Elevation matters, but not the amount you mention. Yes, I took Trig., but that was about 38 years ago!
That is why it is easier for someone like me to install a Cosine Indicator on the rifle, but not for the very slight angle you mention. If 10-15 feet mattered, then if you hunt out West or even in the Ozarks where I hunt, you could just forget about shooting at any distance at all, but not so.
Visualize a line from the porch to the target & a line from the ground to the target. Now visualize letting the line at the porch fall down to the ground level. If you add the entire elevation distance to the ground level of 10-15 feet you would now have a distance
of 203-205 yards. It would be hard to see a 5 yard diff. on target & before ANYONE MISUNDERSTANDS, that is NOT how to calculate this, I am only showing this in the EXTREME & that was not the problem.
Rather, Gravity pulls in a straight line from the shooter to the target at the same elevation, regardless of angle. So, if you are shooting a Deer that is 400 yards uphill from you & this is a 45 degree angle, you need to hold for a 300 yard or so shot & downhill with the same angle will give the same results. The gravity will still pull at a distance equaling the level distance (at Sea Level) from you to the target. To remove variables, like Mac said, I would sight in on level ground when possible.
So that leaves whether the barrel was clean or dirty, barrel temp. & how you were holding the gun when you shot.
1. Was the barrel hot when you sighted it in, did you shoot it alot in the process of sighting it in? If so, you final group could be somewhat diff than a cool of slightlyu warm barrel.
2. Did you rest the forearm in the same place & with the same pressure durring sighting in & shooting at the Coyotes?
3. I would check the effects of fouled vs clean barrel as Stimpy Lu suggested. To me I would have a serious problem with a barrel
that has to have just a certain number of shots going down the tube, but that is a personal thing, I guess.
