Lee Bullet Seating Die Help

[The Reloader]

I was wondering the differences between the Lee Bullet Seating Die (came with full length size kit) and the Lee DEAD LENGTH bullet seating die (came with neck sizing kit) In the die instructions the only difference is the Dead Length one does not crimp. Can anyone tell me the advantages or disadvantages between the 2 Would be a great help! Thanx!

[NESHOOTER]

Some have said it to be of importance on semi-auto feed firearms and when loading compressed on reloaded ammo, the reason of the on the semi-auto is some say it to prevent the bullet from getting pushed back into the casing while firing due to the action of the firearm. and some reloaders say they have seen the COAL change as the compressed powder causes the bullet to rise. I do not crimp in the ar platform nor my bolt guns I find without the crimp the so call ''jump'' into the lands of the rifling is not need when I enjoy greater accuracy without. Very seldom do I load compressed loads.