If you're reloading 2 3/4" hulls to be used in guns with 2 1/2" chambers, you need to know the appropriate service pressure of the gun for which you're reloading. Then, just to be safe--because the extra length, per Sherman Bell's DGJ article, can result in a pressure increase of 1,000 + psi--you should shoot for at least 2,000 psi under the service pressure for which the gun was designed. That should keep you on the safe side.