Ray - that wasn’t exactly my point. I agree that shooting at all with truly poor ammunition is simply silly - why bother with so much good stuff in the world, and the ability to load ammo even better than most of that. However, good quality non-match ammo I found simply fine for practicing. However, you must establish what your rifle does with that ammo in comparison to the top-grade ammunition you would use in a match. As long as you do, I see no difference in practicing with it and practicing with the finest match ammo. Even the point of impact isn’t a problem, as you simply judge by group size. I never altered my zero to accomodate any ammunition I practiced with, nor for range conditions on days I was only practicing, unless I was shooting at the same range, with a good bet it would be the same conditions, as the next match. Not always easy to do in the SF Bay Area, where we have no seasons. Can be hot and dry one day in summer, and cold and wet the next, and you can have hot, beautiful days in mid-December as easy as cold crappy days in Mid-July.
It was when I had a day at practice that I found I was shooting twice the size groups, or more, than I knew I was generally capable of with that rifle/ammo combination, that I call it quits for the day. That was on days with mild conditions. Sometimes you have to practice when the range conditions made the groups worse, as you know, so that you can minimize the effects.
I still think that any Match-designated ammo downgraded to “Practice” was simply because the accuracy of that lot did not quite meet requirements, but was good enough that to destroy the lot would be simply a waste of money.
Ammo lots are often down-grade even in service-grade ammo for various reasons that have nothing to do with its safety to fire. We discussed some of that on a thread to do with German labels on boxes, as I recall.
For those with a wide-open budget, and especially if they handload their match cartridges, of course they might as well practice with their match loads.
I never had that luxury. I could buy good ball M2 through the store cheaper than I could buy the components (Sierra Matchkings, etc.) that I used in my own loads, cost-per-round. Using G.I. also saved wear and tear on the good quality brass I was using. That was before I switched to .223, which by then, I was not shooting in enough quantity nor was the cost as dear to me thanks to a better income, to bother shooting G.I. ball in my Sako.
Well, we all follow our own systems. Maybe mine was why I never became a great shooter - I suspect, though, that it was as much that I did it primarily for fun and was never a really competative chap, and that the budget didn’t allow as much shooting as some could do. Unfortunately, I am back to that in the present situation, and have cut my CAS shooting by 75%.