As stated above the 7WSM specifies Winchester brass. The other two specify nosler brass. I would have hoped that since they were giving reloading data that the base cartridge would have been consistent for a given round. Such as all the 7RM data being within a few gr. water for each bullet weight. The spread in capacity concerns me. I don't use these manuals for much more than a refrence anyway. Like the hornady manual is so vague it's not funny. It would be nice to see consistent data though.
The only reason I asked the question is because sometimes I assume I know the asnswer when the truth is something different entirely. Since no reasonable explaination has been given I assume the info is not as reliable as I would hope it to be and I will proceed accordingly. Just trying to learn.
according to Homer Prowley here is the method for finding case capacity with water but first you need to know some abreviations.
ratio of charge to bullet weight (RCBW), sectional density (SD), ballistics co-efficiant (BC), case capacity (CC), expantion ratio this is the ration of expanding gas in your barrel not how much your bullet expands on impact, (ER)
1. useing brass from the same company, and if possible lot number once fired in YOUR rifle
2. neck size only, then clean, then trim to length
3. weigh them empty, (you need 10 pieces of the same length and weight)
4. now weigh your 10 bullets (be sure they are the same weight)
5. useing the bullet you intend to use, with a q tip lightly lube the inside of the case mouth and with NO primerand no powder place the bullet in the case and chamber it in your rifle. As the bullet hits the rifleing it will seat it to the required length
6. weigh these 10 dummy rnds and add the total weight, divide that by 10 and you have your average (if your brass is the same length and weight and your bullets are the same weight then your 10 dummies should all be the same weight)
7. useing a hypodermic needle fill the dummies with water through the flash hole useing q tips to dry out the primer pockets
8. now weigh them again add the 10 then divide by 10 to get the average weight, (because of air bubbles there may be a slight differance)
9. subtract the " average of the "wet" from the average of the "dry" and you have your case capacity of water FOR THIS RIFLE AND BULLET COMBO ONLY
From this figure of "CC" and from the distance of the base of the bullet from the above "dummy" to the muzzle you can work out "ER", knowing your "BC" and "SD" numbers plus your true barrel length and "CC" together you can now use a slide rule to determine your powder, charge, "RCBW", velosity, chamber preasure and bullet drop.
SO, when you have at hand reams of confermed PUBLISHED reloading data why would you bother?
Gordo, please elaborate on what you are trying to say. Don't beat around the bush. Are you trying to imply that I have reams of accurate reloading data in these manuals?
My question (because I am simple minded) is if anyone knows why the manual has such a large variance in case capacity per given cartridge. Maybe this variance is acceptable and I just am over thinking it.
If you are implying the manuals happen in real life then you have a different experience than me. I rarely see published results. I can lay 5 manuals of different sources next to eachother and get very different "published" data. When I tryand duplicate these reams of data, there never seems to be validation on my end. And YES I try and eliminate variables such as casem mfgr, primer, ect, ect.
But the bottom line is; we don't charge cases with water, we charge them with powder.
It's that simple.
I suggest OP skip on by whatever is going on at that section of the manual, and go to the loading section.
I liked Greyfox's input I'll have to think on it. I've got an old Powley slide around here somewhere. The only use I get out of case capacity is relative comparisons of cartridges. Especially so when someone is talking a new wildcat, similar capacities similar results.
my bottom line is trying to explain CC is like trying to explain the holy trinity to a pagan. It is a nice concept if you can understand it but, leave that to the scientists and lab rats at the offices of Lyman, RCBS, Hornady, Speer & etal
These labs have all the toys to ensure that you can make safe & accurate ammo, so don't get caught up in it.