Actually the most accurate load in one of my rifles is the one that is the most unstable.If I add or subtract a grain of powder or it warms up the groups open up dramatically.I have another load for the same gun that is almost as good as the first load at it' s best but is far more stable.I can add or subtract a grain of powder with no real change in group size.Temperature also seems to have very little effect on this load as well.Naturally I now only load and hunt with the more stable load.There is nothing wrong with the rifle as it is pillar bedded into a mcmillan stock and the barrel(pac-nor) is floated.The sensitive load does under 1/2" at it' s best(from just above freezing to 50 degrees or so but opens up to an inch by 80 degrees.The stable load holds about 1/2" in all temperatures tested.If the gun in question shoots erratically with all loads with changes in temperature or humidity the most likely cause would be bedding as previously mentioned.If however the gun shoots consistantly through variations in temperature with some loads but is inconsistant with others the fault could very likely be the loads.