Originally Posted by semperfi71

The .25-06 will produce heavier bullets with better sectional density than a .243. Which means the .25-06 should penetrate deeper and handle wind better.

I killed 4 or 5 Mule deer with the Sierra 120 grain boat-tail hollowpoint in a .25-06. All lung shots, and all the deer fell to their feet or walked no further than 15 feet. Shots were from 20 feet to about 100 yards. I never found the bullets and they never exited the body. The lungs were described as handejector described, literally mush. I shot one in his bed at about 70 yards and all he did was lift his head and lay it back down.

I killed one antelope with the Nosler 100 grain Ballistic-Tip at about 50 yards. It entered the neck at the joint of the shoulder and exited the opposite side, same place. The entry hole was about an inch in diameter, indicating explosive entry, and the exit hole was about three inches in diameter. In theory no vitals were struck. I assume we damaged the spine/neck. The antelope fell straight down at the shot and never moved.

I own a Ruger RSI Mannlicher in .243 with the 18 inch barrel. With the Speer 105 grain spitzer I get 2800 fps from the muzzle on my chronograph. I have not killed game with it. I suspect that bullet, at that velocity, will not open up as fast as my .25-06 loads have.

I suspect that handejector is correct. The .243 will kill, and I know of a few folks that have used it on elk. But it is like the 410 shotgun. Actually an expert's gun and not a tyro's gun as it requires good shot placement. And the heavy 100 grain and 105 grain bullets do not travel fast enough to open up rapidly to kill quickly. However some brands are more frangible than others and therefore the more frangible may be more destructive.