.257 Bob vs. .270 Win

[StarMetal]

Well, I was hoping the 257 Roberts would win!

I've never shot a deer with a 25 so I can't say about adequacy but I tend to agree with it being a tad on the small side.

On stabilizing heavy boolits, it would depend a lot on the design of the boolit. A RN smooth sided boolit of 120gr would be no longer than a 100gr flat base spitzer J-word. A lube groove GC design would be quite long at 120gr.

I shall be testing mine in a day or two!

I'd be interested to know why a particular boolit only stabilizes above 2500fps? It's not as simple as just RPM. The required RPM is proportional to the velocity, meaning that in theory a given bullet will be stable at all velocities as long as it stays away from the transonic zone. What could be going on?

303guy, what is required to stabilize a longer bullet over a shorter one is more spin right? Wouldn't you say there are two ways to provide more spin, one being a faster rifling twist and the other increasing the velocity of the bullet?

Joe

[303Guy]

StarMetal

According to the twist rate charts, only twist rate is a factor. That being because the faster a boolit/bullet is driven the more stabilization it actually needs. However, at longer ranges, as the projectile slows down, the stability factor would increase.

But at the critical spin rate, i.e. marginal, I have found that with a certain bullet, stability was only possible at full tilt. Less than that and semi- sideways hits at 15yds! (Accuracy at long range wasn't worthwhile)

Then there is the complication of muzzle blast. How else can one explain a 1 in 16 twist hornet stabilizing a 60gr spire point J-word? And that J-word stays accurate over long ranges!

I have speculated that at higher velocities, the boolit might be somewhat escaping the worst of the muzzle blast effects in some cases. Change to a slower powder for the same velocity and maybe that stability will be lost again?

I bet someone has done tests on this! Some interesting test have been done that we just happen to find out about, sometimes by folks on this forum!

Oh, not necessarily relevent on the range but with my 'test tube' testing with long boolits, I have been surprised at how a boolit with or without an upset nose (velocity dependant) will stay nose forward all the way until stopped. Very slow boolits penetrate the best of course - which makes it harder to retrieve.

(Even the 60gr hornet J-word stays nose first with beautiful expansion!)