If you leave the internal springs alone you shouldn't run into any problems. I bobbed the hammer on my S&W 637 and replaced the stock hammer on my Model 60 with a bobbed hammer (no spur at all). I've had no problems with either. It's not enough of a mass reduction to make a difference, the stock springs have plenty of oomph to detonate the primer.
By the way I recommend that you remove the hammer to do the job, no point taking a chance on scarring the gun with a grinding wheel.
