velocity vs barrel leng vs twist??

[axis223]

I'm shooting a savage axis 223 heavy barrel 22inch barrel 1-9 twist and just started reloading.

I really want to match factory 50gr or 55gr v max ammo speeds but don't own a chronograph. the hornady book shows a 1-12 twist barrel I think from a rem 700.

Does a 22 inch barrel 1-9 twist produce more velocity than a 1-12?

[MattB]

All guns will shoot different velocities. The only way to truly know is to get a chrony. I have seen 20" barrels shoot close to published loads for 24" barrels, I have seen 26" barrels shoot 200fps slower than tested 24" published loads. It is weird to me but the data was consistent with many shots. Once you get a chrony you can see the velocity spreads and really know what your gun shoots. It is frustrating that you cannot just copy a load and get x result in velocity or accuracy but that is the fun in reloading.

My savage 12bvss .223 with 1-9 twist shot 3197 and 3200 with 55gr sierra's and 26.1gr of varget. The book says ~3270 with a 24" barrel but I was 70fps slower with 2" longer barrel.

[T. O'Heir]

"...1-9 twist produce more velocity than a 1-12..." Yep. Faster twist'll do that. Barrel length matters a bit too.
"...want to match factory 50gr or 55gr v max ammo speeds..." Forget factory anything. You cannot get the powders used by the assorted manufacturers anyway. And the whole point of reloading is to tailor the ammo for your specific rifle.
In any case, accuracy is far more important than velocity.

[axis223]

want a bit of velocity for 300yard woodchuck and coyote shots. tough critters.

[603Country]

You might try the 40 gr Nosler Ballistic Tip. I shoot it over H335. In my experience with using it on a number of coyotes, it knocks them flat. I assume that's because the bullet dumps all its energy into the coyote and not into the tree behind the coyote. First coyote I shot with it was only because that was the gun and load in my hands. I hoped it would kill him, as he was pursuing the family cat. The cat was hauling tail, the coyote was loping, and the wife was screaming in my ear to not miss. It was a high pressure situation, as you can guess. I let fly with the bullet and the coyote was knocked flat so fast that I wondered where he went. Wife screamed "where'd he go?"

Second coyote, same thing. Then a few more. If I put the bullet into the chest, they go down hard. Such a little bullet. Works good, and you can push it to near 3800 fps. Probably would drift a bit in the wind though.

[ms6852]

According to the book "Modern Advancement in Long Range Shooting", there is a correlation of muzzle velocity at a rate of 1.33 fps per inch of rifle twist. So to answer your question NO. The 1.33 fps is approximate, so going from a 1:9 rifle twist to a 1:12 twist would give you a gain of 3.99 in velocity, and vice versa, going from a 1:12 twist to a 1:9 twist would give you a loss of 3.99 fps in velocity.

I'm on an IPad and do not know how to post links but if you go to the accurate shooter forum they have an article on your topic.

[Mobuck]

While you may "potentially" be able to use SLIGHTLY heavier powder charges with a slower twist rate, the increase may still fall within the standard variation for the load used.

[SSA]

Does a 22 inch barrel 1-9 twist produce more velocity than a 1-12?

No.

[Unclenick]

In theory, Ms6852 has it right. A rotating bullet has angular kinetic energy (energy stored in the rotating mass). A faster rate of twist demands more energy be taken from the powder and put into rotation of the bullet. This not only uses powder energy, but it increases friction with the lands as it is done.

However, the above also assumes you are using a powder appropriate to the task. If the powder is a little on the slow side, that higher resistance can help it burn better, raising pressure and increasing the ballistic efficiency of the load (the % of stored energy in the powder that winds up converted to kinetic energy in the bullet).

Which situation do you have? The bottom line is, until you try a particular load in a particular gun, you won't know exactly what's going to happen. Due to variations in tolerances in the rifle and load components, you'll find you can't reliably predict the outcome. You have to measure. In most instances, something as small as a 1.33 fps/inch of difference in twist is less than normal shot-to-shot variation among your cartridges, so it fails to be a significant consideration in most practical ballistics. Kinetic energy of rotation is small compared to the translational kinetic energy (forward kinetic energy of the moving bullet) is much larger than the rotational energy.

For a 50 grain 0.224 bullet traveling 3200 fps and fired from a 9 inch twist barrel, I get 1137 ft-lbs of muzzle energy, and 3.01 ft-lbs of rotational energy or about a quarter of one percent of the total. If I change to a 12 inch twist, it drops to about 1.7 ft-lbs or 0.15% of the total. Converting to velocity, the 9 inch twist robs the MV of about 4.24 fps, and the 12" twist robs it of about 2.38 fps, a difference of about 1.85 fps.