"a 308 win is hitting pretty dang soft on deer at 800 yards. A 7 RUM is still putting lightning strikes on them."
I am not doubting what you wrote, but I am guessing the cartridge case has a lot less to do with it then you may think.
Lets look at some facts here.
If your 7MM RUM is firing a top end load at max velocity of about 3300 FPS with a bullet having a BC of about .6 which would be a bullet in the upper 160 grain or low 170 grain range, your impact velocity at 800 yards is going to be about 1900-2000 FPS. If your bullet doesn't blow up and it expands to 2X it's diameter (most don't at that range, but it's possible) you have a "working end" of about 56 caliber making the bullet hole in the deer, and the velocity of a 30-30 at brush-hunting range)
If we look as a good high end 308 Winchester load with a 165 grain hunting bullet with a good BC (about .450) we have a muzzle velocity of about 2650 and an impact velocity of 1400 -1450 FPS at 800 yards.
Again if the bullet preformed perfectly and it doubles it's diameter (again, most don't at that range, but it's possible) making a .60 cal "working end" to make the bullet wound in the deer. Velocity at 800 is about like a 30-30 at 150 yards.
Both bullets start at about the same weight.
Is the RUM going to be WAY better? If it is, why?
It's about the same weight (within 7 grains) and it's 450-500 FPS faster on impact. Clearly it has more energy then the 308 round, but it may or may not make as large a wound in diameter. If both get to the off side of the deer against it's hide, or even exit, is that 450 FPS going to be "lightning' compared to the 308?
Is the cavitation of the 308 hole going to be "way" less? And is the 308 going to be "pretty dang soft"?
I have killed a number of deer with a 30-30 firing 170 grain bullets and all were under 150 yards. A 30-30 with a 170 gr chronographs out of a 20" barrel around 2050 FPS with 170s. At say 125yds, that bullet is going about 1600 FPS, yet it drops deer VERY well.
If that is what you have seen, and if you have seen enough of each at 800 yards to have an established pattern to compare (say 10 deer each at that range with each cartridge) I am guessing the bigger reason you are seeing "lightning' from the 7RUM is bullet selection, not power and speed at the muzzle (or at the target.)
I no longer shoot game past 500 meters. I have done it quite a few times when I was younger but I guess I grew out of it.
But the round I have made more instant kills with then all others at ranges over 500 meters (and in about 50 years of doing it) was and is the 270 Winchester. I shot mostly 150 grain Partitions. I have dropped a lot of deer in their tracks, even at long range, and the fact is that none of my long range kills went more then about 10 yards.
My 270 is WAY slower then your 7 RUM. ("Way" being about 300 FPS or a slight bit more) Your rifle can do 3300 FPS with a 150 or 154 and my 270 chronograph 2980 with 150 grain bullets.
And to these preceding facts I have to reconcile the added fact that I made a fair number of kills at longer ranges with my 300 magnums and 7MM Mags, as well as four I remember with a 375H&H.
All of which were more powerful then my 270s.
None of which were generally as dramatic at killing deer at long range.
So that brings me back to my 1st point.
Bullet design and construction.
If your 7 RUM is far faster and more dramatic in killing deer at 800 yards I am going to bet it's not because of the large powder capacity as much as it is the bullets.
Does any of that ring true with you?
If so, please post.
If not, please fill in thew blanks for me (and the others too)
My focus here is not to confront but to exchange information and facts and help educate others and myself if I can.
I am not doubting what you wrote, but I am guessing the cartridge case has a lot less to do with it then you may think.
Lets look at some facts here.
If your 7MM RUM is firing a top end load at max velocity of about 3300 FPS with a bullet having a BC of about .6 which would be a bullet in the upper 160 grain or low 170 grain range, your impact velocity at 800 yards is going to be about 1900-2000 FPS. If your bullet doesn't blow up and it expands to 2X it's diameter (most don't at that range, but it's possible) you have a "working end" of about 56 caliber making the bullet hole in the deer, and the velocity of a 30-30 at brush-hunting range)
If we look as a good high end 308 Winchester load with a 165 grain hunting bullet with a good BC (about .450) we have a muzzle velocity of about 2650 and an impact velocity of 1400 -1450 FPS at 800 yards.
Again if the bullet preformed perfectly and it doubles it's diameter (again, most don't at that range, but it's possible) making a .60 cal "working end" to make the bullet wound in the deer. Velocity at 800 is about like a 30-30 at 150 yards.
Both bullets start at about the same weight.
Is the RUM going to be WAY better? If it is, why?
It's about the same weight (within 7 grains) and it's 450-500 FPS faster on impact. Clearly it has more energy then the 308 round, but it may or may not make as large a wound in diameter. If both get to the off side of the deer against it's hide, or even exit, is that 450 FPS going to be "lightning' compared to the 308?
Is the cavitation of the 308 hole going to be "way" less? And is the 308 going to be "pretty dang soft"?
I have killed a number of deer with a 30-30 firing 170 grain bullets and all were under 150 yards. A 30-30 with a 170 gr chronographs out of a 20" barrel around 2050 FPS with 170s. At say 125yds, that bullet is going about 1600 FPS, yet it drops deer VERY well.
If that is what you have seen, and if you have seen enough of each at 800 yards to have an established pattern to compare (say 10 deer each at that range with each cartridge) I am guessing the bigger reason you are seeing "lightning' from the 7RUM is bullet selection, not power and speed at the muzzle (or at the target.)
I no longer shoot game past 500 meters. I have done it quite a few times when I was younger but I guess I grew out of it.
But the round I have made more instant kills with then all others at ranges over 500 meters (and in about 50 years of doing it) was and is the 270 Winchester. I shot mostly 150 grain Partitions. I have dropped a lot of deer in their tracks, even at long range, and the fact is that none of my long range kills went more then about 10 yards.
My 270 is WAY slower then your 7 RUM. ("Way" being about 300 FPS or a slight bit more) Your rifle can do 3300 FPS with a 150 or 154 and my 270 chronograph 2980 with 150 grain bullets.
And to these preceding facts I have to reconcile the added fact that I made a fair number of kills at longer ranges with my 300 magnums and 7MM Mags, as well as four I remember with a 375H&H.
All of which were more powerful then my 270s.
None of which were generally as dramatic at killing deer at long range.
So that brings me back to my 1st point.
Bullet design and construction.
If your 7 RUM is far faster and more dramatic in killing deer at 800 yards I am going to bet it's not because of the large powder capacity as much as it is the bullets.
Does any of that ring true with you?
If so, please post.
If not, please fill in thew blanks for me (and the others too)
My focus here is not to confront but to exchange information and facts and help educate others and myself if I can.