270 win vs 30-06 ballistic question - Page 2

MTMilitiaman · June 19, 2009, 11:14 PM

External ballistics is all about BC and velocity. That's it, at least for the factors you can control. Wind velocity, air density, the pull of gravity, and other atmospheric factors are well beyond your control. You aren't guaranteed the ability to affect the range either. And mass, caliber, and other such things simply don't matter.

Any two bullets with the same BC and velocity will have identical external trajectories when shot in the same atmospheric conditions regardless of their masses or calibers.

We are talking about the same case here, so capacity is similar, taking into account affects of differing bullet lengths on capacity. This means that with similar bullet weights, the velocity of either is going to be close enough to be a non-issue. That leaves BC. And as a general rule, shorter bullets generally are less streamlined than longer bullets, and therefore have a lower BC. So we see that as lighter bullets are generally shorter than heavier bullets of the same caliber and design, and that as given two bullets of the same style and mass, the one of smaller caliber is usually longer, with presumably a higher BC, mass's only effect of interest concerning external trajectory is the effect it has on a bullet's BC.

So if we are shooting a 150 gr bullet, the .270 is probably going to have the advantage as it is likely to have a higher BC than a 150 gr bullet of the same style and construction for the .30-06. Any slight velocity advantage the 06 might have with the 150 gr bullet is more than likely going to disappear, even within normal hunting ranges, due to the advantage in aerodynamic efficiency the .277 caliber projectile has.

When we get into different bullet weights and/or styles, things get a little more complicated, but still amount to BC and velocity. This is because these two factors determine Time Of Flight (TOF), and this is directly proportional to the amount of drop experienced due to gravity and the amount of drift experienced due to wind. The less time either of these factors (gravity and wind) have to act on a bullet, the less effect they will have on the bullet. If the range is set, then the bullet with the highest average velocity will experience less drop and less drift.

The lighter .270 loads are likely to be flatter than the heavier .30-06 loads, because they have a significant velocity advantage that is likely to equate to a lower TOF, and consequently, a flatter trajectory. So a .277 cal 130 gr SPBT @ 3100 fps is probably going to be significantly flatter than a .308 cal 180 gr SPBT @ 2700 fps, at least initially. If the .30 caliber projectile has a higher BC, then it is losing velocity slower than the .270 projectile. So the difference in velocity closes as the range increases. It then becomes simply a matter of whether there is enough range for the .30 caliber bullet to catch up to the .270 caliber bullet, and eventually eclipse it. At that point, it will have the lower TOF, and therefore the flatter trajectory, even though it is heavier, has more frontal area, and started out ~400 fps slower. It just so happens, however, that this is likely to require a lot more range to accomplish than ever experienced under normal hunting conditions.

So within normal hunting conditions, the .270 is likely to shoot flatter in most cases. However, given enough range, it is possible, depending on individual BC-match ups, for a .30 caliber projectile to shoot flatter than a .270 caliber projectile with an inferior BC, even if the .270 has the highest initial velocity and the lighter bullet.

This consequently is why most extreme long range target rounds are very heavy for caliber and streamlined. The BC advantage of the heavier 210+ gr .30 cal and 300 gr .338 cal HPBT Match bullets easily outperforms the higher muzzle velocities of the lighter 168 to 190 gr and 210 to 250 gr offerings for either caliber, respectively.

5RWill · June 21, 2009, 02:10 PM

Quote:

The ballistic coefficient of 308 bullet #2120 168 HPBT is 0.462.

The BC for lapua's 155gr scenar is .508

handlerer · June 21, 2009, 04:00 PM

I have to comment that some shooters get very confused on this issue. 130gr .270vs 130 gr .308 is not a valid criterion to base a comparison upon. The narrower bullet of a given weight has a superior sectional density. 130gr 270 is good for a medium sized deer, not suitable for 30-06 on deer. A 250gr 30 cal has a sectional density that no 27 cal can approach. Ballistics coefficients are quite complicated and not constant. The form factors are based an formulas developed by Krupp, before WWI, for artillery applications. The application of the superiority of the desired property is what I consider valid.
so, fer instance, 27 cal gives superior penetration at any practical hunting range with a 130gr. A 30-06 can hit targets at 1500 yds with best 240-250gf VLD bullets, the trajectories are different, but trajectory is a variable than can be calculated. Unless you're a competitive long range target shooter, or an obsessed individual, none of this is important. Both will do what most of us want them to do.

5whiskey · June 21, 2009, 06:54 PM

I haven't read EVERY reply, but I will put my .02 in.

I shoot .270 primarily. Why? Because I like being original. I will say that if it's a straight up .270 vs. .30-06 question, .30-06 is WAY more versitile. Hands down.

.270 fills a few niche roles much better than .30-06 just because of sectional density and Ballistic Coefficient of the round. The main advantage of the .270 is flatter trajectory... especially with the 130 grain round. .270 will shoot a 130 grain bullet near as flat as the 7 mag will push a 150 grain bullet (if not more so).

I punch paper at long ranges for sport and relaxation. Something about controlling a projectile well enough to hit a 9" pie plate @ 600 yards does it for me. .270 is an excellent choice for what I use it for, and it's well capable of harvesting any game in North America. The .30-06 CAN NOT be beat for versatility though.

Quote:

Unless you're a competitive long range target shooter, or an obsessed individual, none of this is important. Both will do what most of us want them to do.

what he said

knight0334 · June 22, 2009, 10:14 AM

I dont think a critter is gonna be able to tell the difference between a 270 or 30-06 when its hit. Ballistics shows them both to be similar performer, not worth debating a handful of inches more/less drop at ranges.

Some folks have magnumitis or icantshootanarcism, so they inherently have to use, or suggest to others, guns/cartridges that are more powerful or flatter shooting(depending on the mental defect).

---

4-6 inches more of drop? learn to adjust the elevation or how to hold-over.

not powerful enough? use proper bullets and learn to hit the critter in the right place.

June 19, 2009, 11:14 PM	#26
MTMilitiaman Senior Member Join Date: October 14, 2004 Location: NW Montana Posts: 1,875	External ballistics is all about BC and velocity. That's it, at least for the factors you can control. Wind velocity, air density, the pull of gravity, and other atmospheric factors are well beyond your control. You aren't guaranteed the ability to affect the range either. And mass, caliber, and other such things simply don't matter. Any two bullets with the same BC and velocity will have identical external trajectories when shot in the same atmospheric conditions regardless of their masses or calibers. We are talking about the same case here, so capacity is similar, taking into account affects of differing bullet lengths on capacity. This means that with similar bullet weights, the velocity of either is going to be close enough to be a non-issue. That leaves BC. And as a general rule, shorter bullets generally are less streamlined than longer bullets, and therefore have a lower BC. So we see that as lighter bullets are generally shorter than heavier bullets of the same caliber and design, and that as given two bullets of the same style and mass, the one of smaller caliber is usually longer, with presumably a higher BC, mass's only effect of interest concerning external trajectory is the effect it has on a bullet's BC. So if we are shooting a 150 gr bullet, the .270 is probably going to have the advantage as it is likely to have a higher BC than a 150 gr bullet of the same style and construction for the .30-06. Any slight velocity advantage the 06 might have with the 150 gr bullet is more than likely going to disappear, even within normal hunting ranges, due to the advantage in aerodynamic efficiency the .277 caliber projectile has. When we get into different bullet weights and/or styles, things get a little more complicated, but still amount to BC and velocity. This is because these two factors determine Time Of Flight (TOF), and this is directly proportional to the amount of drop experienced due to gravity and the amount of drift experienced due to wind. The less time either of these factors (gravity and wind) have to act on a bullet, the less effect they will have on the bullet. If the range is set, then the bullet with the highest average velocity will experience less drop and less drift. The lighter .270 loads are likely to be flatter than the heavier .30-06 loads, because they have a significant velocity advantage that is likely to equate to a lower TOF, and consequently, a flatter trajectory. So a .277 cal 130 gr SPBT @ 3100 fps is probably going to be significantly flatter than a .308 cal 180 gr SPBT @ 2700 fps, at least initially. If the .30 caliber projectile has a higher BC, then it is losing velocity slower than the .270 projectile. So the difference in velocity closes as the range increases. It then becomes simply a matter of whether there is enough range for the .30 caliber bullet to catch up to the .270 caliber bullet, and eventually eclipse it. At that point, it will have the lower TOF, and therefore the flatter trajectory, even though it is heavier, has more frontal area, and started out ~400 fps slower. It just so happens, however, that this is likely to require a lot more range to accomplish than ever experienced under normal hunting conditions. So within normal hunting conditions, the .270 is likely to shoot flatter in most cases. However, given enough range, it is possible, depending on individual BC-match ups, for a .30 caliber projectile to shoot flatter than a .270 caliber projectile with an inferior BC, even if the .270 has the highest initial velocity and the lighter bullet. This consequently is why most extreme long range target rounds are very heavy for caliber and streamlined. The BC advantage of the heavier 210+ gr .30 cal and 300 gr .338 cal HPBT Match bullets easily outperforms the higher muzzle velocities of the lighter 168 to 190 gr and 210 to 250 gr offerings for either caliber, respectively. __________________ "...nothing says 'I WILL shoot every last one of you before you have time to reconsider your poor choices in life' like an AK." ~Dave R. Last edited by MTMilitiaman; June 19, 2009 at 11:20 PM.

June 21, 2009, 04:00 PM	#28
handlerer Senior Member Join Date: October 5, 2007 Location: Billings,MT Posts: 277	I have to comment that some shooters get very confused on this issue. 130gr .270vs 130 gr .308 is not a valid criterion to base a comparison upon. The narrower bullet of a given weight has a superior sectional density. 130gr 270 is good for a medium sized deer, not suitable for 30-06 on deer. A 250gr 30 cal has a sectional density that no 27 cal can approach. Ballistics coefficients are quite complicated and not constant. The form factors are based an formulas developed by Krupp, before WWI, for artillery applications. The application of the superiority of the desired property is what I consider valid. so, fer instance, 27 cal gives superior penetration at any practical hunting range with a 130gr. A 30-06 can hit targets at 1500 yds with best 240-250gf VLD bullets, the trajectories are different, but trajectory is a variable than can be calculated. Unless you're a competitive long range target shooter, or an obsessed individual, none of this is important. Both will do what most of us want them to do.

June 22, 2009, 10:14 AM	#30
knight0334 Senior Member Join Date: January 1, 2006 Location: Brookville, PA Posts: 442	I dont think a critter is gonna be able to tell the difference between a 270 or 30-06 when its hit. Ballistics shows them both to be similar performer, not worth debating a handful of inches more/less drop at ranges. Some folks have magnumitis or icantshootanarcism, so they inherently have to use, or suggest to others, guns/cartridges that are more powerful or flatter shooting(depending on the mental defect). --- 4-6 inches more of drop? learn to adjust the elevation or how to hold-over. not powerful enough? use proper bullets and learn to hit the critter in the right place.