Semi reusable threaded rod APFSDS
Posted: Fri Jul 04, 2025 2:57 pm
So, I was thinking of ways to make APFSDS rounds for air cannons, and I realized that threaded rod is basically pre machined to have sabot interface grooves. I 3D printed some fins and sabots and they seem to be durable enough for a few shots as long as the sabot doesn't instantly hit the ground before slowing down. These darts won't actually punch through armor or anything, but I just think it's cool.
So far I have a 1 inch, 1.5 inch, and 2 inch version. I don't have a 2 inch air cannon so I haven't technically tested the 2 inch version, but it's the same design as the 1.5 inch version so I see no reason why it wouldn't work just as well. At the moment, all of the tips are blunt because it's easier than making them sharp.
They work pretty well and, for the most part I have been able to reuse the sabots. The fins and sabots both sometimes shatter when they hit the target so I don't consider these to be fully reusable. It definitely seems to matter what type of filament I use.
Hit Results. 1-4 were against a 3/4 inch redwood plank I'm using as a target.
1.5 inch bore: My cannon is fairly low performance and uses a 1 inch sprinkler valve which I have to open by hand. There's no sights so I can't really give an estimation on how accurate it was since I was just pointing it vaguely at a redwood plank.
Shots 1-4 were roughly 50 feet away.
Shot 1. 50 PSI, Unknown brand rainbow silky PLA construction (I forgot the brand), 6 inch rod. Fins and sabots shattered upon impact. Rod penetrated and stuck about halfway through. Silky PLA was giving me trouble but I was just trying to use up the roll while testing. It's super shit material for structural anything.
Shot 2. 50 PSI, Overture Easy PLA (digital blue), 6 inch rod. Sabots recovered after striking soft ground in good position. Rod penetrated completely and stopped by the fins, which embedded themselves about a quarter inch into the redwood. No layer separation but the fin was no longer tightly attached to the rod.
Shot 3. I fired the dart again at a longer range to see if the fins being loose would be an problem, and it flew around 200 feet with no issues I could see. The trek to the other side of my range is arduous enough that I haven't tried to retrieve the dart.
Shot 4. 50 PSI, Overture Easy PLA (digital blue), 6 inch rod. Embedded itself halfway through redwood target. Sabots oriented vertically. One flew down and shattered on the ground. The other flew into the wooden target and also shattered.
Shots 5-7. 50 PSI. Much closer range (20 or so feet). Backstop was a several foot thick set of tree roots. All sabots were destroyed upon hitting backstop. Multiple sets of fins received light damage, shattering at the trailing edge tips. Probably reusable but I haven't shot them again so far. All sabots were either heavily chipped at the obturator or cracked in half, rendering them basically unusable.
Shot 8. 50 PSI. 20 foot shot against a 2 mm aluminum plate to see if it would penetrate. Aluminum plate was heavily dented but not penetrated. Somehow the fins on this shot were undamaged but the sabots were still destroyed due to hitting tree at close range.
1 inch bore: Target is the redwood plank at ~50 feet. I had trouble testing this one because I just could not seem to hit the target before losing all of the darts. I'm going to 3D print a picatinny rail for my cannon and update the results once I put a sight on it. The air cannon uses flexible hose with a solenoid trigger that I can breech load. The long length of hose likely reduces power, and the barbed connections are a source of leakage.
Shots 1-3: missed. 2 sabots recovered, all others lost.
Shot 4: 80 PSI. Overture Easy PLA (Digital blue), 3 inch rod. Sabots recovered after hitting bush. Rod put a half inch dent into the redwood plank and bounced out. (I May have to sharpen these ones to get them to stick). The fins were undamaged but loose. I'm going to start gluing them on instead of letting friction do the work. I recovered the shot and fired it again but missed and the dart was lost
2 inch bore: I don't have a 2 inch air cannon so I can't test these. I assume they will have similar ballistic performance as the 1.5 inch ones since the sabot design is roughly the same. The sabot is heavier, which means it will slow down slower, so I am worried about it breaking a bit more than the other ones, which is why It has been reinforced with a two additional ribs. (visible in the picture)
So far I have a 1 inch, 1.5 inch, and 2 inch version. I don't have a 2 inch air cannon so I haven't technically tested the 2 inch version, but it's the same design as the 1.5 inch version so I see no reason why it wouldn't work just as well. At the moment, all of the tips are blunt because it's easier than making them sharp.
They work pretty well and, for the most part I have been able to reuse the sabots. The fins and sabots both sometimes shatter when they hit the target so I don't consider these to be fully reusable. It definitely seems to matter what type of filament I use.
Hit Results. 1-4 were against a 3/4 inch redwood plank I'm using as a target.
1.5 inch bore: My cannon is fairly low performance and uses a 1 inch sprinkler valve which I have to open by hand. There's no sights so I can't really give an estimation on how accurate it was since I was just pointing it vaguely at a redwood plank.
Shots 1-4 were roughly 50 feet away.
Shot 1. 50 PSI, Unknown brand rainbow silky PLA construction (I forgot the brand), 6 inch rod. Fins and sabots shattered upon impact. Rod penetrated and stuck about halfway through. Silky PLA was giving me trouble but I was just trying to use up the roll while testing. It's super shit material for structural anything.
Shot 2. 50 PSI, Overture Easy PLA (digital blue), 6 inch rod. Sabots recovered after striking soft ground in good position. Rod penetrated completely and stopped by the fins, which embedded themselves about a quarter inch into the redwood. No layer separation but the fin was no longer tightly attached to the rod.
Shot 3. I fired the dart again at a longer range to see if the fins being loose would be an problem, and it flew around 200 feet with no issues I could see. The trek to the other side of my range is arduous enough that I haven't tried to retrieve the dart.
Shot 4. 50 PSI, Overture Easy PLA (digital blue), 6 inch rod. Embedded itself halfway through redwood target. Sabots oriented vertically. One flew down and shattered on the ground. The other flew into the wooden target and also shattered.
Shots 5-7. 50 PSI. Much closer range (20 or so feet). Backstop was a several foot thick set of tree roots. All sabots were destroyed upon hitting backstop. Multiple sets of fins received light damage, shattering at the trailing edge tips. Probably reusable but I haven't shot them again so far. All sabots were either heavily chipped at the obturator or cracked in half, rendering them basically unusable.
Shot 8. 50 PSI. 20 foot shot against a 2 mm aluminum plate to see if it would penetrate. Aluminum plate was heavily dented but not penetrated. Somehow the fins on this shot were undamaged but the sabots were still destroyed due to hitting tree at close range.
1 inch bore: Target is the redwood plank at ~50 feet. I had trouble testing this one because I just could not seem to hit the target before losing all of the darts. I'm going to 3D print a picatinny rail for my cannon and update the results once I put a sight on it. The air cannon uses flexible hose with a solenoid trigger that I can breech load. The long length of hose likely reduces power, and the barbed connections are a source of leakage.
Shots 1-3: missed. 2 sabots recovered, all others lost.
Shot 4: 80 PSI. Overture Easy PLA (Digital blue), 3 inch rod. Sabots recovered after hitting bush. Rod put a half inch dent into the redwood plank and bounced out. (I May have to sharpen these ones to get them to stick). The fins were undamaged but loose. I'm going to start gluing them on instead of letting friction do the work. I recovered the shot and fired it again but missed and the dart was lost
2 inch bore: I don't have a 2 inch air cannon so I can't test these. I assume they will have similar ballistic performance as the 1.5 inch ones since the sabot design is roughly the same. The sabot is heavier, which means it will slow down slower, so I am worried about it breaking a bit more than the other ones, which is why It has been reinforced with a two additional ribs. (visible in the picture)