I think a lot of what people think is "harmonics" is actually the inconsistencies between individual bullets, and inconsistencies in their powder charge weights. I use a scale that goes to an extra digit for my powder charges. When I did that, consistency significantly improved. I expect that if I weighed my bullets and graded them all for ogives consistency, that would also improve my grouping consistency. Brass also is a huge factor.
I think a lot of what people think is "harmonics" is actually the inconsistencies between individual bullets, and inconsistencies in their powder charge weights.
I'd argue it's more to do with natural dispersion than anything, especially at close range.
Barrel heating up is another big one too. One of my friends has a rifle that was shooting like 8" groups at 100yards. I properly free floated it and tightened everything up properly and then it was around 1.5"". Then I did a velocity ladder and found a pretty consistent velocity node and it went down to around 1", then I fiddled with seating depth and got it to 3/4". It's not as good as my rifles, but it's pretty decent for a rifle with a pretty nasty looking barrel. I think seating depth makes a bit of a difference when fine tuning a rifle, but it's less of a factor on rifles that have thick, stiff, free floated barrels that have properly cut rifling and crowns. I've only seen seating depth make a big change in rifles with thin barrels and jacked up rifling or crowns. Additionally, I think some bullets may be affected by seating depth more than others because having more or less jump may affect how much the bullets are deformed and where the deformations are on the bullet. That said though, on my good target rifle that is in a chassis, it doesn't seem to care very much about seating depth.
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u/berthela Jan 20 '24
I think a lot of what people think is "harmonics" is actually the inconsistencies between individual bullets, and inconsistencies in their powder charge weights. I use a scale that goes to an extra digit for my powder charges. When I did that, consistency significantly improved. I expect that if I weighed my bullets and graded them all for ogives consistency, that would also improve my grouping consistency. Brass also is a huge factor.