Geez, I never get around to doing anything anymore. Not enough time in the day! Here's a pic of the Adco work on the barrel. Profiled, then cut back and pinned. Really makes a difference. If you do nothing else to your rifle then this is something I would whole heartedly recommend. For aesthetics sake you could ask them to give the entire length forward of the gas block a touch with the bit for when they re-park it so it'll match if you worry about such things.
Now I don't have a problem with it or think that the ACR is an ultra heavy rifle but when I took that pic above it got me to thinking about what one could do to shave even more weight off of the front of the rifle. I like my gear to be light and that means everything not just the rifle (my days of humping an M60 around made an impression on me!). Below are my notes on what I might look into doing on my next barrel. Each little thing by itself is trivial but added up they should cut it down even further.
A: 3/16"-1/4" hole drilled through top of piston guide. Reamed of burrs of course
B: 1/4"-5/16" hole drilled through both sides of the piston guide.
C: Shorter shoulder and turned down to smaller diameter.
D: Barrel fluted inside of gas block "window".
E: Bottom of gas block opened and barrel fluted.
F: Shorter journal with taper flush w/ gas block.
*G: Something could be done with the gas block, maybe turn down the fins or possibly shorten it. Light flutes could be milled into the main body behind the regulator.
Going from the factory M4 profile to the first pic was about 1/4 pound. Starting from factory to the above specs will put you maybe around, or just under, 3/8 pound removed.
If the effort involved to do so is worth the result is entirely up to you.