Here's one for you from a book I picked up today on German secret weapons, the first person to have a crack at the idea was Karl Puff in 1903 but technology at that point in time was not able to produce the barrel. Along came Gelrich in the '30's he was able to manufacture hunting rifles with this principle though very expensive they were to produce.
He tried to get interested parties around the world the USA included in this A/T gun, he took one to the USA I think, here it is AD Verbatim;
"However, the Springfield Arsenal, for one, validated the concept, producing a version of the M-17 rifle with a velocity over 2135 m/s (7000 fps) instead of the standard 855 m/s (2800 fps).
Book is by Roger Ford. I think the projectile would have had to have been monolithic as a jacketed one would not handle the gyroscopic forces. Funny thing about the Gelrich gun the USA did not want it and soon found out in the war just how effective they were at A/T.
With Teutonic thoroughness they devised the squeeze section on a threaded system and this could be swapped out in a short time, as that part of the barrel wore quickly. They did not need any special tools or amourers to do it just the troops on the gun. So bit of trivia. The M-17 would be an interesting one to look into.