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general reloading question - Redraider - 04-28-2022
Hi all,
I have seen in many forum discussions, where someone comes up with how much case would be filled by x amount of powder, where in the world is this information available? Surely it is not trial by load at a time!
Any help you could provide would be appreciated.
Thanks
Redraider
general reloading question - grayfox - 04-28-2022
Most of those can only be generically applicable to you, as a fired case from your gun will have a different volume than the ones they have from theirs. Plus sometimes it diverges due to where on the case they are designating as "full," and whether they are taking seating depth into the picture (Nosler in their load data seems to have differing case volumes for different bullets/same cartridge, which implies they are subtracting the room that the bullet takes up). Filling to the case mouth is one variable but I don't personally find it very useful, since I can't have a bullet seated with that much powder.
One method to get a "feel" (and again, generic), is to use GRT tool or quickload.
For your own cases, you can find the water volume by filling up a fired case (with a primer, used or new, to plug the firing hole), and measuring weight before and after filling. I use grains for capacity. If I'm interested in a close-to-accurate number, I fill up a case with my powder to the shoulder and measure how much it took for that powder to do it. Most bullets you would seat them to that point anyway, to have sufficient bearing length to stabilize the bullet.
But GRT tool will give you a %full (less bullet take-up) for their generic cartridge when you load a bullet/powder to a given seating depth. From that you can refine to your gun by adjusting the case volume number after measuring it like above. But GRT gets me pretty close most of the time.
There are real precise methods, typically used by OCD or competitive shooters, I imagine those are online somewhere, maybe some of them will chime in here also.
general reloading question - Redraider - 04-29-2022
Thanks for that info, I will have to look up "GRT" tool, as I am not familiar with that. When I started reloading, I was after the best velocity with good accuracy, but that left the case low on fill capacity. Now, I would like the get those same end results but with a fuller case, but don't really know how to get there. Is there a general rule as to what makes a particular powder have more bulk to better fill the case?
I ask this because my Hornady manual states nothing about case fill percentage, and was wondering where this data comes from.
Thanks again
Redraider
general reloading question - Zeneffect - 04-29-2022
If velocity, accuracy, and consistency are all good (sd/es) then not full case fill is irrelevant. Often times I wish I could use less powder because cost and hard to get these days.
Case fill is usually from some software (Quickload or GRT) and isnt as accurate as one would be lead to believe. The case fill will be dependant on what the software thinks the kernel size is and volume of case that you measure and enter. I have seen discrepancies in kernel sizes showing overly comressed when it is not.
GRT = Gordon's Reloading Tool. It's freeware online
general reloading question - outbreaker - 04-29-2022
I will add that determining the Optimal Charge Weight (OCW) for your rifle/bullet/powder/primer combination is far more important.
As far as case fill, so long as I am above 50% I am fine with it. Why 50%? Prevents accidental double charges going unnoticed.
general reloading question - grayfox - 04-29-2022
There is a chance of second detonation for low case fills, not completely sure of the fill % but the rule of thumb I have seen is to try to be at least 80-85% full, those are the % I try to deal with. GRT also has a warning pop up if you're down in the "too-low" fill range as calculated by its program.
Barrels have accuracy nodes (according to Chris Long, and his optimal charge weight paper - excellent one by the way!) according to barrel length, and probably some effect of cartridge size/bullet seating but I haven't figured that completely out...
Anyway, a barrel can have more than one MV node as velocity and powder load increase. Sometimes you can find a node at a different load/MV than his theory predicts but when you find one of his nodes, you have got one for sure.
GRT will also predict nodes/powder charge/bullet seating for you although it seems to differ from my own "working formula" that I adapted from Chris' work. At any rate they are all guides.... the barrel will tell you its real story.
Powder of course have differing densities from each other, and differing size of granules, so each one will fill a given mfr/your barrel-shot cases differently. Ex, Lapua cases from your gun will have a different volume than Hornady cases from your gun. That's why you start low and work up.
Having said all that, one "cheat" rule I have pulled out from time to time, is if you can find one node, then a second one could (***COULD***) be about 3% powder weight away, assuming that is still within safe pressure and loading for your rifle. It gives you kind of an idea, and is not hard-fast nor guaranteed at all (standard disclaimers apply). Also, as something that might get you in ballpark, if you find the off-node (load/MV where you get a really high SD/ES dispersion), you might look in the area of ~1.5% powder away from that one.
Example MV nodes from Chris Long's theory, for 22" barrel Grendel OAL at 2.260 (NOTE the 52000 psi limit always applies so you might not get up to a given node!!!)
2365 ft/s
2500
2735
2915