This article was originally posted on Thefirearmblog.com
After a temporary pause in producing video content, Royal Nonesuch is back. This YouTube channel is known for the variety of homemade gun projects. Not only he is back but also plans to start even more entertaining projects. He also applied for an FFL and SOT which will allow him to expand the range of weapons and mechanisms he can experiment with. Among his first new project is a gun utilizing an advanced primer ignition (API) mechanism with an extended chamber. Let’s see how the host of the channel describes his project.
Any open bolt blowback system is basically an API. Royal Nonesuch’s project is similar to the operation mechanism used in autocannons (Becker, Oerlikon etc.) where rebated rim cases were used in extended chambers. In this version of the API system, after the round is fired the bolt and cartridge case move rearward for a certain distance inside the extended chamber and supported by the latter. By the time they clear the chamber the projectile has already left the bore and the pressure is decreased to a level safe for the extraction. The advantage of this system is the simplicity of the mechanism with a much lighter bolt than it would be required in case of blowback operation without an extended chamber.
Evidently, there are at least two issues in this project. First, how will the headspacing be accomplished? The .45 Long Colt is headspaced on the rim and the .45 ACP – on the case mouth. Unless he redesigns the chamber to allow the .45 ACP headspace on case mouth inside the .45 Long Colt chamber, it may cause issues. Maybe, it will headspace (sort of) on the riflings, but that’s not too reliable. Second, with a non-rebated rim, you cant have an extractor in the bolt of this gun – there is just no room for it.
Royal Nonesuch probably knows about these issues too and I understand that this is more of a fun/experimental project. However, I think there is at least one commercially available cartridge with a relatively deeply rebated rim and straight walled case which can possibly be used to build a fully functional API gun with an extended chamber. I am talking about the .50 Beowulf. He will need to make a custom barrel for it but I think it may worth the result.