The sniper behind the rifle is what makes the ultimate rifle.
Ok sure, i know that's not the answer you are looking for, but it's 100 percent true. You can have a less than perfect rifle, not great equipment, so so cammo and no dedicated radio channels (hehehe) but if you know your gun, i mean really really know it people will look at your POS MB-01 and think it was FedEx'ed straight to your door by Odin himself (yes that is a thors hammer reference for anyone who didn't get it)
So, that leads to the answer you are actually looking for.... what makes the ultimate rifle??
C O N S I S T E N C Y
If your rifle shoots 10m or 100m if its consistent and you , as the sniper, know how your rifle shoots then you have the ultimate rifle on the field. Oh, and i don't mean 1 MOA at 100 yards either, im not talking about accuracy. If your rifle shoots consistent 2 foot groups at 100 ft, but tends to average most shots a little left and up and flexes when you hold the stock a certin way etc.... see what im getting at.
I took out a UHC Super 9 one day just to prove this point. Sure , i messed with it a bit ahead of time, but more importantly i put 1000 round though it in my back yard. What happened? I won....
Why? Because I'm the sniper, not my rifle. ;-)
So when you build, build for consistency, and when you train, train a lot and use that consistency to your advantage .