Red dot laser bore sight things are dirt cheap.
$10 Amazon
The photon beam is straighter than any cleaning rod unless you live next to a black hole or neutron star.
Chamber the laser and stick a sheet of white paper on the silencer (to use Horace Maxim's historically correct term) exit hole.
Is the dot centered??
With a .30 can on a 5.56 you have a lot of "wiggle room".