Is the idea here that the bullet would be maximally supported along the bearing surface while providing more powder capacity than if the bullet was seated beneath the neck/shoulder? I'm trying to envision whether the pressure generated by the powder has a different effect on a bullet protruding within the case body versus a bullet with base flush with the neck/shoulder. For instance, a 200 gr bullet seated at COAL for a 300 WSM would have a lot of bullet inside the case body. My gut feeling is that it doesn't matter as the bullet has essentially no give and can only be pushed in one direction - out.
Pretty much. In my mind it optimizes case capacity and neck tension, personal preference really. I haven't noticed any effect at all on the opposite though, I have a 25 Creedmoor that didn't have near as much throat as I expected so the 133 Berger is seated pretty deep, it's my tightest shooting rifle.
I'm curious what your load density/case fill is with the bullet seated that deep and if that was a contributor to the tight grouping. My understanding is that velocity SD is minimized by having a case near 100% capacity, and a consistent velocity leads to less dispersion and smaller group size. But I realize we might be splitting hairs if we're talking the difference between 95 to 100% case fill; O would expect a perceivable velocity SD difference for a large difference like 80 vs 100% fill due to changes in how pressure builds.
I doubt it. At 100 yards if there is an affect on dispersion from velocity I'd be hard pressed to believe you could distinguish it. I had a rifle I tested a couple powders in and got results from 20fps ES all the way to 125fps ES for 10 shots, both groups ended up about 1.3-1.5" with the same bullet. And there are a lot of loads out there that with a large sample size produce 50fps ES but hit MOA targets at long range. When you get a good combo that shoots it doesn't always pencil out perfect.
I usually start with a slower powder and try to get good case density, but I have seen sometimes that doesn't yield the best results. My 284 Win for example, shooting 165's I tested H4831, N565, and H4350. The 4350 had the best velocity by 100fps, produced the least dispersion right at 1", and had an ES of 35 over 10 shots with new brass. I think the effect on pressure and case manipulation by seating deeper is negligible in comparison to something like changing the powder and burn rate.
Good point, a quick ballistics app calculation shows 0.15" difference at 100 yds for 300 WSM 165 gr TTSX at 2,900 and 3,000 fps. That means a potentially 0.3" group radius increase which would be lost in the noise for most reloaders such as myself.
It doesn’t. 4-5 groups and I’ve generally found something that works. YMMV
Too finicky for me. I’ve never had to deviate from COAL.
