I only shoot 223,but i can tell you 100 yards is not enough for any test. Your bullet at that distance does not have time to be off if it is going to be. The test for accuracy is distance. What im saying is at 100 yards the amount off your bullet is will not show up very well unless you are way off. In other words at 100 yards if you are say shooting .5 inch groups,that same load would be compounded at a greater distance. First you need to decide what kind of accuracy you are looking for. I seldom shoot less than 300 yards.
Also at great distances everything must come together. I had a situation this summer where i was shooting one hole at 100 yards,then when i went out to 300 yards i was shooting high and to the left.After reajusting scope i would come back to 100 yards and be off again.Finally dawned on me.I went and bought a scope level system and found out my scope was about 1/16th of a inch kiddy-wampas. Got everything set right and now im at 500 to 1000 yards.(not doing to good yet) Damn eggs are small at 500 yards.. So back to your question,You need to do the extra walking and get the targets out there farther. Another test you can do if you can't get that far out is get a big pc of cardboard 2 foot wide 4 foot high.Draw a line in middle from top to bottom the from side to sidee in middle. Place first shot at crosspoint of lines,then set scope for 300 yards or what ever you choose,shoot again,if your bullet stays on the vertical line and not off to left or right you might be doing good,Raise scope again and fire again and see if it still stays on vertical line. It's not a sure fire test,but gives you an idea of how things are going to go. Still not a substitute for actual distance shot though