Re: which caliber for all around use?
.22 LR, it was widely talked about at small bore matches, gains nothing for accuracy after about 17". Velocity, not sure but I believe there is very minimal if any gain past that.
Other rifles, (and even handguns) I think it varies considerably by caliber but a longer barrel certainly promotes greater accuracy by several factors.
-longer sight radius (which is independent of the actual topic here but worth mentioning)
-more barrel to fully get the projectile spinning consistently to stabilize correctly upon exit
-highest possible velocity and also most uniformity in velocity/pressure
but at what point does it become too long, or a detriment? let's use .308 and .223 for examples as they are among the most common.
testing has shown that after a certain point (barrel length), velocity and accuracy gains are very very minimal past a certain amount, say around 18". past that, your gains are small if any in many calibers.
16" in .223/5.56 is a good length and gains past that are very minimal. I would say 18" would be a good 'minimum max needed length' for .308
time to start digging through my book and the internet...
"Loud noises don't end gunfights.... well placed shots do."