FX Superior Heavy STX Barrel Liner – .22 700mm Pellet/Slug
The FX Superior Heavy Smooth Twist X (STX) barrel liner is a replacement rifled liner designed for FX PCP air rifles. It features FX’s patented outside pressing method for creating the rifling. This 700mm liner is chambered in .22 calibre and has a 1:16″ twist rate, optimized for heavier pellets and slugs.
The “Heavy” designation refers to the twist rate, not the barrel wall thickness. It is not suitable for lightweight projectiles such as the FX Hybrid Slug, which perform better with the standard Superior liner.
Specifications
| Parameter | Value |
|---|---|
| Calibre | .22 |
| Length | 700mm |
| Twist Rate | 1:16″ |
| Application | Heavier pellets and slugs |
| Barrel Type | Rifled (STX) |
FAQ
What is the difference between the Heavy and standard Superior liners?
The Heavy liner has a 1:16″ twist rate, optimized for heavier pellets and slugs. The standard Superior liner is better suited for lightweight projectiles like the FX Hybrid Slug.
Is this liner compatible with all FX PCP rifles?
This liner is designed for FX PCP air rifles that use the Superior STX barrel system. Compatibility depends on the specific rifle model and existing barrel configuration.
Does the 700mm length provide better performance?
Yes, the 700mm length offers maximum dwell time, potentially resulting in higher muzzle velocity and flatter trajectories when used with appropriate ammunition.

Austin Newman –
Installed the Heavy STX liner in my FX PCP and noticed a significant improvement in accuracy with heavier slugs. The 1:16 twist rate keeps the slugs stable at longer ranges. Performance is consistent and reliable.
Maria Wilson –
Works well with my .22 slugs. The twist rate is perfect for heavier rounds. I didn’t see much difference with lighter pellets, which makes sense given the design focus.
Stephen Hart –
The liner fits perfectly and the installation was straightforward. I’ve used it with both lead and steel slugs and the consistency in shot grouping is excellent.
Piers Marshall –
Good for heavier ammunition, but not ideal for hybrid slugs. I expected better performance with lighter rounds, but the twist rate is clearly optimized for heavier loads.