Rich Coyle
Well-Known Member
About twelve grains of water less and matching .264 velocity? What pressures to do think you are running?
.257 wildcat build
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About twelve grains of water less and matching .264 velocity? What pressures to do think you are running?
elkaholic
Well-Known Member
With the 3300' load, probably high 60's. I usually don't shoot anything much over 3250', and brass will hold up at that velocity. I am not the only one getting this, by the way! This case is VERY efficient! I can get almost 3100' with 180's in my 7 ss, and it will operate well at a little over 3000'......Rich
Welderboy11972
Well-Known Member
What does changing the shoulder angle do? Other then make the case shorter. I'm still in the learning process of all this.
elkaholic
Well-Known Member
It does several things. It increases capacity over a lesser angle. It directs the flame point more inside the neck rather than into the throat which helps cut down on erosion. It keeps the case from stretching as easily, and some think that it aids in more consistent ignition, although I am not so sure about that. The only reason factories don't use it is because the cull factor is higher when manufacturing brass and some rifle magazines won't feed it as easily. All around though, it is a better design
Unless you give consideration to case dimensions, it is not correct to say the shoulder angle increases case capacity.
If you take a SAUM case that has a 30° shoulder and push the shoulder/neck junction back to create a 40° shoulder and to make the neck longer, you have decreased the capacity.
If you take a SAUM case that has a 30° shoulder and push the shoulder/neck junction back to create a 40° shoulder and to make the neck longer, you have decreased the capacity.
elkaholic
Well-Known Member
That is true. All else equal, when just the shoulder angle is changed, capacity increases. In the case of the SS, shoulder was pushed back, body taper was removed, and shoulder was sharpened. The net result was very close to original capacity with greater efficiency, less case stretching and a longer neck. I was not trying to say that the sharper shoulder gave the SS more capacity than the saum, but it gives some back after pushing the shoulder back and the body taper recovers the rest. Add to that the fact that the bullet does not have to be shoved into the case, and you have MORE useable capacity.
In the case of an A.I. design where the neck/shoulder jct. dimension stays the same, increasing shoulder angle increases capacity because the shoulder is blown forward at the body/shoulder jct., leaving the shoulder/neck jct. where it was. I was basing my quote on blowing it forward to get the 40 degree and you were basing yours on pushing it back.
Thanks for pointing that out......Rich
Welderboy11972
Well-Known Member
Let me make sure I'm understanding you right. Your really moving the shoulder/neck jct back to get the 40°. The length of shoulder you loose by going from 30 to 40, is moved to the neck. ( not the exact mesurement, but close) Is that how your making the necks longer?
elkaholic
Well-Known Member
In the case of the SS, the shoulder is moved back, not for the purpose of changing it to 40 degrees but rather to make a shorter case. The shoulder is then sharpened to 40 degrees by BLOWING THE CASE FORWARD at the new neck/shoulder junction by fire forming in a chamber with a 40 degree shoulder. YOU HAVE TO HAVE A POINT TO HEADSPACE ON! At the same time, the taper is blown out of the case by having the chamber diameter larger and BLOWING it out. You never PUSH a 40 degree shoulder into place by using a die to re form a 30 degree or whatever! This will destroy the case every time, especially when you are removing taper from the case as well. There is nothing to support the brass in the die and it will bulge at the body/shoulder junction or simply wrinkle the shoulder.
To be PC when I said in an above quote that (40 shoulder increases case capacity) "EDD" was correct; however, in the real world of wildcatting, the 40 shoulder is ALWAYS created by blowing it forward from an old neck/shoulder junction (ex: Ackley Imp.) or by creating a false shoulder on the neck to headspace on and blowing the shoulder forward (Ex: 6.5 Sherman) Long Action version.
Just so it is covered in advance, someone will probably say that "you can seat a bullet into the lands to provide something to headspace on" which is true, but not the best way to do it. I hope this makes sense......Rich
Welderboy11972
Well-Known Member
Yes I see the big picture now..lol
I deal with degrees and lengths everyday. My mind kept telling me that the extra brass had to go some where and I couldn't figure out where it was going.
I realize now how it is done. Thanks for explaining that for me.
I deal with degrees and lengths everyday. My mind kept telling me that the extra brass had to go some where and I couldn't figure out where it was going.
I realize now how it is done. Thanks for explaining that for me.
elkaholic
Well-Known Member
You are welcome......Rich
You were correct about the brass going from the shoulder to the neck.
I have a 6mm Wildcat. I change the shoulder angle from 17.5° to 26° by moving the neck shoulder junction back in a form die. It makes the neck longer.
I have a 7mm and a 30 caliber Wildcat that I push the whole shoulder back .225" with form dies. The necks get real long on those two.
elkaholic
Well-Known Member
Welderboy11972
Well-Known Member
Ok thanks guys
So it just depends on what benefits the caliber you are working with. I think I get it now.
So it just depends on what benefits the caliber you are working with. I think I get it now.
elkaholic
Well-Known Member
Correct! Also, what method is possible.....Rich
