TWIST vs. VELOCITY vs. bullet weight

[CZ]

I HAVE A QUESTION??????
IS THERE ANY RELATION BETWEEN TWIST-VELOCITY- BULLET WEIGHT.-
Would be true that if Ipush a bullet faster, the more RPM and less twist would
I need???
Anyone who can explain this relation????
for heavy weights in normal twist, example.- .243Win T10 and using Sierras 107gr.-
the faster I get them out better stabilization????

 

[baltz526]

If you look at the 223 vs the 22-250 shooting the same bullet. For example a 50gr sierra blitz. in a 223 with a 1-12" one reloading book says at 3069fps it has very good accuracy. In the 22-250 with 1-14" it has very good accuracy at 3230fps. Sugesting it takes a higher velocity in a 1-14" twist to get the best accuracy over a 1-12" Both cases will push the bullets faster in the same barrel, This also leads me to think that velocity/twist/accuracy are tied together. The longer the bullet is, the faster you need to spin it. A 55gr nosler ballistic tip i have measures .805" at 3500fps in a 22-250 1-14" it shoots fine/fair shoot it out of a short barrel 223 1-14" and i doubt it makes round holes in a target or will be accurate. UNLESS you get the velocity up in a longer barrel 223. Then what will that bullet do at 500yds even if it shoots 1" 100yrd groups it might hit your target sideways in a 4' group.

 

[chet]

we all know that "spin" is what stabilizes a bullet.

is it Rotations per (unit of time)?

or is it Rotations per (unit of distance)?

or are these two the same thing?

I'm thinking unit of time..... but I'm wrong at least half a dozen times a day :mrgreen:

 

[Antelope_Sniper]

It's RPM that stabalized a bullet.
There are two ways to increase RPM:
Increase the barrel twist.
Increase the velocity.

In general, if you are dealing with a bullet that is marginally stable at the velocity for a given round, it is best to drop down a bullet weight. Shorter bullets take less RPM, and the increased velocity will provide more RPM as well. IMO it might be a little difficult to start with an unstable bullet, then try to work up the load to a point where it stabalized, while at the same time worrying about pressure levels, and at what distance down range, and what temperature/air pressure the barely stable projectile will destabalize. Much easeir to drop down a weight and load the gun for what it was designed for. If you really want to shoot the Loooong bullets you can always rebarrel.

In general, the factory rifling in the .243's is designed to stablize cup and core bullets up to 100gr in mass. The old 6mm's with their slower rifling were designed for 90-95gr class bullets. In an off the shelf rifle, the 107's are probably pushing it, but in the end it's your rifle that will make that decision for you. The 95br BT's have a reputation for being a very accurate, bang flop deer slayer. Why not give those a try?

 

[CAhunter]

CZ All good info and Antelope is right on the money. Also note that many factory 243win have a 1-9.25 rate of twist. I am having no problem pushing the 105VLD in my 243AI either. As stated your rifle will tell you what it likes. If you are building one I would go with a 1-9 twist for the 107.