Just curious about why the 300 Win Mag has such a slow twist rate? Most barrels/guns I’m seeing have it as a 1-10 twist, but I’ve always read you want a faster twist rate with heavier bullets to stabilize them. Since it is regularly shooting 150-220 grain bullets, why is it not made with a faster twist barrel?
As I understand it, it’s a little more complicated. From what I have learned, it is actually more the length of the bullet that drives the need for faster twist rates. Usually that means heavier bullets, because for a given caliber, a heavier bullet must be longer. I think, for a smaller bullet diameter like 6.5, 6.8, 7mm that translates to quite long bullets in the heavier weights. As I understand, the 1:10 twist in the larger .308 cal will effectively stabilize a wide range of bullet weights from 130 up to 220 grains.
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Had to do with SAAMI specs and what large companies are willing to put out there. With custom rifles and hand loads a person is able to make adjustments out of SAAMI spec. It’s why there’s potential for a custom 7 RM to outperform a 7 PRC with additional free bore and seating the bullet out further.
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As mentioned above, it’s more about length rather than weight. However for some strange reason no one seems to talk about bullet lengths. The information is out there but you have to look a little bit harder for it. And since there is a direct relationship between length and weight, people just talk about the weight.
Also keep in mind that when the 300 Win Mag was developed, speed was the name of the game. Everyone wanted to create something that went faster and faster. High ballistics coefficients, Etc wasn’t really the big thing back then. Also back then it was almost exclusively cup and core bullet designs. Over-twist one of those going quite fast and you’re liable to tear the bullet up.
The guy on the reloading Weatherby YouTube channel did some testing with long high BC bullets in his 300 Weatherby Magnum with a slow twist rate and had good results. However, I believe his testing was just shooting for groups, he wasn’t doing any kind of fancy in Flight analysis or anything.
Also, Berger has a stability calculator on their website. You can enter the data for a particular round, bullet with twist rate, speed, length, Etc and see how well it will be stabilized.
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there is a hornady podcast 085 that covers twist rate with senior ballistician Jayden Quillen. Covers it better than I can of course.
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