I've never had a problem with bulges on my 45-70 cases, and I load with a RCBS single press using a standard Lee three die set.
What I do is expand the case mouth just barely enough to be able to place the base of the bullet into the case without it falling out, lining it up as straight as I can, (but it doesn't have to be perfectly straight), and then place it onto the shell holder, and then raise the cartridge into the preset die just until I feel contact and just put a little pressure and then back off and lower it, and then using my other hand, I turn the cartridge about 180* on the shell holder and again raise the cartridge up into the die and press lightly again, and then continue this motion of press, backoff, rotate, press, backoff, rotate, another time or two until the bullet easily seats into the case.
This can be done faster than what it sounds, and it's just a matter of slowing down a little right at the start of seating the bullet just a little at a time until you feel the bullet smoothly seat, and you will develope the feel. What I have found is that the die itself will straighten the bullet out if given the chance.
Like I said I've not had any problem with bulging cases yet!
I use this method loading 405 grain cast bullets of .460 dia. with no problems at all!
