Minimum Body Taper
What is the case minimum body taper that will manage to do what it is supposed to do? Surely the SAUMs are not anywhere approaching that perfect angle - are they?
Other than each experimenting for themselves, how do or can one arrive at that point? (ie. without just taking what is on the shelf . . . ) Is there a "rule of thumb"?
There seems to be quite a range of tapers - even with chamberings that have come to be in the past decade or decade and a half. Why these days are not all of the chamberings "straight walled"?
* I'm meaning straight walled in the sense of minimum taper from the head (or base) to the shoulder (NOT through the neck). Believe that the "improved" cases are good at maximizing powder capacity for a given case. *
I appreciate all of the thoughtful input: ideas, thoughts, etc. Thanks guys!
Other than each experimenting for themselves, how do or can one arrive at that point? (ie. without just taking what is on the shelf . . . ) Is there a "rule of thumb"?
There seems to be quite a range of tapers - even with chamberings that have come to be in the past decade or decade and a half. Why these days are not all of the chamberings "straight walled"?
* I'm meaning straight walled in the sense of minimum taper from the head (or base) to the shoulder (NOT through the neck). Believe that the "improved" cases are good at maximizing powder capacity for a given case. *
I appreciate all of the thoughtful input: ideas, thoughts, etc. Thanks guys!
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The 444 Marlin may give a clue? http://www.saami.org/PubResources/CC_Drawings/Rifle/444%20Marlin.pdf Off hand, i cant think of any longer "straight walled" cartridges. Might be some black powder ones?? 0 -
quote: Why these days are not all of the chamberings "straight walled"?
A taper lets the round chamber better. Less drag.0 -
quote:Originally posted by 243winxb
quote: Why these days are not all of the chamberings "straight walled"?
A taper lets the round chamber better. Less drag.
Yup. Straight walled cases are more "efficient" in burning powder and returning bang for your buck with a given volume of powder, but tapered cases are well understood and preferable if there are any pressure or chambering (feeding or extraction) issues which is why they are typically used in dangerous game rifles and military arms.0 -
Many of the "newer" cartridges are utilizing the straight (or straighter) design. The Short Magnums and the 6.5 Grendel to name a few. These "straighter" cartridges are chamber in both bolt actions and semi-autos and they seem to feed just fine. I also have two Ackley chambered rifles and have zero feeding issues. 0 -
quote:Originally posted by nemesisenforcer
quote:Originally posted by 243winxb
quote: Why these days are not all of the chamberings "straight walled"?
A taper lets the round chamber better. Less drag.
Yup. Straight walled cases are more "efficient" in burning powder and returning bang for your buck with a given volume of powder, but tapered cases are well understood and preferable if there are any pressure or chambering (feeding or extraction) issues which is why they are typically used in dangerous game rifles and military arms.
nemesis,
The amount of taper in the case body doesn't affect efficiency so much as does shoulder angle. What a tapered case provides is better extraction. What a straighter case provides is more grip from the case wall to the chamber, thereby allowing more pressure. More pressure because less case thrust on the head of the case. The pressure is, to a degree, taken up by the case walls. What will still happen with either tapered or straight-walled cases, if you get to much of a particular powder, is blown primers. So, there is a little bit of an advantage, but not so much as the sky is the limit.0 -
quote:Originally posted by sandwarrior
quote:Originally posted by nemesisenforcer
quote:Originally posted by 243winxb
quote: Why these days are not all of the chamberings "straight walled"?
A taper lets the round chamber better. Less drag.
Yup. Straight walled cases are more "efficient" in burning powder and returning bang for your buck with a given volume of powder, but tapered cases are well understood and preferable if there are any pressure or chambering (feeding or extraction) issues which is why they are typically used in dangerous game rifles and military arms.
nemesis,
The amount of taper in the case body doesn't affect efficiency so much as does shoulder angle. What a tapered case provides is better extraction. What a straighter case provides is more grip from the case wall to the chamber, thereby allowing more pressure. More pressure because less case thrust on the head of the case. The pressure is, to a degree, taken up by the case walls. What will still happen with either tapered or straight-walled cases, if you get to much of a particular powder, is blown primers. So, there is a little bit of an advantage, but not so much as the sky is the limit.
The "Squirt Affect". I believe Ackley did some tests with a 30-30 lever gun with the rounds chambered and the action not locked up. The parent 30-30 with it's large taper didn't fare very well. The 30-30 Ackley with minimal taper stayed in place and had little or no "Squirt Affect".??0
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