I made a few drill bushings and seemed to work OK.
Started with a drill bushing that was 9/16". Wanted to have something substantial and not wimpy like a 1/4" that could deflect easily.
Then switched to the 5/8" bushing and then removed all and reamed to 11/16".
Nice and snug.
I first squared the jig with a dial indicator, and centered the mill over the jig bushing with a co-ax indicator. All was pretty square and centered before starting any drilling.
If the hole is off 1/64", with the TM receiver that has the scope rail forward and bored for the barrel, there could be an interference issue. Just something to avoid before actually doing any drilling.