So I have been thinking about getting a big bore AR upper. I would like it to use regular GI mags or Magpul Mags. I was thinking something along the lines of .458 SOCOM or .50 Beowulf. Either of those would mean I would likely have to get into reloading if I want to go shooting much. Does anyone have experience with either of those cartridges? Anyone know which would be the least expensive to shoot if I was reloading? Any recommendations? Thanks.