For a "professional," frankly, you disappoint. You have not gathered all the data/"done your homework." In what length barrel was the velocity you quote achieved? As indicated, many "tests" are run in "test" barrels and often they are 26 inches long (or longer). Frankly, I am very annoyed, think it borders on "fraud" (my training) that the factory only sells guns with 22 inch barrels or 24... but quotes test barrel velocity. Yes, there is variation between any two guns. Mr. Ackley in his books makes the point that several gunsmiths who happened to build on "fast" barrels advertised their wares widely quoting these unusual velocities but no one who bought, as a rule, came too close. And, you cannot buy the powders that the factory's use. They don't know what they are buying when they buy by the train load. (With IMR in Canada, I wonder what the exact relationship with Remington is?) They test and work up loads with it in a lab and then set the machiens to load 10,000 rounds or so... testing constantly. and sometimes they get results far exceeding anything "commercial burn rate" powders/ "cannister powders" can achieve. Then there are bullets. Sometimes you can get factory bullets. Sometimes not. Different metals, different friction.
If this is so important to you, a re barrel is no guarantee. You can buy different bullets and try many different powders and MAYBE... (is it worth it???)
Jack O'Connor used to say that for rifles working at 2,000 you could reduce quoted velocity by 25 feet per second per inch. For rifles working at 3,000, it should be 50 feet per second per inch. And this is very, very general.
If the gun is meeting your needs, i.e. "it ain't broke" why fix it. On the other hand if you want an expensive custom rifle... go for it. But in those boomers, well you better like the smell of liament, oh, right, your a druggist... enjoy...