I've seen lots of details about the twist of a rifle barrel. 1:7 1:9 1:11 What is that stuff?
Well I knew it was about how much twist the lands and groove in a barrel have. I guessed it was how many inches before one groove spun all the way around the interior diameter. So 1:7 is a tight spiral, spinning the bullet 360 degrees in 7 inches, and 1:20 is more liesurely. And I have known for a long long time that this bullet spin from a rifled barrel is what helps the round 'fly' straighter.
But I saw in some things I read that people care about how much their barrel has, and will change out a barrel to a twist ratio they prefer and they feel is superior. So I had to research to be sure this wasn't yet ANOTHER thing I needed to worry my little brain over.
Chuck Hawks was one of the first sites on the list when I googled 'rifle twist' and quickly told me all I need to know. Wikipedia wasn't shabby at enlightening me, neither.
From Mr. Hawks I learned that the smaller the ration, 1:7 say, and faster the spin, the more pressure builds up and the tougher a bullet jacket has to be. Pointy Spitzer bullets need faster twist. So do heavy bullets. Fast bullets don't need so much. And, most importantly, rifle makers have devoted a lot of Brain Juice to the subject to find the ideal twist rate and have been noodling this subject for longer than I ever will and I need never worry about it. Custom barrels that have deviated widely from the accepted consensus rate are best avoided, generally. Monkeying with it is asking for trouble, or it's for a VERY peculiar/specific-to-some-load someone wanted to fire, and THAT is asking for trouble on a rifle that I want to use.
When I become an Olympic quality rifle match Grand Champion type, THEN I might worry about twist rates for a rifle I need to win the 10,000 yard bullseye shoot. But then again I might not. Until then... Relax.
I should have known not to concern myself in reading Jeff Cooper's writings on details of his big-game hunting rifle Baby, and the development of the Scout rifle.
Chuck Hawks lists the common twist rates of various calibers here.
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3 comments:
I think it something worth keeping in mind. With many calibers you will only ever have the option of one twist rate. With others like .223 they come in a few different twist rates. If you want to shoot 5.56mm one twist if better, while if you are hunting with heavier .223 bullets another will be better. Last year there was a .223 rifle I was going to buy until I found out the twist rate was not going to suit the ammo I was planning on using with it.
I like shooting low velocity .22 long/nearly-shot velocity rounds and accuracy goes out the window (but its fun when you can only hear the click of the firing pin). Maybe when I have more $$$ than I need I will get a custom barrel with a custom twist rate to handle these bullets.
Well, there are some times when you want to know what your twist rate is, but you/they are right in that you can mostly ignore it.
Since bullets spinning themselves apart is really quite uncommon these days, the main instance that comes to my mind are when you want to use larger-than-normal bullets.
For instance, if you want to use your .308 for going bear or moose or elk hunting and want to use the 180-220 grain bullets on such a large beast, it will make a difference that your Browning 308 barrel has a 1:10 twist while the same bore size 30-06 barrel has a 1:12 twist. Yes, the manufacturers put a lot of time into figuring out which twist to use (as evidenced by Browning taking the time and money to make two different 30 caliber barrels for the same model guns) and in this case most of the people using the heavier bullets are generally going to be using the 30-06 instead of the 308.
The Aguila SSS (Sniper SubSonic) ammunition is basically a 22LR with a 60gr bullet. Many rifles won't stabilize this round well since they have twist rates that are designed for much lighter bullets. Technically, it's the fact that they are shorter, but the two terms are relatively interchangeable. If it doesn't stabilize, your accuracy can suffer tremendously.
Look at 44Magnum rifles. The Winchesters had a much much faster twist rate than the Marlins and many people experience considerably better accuracy with the Winchesters when using heavy bullets because of it.
OK, GunGeek, you hooked me.
I have a Marlin 1894C in .44 Magnum and haven't shot it farther than 100 yards yet. It does fine out to 100 yards, and with it's patridge sights I can shoot 4-6" groups.
I am going to upgrade the sights to an aperture rear and a Williams Firesight front, which should give me better definition and tighter groups.
I also reload, and so far, have reloaded only 240-gr, Cast Lead semi-wadcutter for practice, and I shoot factory Remington 240-gr to sight in for war loads. There is 185 and even 165-gr available. Would one of those be better for accuracy out to 200 yards?
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