MK18 - What suppressor leaves the smallest gap?

With the tax stamp going away Im starting to look around for a new gun.

looking at either upper, rifle, or pistol - I haven't decided. but the main thing is what suppressor setup leaves the least amount of gap between the suppressor and hand guard?

I have a couple saker 556's now that I swap around on my current ARs but im open to any suppressor as this will stay on the gun all the time