Complex sentence: When the rounds are fired, the barrel, magazine, chamber and operating mechanism recoils back against recoil springs several inches and only when it strikes the buffer at the back of the rifle does the user feel the recoil.
Split into simpler sentences: When the rounds are fired, the barrel, magazine, chamber and operating mechanism recoils back against recoil springs several inches. Only when it strikes the buffer at the back of the rifle does the user feel the recoil.