Speaking from a stand point of a long time .243 user i'll add my two cents.First I have killed roughly 13 deer with a .243,specifically a Ruger M77 MarkII.Until two years ago I used Federal Premium in 80 grain bullet weight.I have since swithed to the 100 grain,same brand.I had been shooting the 80 grain simply for less recoil,and faster bullet speeds.Of the deer I have shot,all but one dropped within 30 yards of being hit.The one exception was 100% my fault.While I like an easy headshot (no wasted meat) I have had no choice but to place the bullet through the shoulder on several,and several more went right into the "engine room".I can't honestly tell you if there is a differance between the 80 and 100 grain shells other than listed ballistics.I switched to 100 grain because the cost of the 80's went to almost twice that of the 100's.Here is the bottom line,make sure you practice shot placement A LOT.Once your shooting is almost automatic your set.Don't ever rely on "knock down power" to kill a deer.It makes for lazy shooting in my experience.I have helped track numerous animals that were hit with 30-06's,300's and 308's.Knock down power will never replace fine marksmanship.Good luck!

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