Champion is the second-Gen of the SR mag...seems to function better with less issues. I've got two of 'em.
The BIG thing...if you are gonna use 'em, you will need to bed or pillar bed your stock.
It keeps the tensions the same every time, so there's no issue with angles...they are fatter than OEM mags,
so you absolutely have to bed to keep the variables out of play (meaning the same thing is done every time you put your rifle together).
Other than that, avoid Remington Golden Bullets & Thunderduds...lousy consistancy of size/powder/primer.
They love CCI/Blazer/Eley/Fiocchi/Federal ammo...and most others.