I've heard anecdotal reports of increased recoil, even with British shells especially designed for guns with 2 1/2" chambers (but in slightly longer cases), on a few very old guns with short and sharply-angled forcing cones. Seems to be more a function of the cone than it does chamber length. Like Joe, I've shot a lot of 2 3/4" shells, reloaded to appropriately low pressures, in guns with short chambers, without any significant increase in recoil. Sherman Bell, in his "Finding Out for Myself" series in DGJ, did report a slight increase in pressure with some 2 3/4" shells in 2 1/2" chambers. But a pressure increase does not necessarily equate to a recoil increase.