I recently got a Mueller 3x10 Extreme to play with on my G2 Contender rifle. Previously it had a 3x9 Bushnell Banner. The Mueller has target turrets and very good glass along with finer crosshairs than the Banner had. I tested Federal Champion #510 and #714 which is a standard velocity version of the 510. The 510 was easily able to stay in 1/2 inch at 50 yards, 10 shots is a ragged hole. The 714 was better as I was able to keep 10 shots in the head of a chicken target at that range. One thing I have noticed about the 510 is that there are some good lots and some So So lots and that the bullet lube leaves a lot to be desired. To overcome the lube issue I wipe some white crisco on the bullet by getting some crisco on my thumb and trigger finger and rolling the bullet end aound between my fingers. I do this with both types of ammo. This helps in two ways, first the lubricant stays soft in the barrel and secondly it almost elimintates point of impact change between the two different rounds at least to 60 yards or so. This way I can practice with the cheaper 510 and save the 714 for matches. It is a bit harder to find and somewhat more expensive. I also look for flawed bullets while I am doing this. You would be surprised how often you find bullets with obvious casting flaws or that have been seated poorly in the cases leaving the brass somewhat creased. I have a heck of a collection of higher end 22 match ammo at hand but at the start of my season I like to use the cheaper stuff simply because I am not yet shooting my best offhand.