Well, all I can say is to take a physics course and learn about conservation of energy. Then explain why that mechanical deformation takes the form of round globules of lead or steel (just like solidified droplets) if there is no heat involved.
Also, why would a barrel expand from pressure at the base of a stopped bullet when it doesn't expand from the same pressure behind a bullet that is moving. (Actually, it does, but the expansion is so small as to be negligible.)
Also, note that as a general rule, mentioned in conjunction with the 9/11 building collapse, is that heat reduces the strength of steel by one half or more. So a barrel that is 1/4" thick becomes effectively 1/8" if heated. By that non-existent heat from that non-existent kinetic energy.