If you want to check the throat a not cost way to do it is to load up a round with no power or primer and seat way long, as close to falling ouit as possible. Good long 200 gr .30 works well.

Tricky part is to get the firing pin out of the bolt as too much cam action with it in.

If you know how to do that you are then good. There is a knowledge groups who says to remove th extractor but I don't find that to be needed.

Round gets put into magazine, run bolt forward carefully and feel for resistance. If no resistance with it long your throat is eroded and you need a gauge to see how far.

If you get resistance and hopefully before even the bolt handle starts to turn down, seat the bullet .020 deeper and repeat until it goes in smoothly and the bolt handle goes all the way down easily

Measure the COAL and you have some ideas of where you stand.

Best I can do is 3 inches 5 shot groups at 100 yds, but my eyes are an issue