quote:

And I doubt that the 6.8mm versus 7.0 mm bore difference means anything.

6.8 = 0.26771653543336
7.0 = 0.2755905511814

.277 = 7.035799999992402
.284 = 7.2135999999922085

Funny even the nomenclature is wrong! LOL.

FWIW, I have run:

M70 20" 7-08 = 2850/139 w/Varget and IMR4064
700 21" (2 rifles) = 2950/139-140 " "

700 24" 270 = 2850/150PT (IMR4350)

Not a thing I would do w/one that I would not attempt w/the other. I don't think ANY animal at same range/shot placement would notice or argue either

Good bullet thru vitals = death

quote:

Originally posted by 1894mk2:
At risk of revisiting an old chestnut .....Is a 21" 270 likely to produce any more velocity than a currently owned 20" 7-08 that manages 2,800fps with 140s?

Just happen to have been offered a bargain, after the initial desire to snap up a bargain a little voice is telling me I am only going to get a very slightly faster, much louder, much heavier rifle which in the cold light of day doesn't seem such a bargain.

1) How do you know your current 20" 7-08 gets 2,800 fps w/ the 140s?

2) Not enough ballistic different between 270 and 7-08 to warrant replacing one with the other.

3) If you don't reload, Might find the 270 ammo less expensive and more avaiable.

I have a Winchester Model 70 compact, and a BLR in 7mm-08, and both have 20 inch barrels. I shoot remington green box 140 grain in both, and both get about the same velocity. Which averages about 2750 fps. I once loaded some hornady 175 grain spire point behind the max load of H4350, and they averaged about 2475 fps which kind of surprised me.

1894

The curiosity is killing me. What was the rifle in question?

Best

JB

6.5BR, The nomenclature is correct.
The metric designation mostly are the diameter of the bore before rifling.
The inch designations are mostly the size of the bullet that fits the bore + the rifling.
So the 6.8 mm is the .277 and the 7 mm is a .284
They drill a 6.8 or .267 hole then add rifling about .0045 deep. Two times the .004.5 = .009. .009 + .267 = .276 which is real close to the 270's .277 size bullet.
If you use this calculation on most cartridges you will find it applies.
The 30-30,308, 30-06, are all refered to as 30 cals. If you look you will see they all use a .308 dia bullet. 30 cal = .300. .300 + .008 + .308
Not that any of that really answers the question origanally asked.
In even barrel lengths, equal bullet weights and equal chamber pressures the 270 Win will get 150 to 200 fps faster velocity.
In the feild out to 300 yards they run pretty much the same. From there out to 500 yards+ the 270 has a very slight edge. A few fps and ft/lbs of energy. You can look up the differences on most any ballistic calculator.
Will the animal be able to tell the difference, I doubt it. Dead is dead.

Whether you pick an 18" or a 24" barrel, I see very little difference in "killing power" for deer sized animals between the 7x57/7mm08, and the 270, 280, 308/30/06.

For bigger game like elk I prefer the 308 and the 30/06 because of their heavier bullets...

But with proper bullets, the 270/7mm will do.