Straight wall rifle cartridges

1

1972RedNeck

New member
Not really a reloading question, just a cartridge design question:

Why aren't there any straight walled rifle cartridges?

Obviously there are a lot of straight walled pistol cartridges that work well in rifles, even at high pressures (454 Casull up to 500 S&W).

So when Ackley and Weatherby were hot rodding rifle cartridges, why didn't they make them with true straight walls to gain more capacity? Why did they leave that .010" ish taper?

I realize the difference would be negligible, but I'm just curious as to the "why"...
 
Why aren't there any straight walled rifle cartridges?
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There are lots of straight walled rifle cartridges in the sense that they have no shoulder, but there are few rifle length cartridges that have no taper the way some pistol cases do, and no modern ones that I know of.

The benefit of the taper is as mentioned, it aids in reducing the force needed to extract the fired case. With a truly straight case after the brass springs back, and you begin pulling the case out of the chamber, the remaining "grip" of the case in the chamber extends the entire length of the case, and is essentially present until you have the case all the way out of the chamber.

With a tapered case, even a slight taper, as soon as the case begins moving backwards, the case is being pulled back, and away from the chamber walls as it moves back, eliminating friction as the smaller end moves through the larger rear section of the chamber.

IF you look at the older rounds made for use in Africa, all are tapered and some to a large degree.

Length matters. As does the system of extraction. And long, perfectly straight cases are the most likely to stick in the chamber.
 
I’m confused…
350 legend, 360 Buckhammer, 375 Winchester, 444 Marlin, 45-70, 45-90, 450 Marlin, 458 win mag, 458 Lott…..to name a few.
 
A negative taper (head thinner than mouth) is disastrous for extraction. A zero taper (strictly straight wall) is too close to that. A positive taper (mouth thinner than head), however slight, builds margin against it. Pedantic or not, it makes engineering sense.

-TL

Sent from my SM-N960U using Tapatalk
 
First point, why is accuracy in measurements a desirable thing while accuracy in terminology is "pedantic"?? :rolleyes:

A cylinder has straight, parallel walls, if there is a taper, its not a cylinder, its a cone.

A zero taper (strictly straight wall) is too close to that.
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Too close for what??

Yes, taper (even as little as 0.001") makes engineering sense, but there are still a number of VERY successful rounds that weren't designed with any taper at all still "alive and well" on the market. And there are a host of straight cased rounds, and tapered case rounds on the "obsolete" list, as well.

Going by the case drawings and specs given in the Hornady manuals I just looked at, (which is by no means 100% inclusive of all cartridges ever made) there are a number of truly straight (cylinders) cased rounds still in production today.

.25acp, .380acp .38acp (.38 Super), .38 Special, .357 Magnum, 10mm, .41 Magnum, .44 Special, .44 Magnum, .45 Colt and .45-70 are true straight cases.

Lots of other rounds that have a degree of taper, but no shoulder are described as "straight" in casual conversation because the taper is very slight and they have no visible shoulder.

The truly straight wall rifle rounds I can think of all come from the blackpowder era. The .45-70 is the most common survivor today.

The .350 Legend is a modern round, described as "straight" but its not truly straight the base is 0.012" larger in diameter than the case mouth.

The longer the case AND the higher the pressure, the more some degree of taper matters.
 
Not sure if this is a thing, but I think a better terminology would be something like either straight walled tapered cartridge, or straight walled non tapered cartridge. No confusion there, or if this is confusing perhaps reloading ammunition isn’t for you. I’m not directing this at any single person, just a personal observation.
 
I’m not the OP, but I wonder if the op was looking for a debate on the definition of a cylinder or was he looking to understand cartridges that use more of the classic straight wall cartridge definition.

That definition is more like a cartridge that appears to have a constant diameter, but may have a slight taper and headspaces on the mouth, flange or belt, but never on a shoulder.

An answer to the why Ackley and Weatherby didn’t work in this area is because they were velocity chasers. Their followers bought into the idea that every factory round needed another 50-100fps. This is because 100fps is usually still in the same bullet performance envelope. 200fps faster and 50yd shots blow up in general. This was before monos.
 
I guess it could depend on how pedantic you are....:rolleyes:

It can be argued that a "straight walled" case and a "straight case" can be different things. A straight walled case has straight walls because there is no shoulder. It can have no taper, a small amount of taper or a large amount of taper and still be a "straight wall" case.

A "straight" case is also a straight wall case, where the case walls are parallel from mouth to base.

General use terms generally describe the most obvious features and can be technically "sloppy" sometimes.

Particularly in English.....:rolleyes:
 
The current SAAMI drawing shows the 45-70 cartridge with a 1.44° included angle taper. However, the CIP has the taper at half that. I am inclined to think the SAAMI taper could be an updated design for improving lever gun feeding. A trapdoor action, after all, can even handle a reverse taper.

Also, just to be pedantic, a symmetrically tapered cylinder that doesn't come to a point is not a cone but a conical frustum, meaning forming a cone was frustrated by falling short of including the pointed tip.

1972Redneck, if you take a large capacity bottleneck case and make it straight, it gets very long and, assuming matching wall thickness, it gets heavier than the bottleneck case that holds the same powder charge as the surface area to volume ratio is getting bigger with a long, skinny case. Efficient use of volume is important to carry weight and packing efficiency, as is the ease of feeding from a magazine. That last point means the designer is not having to require a bolt to be impractically long and heavy in a modern rifle chambered for the same round. Moreover, powder burns less efficiently in a long, tall case as the flame front has to travel further to get from the rear to the front of the powder column. Finally, for a given exterior barrel length, a long cartridge gets less rifled barrel length than its shorter counterpart, so a little velocity is sacrificed by using one.
 
Also, just to be pedantic, a symmetrically tapered cylinder that doesn't come to a point is not a cone, but a conical frustum, meaning forming a cone was frustrated by falling short of including the pointed tip.
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I would also be frustrated if my nose was cut off, any elephant would...:D

"Truncated cone" :rolleyes:
 
Yes, exactly the same thing. It even says so here. However, frustum was first used in 1658, whereas truncated turns up belatedly circa 1704, making frustum the original and more smarty-pants word. And, if we are to be pedantic, well, in for a penny, in for a pound.;)
 
One advantage of not using a straight walled case, is that you can then have bottlenecked cartridges with relatively good ballistic performance.
For example, I'd rather hunt with a .308Win instead of a .30 Carbine. ;-)
 
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