It could be attributed to a couple of things.
[ol][*]First off your rifle is brand new. Some, not all rifles, seem to need a break in period where during that time they just will not hit anything consistantly. I had a rifle like that and it about drove me nuts.[*]Another issue is your scope. Perhaps it is not mounted solid, or perhaps the optics in it are bad. I believe the Red Heads are the Tasco Brand (I was told).[*]Another issue is, perhaps the rifle just does not like the 250 grain SST although that would be strange because most rifles do shoot them well.[*]Finally the pellets might be bad. I seriously doubt this, but it does happen.[/ol]


[ol][*]I would get some J-B Bore Paste and scrub the barrel of the rifle real well. Then give it a good cleaning. This will help smooth out any ruff spots in the barrel if they exhist. The rifle being new just might need to be broke in.[*]If you doubt your scope on way to check it is to remove it and shoot over the open sights at 25 yards and see if the rifle will group with open sights. If it does then put the scope back on and it should also group at that same range with the same load. Another way is to have someone other then you shoot the rifle and see if it behaves like that for them. Check the mounts also. Or if you have a different scope around the house, throw that on and see what happens. All you are trying to do at this point is to rule out things that might be going wrong.[*]Try some projectiles other then the 250 grain SST's. I would suggest some 240 grain XTP's or some 375 grain Buffalo Bullet SSB sabots. You can buy them through Cabela's. My CVA Staghorn Magnum shoots them very well. Of course there are powerbelts, but I hate to recommend them because of the cost.[*]Last reference the powder, get some new pellets or even better, some loose powder. And see if that makes a difference. Again, all we are doing is taking and checking all phases of the shooting sequence. And at least you were smart enough to try different strength charges to see if that made a difference.[/ol]
The swabbing of the barrel is very important. This is especially true when sighting in. You want each shot to be as close the next to the way they are being shot. Swab the barrel between shots. I swab with with isopropyl alcohol and windshield washer mixture. What ever method works for you is good.

Personally I sight in my scopes at 25 yards. At that distance I want that rifle to shoot a ragged hole. Then I move back to fifty yard and so on until I am back as far at the longest shot I might have to take. Keep at it. And good luck with the rifle. You have a good one there.