If you add up the differences, you only shave about an inch off of total length, if that means anything.
The barrel length difference is 1.5", but a Vortex is about 1/2" longer than an A2, so your total saving is 1".
If you feel that you absolutely need that one inch, go for it, but that's alot of pain and suffering to go through to shave an inch off your rifle. I'm not a door kicker, CQB guy, but I can't see where an inch would save you anything. Hell, if you notch your buttstock out, you just lost it. On the flip side, notch your buttstock in one and lose that inch without mods.