I need an explanation how increasing the shoulder angle while leaving the neck/ shoulder junction location essentially unchanged could possibly reduce capacity.
Doug & Alan -
Howdy !
762Ultramag asked this question in his original post:
1. “ …would reducing the case taper from .014 to .010 have any downside “ ?
2. In the same post, 762Ultramag also said:
“ I’m designing a 25 X 47Lapua Improved reamer… “
3. In his 03 Sep post input, 762Uitramaga stated: “ I’ve blown several 30 degree shoulders out to 40 “.
Commentary on item 1, above:
The way to reduce case’ sidewall taper from the standard ? X 47L taper amount, would be….to increase shoulder diameter.
Commentary on item 3, above::
When he used the term “ blown “ along w/ the term “ out “ when talking about 40* shoulders, what 762 Ultra maga was/is talking about; is sharpening the shoulder angle in-conjunction with a widening of the shoulder diameter…. same as noted in item 1.
That is how I understood the circumstance; after his 03 Sep follow-up post
In my 03 Sep post response, I asked a return question:
“If case growth after firing has already been minimized in the standard 6.5 X 47L case…”
- [ the “ standard “ case having a 30* shoulder and nominal .454” shoulder diameter ] -
“… what is gained by further sharpening the shoulder angle; especially when that
in-and-of-itself reduces the case’ capacity “.
I was talking about JUST a shoulder angle change, WITHOUT doing a shoulder blow out.
I suggested to 762Ultramaga that “ IMHO - you should consider going the other way…
reducing the shoulder angle… a bit “ . I did not suggest to him ( also ) “ blowing out “ case shoulders.
*** To give 762 Ultramaga an EXAMPLE of reaching desired case capacity via use of a more-modest shoulder angle ( shallower than even 30* ) with no shoulder “ blow out “,
I described my “ .22-35 Remington wildcat ***. I mentioned that it uses the stock
.35 Remington parent case’ base and shoulder diameters, and therefore….no shoulder
“ blow out “.
Consider different design iterations of an example “ wildcat, where case’ oal, base & shoulder diameters, shoulder location on the case; and calibre all remain the same. Given input parent case conditions * like those I mentioned for my .22-35 wildcat…
- Changing location of the shoulder/neck juncture on the case’ design by sharpening the shoulder angle, results in less powder space under the case’s shoulder area.
That is because some of the shoulder area was converted into increased neck length.
And…as a practical matter, when shooting long-er VLD bullets; the rifle cartridge’ case neck will typically be pretty well fully occupied by the long bullet’s body. Powder space will then likely only be found in the space covered by the case’ shoulder area.
This can be visualized by considering a 2D side view of the case. In such a view, case features like rim thickness, ejector groove “ height “, case sidewall “height”, shoulder
“ height “; and neck length…. all together combine or “add up”; to give the case’s oal. Using this visualization, it can be noted that the shoulder’s “ height “ ( 2D side view ) will be reduced as the shoulder angle is “ sharpened “, while neck length will increase at its bottom end; when other case dimensions remain constant ( as noted above ). When using bulky, s-l-o-w “ burning powders, this “ space “ needs to be put to good use.
762Ultramaga said… “ I’m looking for enough capacity increase… “
I suggested that a shallower shoulder angle to gain increased powder space under the
“ shoulder area “… in-lieu of a longer neck resulting from adoption of a “ sharper “ shoulder angle.
As always, whether responding to other’s posts, or… even when starting a new post of my own; my intent and fervent hope is to be accurate, clear; and concise.
If I failed to be clear in my responses back to 762 Ultramaga, or you other guys;
I offer my sincerest appologies . It was not my intent.
Oh… I almost forgot… again ! “ .22-35 Remington “ has a 26* shoulder angle.
With regards,
357Mag
