I think … therefore I am.

Just my opinion, but I see no reason for so many, deep “lube grooves” in a bullet for an airgun…. You might consider making the central portion just 0.002″ smaller than the lands in the barrel, and only having two points of contact that are the groove diameter, at the back of the head, and at the base….

Bob

For a .25 cal, I would make the center section 0.240″ diameter, and eliminate the two middle bands, leaving only the back of the head and the drive band at the base in contact with the rifling….

Alternately, you might consider moving the rear drive band forward slightly, to leave an area slightly smaller than the lands at the rear of the bullet…. similar to what is done in a PB bullet designed to hold a gas-check…. Then if there is any problem caused by sizing, or the sprue cutter, it doesn’t affect the base of the bullet, causing accuracy issues…. I mention this because many airgunners find that GC designs are more accurate than FB types….

I notice your dimensions don’t add up correctly…. The bands and grooves are…. 2 + 1 + 0.5 + 1 + 0.5 + 0.5 + 0.5 + 1 + 0.5 + 4 + 0.7 = 12.2 mm, but the overall length is only 10.6 mm ?

Bob