Might want to focus on just the beginning push off (start/middle range) of the bench, for a while. If you have a PR (or A frame, etc), than so much the better. Could do these in a Smith because your just going to push for a short range. For full range, Smith is not always the best machine to use.
If your the type of guy who bounces the bar off the chest or just comes close to the chest each reps, than the pattern of benching will have to be relearned. Work the bench from the dead stop position, rather than taking the bar off a overhead support or having a guy hand the bar to you.
Set the pins (or whatever) at chest level, take your normal grip, and press the bar 4 to 5 inches up (don't know how long your arms are or natural leverage). If you do have a PR, you can set another pair of pins at the 4-5 inch mark, acting as stops. You want quick and strong reps, relearning to fire off the nerve paths from that dead stop starting position. Do higher reps (10-12) to begin and a lighter weight. Want to set a new pattern of pushing off the chest. After each rep, pause at the bottom position for a couple of seconds, than begin another fast and strong rep.
Than, in a few more workout, start with the 10-12 reps range as more of a warmup. Adding extra weight as the sets progress. Give this style of training a few weeks to get adjusted to. Also practice your regular full range benches, in the same workout, after the dead stop work. The dead stop starting position can be an ego buster, because you will be using much less weight than normal in the bench. But you should gain more strength, workout to workout. That 275 should feel somewhat light after awhile.
Most BB'ers, with very good chest/pecs, will handle 230 to 260 for bench work (though a lot of them avoid any regular BB benching now days). Going for higher reps and more of a feel for the exercise. And a faster pace during the workout. 275 is a good number, if the reps are good reps. That magical 400 is not that common in the BB'ing world, no matter what the mags or video's try to tell you. In the Pl'ing world, even with lighter classes, fairly common. Good Luck