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Swiss Schmidt-Rubin Straight-Pull Rifle Database

Tinck Arms — 3-Position Adjustable Gas Block (MR556 / MR223 / HK416 compatible)

Precision-machined gas block designed to convert MR556 / MR223 rifles to the modern A5-style gas system while offering reliable, tunable performance for both suppressed and unsuppressed use.

Key features

Hardened steel construction with black Melonite finish for long wear resistance.

Titanium leaf spring for positive indexing and long service life.

3-Position selector:

N (Normal): Standard ejection-port vent closed for unsuppressed use.
SS (Semi-Suppressed): For semi-suppressed use.
FS (Fully-Suppressed): For fully suppressed use.
Three-position — tune perfectly for your suppressor.

Pre-installed gas vent screw: 1.5 mm (factory installed).

Additional jet sizes included: 1.1 mm, 2.0 mm, and 2.5 mm — swap quickly to tune gas flow for different barrel lengths, ammunition, or suppressor setups.

Rear-pin retention like the factory HK416 A5 — held in place by the rear pin only.

Ejection-port-side vent with selector cap — easily switch between modes.

Indexing tab: 3 mm width with a 0.75? profile

Compatibility

HK416 series

MR556 / MR223 platforms

For MR556 A4 you are risking misalignment because the tab is to small
Note: Not intended for use with barrels under 11?, due to interference between the adjustment knob/cap and muzzle device or suppressor. May require barrel/gas port modification.

Listing one-liner
Premium 3-position adjustable gas block — MR556/MR223 & HK416 compatible, 1.3 mm pre-installed jet + 1.1 & 1.5 mm spare jets, N / SS / FS modes, 3 mm indexing tab with 0.75? profile.