Checking for concentric threads

[jwise]

I have a recently acquired M85 which I want to suppress. I bought an adapter (I know, the 'A' word) to go from 26mm LH to 5/8x24. I would have gone all the way to 1/2x28, but they didn't have any available, and the 5/8x24 51T mount cost the same as a 1/2 x28 mount, so who cares?

I picked up the mount the other day, and the adapter came today.

Here is the adapter installed:



And the 51T mount:



And with the M4-2000:



I checked the line up by looking down the bore (took the bolt out to do this), and then shining a flashlight down the chamber.

Here's a pic of the light coming out the muzzle:



What other checks should I do before locktiting the adapter/mount?

[Bendersquint]

I would actually measure for concentricity, flashlights are not a valid means to verify concentricity.

[jwise]

How does one "measure" for concentricity?

I plan to take this setup to my gunsmith to have him look at it, but I wanted to check as much as I could myself so I don't waste his time.