I'm surprised....as the man suggests, don't conjecture..... test it. Or perhaps find somebody else who has, or what they observed. ????
Ned Roberts comments on the idea, but his book is discussing target shooting at 40 rods (220 yards), with patent breech caplock rifles and false muzzles. How many of us are concerned with that?
"When I was a boy, many of the most expert shots with the muzzle-loading cap lock target rifles always used a tin or brass tube a little smaller diameter than the bore of the rifle and about an inch longer than the barrel, with one end funnel shaped through which the powder was poured down the barrel of the rifle. After careful wiping of the bore after each shot, this long tube was inserted in the bore nearly to the breech and held with one hand while pouring the powder into it with the other hand. In this way, no grains of powder adhered to the side of the bore, but the entire charge was deposited into the cone of the patent breech and base of the bore so that none of the grains were crushed in seating the bullet. This tube was then withdrawn and the bullet loaded through the false muzzle with the bullet starter as usual. These men firmly believed that by loading the powder through this long tube in this way they secured finer accuracy and made somewhat smaller groups at all ranges. Uncle Alvaro and many other experts call this "an old maid's idea", said that it did not improve accuracy, and only caused so much more work in loading and so much more equipment to carry around. Be that as it may, we noticed that these men who used these long loading tubes very seldom made any smaller groups, or won any more matches, than the riflemen who did not use them in loading. Of course, it is possible that these advocates of the long loading tubes did not have as super-accurate rifles as the others even though their rifles were by the best makers..., However, it is a hint worth trying, especially if you are in the habit of leaving the bore of the rifle somewhat damp after cleaning for each shot." The Muzzle-Loading Cap Lock Rifle
What I find interesting is neither according to comments now, or apparently back then..., while the fellows following this practice did not win any more matches than the competitors who did not, nobody seems to consider that with that particular rifle, the practice might be needed to have a group accurate enough to contend for a winning score.
Simply because my rifle shows no improvement in accuracy when using a tube, does not mean that my fellow competitor's rifle will not show a marked improvement from using such a tube.
I noted neither Mr. Roberts, nor his "Uncle Alvaro", ever checked the rifles where the tube was used to see if omitting that part of the procedure caused a group from that particular rifle, to worsen.
LD