The way Ed Rayl explained it to me, while the overall barrel size might come into play a bit, the main consideration is the threaded size and area of breechplug and mated end of the barrel...and that's why you need to discuss with somebody like Ed Rayl who knows the various barrel configurations, does that stuff for a living, etc.
As it was explained to me, the boring operation requires the breechplug to be unscrewed so the bit can pass completely through the bore end to end. The concern being that if it cuts down into the threaded area of the barrel too much, there won't be enough threads left for the breech plug to safely re-engage when its screwed back into the barrel.
For example, my GM 7/8"x 42" x .45cal barrel was terribly nose heavy, couldn't still hunt with it...called Ed to bore it out to a .54cal smooth to make it lighter, but he wouldn't bore it out that far because of the GM breech plug used in their 7/8" barrel...so I had him take it to a .50cal, with round bottom grooves instead...turned out to be a great result as it lightened it a half pound and its a proverbial tack driver.
So you really just need to call Ed Rayl or some similar top name machine shop operation...another possibility is Dennis McCandless, Custom Breeching, Los Cruces, NM...you need to discuss it with the pros who can tell you if it can even be done on that particular barrel, what your options are, etc.