PCARS 100mm Covered

Swappable PCARs for Foam Dart Blasters (HPA & Springer)

A set of printed PCARs for tuning spin on foam dart blasters. The idea is modular: print the twist rates you need, label them, and swap them in seconds to retune your blaster for a different velocity or different conditions — no rebuild, just clip on the one you want. The collet system is the Sillybutts system, since that's the one most people are familiar with.

You'll need 1 or 2 O-rings: one between the collet and the PCAR on the barrel, and maybe one between the PCAR cover and the PCAR.

I'm getting very small groups at 30 metres — comparable to or better than a high-end machined BCAR.

These came out of a fair bit of bench testing on an SBL O2 / NarfCORE setup and an Apex Prime springer. The short version of what I found: the twist rate you want scales with velocity, roughly twist (mm/turn) ≈ 2 × your velocity in fps. So a 300 fps setup wants about 1:600, 350 fps wants 1:700, and so on — then fine-tune up or down for your best group. The FPS ratings are just a starting suggestion; what actually decides the spin you need is your dart, your local climate, and your printer.

Tuning — what to look for

Once you've picked and printed a PCAR, fire about 10 darts through it to clean it out, then start testing.

Example: for a 300 fps blaster I'd start with PCAR 600. Fire a dart and watch it travel.

• If the dart fishtails or tumbles, the spin's too slow — try PCAR 575 or lower.

• If the dart spirals off in a piggy-tail, or just veers off course, it's probably too much spin — try PCAR 625 or higher.

Included twist rates

• 300 — 1 turn in 300 mm. Fastest twist. Recommended for 150 fps blasters.

• 400 — 1 turn in 400 mm. Slower than 300, faster than 500. Recommended for 200 fps blasters.

• 500 — 1 turn in 500 mm. Slower than 400, faster than 600. Recommended for 250 fps blasters.

• 600 — 1 turn in 600 mm. Slower than 500, faster than 700. Recommended for 300 fps blasters.

• 700 — 1 turn in 700 mm. Slower than 600, faster than 800. Recommended for 350 fps blasters.

• 800 — 1 turn in 800 mm. Slowest twist. Recommended for 400 fps blasters.

Printing the PCARs

• Printed on a Bambu P1S and P2S in PETG. PLA should be fine.

• Print one at a time, upright, front end down.

• No supports.

• 0.20 mm layer height.

• 4 wall loops and 4 shell layers (but choose your own).

• I used 40% infill, but I'm a psychopath.

Printing the cover

• No supports.

• 0.2 mm layers.

Printing the collet

• 0.2 mm layers.

• But whatever you like.

Notes from testing

I've done a heap of testing over about a year. A few quick things I've learnt: twist pattern (linear vs progressive vs others) and land count (3 vs 5) didn't make a meaningful difference, so these are kept simple. I tested a lot of different crushes and profiles, and this one is the best. FPS loss is close to what you'd give up on a high-end machined BCAR.

This one's made for an HPA blaster, so it's 100 mm long versus the 80 mm I run on my springers — but it works great on springers too. I'll upload 60 mm and 80 mm versions, with and without covers, over the next few weeks.