Are you sure about the weight?
And then there's this thing called "balance." I know how an M1 balances and I know how the vARmint rifle feels when the barrel weighs about as much as the rest of the rifle.
Increased accuracy won't come from the 24" barrel. You can get the same groups from a 20 or 18" barrel. You should get some extra velocity though, if the right powder/bullet combination is used.
Good luck with it. The neat thing about the AR15 is that it's not too hard to put a different barrel on the upper or build a whole new upper.
One other thing/question. Stock, buttstock actually, what are you looking for? My vARmint rifle first had a carbine stock on it. The idea was to make it adjustable for different shooters. No one shoots it but me, every few years, so I put an A2 stock on it and put the carbine stock on another rifle. I'm 6'3" tall with arms long enough to not look funny and I still don't like the A2 stock. I can get my nose on the charging handle but it's a stretch. The older, A1 buttstock is a much better fit for me. I put one on my 18" build and really like it. If I shot the vARmint rifle more I'd find/buy/install an A1 butt stock on it, too.
vARmint rifle with the carbine stock on it. Scope in a 2.5X10 Simmons I had higher hopes for. Big objective lens but still not as bright/clear as my smaller Nikon/Bushnell (older Bushnell scopes).
18" build, still haven't really "wrung" this one out yet. Too much other stuff going on. Might shoot it at 100 yds. today.
Not a comparison of functioning, weight, accuracy, etc. Just a couple of pictures of two rifles I put together, only one of which I take to the range or on road trips.