Biggest issue I have with shooting cards in practice is not getting frustrated with the fliers I get with practice ammo. I shoot a LOT and I just cant use all SK and Lapua. I been using a lot of TAC-22 and Federal automatch. Some days they shoot really good, some days not so much.
So, here's what I do and it may be wrong but it works for me.
When I get a new lot of practice ammo I'll shoot 3-4 cards and get an idea of an average. I had some Tac22 that would run 215-225 on our usbr cards. If I wan in that range then I knew my mechanics were good. Under than consistently and I had a problem, over 225 and the law of averages kicked in and it is what it is. My new Tac is 210ish on average.
It is frustrating because Tac includes 5-10 free flyers on every box.
I try to buy practice ammo by the 500-1500 rounds so I'll not have a surprises.
My neighbor only shoots Sk or lapua even when he practices. I'd have to sell my body at the local club for extra funds if I did that.
