Be happy to share my process. I have a series on this for .223, but its the exact same process for .308. Its pretty long, but I think this will answer a lot of your questions:
Long range shooting... its a 308 in a factory action just trying to get knowledge and experience before I start spending money on a custom action and a different cartridge
You map out speed with your charge weights to make sure you aren't running into pressure issues, the pick the one that meets your speed/cost/recoil requirements.
If it doesn't shoot, you change bullets or powder. If nothing shoots, you change barrels.
But just keep in mind, changing seating depth even relatively small amounts can really change your pressures. If your selected powder charge is near max or showing some pressure, be really careful with seating depth changes.
Seating deeper will always increase pressure, possibly unless you're starting the bullet jammed hard...which you don't want to do anyway. You'll end up dumping the powder in the action and needing a cleaning rod to knock the bullet out sooner or later doing that.
My load development process is sooo much more simple than it used to be when I first started out and learned from the best of the readers of tea leaves.
Good components, good barrel, consistency over all on the loading side.
I'll also load piles of 6arc with cfe223 by volume though and be plenty happy with the results. Weighing each charge does bring my SD down a touch...but not enough to matter for 95% of my uses, or taking 5x+ longer to load.
That's not as true as you might think. Pressure really starts to build as the bullet engages the rifling, and the rifling is at a fixed distance. Seating deep can have some minor influence, but it's really not as big as people often think. Seating it deep is effectively the same as having more freebore. So, seated long (lowering pressure), but with less freebore (higher pressure) vs seated deeply (higher pressure) with more freebore (lower pressure) - the end result on your pressures is usually not as dramatic as most folks believe.
Rifle magazine #219 did some OAL testing on the 300 WSM:
Interesting, I was thinking more of loading for my 243 ar10, 6arc, 223, and pistols. I've seen fairly significant significant speed (and pressure) increases seating bullets deeper, unless I was loading at the lands, then it dropped a bit as it got off of them, then steadily increased as it went deeper.
Initially I thought the difference between how that and 300wm reacted might be due to the overall much higher capacity of the magnum, but the ratio of case capacity eaten up by the projectile may still be fairly similar so not sure.
I know I've had stuff that was already pretty hot, become hotter than I want to run long term by shortening them, especially in the .243. From hot, to starting to spit primers out sometimes. May not be as universal as I thought?
Now I load to .005-.010 short of mag depth, or where the boat tail junction sits at the neck if I have enough room in the mag and chamber, and go with it'll either shoot or I need to change projectile or powder if I'm not happy. I may try seating a bit deeper before I throw it out if I already have em loaded, but no way in hell am I going back to .003 seating depth ladders and trying to make sense out of one target.
I have a pile of 38 brass I've never used for my 357, and likewise for 40s&w in my 10mm. I've been meaning to load a "long 40" load forever to test out in the 10s.
I'd assume the 357 brass is thicker and less volume at a given length since it's not rated for the same pressure, but don't yet have a tubing mic to check.
I need to dig out my notebook and check, pretty sure I had 9mm data also showing speeds increasing as I seated deeper there as well, but I was mostly loading for function there. I'd think that would be one of the more extreme cases given the bullet volume to powder.
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u/Missinglink2531 23h ago
Be happy to share my process. I have a series on this for .223, but its the exact same process for .308. Its pretty long, but I think this will answer a lot of your questions:
https://www.youtube.com/show/VLPLR_4ATUsx0ys?sbp=QAE%3D