Agreed with Dixie for the most part.Thats about trueing the receiver face ,and that may be the foundation the barrel rests on...unless like a military Mauser barrel,the barrel has no shoulder.I do not know your particular rifle.
In any case,the critical surface the barrel tightens against should be square to the threads so when the barrel tightens there is a good,evenly loaded 360 deg foundation for the barrel.
That's all good,but realize its done with the barrel out,and you have removed steel,so your front sight will not be indexed any more and your headspace has shortened.Bummer.
And your bolt face may not be square to the bore,which was your question.
I'm not trying to rain on your parade,you are thinking right!!I'm trying to let you know there is a lot to what you want to do.
The receiver threads are likely cut in a different operation than the receiver bolt bore.They likely are not perfectly co-axial.Some blueprint jobs involve re-chasing the receiver threads co-axial to the bore.That is not easy.
Then there are the surfaces the locking lugs rest on in battery.Worn? set back?
Careful with the idea "lapping lugs".What are you lapping to?It helps if these surfaces are flat and true...and parallel to the receiver face.They are rather tricky to get in to face,with a facing boring head or rotary table,and realize they may be pack hardened.
That flat established,I prefer a threaded bushing with a spring loaded plunger screwed into the receiver to put a central,even load on the boltface to check lug bearing.Sharpie marker on the bolt lug faces tells the story.
I save some time using high spot technique and stones to lower the hi spots on the bolt lugs till I get good bearing,then just a finish lap.Use the center load plunger on the bolt face for lap pressure.Grabbing the bolt handle is an off center load.Not so good.
OK,all that done!! Now you would be ready to square the bolt face .
One way,A threaded bushing that screws in like a barrel shank with a precise hole in the center to guide a lap,,if only a little steel needs to come off.(Several ways to do this,a sinker EDM would be great!!A careful mill setup can work,but,low tech,lapping through a bushing is one way)
Of course,all this changes the headspace,so you may need to set the barrel back a thread,re-index the front sight straight up,and recut the chamber.If the barrel has any extractor cuts,those will need rework...
If you want education,go for it!!If you want a tack driver,consider the sows ear/silk purse story.A Winchester/Savage/Remington etc maybe?
Or,let it be what it is and shoot it!!