Plenty of rifle image in the videos. Minus the easily removable stock, a carbine-length Mauser is only about 32 inches long. Standing, measure from your knee to your shoulder, then slide a 32 or even 40 inch wppden rod under your shirt and upper pant leg. You will have limited hip motion but your knee will function.
It was an unmodified Mauser 98. They are 44.5 inches long with approximately 24 inch barrels. Look for the pics.