Tom -- what kind of gun is it? Stoutness of barrels is a bigger factor than chamber length. I wouldn't be too worried unless we're talking thin, European, ancient etc.
Per what Judge says the kind of gun and thickness of barrels is important even short shell i.e. B&P can be higher pressure
BTW I went downstairs and measured 10 Kent Bismuth once fired hulls and all measured 2-5/8 inches. They are Cheddite hulls I believe and I have found that it is common to see factory loaded Cheddite hulls labeled 2 3/4 and the hull still measure 2 5/8. I found this true for b&p 20ga, 16ga etc. note while common some end up being 2-3/4 too, so yo have to check
Going back to what Judge states, make sure your gun is suitable for 11,000 PSI and not just 8000 PSI
That said i have shot kent bismuth in a solid 2 1/2 chambered Greener without issue
