u/Nyancide

IMR 4064, Unique, Bullseye, some Reloaders, etc.

I did not make the file, I just tested it.

I did 5 rounds of 5.56 and 5 of 5.7x28. Projectile weight was about 20 with the current design using PLA. I would like to do this with something that is a little heavier, and a more precise design. Every round chambered flawlessly.

Shooting: Did not cycle in my Hellion. I did not expect it to. I did not shoot suppressed. Could not obtain a velocity with these 5 rounds due to issues capturing with the Garmin (our error). Suppressed would fire and not move the bolt. Regular would fire and half cycle. I preferred it to not cycle at all than to half cycle and jam.

The 5.7x28 was shot from my Stowaway. No issues. Would likely cycle in my Five-seveN. I'll test that next time.

Barrels: No fouling after the 5 rounds of 5.7x28. Crisp as it was. For the Hellion, no fouling at all. Fired once with the anti drone, then once with FMJ.

Accuracy: Not very accurate in either gun. Groups are mostly together, but the placement was a little inconsistent. That could be user error, my optic is not perfectly zeroed on either of these guns. Rounds at distance did not seem to hit paper in a way we could verify well, but did hit steel.

Magazine: Nothing broke inside the USGI magazine. I was worried the 3D printed part might break or snag, but no issues.

Loading, powder: I am not going to be held liable for anyone injuring themselves. If you load anything, that's 100% on you. For the 5.56, I used Winchester primers. I use W748 for basically all my semi auto rifle stuff (5.56, .308, .224 valkyrie). For my 55 gr loads, I'm conservative with 24.3ish grains of W748, that goes about 2650 fps and is only for plinking. I used the exact same load for this experiment for a few reasons. I did not want to create something that might be too dangerous, as 20 gr 5.56 anti drone BB rounds with 3D printed bullets has no load data. I bet I could go to 27 or 28 grains without issue.

I had zero pressure signs of course. I think with a higher amount of powder and velocity, accuracy would increase.

For the 5.7x28, I did increments of 0.2 between 4.5 to 5.1. All seemed fine but I would stick to 5 or a bit more most likely.

Loading, "bullet": This was a bit annoying. The design fits 3 BBs. The trouble I had was just seating the bullet. If you sat it down to a proper depth to fit in a magazine, for me it would usually mess up and cause the neck to be crushed and the BBs shoved inside the case with the 3D printed clamshell broken.

To fix this, the easiest and most simple solution was to load it halfway to the point where it was in the case and wouldn't fall out or move. With every round, it would force some of the 3D printed material out on the side. I just ripped those little pieces off. After all of the bullets were seated about halfway, I went back and redid them to sit at the proper depth and it was perfect.

Overall, I would continue to experiment with this and likely will. A shotgun is still easier to use and more reliable imo, BUT, its cool.