Originally Posted by 3006savage
Montana I do not want to come across as agrumentative but I would ask you to consider the following:
The 168 grain 280AI round at 3050 FPS is generating 3474 FTLBS/KE at muzzle.
The 130 grain 6.5AI at 3150 FPS is generating 2864 FTLBS/KE at the muzzle.
The two case capacities are identical. The comparison you ran assumed the 284 bullet from the same case generated 610 FTLBS/KE more than the 264 bullet. The small bore diameter difference of .02 should only contribute approx 150 FTLBS/KE more for the 280 AI.
I used a relatively conservative velocity estimate for the 130 grain bullet and the 3050 for the AI is MAX. That contributed to the different results but if you run numbers between the two and just allow an additional 150-200 LBS/KE for the 280 AI at the muzzle regardless of bullet weight you will be very close to the real world performance for the two. This yields a velocity difference of around 300fps between the two.
No worries here, not being argumentative either. The discussion intrigued me so I started doing a little research when I read the 6.5 was out performing the 280.
Yup, the 3050 fps estimate for the 280 would be max or close to it, and I have no data for the 6.5, so I have to go by what you say there. Can't comment much on their case capacities other than the parent case for both is the .06 and they are both AI's.
As for KE calculations that's basically a velocity squred times mass thing. So mass is a bonus and velocity is a BIG bonus... but... I personally dont put a whole lot of stock in KE. I used to, but not much any more. I look more at bullet structure and performance along with SD, frontal, mass, and momentum.
Also, when comparing the 300 Dakota to the 338 Dakota which also have the same case capacity and a .03 neck dif, The 300 drives a 180 bullet @ about 3100 and the 330 drives a 225 @ about 3100 for KE levels of 3840 and 4800, a dif of almost 1000 ftlbs from the same case. I dont know why, but there it is.
Bottom line is one guy chooses a 6.5-06 AI and another a 338 RUM for his own personal reasons. Me... I'm a 7mm to 300 kinda guy. The bigger the gun the more terminal thump it's going to give. A 7mm is going to give more thump than a 270 and a 300 is going to thump more than a 7mm and 388 is going to thump more than a 300, and all will have similar external ballistics give or take.
So enjoy your 6.5... it should be a sweet shooting gun to give you lots of memories.