The most commonly used bullet in a .243 weighs 100 gr. The most commonly used bullet in a .308 weighs 150 gr. The sectional density of a 100 gr. .243 is .242. The sectional density of a 150 gr .308 is .226. I thought higher sectional density was better.

It is for penetation, some people think the SD of the.243 is a bit much for whittail and cosider the 80 to 90 gr better.
When one compares calibers one needs to compare bullets with the same SD. So comparing a 100 gr .25 to a 100 gr .24 is not the same, or a 150gr .308 to a 100 gr .243, etc etc etc.

The demise and decline of the 300 Savage is a sad deal because its actually a helluva good little cartidge.

A higher SD is not alawys a plus. You can get a SD that is to high for the intended game and get lack of expansion. For deer I like a SD od 200- 230 about the best. You do also have to look at bullet construction as well but based just on SD I like the little bit lower SD and a guide line. If I was to use a 243 again I would opt for the 85-95 grain bullets from Sierra and Nosler.

You are correct about the 300 Savage, it came out as a caliber to out do the 30-30 from Winchester and to match the 30-06. It beat the heck out of the 30-30 but fell short of the 30-06. However just like the 308, its about as perfect for deer as it gets. I may break out the 700 Rem Classic in 300 Savage for this years deer season.Or maybe the A-Bolt 308.

If you like the .300 Savage, and like lever guns (who doesn't?), might want to look at the new .308 Marlin Express. The ballistics are almost identical to the .308 Win with 150gr Hornady Leverevolution ammo. It's a brand new cartridge, and how well it will catch on, but it doesn't look like a bad little round. Might also catch on with the Encore pistol crowd.

Mike