1911Tuner
Moderator Emeritus
Hopefully head space won't be changed drastically.
It'll depend on the static headspace dimension as it is now and the thickness of the step.
Definition:
Static headspace is determined by the distance from the breechface to the chamber stop shoulder. This is fixed and only changes through wear or damage.
Dynamic headspace is the difference between the static dimension and the length of the case, and it changes from round to round unless all cases are trimmed to exactly the same length.
The .45 Auto cartridge has a pretty generous static headspace range. The GO minimum is .898 and the NO GO maximum is .920 inch...and most case lengths run to about .885-.890 inch...so you can wind up with an average dynamic headspace of nearly a 32nd inch and still be in the allowable range.
Headspace excess can come from two directions. If the chamber is just a little too deep, it's pretty much a non-issue as long as the firing pin can reach the primer and fire it reliable. If it comes from the rear...such as happens when lugs deform or the breechface itself is set back farther...it lets the case back up in the chamber. If it backs up far enough to lose chamber support forward of the case head...it can be serious problem.
Gauging the headspace only tells you whether it's within the allowable range...or not. If it's excessive, it doesn't tell you why. The gauges can show a condition of excessive headspace, and the gun can be perfectly safe to shoot...or not.