Confusion about when it's my navigation, and when it's ATC

Mxsmanic wrote:

Three hundred feet seems generous for altitudes. I thought I read
somewhere that I was supposed to be within 100 feet, or was it 60
feet? Now I can't seem to find a specific tolerance in the FARs. Of
course this isn't normally a problem if I'm on autopilot, but when
flying by hand I still have trouble holding an altitude.

Autopilot does work quite well in MSFS, really. In real
flight under IFR, the bounds of permissible altitude
deviation as seen by ATC via our Mode C squawks are derived
from published FAA documents, not the FARs. Google is fun;
site:www.faa.gov. Knock yourself out. I also can hold
altitude quite well within 10's of feet in a real
no-autopilot airplane in even raucous meteorological
conditions. Years of MSFS sim weenie experience taught me
how, I must admit.

F--