257 WBY pressure/accuracy question

[rcol317]

Was helping a friend that is just getting into reloading and was having accuracy problems. I've loaded for 40 plus years and am puzzled. He's shooting 115 VLD's and @ 100 yards and 200 yards is getting 1 1/2 MOA groups but @ 400, 500 and 650yards is getting 1/2 Moa accuracy. at 650 yards 3 shot group can cover with a coffee cup? I shot the load and found he is WAY over loaded for pressure and will need to back off the load quite a bit. When I asked him how he came up with load he said "just kept adding .5 grains until is shot well. Lucky is a high dollar custom rifle the action held together. Note: PRINTED LOAD DATA IS IMPORTANT

I was stumped why it didn't shoot well 100/200 but shoots well @ 400 yards plus?

 

[CatShooter]

I was stumped why it didn't shoot well 100/200 but shoots well @ 400 yards plus?

Most likely, parallax.

 

[Chappy]

Was helping a friend that is just getting into reloading and was having accuracy problems. I've loaded for 40 plus years and am puzzled. He's shooting 115 VLD's and @ 100 yards and 200 yards is getting 1 1/2 MOA groups but @ 400, 500 and 650yards is getting 1/2 Moa accuracy. at 650 yards 3 shot group can cover with a coffee cup? I shot the load and found he is WAY over loaded for pressure and will need to back off the load quite a bit. When I asked him how he came up with load he said "just kept adding .5 grains until is shot well. Lucky is a high dollar custom rifle the action held together. Note: PRINTED LOAD DATA IS IMPORTANT

I was stumped why it didn't shoot well 100/200 but shoots well @ 400 yards plus?

Them Bergers might not be full stabilizing till they get out further. I haven't had this problem in my .25-06 Remington, but did have that problem in a .260 Remington AI with 140 Berger VLDs where they wouldn't shoot worth a crap at 100, 200 yards but would blow matches out at 300, 400 and so on.