According to my crude comparator I'm getting 0.002-0.004" of shoulder bump this way. Sounds like I just magically got the right combination of stuff for it to work out that way?
I had read and been told that sizing brass this way dramatically overworks it and results in exceptionally short case life and risk of case head separation with belted magnums. According to my comparator and rifle, it's what it takes to get it chambering like I want it to. Am I about to start blowing case heads this way? How do you even properly check if you're in danger of splitting a case head?
I haven't heard of this risk with shoulder bumping belted magnums. The whole purpose of shoulder bumping is to minimize working the brass each firing, so I dont see how it would stress the case head area. You bump the shoulder the minimum amount to freely chamber and that amount is all it will grow when fireformed. The belted case will still headspace normally on its belt with these cases as long as youve moved the shoulder enought to not contact the chamber shoulder wall.
It's definitely common theme everywhere. Ranges from "just follow the directions" to quantum mechanics. Seems there's a vast range of things that works for different people. I just want to make sure that what I have going on here isn't unheard of, and it seems it isn't.
The very basics of handloading has been producing quality hunting ammo for handloaders for centuries. Most of the rabbit holes hunters go down are not needed, even shoulder bumping is subjective.
Basic handloading starts with deciding two paths, neck sizing or FL sizing. Each have their merits and weaknesses but anything extra or different from the dies instructions are optional rabbit holes that are not needed. People try new or different things and find something that works for them, in their rifle, with their components... do not mean it will work for you and yours. The problem is when they swear by it as "needed" . Learn to identify the rabbit hole advice and tuck them away for some day when you've gained the experience handloading to decide if you need improving your hunting round and you'll find you dont need them.
A note about shoulder bumping (SB), its a subset of FL sizing. You don't need to do it but the advantage is it greatly reduces working the brass and less brass movement in the chamber (theoretically, more accuracy) improving case life. Thats it. The difference between FL and SB is the distance between your fireformed datum and a fully sized datum out of your die ( roughly .012" off the top of my head as a general rule if I recall but dont quote that...). FL sizing takes the brass to its minimum saami spec so it fits all chambers, thats it. Most FL dies usually go a couple thou smaller to assure any tolerance stackup issues with every rifle. SB sizing eliminates that larger difference in brass growth in the chamber when firing. IMO its worth it to learn and the better way to go but it is a little trickier to learn. In my experience I didn't get it until I started annealing the brass so it forms in the die consistently (each time you fire it gets harder, less springback etc., annealing brings the brass back to its original hardness which is more malleable). For me, annealing was the kingpin to learning shoulder bumping. Now I can quickly bump it around .002-.004 every time I set up, consistently. Note: you do not need an expensive annealing machine to properly anneal brass.
That said, again, its optional. I have a friend who's FL sizing (not SB) and nothing more and is hitting 10in gongs out to 600yds with his hunting rifle. He gets sub moa groups at 100yds. All he's doing is following the FL dies instructions, found his best charge weight and seating depth was all he did to dial in his handload. Note: hes running a belted magnum too so maybe SB isnt needed with belted magnums. IDK but were counting firings to see whos brass lasts longer, jury is still out.
I would ditch the socket and get the right tools for the job, a Hornady case gauge is cheap and will be more precise measurements than your socket. But I give you merit for that idea, I could get that to work if needed but I question if its precise enough to measure consistently and know your getting say as little as a .002" bump. Bottom line is as long as it freely fits the chamber but consistency is what makes handloads accurate handloads.