ProPoint sight question

[Johnny]

I took my Mini-14 out to the range to sight in a new Tasco ProPoint. The target was a concentric ring type with a blaze orange center, so it was difficult to place the dot on target at 100 yards. At 50 yards, the rifle was firing under 1/2-inch groups; but once I opened the range out to 100 yards, it started to shoot high and left and the groups opened out to seven inches! My question: has anyone ever run into a similar problem with a red-dot sight...or is the problem me?

[DFBonnett]

It is likely a combination of the rifle and the sight, assuming you are doing your part. Minis are noted for shooting larger groups when hot. My Mini will open up to about 4" max shooting with a 4X Burris.
Dot sights aren't designed for precision shooting so that may be a factor. My AR does considerably better with a scope than with a dot sight.