New shotgun (will provide brand and what occurs with warranty service) shoots well, but, finding plastic from wad and burnt powder is being lodged between barrel and entrance to choke tube. Measured all of the chokes for OAL and distance from leading edge of chokes are all within 0.002". With any of the chokes installed, a crescent of the barrel machining can be seen at barrel/choke junction in the same location. When viewing the choke/barrel junction with my borescope, there is a gap between the barrel and choke entrance. ARGH! Coenctricity & barrel/choke depth seem to be the culprits. Any other suggestions? Imagine this is a barrel replacement.