accuracy went south

the last few times out at the range i notice my accuracy is getting worse especially in the last 500 rounds or so, gun is a savage model 10 in a 6.5 creedmoor, barrel has approx 1700 rounds thru it, my buddy has the same gun with over 2000 rounds and his accuracy is still good. i know every barrel is different ect, so before i give up on it, i was thinking of different OAL of a loaded cartridge, mainly i have been shooting anywhere between touching lands and as far a .040 off the lands. has anyone been down this road and tried something and revived the accuracy. i am going to try loading .050 to .070 off the lands. tried 140SMK, 140 ELD, 140 Nosler RDF, 130 TMK, 130 Norma Golden Target, and the new 130 nosler 130 RDF, some 123 SMK. there are a few others in there somewhere, mainly used H4350, some Varget with the 130, and recently been trying Superformance powder. groups used to be around 7/8" and few 3/4" at 200yds recently groups are around 1 1/2 and some larger. i have changed it into 2 different stocks, the only thing i did not try was another scope, the scope is a Sightron SIII 8x32x56. so before i finally give up on this barrel, any thoughs what to try. no copper in barrel i cleaned it well after 50 shots.

thanks
chet

Did you borescope to determine no copper? Just eyeballing isn’t accurate.

A cheap option is buying a digital camera from amazon or similar that will fit your bore, not as good as actual borescope but gives you an idea and let’s you see with more clarity.

How much did the groups open up? Disregard I think you covered this.

You might consider cut and crown.

I agree. Copper buildup would be the first thing to look for. Throat if you push it hard. Powder lot, move up and down the load a touch. Check tightness on all of your rings and bases. Plastic flows, check action screws.

Throat erosion can be measured, you don't need a borescope to know it's there (and roughly its extent)
Seating depth/ OAL touching the lands on the new barrel, vs. now? As the throat erodes, bullets need to be seated further out to maintain whatever jump you've decided on.

I would give it a gentle cleaning, not a full scrubbing and see what happens. If accuracy comes back and goes away again quickly, I'd try a more aggressive cleaning, if it doesn't come back after that I'd get a new barrel. In fact I'd probably go ahead and get a barrel on order anyways because it's always good to have one "on the way"....

I would also check all screws for looseness- scope ring, scope base, and action screws.