From most of the data I find the .270win generates higher velocities with the same weight bullet, let's say, 140gn than the 7mm-08.
Doesn't the larger neck mean more effecient relaese of gas to propel the bullet? The .260rem is slower again, but often the .308 seems to lag too.
What gives?

There are lots of factors in velocity, but clearly the .270 has a bigger case and room for more powder. I asume you shoot hand loads.
The .270 is only .07 less in diamiter than the 7mm08 , so I can't belive that matters much.
Also your barrel , can change things. Not just length either.
A really smooth barrel will alow the bullet to pass with less friction, But as far as I am concerned the 270 should have a velocity advantage over the 7mm08 of at least a 100 to 150 FPS all things equal.
Both are great deer rounds , besdids the 7mm08. You mention 2 other rounds I like, the .308 and the .260.
But Logiclly speaking the 7mm08 and the .308 are so close together as to be balistic twins.
The 260 is cool cause there are excelent hunting bullets from 100 to 160 grain.
And I may be blasphemous here but to me all the rounds listed are prety much interchangable in most hunting situations .
The .270 has a little more range then the rest, but not enough to matter, beacuse the rest of the rounds you mention are all great deer rounds at least as far as most people should shoot !
...tj3006

cae volume, pressure, bullet SD (to compare weight over different calibers), barrel length, and consistant loading methods

the 270 has 67gr of H20 Case
the 260 has 53.5gr of H20 Case
the 708 has 56.5gr of H20 Case
the 280 has 67.5gr of H20 Case
the 308 has 56gr of H20 Case



When a case has ~18.5% more case, and is loaded, with the same methods, to the same pressure, with the same bullet SD, in the same length barrel, it will ALWAYS go faster.

BUT, top loads of the smaller may beat bottom loads of the latter

jeffe

As we do on many things, I agree with TJ! there is no practical difference. capt david

Hey Captain David.
I,m glad we agree on the interchangability of so many popular rounds, And while I certainly belive thats true ,I wonder why I own so many rifels chaberd for so many interchangable rounds.
I think 12 step program is in order.
Just kidding of course, its a healthy adiction.
...tj3006

Me too, I have a 7x57, 308, 30-06 and a new semi-custom 280 that is in the mail as we speak. for every thing I do, here in Texas, they all do the same thing. Close my eyes and pick one. I suppose the 280 is enough flatter from 300yds to 400yds to make a little difference, or at least that's what I told myself. capt david

I am about 99.9% that my 21" Rem. 700, 708 with 139/140 shot 2960 with top load of Varget.

I have no interest in choosing a 270 over my 708, but a 270 is a good round in itself, no reason to sell one.

I think the 270 is way over rated really. It dosnt look to be a very efficient capacity/caliber combination at all, particularly in the lighter bullet weights.

...mind you thats only my thoughts based on my short play with one and working up some hand loads in 100g and 130g bullet weiths.

For example, the 100g bulets were using 57g of AR2209 and giving 3100fps.

Compare this to my 243 with 100g bullets and 38g of AR 2206H and getting 2900fps. Thats a 200fps increase for 19g of powder and twice the felt recoil.

OK it may be better with 150g bullets, but I think a 7mm08 will get pretty close with 10-20g less powder and less recoil.

It dosnt look so bad when you compare actual case capacity, but when you compare actual powder weights used, the difeerent is more significant.

I sold it pretty quick as I couldnt handle the recoil.


Thats my thoughts.

Cheer

Grant