Redding Instant Indicator for 220 and 6mm Beggs
Don,
For the purposes of using it for a case length or bullet seating comparator as previously discussed you could probably use the Redding 6ppc model. That probably comes with a 0.237 bushing for the bullet seating setup. You will need to also buy a 0.219 bushing for the 220 Beggs. Note that if you have barrels with tight bores (0.236, 0.218) you may want to use matching sizes of bushings for bullet seating. The setup gauge for the 6ppc (looks like a brass go gauge) will not be useful for either the 220 or 6mm Beggs.
The better answer would be to contact Redding and they would probably work with you to provide a customized Instant Indicator for both the 220 and 6mm Beggs. Expect a long wait and serious cost though.