This is a 1:1 scale replica of an Ar-15 or m16 barrel. THIS IS NOT A REAL BARREL AND CAN NOT BE MADE TO FIRE, EVEN IF PRINTED IN METAL. THIS IS FOR MODELS OR PROPS ONLY, NOT TO PRODUCE A FUNCTIONAL FIRE ARM.Print each cut and use acetone to weld them together, pretty basic. If you want a carbine length model, leave out piece 3 and glue 4 directly to 2. After you have finished visit: https://www.youtube.com/user/americannerdproject Thanks!