what loads to use on 99F .308 win

A while back I inherited my grandfathers model 99F chambered in .308. I brought it to the local gun shop and had them mount a Leupold 3x9x40 rifleman scope on it to replace my grandfathers old dated scope. when the gun store installed it and bore sighted it I did not notice but it was touching the rear dove tail iron sight. I shot it about 20 times at targets around 40 yards. eventually I brought it to my family friend who is a gun smith to check everything for me and he found that the scope was touching iron sights so he removed the scope and I sent it to Leupold to have it all checked out making sure nothing was damaged internally. once it came back he reinstalled it so it was not hitting the iron sights and we zeroed it in at 100 yards. with Winchester 180 grain ammo it was all over the place but with 150 grains it was holding groups in the center of the target. my question is what will cause that and what is a good round these rifles like to shoot accurately.

thanks Nick

Nick, Do you reload or are you looking for a factory load. In factory I like Federal and Hornady stuff. There is a myriad of reasons that one ammo works and one does not. Some of it you and some of it the rifle. Twist and barrel harmonics are two reasons. Some rifles don't like some bullets as well.

Hmmm, curious.

Sometimes a bound up forearm will throw your rounds off but it would do it with both the 180's and the 150's.

I do not reload i just shoot factory ammo. I bought multiple manufactures in 150 grain from barnes to hornady to perfecta and i also bought some 168 grain ammo im going to try.