I do not think modern carbon steel or stainless steel, after machining - has any "pores" - is not cast iron or cast bronze like cannon barrels were several hundred years ago. But, what "works" is important - I might disagree "why" it works, but I do use a borescope to see what is in there when I start, and what is in there when I think I am done. I am not a high end target shooter - most of my targets have an inch diameter circle on them - if I can put three or five rounds into that 1" circle at 100 yards - my load, my rifle "tuning" is done - is good enough for me. I did have a Savage 112V in 22-250 - I watched an acquaintance use it from sandbags at 100 yards - was a five sided lumpy "hole" on the target paper - the case head of a fired 22-250 shell completely covered the hole in the paper - so likely a 1/4" C-C group - my rifle, my 10X Lyman scope, my hand loads. I fired probably hundreds of groups with that rifle - I never did get a group that close together - I think he was just a better shooter than I am - I do not know why he shot such a good group, but he did it.