u003cbr/u003eThe full form of this is Total Runout Indicator or Total Indicator Reading. It simply means how much runout your cartridge has when shot from the rifle.u003cbr/u003eu003cbr/u003eu003cimg alt=u0022What is T.I.R., and how can it be measuredu0022 src=u0022https://proreviewbuzz.com/wp-content/uploads/2020/04/What-is-T.I.R.-and-how-can-it-be-measured.jpgu0022/u003e