Gap for handguard retaining cap on pistol length gas?

I know that on carbine/mid/rifle length gas systems, proper gas block alignment involves a 0.020” ish gap between the gas block on barrel shoulder to account for the lack of the handguard retaining cap with a free float rail.

I haven’t been able to find out of this should be the case with a pistol length gas system or if it should be pushed up to the shoulder due to the delta ring style handguard not being used on pistols.

Upper in question is a PSA 8.5” .300 Blackout. Barrel wasn’t dimpled and set screws were barely finger tight. I dimpled it, loctited, torqued, and staked them, but didn’t leave any gap.

So far it has run 100% with subs and supers, both suppressed and non with an H2 buffer, but I want it to be right. My concern wouldn’t be a relatively small gas port not being perfectly centered in a large gas block hole, but rather there being some sort of “lip” from it overhanging the port slightly and building up carbon deposits, clogging it over time.

The hole in the gas block is large enough to account for that 0.020". I wouldn't expect you to have any issues as I have run thousands of rounds this way before I knew that there was supposed to be a gap. The gas block hole won't be perfectly centered over the gas port, and the gas tube will protrude into the receiver a hair more, but I bet you'll never feel the difference.

The best way to check this for sure is when installing.

Put on the the gas block upside down so the gas port can be viewed through the bottom set screw hole.

You'll quickly be able to tell if there should be a gap or not depending on the particular barrel and gas block combination.

In my experience there is no right or wrong. Have several ARs and assembled many more. These include carbine, intermediate, and pistol length. Perhaps 1 or 2 I used an old-style cardboard business card as a "gauge" which placed the gb at its happiest point. All others were seated fully against the shoulder. Each and every one I tested for maximum flow before finalization.

The inlet in a gas block will be larger than the gas port by a margin that is greater than the thickness of a handguard cap. This I am confident of.