I'm trying to figure out how to order the correct length barrel for a Pistol 5.56 Radian Receiver that will be suppressed.  I will be using the Dead Air keymo devices.

My hand guard measures exactly 10"  from the face of the receiver(the seam between the handguard and the rail).  The Hand guard was listed at 10" when purchased.

So how long to get the barrel to make sure I will have suppressor clearance without getting much space in there?

When I ordered an SLR recently, they said .75" on theirs.  So the 7.25" hand guard is made for an 8" barrel.

The barrels are coming from Compass Lake as custom barrels.  So I imagine they are exact in their measurements.

This might help, but different suppressor mounts will have differing clearance.

I did look over that in a lot of detail.   But still don't have a lot of confidence in where the barrel starts.  Looks like the safest thing is HG + 1"

I go with an inch. That's using griffin mounts. On my (2) 11.5s, using MI handguards there's a slight gap between the handguard and suppressor, but it's minimal. On my 14.5 with a FCD handguard there's almost no gap. The mount will make a difference, but id say an inch is a good bet. 10" rail = 11" barrel.

FWIW, this is a 10.5" barrel and 10 inch rail

(Claimed)10.5" rail and 11.5" barrel.

Thanks folks for very useful info.  I'll get the 11" I think.

I'm using Dead air key Micro mounts