These are American Anti-Tank rifles that should be added. Either could be added to the RT, as an event prize, and a season reward. Anti-tank rifles may have quickly went obsolete but I still think they’re neat!
Winchester-Pugsley Anti-Tank Rifle, developed in 1918 for WW1 but the war ended and the project was cancelled
M2 Anti-Mechanization Weapon, a prototype M2 Browning MG converted into a semi-auto anti-material rifle
Winchester-Williams Anti-Tank Rifle, prototype AT rifle developed in 1944 but was declined because AT rifles were obsolete, attempted to be offered to Canada
.9 vs .5 inch 
T1 & T1E1 .6