That's an interesting thought. I think I've got 550 grounds down the barrel at this point. Is it possible for the throat to wear that much in a stainless barrel after 500 rounds even if I usually only let the barrel get warm while I'm shooting and not hot?Also, your groups probably opened up because the throat is getting some wear now. Try seating your bullets .005 closer to the lands and see if that doesn't tighten it back up with the 57.5 load.
I went back almost to square one as much as I can at this point and am going to the range today.Yes. Stainless isn't a cure-all and actually wears faster then chrome moly barrels, everything else being equal. 50K-60K psi and a hot flame at the throat isn't any ones friend. Try it and let me know what you find out.
I REALLY want to not clean my barrel at all... but I'm terrified of getting that layering of copper/carbon/copper/carbon that is apparently really hard to remove. So I'll give it a few more efforts with only cleaning with hoppes to get the carbon out.Change scope, stop cleaning, and if that doesn't work, try a different bullet/load. I almost never clean a rifle barrel these days. And they are shooting very well. If after a few hundred rounds group size starts changing, I'll take them back down to clean steel.
If none of that sounds appealing, trip this one and buy or build something a bit better. I added up range trips, gas, reloading time and supplies, etc on a few guns. Adds up fast. That was when I just went to McMillan stocks, good gunsmith, great barrels and scopes, and most of my load development got down to about 20 rounds. Well worth it to me.
Changing too many things at once will drive you nuts. Systematic is the way to proceed. Let me know how you make out today.
I agree with Rflshootr, If you change three things before you shoot, you will never know what the problem was even if you manage to correct it.
Loook to see if you are still getting two distinct separated groups next time you shoot.