In looking at the AEA Defender barrel, I see a problem that I have seen before with other AEA barrels. There is an old saying “A little knowledge is a dangerous thing”. It is not enough to understand a 17-caliber or 22-caliber air gun and extrapolate what you can do at larger sizes. Someone in an organization building big bore air guns needs to have a good working knowledge of firearms and how (Why) they function. We are dealing with pressure and pellet weights that bad math or poor design can best case scenario cause function issues and worst-case scenario cause injury or death.
The unusual thing about the .457” barrel for these is the same thing that I recently saw in the Zeus 58 caliber barrel and that is there is almost no chambered area for the pellet in the barrel, the rifling goes nearly to the edge. Now if you were using a traditional pellet design that looked like an enlarged 22 caliber pellet with the large skirt at the base and every other portion of the pellet being smaller (The typical bell-shaped pellet) then this would not be an issue. Unfortunately, just about every .457” pellet on the market looks more like a traditional bullet than a traditional pellet and you can seat the pellet about 1/8” into the barrel before you run into an issue.
To be more specific you have about 1/8” that is.457” at the back of the barrel, then when the rifling start 1/8” in you have about 2 inches at .454”, and then for some reason, the front of the barrel chokes in further and the diameter at the top of the rifling is .452” based on my roller gauge readings. I have also made a video that will be released on December 6th, 2022 on YouTube that will show this. The answer is two-fold, you need a round nose pellet that has more of the contact rings in the back half of the pellet. The second thing is the pellet needs to be sized .456”.
The video shows the results of this and a pellet that was pushed down the barrel to show good contact with the lands and grooves. What it comes down to is a .456” sized pellet that can be pushed by hand nearly inside the barrel and with just hand tightening on the red adapter, it finishes the last 1/32” of the seating process. Perhaps this could be accomplished with a .457” pellet (Basically using the adapter as a sizing tool). But those threads are pretty fine and I think you could end up damaging the adapter after a few uses.
Ultimately, I do hope this means that people might want to buy my .456” pellets for the Defender 2.0 .457”, but even if you don’t, you can use this information to properly size your pellets.