Simple tool to mount a gas block correctly

[montana]

I like that. It gives you axial and clock location.

I still determine the clock location with trouble-shooting the mounted gas tube and block with the upper receiver upside-down and a stripped bolt carrier and key.

The clock location gets determined by the position where the gas tube doesn’t bind or clip the carrier key with the receiver upside-down.

You do it upside-down to simulate magazine cartridge stack pressure up against the carrier.

Exactly what I do too for final adjustment. Then I verify with my bore scope...