1.6mm Upgrade Spring
This result was achieved with a custom-made 1.6 spring and Worker Bambu 1g darts. Consistency drops noticeably when using unringed Worker darts at this fps.

With the standard 1.5 spring, expect ~190 FPS with a good air seal.
1.7mm Upgrade Spring
Updated 29/09
The 1.7 spring has been put on hold for now. The screw hole on the slider can’t handle the stress.
The test was conducted using the Loki’s standard double-threaded barrel.
Switching to a 310 mm Worker inner barrel may result in slightly higher FPS.

I wouldn’t call the priming effort “easy,” but it’s definitely manageable for regular play. The Loki has a very short priming stroke, so the key is to use a quick, decisive pull rather than trying to prime it slowly. Do that, and there’s really no issue.
After all, the FPS is very appealing.