A muzzle loading bullet gas check has external recess and ridge system, and / or an internal locking ridge system. The preferred gas check has an opening or recess on its front end for receiving and frictionally engaging a rearwardly extending post of the bullet, the opening also preferably including an internal radial ridge for gripping the post and / or locking with an indent on the post. The barrel-interacting part of the gas check has one or more external recesses and adjacent radial ridges / edges protruding relative to the recesses, which serves to reduce the total surface area of the gas check contacting the bore. The recesses do not touch the bore of the firearm, resulting in less friction and easier loading, while the outer ends / surfaces of the ridges / edges do touch the bore to retain the bullet in the bore during handling and hunting and to effectively capture gasses after the firing explosion.