Well said Frederick. This is where Purists become Anal ("pure anal" -- sure sounds like an oxymoron). As a collector who is also, by profession a futurist, and by avocation an historian, I take a very long view on restoration -- from an artifact's origins, its current usage/utility, and what is going to happening to it 100 years hence.
The purely anal "preservationists" view (such as starving dry wood by withholding a nurturing drink of linseed oil) is both perverse and will actually result in the future degeneration of the artifact (which is not "preservation" but just a twisted "dust unto dust" approach to any future historian).
Frederick, I'm with you on this one -- a gun should shoot accurately. As long as the improvements don't materially alter the gun (drilling multiple mounting holes, chopping up stocks, etc.), then march forward stalwartly as the warriors did on the battle field generations before.
If we ask the question: "What will future generations think about what we did when we owned this historic weapon?" and can answer that question honourably with integrity, then we should not hesitate to take action to keep these weapons shooting accurately and properly maintained. I am delighted so many BritishArmourers, ardent collectors, fastidious researchers, and knowledgeable restorers have contributed to this website with their highest standards of excellence to keep the tradition alive for future generations.