270 WIN Erratic ES, Great Accuracy???

[montana_native]

I have a Remington 78 Sportsman in 270 Win that I call Frankenstein. It's an old beater *** elk gun that's been stepped on by a horse, dropped off of a small cliff and run over by a four-wheeler but still keeps shooting great...which is why I won't bring another gun along when we horse it in to camp. They just get beat up too bad.

I developed a load for it a few years ago with H4831sc, 140 Accubonds and Federal 210's. It consistently shoots around 0.75" at 100 which I thought to be pretty good for that gun.

Last week I decided to chrono it for the first time and the velocity ranged from 2798-2864 and it shot a group just over 0.500" at 100 yards for five shots. At what range will this velocity variation become an issue? Is it an issue at all? What are some potential causes of this? I don't forsee ever having to make a shot over 4-500 yards where we hunt but just in case...

I'm more curious than anything else. I've never had an issue shooting anything with it...yet. Knock on wood.

Thanks.

 

[royinidaho]

I could recite the 20 year episode that followed my purchase of the first Oehler chrono with the paper screens and discovering that my highly successful game killer 270 Win was pushing the 130 Sierra at only 2900 fps. After thumping may mulies and a moose how could it kill anything at only 2900 fps MV?

But I won't.

I wouldn't mess with success. Other wise you'll end up catching Tinkeritus and you life will be come a big expensive mess.....

But......... you could consider stuffing some RL-22 in there ahead of a CCI-200 primer.

 

[jmason]

Well you can shoot your load at long range and see how it prints. I don't shoot the AB's in my 270 but do shoot the 140 BTs at around 2950 in 26" barrel. I have a good ES/SD there. I believe about 57-57.7 gr of 4831sc will get you there. People are getting higher velocities w/ rl 22 as Roy pointed out, but I don't suffer from tinkeritis as badly as Roy does. I really don't think anyone has it as bad as him. He has the worlds worst, and most documented case I believe.

 

[bigngreen]

Run it through the JBM ballistics online calculator, run one at your low velocity and one at you high velocity and compare them side by side then you can see were things start changing.

 

[Sandwarrior]

You're just not going to see a big spread in groups until velocity and BC make a huge difference. That's beyond 300 yds.

A lot of people think it's velocity that gives the harmonic node of accuracy down the barrel. To a lesser degree it is. But the real harmonic hero/culprit is the vibration caused by the powder charge. Say you worked up a load of 54.5 gr. of H4831sc, which just happened to be in a node that ran from 54-55.5 (gr. of powder) in your rifle. There wouldn't be anything throwing that bullet off at all. The drop of 50-70 fps isn't hardly noticeable @ 100 and won't make but 2" difference @ 300. Say for instance that the accuracy node you hit happened to "spring" the bullet out of the end of the barrel (as opposed to throwing it left or right). At that point velocity won't make a difference until even further out.

-Hope that helps