This study investigates the kickback force (F_K) experienced by firefighters during fire suppression using hoses of varying diameters and different nozzle sizes. Rigorous ground tests were conducted, where a fire engine was employed to propel water through a 200 ft hose line, simulating real-life firefighting scenarios while using the hip grip and clamp techniques for hose advancement. Two distinct hose sizes, 1^3/4 and 2^1/2 in., were employed with solid stream nozzles of varying diameters, facilitating the examination of kickback forces at different attacking angles. The findings substantiate that the F_K exhibits variability in response to changes in the attacking angle when utilizing the clamp technique, which encompasses angles of 45°, 30°, and 15°. The 45° angle exhibits the lowest force, while the 30° angle manifests the highest force, demonstrating a notable discrepancy of up to 25% compared to the 45° scenario. The F_K observed at the 15° angle for the clamp technique closely approximates the corresponding values derived from the hip grip hose advancement method. The results also underscore the necessity of regarding the NFPA nozzle reaction force as an integral component of the all-encompassing F_K experienced by firefighters during hose line operations. The NFPA nozzle reaction force resulted significantly below the actual F_K observed in all tested experiments, displaying the most substantial difference of 50% in the case of the 30° angle utilizing the clamp technique.