Here's a 20 shot group at 800 yards made before F class became a competition. Used a 13 pound scoped 308 Winchester palma rifle on bags from prone. First two marked shots were from the clean barrel, they typically leave several fps slower.
https://thefiringline.com/forums/attachment.php?attachmentid=110149&d=1570130518
https://thefiringline.com/forums/attachment.php?attachmentid=110149&d=1570130518
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