I'm going to go in a limb here and guess you're being paranoid, that you've been agonizing over this since you got the rifle, and that you haven't done a lick of harm to the .577

Unless you know for double damn sure that you screwed the pooch, put the rifle in the vault, have a warm glass of milk, and get some sleep.
Shoot it again tomorrow!

Did you cast the chambers before you shot it?
If so, do it again and compare the chamber castings.
How many rounds went through it?
Compare the first pair of cartridge brass with the last.

Once you confirm that you've done nothing to hurt your .577, look at Marrakai's and Curl's loads and compare them to what you've been shooting.
Might be another couple of recipes to try.

Cheers
Tinker