No personal criticism of you, but I've found the opposite to be true. This with lined MLer's allowed in NSSA competition over many years at their Spring and Fall National Championships and done by Bobbie Hoyt.
He turned dozens of "Reject" Navy Arms Smith Carbines with REVERSE taper bores (meaning smaller at the breech and larger at the muzzle) into great shooters by relining them. I've seen his work on many other MLer's that shot great afterward as well.
However, the one that REALLY stands out in my mind after viewing dozens of such NSSA Arms Hoyt did, was an 1855 Rifle (not the longer Rifle Musket) on which he performed almost magic. The barrel had been cut off a little under 8 inches and smooth bored when they "sporterized" such guns after the UnCivil War.
Hoyt "stretched" it back out to full length, which means he added on the outer barrel shell to proper full length and lined the whole thing. Even when using my Opti Visor PLUS a powerful magnifier with it, I could just barely see it at the muzzle, BUT I could not detect the spot he added on the piece to make the barrel full length. But that's not all.....
I knew the owner VERY well. He was a very good shot, but not a great shot. Still, the first time he fired it in National Competition, he placed 3rd in the individual championships. After getting over me being stunned by his score, I later kidded him the Rifle got him into the Top Three, not his shooting.
I have never had the need for Bobby's services, but recommended him to dozens of folks who used his services. Trust me, I looked long and hard for a "sporterized" original for him to work on, but never found one at a good price.
Gus