Good points Leon. Frankly the concept of .25 MOA for a non-benchrest/varmint/target rifle blows my feeble little mind. As I said above, that is fine for the "one-percenters" but IMHO wasted money for the general population. It sure would remove the rifle as a source of blame for a miss, though. Again, my main point is practical field accuracy for the average Joe Deerslayer, not highfalutin' toys for the maximum-accuracy crowd.
I do have one minor quibble, that is adding group size to shooter wobble. While this is true if you shoot a five or ten shot group (which allows multiple chances for your rifle to throw shots to opposite sides of your aim point), it does not hold true for one single shot. In this case the rifle can only be off in one direction, and the amount will be the radius of its error, not the diameter of its error, so for an individual shot the extra error is only half what we consider if we are looking at it from the perspective of group diameter. One does not (or should not!) shoot 'groups' on a deer's shoulder. The ONE shot you aim and fire is what counts. This means that a two-minute difference in total group size actually makes a one-minute maximum amount of deviation of the individual shot from where it would have gone otherwise. For really good shooters this may matter, especially on small targets or far away. For a guy already holding steady well within the kill zone of a deer or elk shoulder at 150 yards it is moot. At 400 yards on an antelope it is another story.
Also, your example assumes that the rifle will almost always be adding its error to the shooter's error. This will not be true on each individual shot, but only one out of every few shots. The shooter may pull one a little left, yet the rifle may throw it a little right (or high, or low). If you shoot enough shots then both shooter and rifle will err to the same side in all directions, which will produce the sum of rifle & shooter error as a group DIAMETER presumably centered on the aimpoint. For ONE shot, this actually has, I think, a less than even chance of happening, since the rifle will be erring its shots in random directions, same as the shooter. Any given shot has as much chance of erring (due to rifle inaccuracy) high as it does low or right or left. So if a shooter pulls one a little left, he probably has around a one in four chance of the rifle throwing its error left as well. And this is what takes place in the field - for one shot. So, it seems to me that any given shot does not necessarily sum both errors, and will only do so a minority of the time.
Consider this: My .243 shoots slightly over 1 MOA at 200 yards from the bench and sandbags (multiple 5-shot groups). From sitting w/tight loop sling I have a 3 MOA wobble and can shoot within the inner 2 MOA of that. By your math I should be always be getting slightly over 3 MOA (6+ inches). Yet with that rifle I have shot 2 or 3 5-shot groups under 3 inches (1.5 MOA) from sitting at 200, and when I shoot zero pairs from sitting at 200 (frequently, since the rifle's zero wanders all the time) they are more often than not within 1.5 MOA or less of each other. Now I have shot the occasional 6" pair or 3-shot group, but that has occurred at about a one-in-four rate.
So what does this mean? I will gladly admit I think you're a heck of a lot smarter than me, but my range results do not add up to your figures. Any ideas?