You're gonna reverse engineer more potential from a 25WSSM huh?
Let's see...
With .303 in neck length, and a 30deg shoulder angle, the flamepoint is 73.5% up the neck. A 6PPC has a flamepoint of 73.7%
According to The WSM/WSSM patent higher efficiency is gained from a case when the length of the wide-body portion of the case is below 3.33x the dia of wide-body.
For instance, a WSM case measures 1.56" wide-body length, and has a dia of .555"
1.56/.555 = 2.81 (this is good)
A 30:06 ratio is 1.82/.471= 3.87 (this is bad)
A 6PPC is .939/.438 = 2.14
A 6BR is .923/.471 = 1.96
A 25WSSM is 1.02/.555 = 1.83
There is actually some merit to this, where more of the powder is burned within the chamber instead of down the barrel some length, or even beyond the muzzle. Less powder contributing to accelerated mass means less recoil, and the WSM/WSSMs do seem to recoil less. Efficiency of the WSSMs does seem higher than other -longer cases of the similar capacity. But not alot.
In QL the term 'Weighting Factor' can be calibrated for this bottlenecking of powder. It works well.
I have made WSSM brass from WSM. I've made same capacity cases from 284 brass as well. There is no way to get around thickness from forming on pre-made brass. To get thinner brass in WSSM, it would have to be maufactured thinner from the git-go.
So I turn the necks, and my WSSM chambers are tight neck. Works well albeit more work.
The bulk Win brass sold is very good quality. Best I've measured in any cartridge including those I primarily use Lapua and Norma for.
Remember though, WSSM brass has tremendous springback. It takes trial and error(and alot of tools) to turn and end up with a perfect product. It is very tough. I have well over 20+ reloads on my 26WSSM, and have not annealed. Actually, I'm just now at the point where neck tension is beginning to vary, so I'm annealing the next brass to be loaded. Pockets are still like new.
If you stay moderate with loads, 50 pieces of this brass will wear out many barrels.
Anyway, the WSSM has only 10thou of body taper already. Less would likely be tough to pull from a chamber after firing. The 30deg shoulder puts the flamepoint in the neck and allows better feeding. A coned breech is needed anyway. I went to 35deg for the flamepoint in 26cal. It formed this in one firing. Haven't seen case growth at all, and bumping has been reasonable at 1-1.5thou for .0005"HS. But I carefully measured my lot of 25wssm brass and went no more than a thou over for any dimension, on my reamer print.
Make sure you put enough BARREL metal around your chamber. If the chamber expands too much, if it's loose, and WSSM brass decides to spring back alittle less...You'll be beating bolts open.
Use a magnum action as this is not a short action cartridge with 140gr bullets anyway.
Improvements? I don't see it.
With all accounted for, any further gains just aren't worth it.
Winchestor did well except for going down to 24 & 22cals with these.
That was an utterly stupid move on their part. If I worked there, I would likely have been fired for bringing that to their attention.
