I can't source this atm, but I believe the forces exerted by firing a bullet badly damage the structural integrity of the plastic without any absorbing "barrel.

I can't source this atm, but I believe the forces exerted by firing a bullet badly damage the structural integrity of the plastic without any absorbing "barrel." Current 3d printed plastic can't hold that caliber of explosion, hence the need for a swappable -padding- that absorbs the damage to protect the gun. This solution is obviously better than destroying your gun with every bullet, but it doesn't really solve the practicality problem.