I just looked through a batch of .454casull handloads and found some that are not so well seated, a little deep. I think because they die was not set to the correct depth to crimp, and the slugs just slipped into the case, they are not very tight either.

They are very light practice loads, if I go through them and crimp the loose ones they should be o.k. even if a little deeper than I'd like?

If you have loaded with fast burning powder it should be OK. For full loads it is just as important to have the case tightly grip the bullet, without it you can't get proper burning of the powder.The crimp should not be excessive because it may effect accuracy.

As a rule the deeper a bullet is seated in a handgun cartridge the higher the pressure is, This is realy true with small capacity auto cartridges, what affect it has on the .454 I can't comment on but if they are seated too deep is it worth it to shoot them?

pull them and start again!! Why risk hurting yourself or your gun