As pointed out by a couple of people, it is not a question of this ammunition being bad. The group size at 125 yards will be about 2.5 times what you are shooting at 50 yards, and with your scope you should have no problems in duplicating that level of accuracy. It doesn't matter if it is a pump with 18 inch barrel or bolt with a 26 inch heavy barrel.
So, is the group at 125 the same relative size or not? If it is 2.5 times the size, there is no ammunition problem, or rifle problem. If it is significantly larger, then it is likely a question of your target, as your shooting routine is sufficient for 50 yards. Sometimes shooters try to use too small of a target, making it harder to shoot accurately (yes, I know that if you have a .22 Super duper with a 24x scope you can shoot at postage stamps), but this is a hunting rifle.
All this assumes that you are shooting your groups at 125 yards with the same setup as you are using at 50.