I have a 3.5x ACOG on my 16" .223 carbine and do not feel under-scoped. I like to call coyotes and bobcats in close and like the field of view and brilliant optics.
I use a 2.5-10 B&L on my .221 Fireball CZ, and have not yet made a shot at an animal with the magnification above 2.5x.
When I was but a lad, I used to thin-out the ground squirrel population in my area of S. California. I used a Winchester M75 (.22LR) with a Swift 4x on it. With Eley 10-x, I was able to snipe those rodents out to 200 yards with great reliability (and low wind conditions).
Figure the modern 4x scope is far superior to the optics used by civil war snipers, who "made" shots past 1,000 yards. The magnification was only 2x or 3x, generally. (I have an original copy of "Berdan's Sharpshooters in the Army of the Potomic".)
You cannot go wrong with a quality fixed power scope in the range of 2.5, 3x or 4x, for a calling rifle (with typical shots less than 250 yards). That is what I think.
