Virginia7

For me, the "in" cartridges still include the 30-30, along with the 22LR, 243Win.(for varmints ), 6.5x55, 270Win., 7x57, 280Rem., 308Win., 30-06, 358Win., 35Whelen, AND 375H&H.
Oh, and also the 45-70.

James B

Me too. The 300 WSM while a good cartridge is still a wet behind the ears Newby. It nee4ds quite a few more year to become an established IN caliber. Other rifles still outnunber them big time. The gun stores here sell about one WSM out of ten new guns. It may become a In cartridge but it has to pay more dues before it will get my vote. No cartridge in the last 20 years has made the gains that the 243 have made IMO I am not a fan of the 243 but There are a jillion of them around..

JagMagMan

I'd define the "in" caliber, as the hot seller at the present time. I don't think it can be defined by ammo sales. The top ten are mostly estabished calibers.
The hot sellers of today are have to be the WSM's, especially the .300 WSM.
As for me, I've never been a trend follower! I like to go with some of the odd-ballers like the 6MM Rem. and the .264 WM. While my two "go to" calibers have always been the .308 Win. and the 7MM RM, I did not choose them because they are popular. (most of my buddies carry an '06, so my .308 and 7MM ARE odd for the group!)Iprefer quality and preformance over fadstyles! (and even that is subject to debate!)
I know that gun makers have to come up with new calibers to make money, just as the auto makers do. But only time will tell if these new calibers will be here in 20 or more years! Besides most game couldn't tell the difference in being hit by a .300 Savage or .300 WSM!

bigbulls

Assuming the word "IN" is meaning the hot item to have right now then there are two "in" cartridges.

One being the .17 HMR and the other being the .300 WSM. Both of which will eventually become "old standards" like the .22lr and the 300 Win mag.