist calculators don't always tell you anything that's accurate.
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January 28, 2020, 02:30 PM | #8 |
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I wonder about the practical effects in a hunting rifle, especially a No 1 which can be tricky anyhow.
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January 28, 2020, 02:47 PM | #9 |
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I have 243 and 243AI and I do reload.
Your not reload, going to shoot Buffalo Bore 85 grain TSX ammo. I would give them a call see what they have to say. I think Buds is sell new standard #1 243.
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January 28, 2020, 07:00 PM | #10 | |
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Quote:
I have 55 grain varmint bullets that run at 3700 fps out of my 1:7, never popped a single one. Sometimes theory is just a lot of words. |
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