Well I have cheap digital calipers. Also good dial calipers, good veneer calipers, and a decent 1" micrometer from my machinist days.
I used the cheap calipers to measure the opening in the cap and the 810 adapters.
I just didn't measure a 510 tip before posting, going off memory.
My point was there's a nominal size that 510 should be. Poor tolerance leads to out of spec parts, but there is a nominal size.