Chris:
If you have trouble getting the longer cases, you could consider shooting 'nitro-for-black' loads in the rifle using 3-inch brass, and 440gr Woodleigh jacketed bullets. With smokeless powder and thin-jacketed bullets, the 1/4-inch bullet-jump would likely be of no consequence. I do this in a Tolley .500/.450 x 3 1/2, using 3 1/4 inch brass. In fact, I didn't realise my rifle was chambered for the longer case till Tinker pointed it out! (he has one, too!)

Wrightie's book has the 'good oil' on loading N-for-B.

If you do decide to go N-for-B in the interim, you will need filler-wads of course, which is daunting to some but no trouble really once you understand the basics. Many of us do it on a daily basis with perfect safety.