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Discussion in 'General Rifle Discussion' started by hoghappy101, Oct 3, 2012.
Whats the shooting difference between a 1in 7 or a 1in 9 twist barrel.
One complete revolution of the bullet in 7 inches of forward travel versus one complete revolution in 9 inches of forward travel.
Did you mean specifically as in which grain bullet are they best suited for? Or in terms of accuracy?
The 1 in X number is just how long "X" in inches it takes the bullet to make a 360 revoluation inside the barrel. 1:12? 12 inches.
Dillinger is correct. If you would like to look into it further. Go to the above Search Box and type in Barrel Twist and hit GO.
Then scan down the topics and you will see a section titled "Understanding Barrel Twists" Maybe that will also help.
2" is all.
Thanks ,thats a big help.l guess what l was really going after was wondering which one would be the better shooter at say 100 yds.or would either be better ?
What grain round? What "bullet" are you shooting?
What ammo are you going to buy and shoot for 100 yard accuracy?
Different grains for different twists...
Not really planning on shooting any certain ammo or grain . The question was really to settle in my my if the barrels would shoot different. Besides just a bullet spinning more or less.
If you don't match up the bullet with your rifling twist rate then you can get bad performance. Over stabilizing a bullet with a faster twist rate doesn't cause many problems. But, not stabilizing the bullet can cause bullets to wobble or flip and tumble in flight ruining consistent flight paths for any kind of repeatable accuracy.
So I wouldn't shoot bullets over 62 grains out of a 1:12 barrel or anything much heavier than 70 gr out if a 1:9 twist and expect lo g range accuracy when dei g with .223 caliber projectiles.
As the folks have said- the rate of twist has to be correct for the weight and length of the bullet.
I shoot a 400 grain 50 caliber muzzleloader with a twist of about 1 in 42 inches. If the barrel had the rate of twist of an AR15, the big soft HEAVY bullet would skid over the rifling instead of being spun by it.
Likewise, a bullet that needs a fast rate of twist for stability (1 in 7 inches) if fired from a 1 in 42 would probably be traveling sideways or backwards.
One other consideration is the bullet construction. I have seen 52 gr HP "Match" bullets literally disintegrate upon leaving a 1/7 barrel. The rate is way too fast for the thin jacket to hold up.
I have rifles in 1/7 and 1/9 They both shoot very well with bullets from 55 - 62gr
Not to answer a question with a question--- but I'm gonna anyhow.
What rifle are you shooting and in what caliber? Will you be hunting with it? Those two answers combined with the 100 yards range you mentioned will give us a better foundation on which to build our advice on.
most of the "twist" rates you will "hear" about, deal with the .223/5.56 due to it's popularity.
1:7 (or a faster 1:6.5) twist bein fast rate of twist - good for heavier (longer) projectiles that need to "spin up" faster in order to stabilize faster in flight to target.
1:9 twist bein middle ranged twist - good all around twist rate for most semi-light to semi-heavy projectiles
1:12 twist bein a slow rate of twist - good for semi-light to light projectiles
there is data that shows too fast a rate of twist will "over-rotate" a lighter projectile, and cause it to "spin" apart........copper from lead.
Dont mean to hyjack this post but for a 1/7 twist stanferd length, 5.56 target practice a heavy liad is the best? Something around 70 grains or so. And for linger distances do i just look for a heavier load
Your post is a little confusing to read but I will try to answer. If you are shooting an AR15 in 5.56 at 100 yards, the typical bullet weight we find most commonly is 55 grains. That is not heavy by any means, but I think that 70 grains would be a bit fat for that range- meaning the bullet weight is more suited to a longer range. I also have a Savage Model 12 in .223 that has a 1:9 twist, it shoots 45 grain Hornady V-Max (handloaded with H335 powder) with great accurac at 100 yards. If I were shooting longer range as I will do one day I will be using a heavier bullet and adjusting my powder charge accordingly.
By "heavier load" are you handloading your own, or are you just talking bullet weight in a factory load? If handloading you need to lower your powder charge as you increase bullet weight. If you don't then you will over-pressure and can risk blowing your gun up.
Not into reloading yet, got the reloader but im waiting till i understand that. I understand heaver load less powder charge but i was refering to factory loads. Im just learning the diffrent types if ammo. My trainer reloads my ammo and i think he uses 55 grain soft tips. Ive only shot 50 yrds as i was sighting in my rifle. Just got it so the aimpoint needs to be tweaked
Barrel twist is not about weight of the bullet it is about length. It just so happens that when you make a bullet at a given diameter longer it gets heavier.
If you had a 80gr 224 and a 60gr 224 that were the same length ogive and bearing surface you would need the same twist barrel for both.
It certainly can be confusing. Some 50 cal rifles have the same twist as a smaller .22LR. I think it does have an impact on the performance by weight of the bullet, but you need to consider the length of the barrel. A 16'' barrel with a 1x16 twist will have one complete revolution of the bullet before it leaves the barrel. A 16'' barrel with a 1x9 would rotate the bullet completely more than once before it leaves the barrel. As the barrel gets shorter, you'd need a much faster twist to get any stabilization of the bullet. It's too scientific for me to comprehend, I'll just leave it to engineers. Since I'm mostly a pest hunter (birds, mice, rats), I just stick to light bullets (30 to 40 grain) and fast twists, because that's what I was told to do. It still confuses the crap out of me, though.
Edited: I got that backwards, a 1x9 will rotate the bullet more than once, so for a shorter barrel (carbine or lower) it seems like that would be the better twist.
OK, lets start by getting the correct terminology. Best that you get a reloading manual and read it (the sooner the better- even if you don't plan on reloading any time soon, the information will help to make you a better student and to understand your cartridges).
A "Load" is a particular recipe, the projectile, or bullet, is a component of the load. Your description of the bullet your trainer is using "55 grain soft tips" is too vague, it would be more helpful to know more, such as "Hornady 55 gr. JSP (Jacketed Soft Point) and the Hornady number for that projectile (Hornady uses 4 or 5 digits I think for the part numbers).
Get yourself a manual. it will help us all out and help you to understand shooting better, making you a better shooter. Also read the sticky referenced earlier on barrel twist.
I think I understand what you are trying to say but it isn't accurate, there is no requirement for the bullet to make one full rotation inside the barrel in order to be considered stablized, nor will it be "more stable" with a longer time to follow the twist, the proper rotation can be established quickly and continues along that rotation after it leaves the barrel.
Consider a pistol barrel. If, as you said, a shorter barrel needs a faster twist then your logic says a 4" barrel would need something faster than 1:4 when in fact pistol twists are much slower than rifle (as slow as 1:20 or higher). They can still stabilize the bullet because it has a shorter length and easier to stabilize than a longer pointed bullet. Think baseball vs football ... which needs some spin to be thrown accurately?
It is the bullet length/diameter/shape (and associated increase/decrease in weight) that drives barrel twist rates.
There are several twist rate calculators and none of the them consider barrel length. Barrel length will impact velocity and that is used to calculation the actual RPM of the bullet but that is secondary.