most of the guys I know that own a 7mm mag BAR , say the 140-168 grain ammo is the most accurate.
several have mentioned federal and hornady ammo as being their choice

https://www.ammograb.com/7mm-rem-mag/

https://www.ableammo.com/catalog/cheap-7mm-remington-mag-centerfire-rifle-ammo-for-sale-online-discount-prices-c-10480_14658_14799.html


btw about every 200-250 cartridges change out the recoil buffer, and clean the gas system,
its not a big deal but its a big help in retaining accuracy and obviously clean the bore and action after each trip to the range

https://www.midwayusa.com/product/91...hort-long-trac