Hmmm, I don't see any problems with the .50's, but lets examine a couple of things.
First, you need to remember that it can take up to two seconds for your damage to register and feed back to you visually. A four second burst won't tell you much, since the first bb might have killed him but you didn't see him "die" for a few seconds.
The second issue is convergence and range. I know you are used to those big cannons, but the .50's don't work the same way. What is your convergence set to and what range are you hitting at? Although you can get pretty long range hits with the .50's, I don't find them very deadly unless you are closer, like 300 yards.
This is of course assuming that nothing else funky is going on. What video card are you running and what drivers? Do you see any graphical anomalies? Do you have v-synch disabled? (Although lately many folks disable it on the GeForce 2 cards and have no problems.)
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Lephturn - Chief Trainer
A member of The Flying Pigs
http://www.flyingpigs.com "A pig is a jolly companion, Boar, sow, barrow, or gilt --
A pig is a pal, who'll boost your morale, Though mountains may topple and tilt.
When they've blackballed, bamboozled, and burned you, When they've turned on you, Tory and Whig,
Though you may be thrown over by Tabby and Rover, You'll never go wrong with a pig, a pig,
You'll never go wrong with a pig!" -- Thomas Pynchon, "Gravity's Rainbow"