I am considering a carbine build and am wondering if it is truly practical to have a rifle in .308 with only a 17 inch barrel. My liking of this caliber stems from the fact that it is powerful and performs at distance. At the moment I have a 21 inch version as it fulfills this roll perfectly.

What kind of performance loss in terms of point of impact, velocity, and fragmentation (if that even occurs at 21 inches) occurs with a 17 inch barrel versus a standard 21? Also, would an M4 be better suited for a carbine role than the FAL? Thanks for your input.

generally speaking you're going to lose about 25fps per inch of barrel you remove. the actual rate of loss per inch should be less initially and increase as you get closer and closer to the breech.
i believe (given equal barrel length) the 308 will have about twice the energy of  a 223 at the muzzle & 100 yards. nearly 3x at 200.
i don't know about the fragmentation.
which is better suited to carbine use? i guess that's a matter of opinion, with the exception of the tele-stock which has to be a plus for the M4.
tho i have no doubt the M4 is a fine carbine, i love my shorty (16.5") FAL (even if it does weigh more) & personally wouldn't trade it for an M4.

Quoted: i love my shorty (16.5") FAL (even if it does weigh more) & personally wouldn't trade it for an M4.

That look almost exactly like the one I sold!!......I'm such a dumbass

IIRC your files threads were part of my inspiration. didn't you have a short stoll?

I 'm getting an 18 "FAL  from ORF soon . I believe this is a great length .

What is the Para FAL barrel length ?? Wasn't it about 18 ??

My 21 " was just a tad to long for my liking .

para barrels were 21 & about 17.5" IIRC

I wasn't really worried about the velocity loss when I had the bbl. shortened to 17.5. I did it mostly to stow in the trunk of my little Hyundai. It's still not short enough to put it where I wanted it but it'll have to do.
M