Left Rear Caliper Rebuild Question

[Travis71280]

Hi all, I'm in the process of rebuilding my left rear caliper after I found that the piston dust cover deteriorated. I took the pistons out to clean them up (they had some surface rust) and I noticed the pistons will slide in freely (with the seals out) bud they don't slide in all the way. Are they suppose to be tapped in the rest of the way? Just didn't want to tear anything up. Thanks in advance.