.30-06 vs. .308 Win.: Long Range Choice?

I thought this thread was supposed to be about 308 vs 30-06

krochus, this is an interesting thread (to me anyway) and it'd be a pity to have to start a new one so if the OP, namely Bart B., is ok with the direction that the thread has taken then maybe it's ok with the moderators. By the way, you make many excellent points so if you want to get this thread back on track then I'm all ears ... and there's no sarcasm intended.


Bart, I find two comments particularly interesting ..

We all got data that faster bullets struck higher than slower ones by an amount virtually equal to what ballistic software predicted.

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This has always been my experience and yet I've read numerous posts here stating that higher velocity loads hit lower on the target. I suspect there are many variables involved and either may be possible.

But the barrel probably doesn't start flexing/whipping before the bullet starts down the barrel.

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I've read on Varmint Al's web site and the OCW web site that "The velocity of sound in 416 stainless steel is 14,900 fps and a stress wave has time to propagate up and back the full length of the barrel 4 or more times after ignition and while the bullet is traveling within the barrel. The muzzle end of the barrel has ample time to "know" that something is going on at the breach end before the bullet exits."

This vibration of the barrel must surely have an affect on accuracy and this it the crux of the OCW method which I follow for my load development. I'm not married to the method but so far it's worked well for me and I have empirical data that there's method to the madness.

Another interesting thing I just read on Al's page is that a fluted 22" stainless barrel with the SAME exterior/interior dimensions as a non fluted barrel deflects LESS!! He shows a 0.0016" deflection for the non-fluted barrel and a 0.0013" deflection for the fluted barrel. I'm going to run my own model to see if I get similar results.

Zak, thanks and I hope the results will help people who are trying to decide on a barrel contour and length. I don't think it's intuitive that a 26" barrel can deflect as much as 0.010" under its own weight. Those Palma barrels are typically 30" long so the deflection would be even greater.

That 2700fps figure...

Is the muzzle velocity. The bullet ain't doing that till somewhere near the muzzle, so I'd definitely figure in some extra acceleration time into the mix.

Faster bullets may also hit higher due to less flight time/less drop.

You want to really play with "barrel time", shoot a BPCR .45-70 with 32-36" barrel. At 1200fps, if you're not following through on your shots, you will indeed learn something.

I find the .308 marginal for 1000 yard stuff, without resorting to tricks like very hot (bolt gun) loads, F-T/R class loads, or Palma-length barrels to keep the velocities high. I keep my M14NM set up for 800 yards, any hotter and I'd batter the action - not good if I don't have a Camp Perry AMU trailer with spares ready to go. I'd go for something like USSR's .30-06 F-Class gun, if I didn't already run a 6.5-06 for the same game.

BTW, you focused on the THR links in Krochus' sig line. Those are in all of his posts, they weren't brought into this thread for the sake of .308 vs. .30-06. They're basically the same as my Pooh quote.

Bart B. said:

krochus comments:Well, yes, it is. Because your put stuff in this thread about your 7.62x39 adventures and exploits, I knew it would be alright to put stuff in about some of my other advertures and exploits not related to 308's and 30-06's.

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It's my sig line it ends up in all my posts unless I click a box to do otherwise

Leaving a round in a hot barrel longer than about 30 seconds often heats its powder up enough to shoot the bullet out enough faster that it will strike higher than normal.

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In 1000 yard F Class competition, if we are faced with changing wind conditions during a relay, we will either wait to chamber our next cartridge or extract an already chambered cartridge if it's been in the chamber for any length of time.

Don't have access to a 800 yard range, but...



Don

Nice shootin' Don.