Attachments have changed greatly in Season 13 and need to be manually redone on the site. This will take quite some time, so apologies if this section isn't helpful right now.
Attachment Details
SP-R 208 - .300 5 Round Reload
Ammunition
Added in version 1.0.20.0 1.0.20.12
.300 caliber ammo increases damage at the cost of mobility.