What kind of shifters are you using? You say that you have a Sram rear derailleur which tells me you must also have Sram shifters. Does your front shifter have only 3 positions or does it have a plethora of clicks? If it's the former, and you're going to upgrade the shifters anyway, I'd suggest getting a set with friction front shifter (the plethora of clicks). I'm thinking that should solve your problem.

Another thing that comes up is the cable routing to the front derailleur. Many Shimano front derailleurs have a little "L" shaped finger in the cable path. It's important that the cable pass OVER that finger it it'll take too much effort to shift onto the big ring.