I think we are discussing to very different types of rifles and shooting, bench rest and your average hunter's rifle that is carried day in and day out and used in a variety of situations. I can see a lot of reasons to cone a hunting rifle and no reason what so ever to cone a bench rest rifle
My flintlock is just such a rifle, it is coned, very accurate and will be headed to the woods with me tomorrow when B/P season opens in Alabama.
If I can do this with it off a sand bag, imagine what someone who doesn't have 76-year-old eyes and can actually see the sights could do, for me the rear sight is a blur.
This tells me my coned rifle is very accurate, past 50 yards all bets are off but I suspect this kind of accuracy will hold up at further distances.
Like I said, I was shooting low and had filed the front sight down as far as I could so I added 5 more grains of powder, held a little higher and hit high. I went back to my 6 o'clock hold and punched the next two holes.
This target isn't the least bit anecdotal and is the real deal, at least for me. This particular rifle shot much better coned than it did before I coned it and I put a lot of shots through it before it was coned it. The barrel was a re-bore that had "issues", coning helped it shoot better because it got rid of an overly tight bore. I had to shoot .526 balls in the rifle before coning because of the tight bore, after coning, a .530 and an .018 patch load easily.
I can't say across the board that coning will help or hurt the accuracy of someone else's rifle, I can only state what my experience with the process has been.
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