Some of the things that can affect RATC are as mentioned, high bolt and letting the hammer down from half cock, also improper bolt timing/worn hammer cam or bolt leg. The bolt on a Colt should drop in the lead-in unless it's an oval bolt stop like Walker/Whitneyville or 1st Dragoon models. Also Remington NMA/NMN models should drop the bolt about half a bolt width before full engagement.