Yip retards will be retards I suppose....
Not here to argue but facts are that is the best way to tell if a gun fits, unless you as the shooter no exactly what your sight picture needs to be, even then it is reassuring if someone you respect as a shooter confirms.
It is quite likely that the owner of the shop didn't really no what he was looking for and just said it fits perfectly however. Takes a fair bit of experience to work out what your looking for.
Next best way is to shut your eyes, mount the gun then open your eyes, if your in line it fits ok.
Or practice mounting in front of the mirror, done that countless times
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