I have a buddies Sako 75 in 7STW the rifle has been taken great care of as far as cleaning and such. I worked up a load for him with 168 bergers and it didnt shoot great but it would hold a 1" group easily. but he said it was good enough so I let it be. Few months later after shooting it a few times he calls and says it is shooting 8 " groups. So i went and got it and checked the obvious things, action screws, scope mounts to gun and scope. went and shot it and got about 3" so I tried a new set of sako optilocks and 3" groups, so I changed scopes to a scope i know is good and still 3" groups. so I loaded up bergers close to the lands thinking maybe they were too far away being loaded to fit the sako magazine... still 3" groups. so I tried partitions and 3" groups again. so I took it to the gunsmith and had it bedded went and shot it and yet again 3" groups.. the rifle has less than 100 shots through it. so I checked the crown its good, bolt lug recesses are good and clean and lugs have good even contact. stock does not appear to be cracked and everything appears to be fine. what do I check next? the rifle used to shoot why will it not now? maybe he shot it with debris in the barrel and now there is a slight bulge? I have run tight patches down it and it feels fine.. no loose spots. Someone help me out give me some ideas. I am tempted to send it to hill country in texas or just tell him to have the thing rebarrelled and gone over while its in pieces.
" Real elk guns start with the number 3 or bigger and blow two holes, one in and one out." - My Dad
Have either of you ran any different bullets through it other than THAT particular lot of Bergers? I know it's rare for good companies to have a bad run of bullets and let them get all the way to retail, but you've already covered most of the obvious issues.
So what's left....hmmm?
1. Rifle wants a different bullet.
2. As the barrel heats, could it be contacting the stock---even though it may not do so when cold?
3. Has headspace been verified?
4. What's the twist rate of the barrel? Surely it's fast enough to stabilize the 168's, but is there a tiny chance that it's been rebarreled at some point?
5. Other than that, I'd have to say to slug the barrel and mic the slug to make sure that the tolerances inside the barrel are up to spec.