Home Forums Hunting & Shooting Ask The Gunwriters Cartridge Efficiency: Why case shape matters

You would have loved my first wife.....she was short and squatty, too! <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" />

One thing that helps the short mags as far as accuracy goes, is the extremely short throats they have. Most common cartridges have overly long throats on factory barrels. Probably a quest for liability concerns from the bean counters...

Simply put- If you take a 300 WinMag and a 300 WSM and have them chambered by a good gunsmith, the accuracy would likely be the same. The Winnie would be a little faster given equal barrel lengths but not by a huge margin. As was stated earlier, the standards are much easier to deal with as far as finding Factory ammo in a pinch.

I think the 300 WSM has a good chance of making it in the long run but the other short mags will likely fall by the way side. After all, this is 30 caliber country...

Mickey is exactly right. He also knows how to put a rifle together to SHOOT. I have shot some of 'em!

Winchester hit the jackpot with the .300 WSM. At one point shortly after its introduction they were selling 700% more than they projected! I believe it will be a standard cartridge for a long, long time.

The rest are iffy. The second-best-selling WSM is the .270, but it is way behind the .300. The 7mm never really got out of the gate due to taking too long to be finalized. The WSSM's are dead in the water.

I have heard conflicting reports about the .325. Here in the West it hasn't sold well, but I have heard the Southeast boys like it. Must be deadly on those 100-pound doe whitetails and barbecue pigs. I never could understand what it was supposed to do that any .300 magnum wouldn't, but then I often get in trouble by asking too many questions.

MD

But one cartridge does not a business make. Really, it should not break one either. It's not as simple as chambering too many rifles in their WSM/WSSM line, but when you're on the ropes, if you gamble, you must accept the result. That idea didn't help things.

Is it fair to say that chambering and marketing the WSM line of cartridges in their rifles was worth the result? Time will tell. Personally, I don't think so. Whether you like short and fat or long and skinny (sounds a tad kinky) the writers of tomorrow will have a field day reviewing the events that we are living through.

I expect that their future conclusion will be "obvious" for all to see. Why couldn't the company see it that way back then?

I don't think I'm bright enough to understand what all of the fussing and fuming is really all about as it applies to case shape and configuration, short versus long, the significance of powder efficiency ratios, etc. From my ignorant point of view, a lot of it seems to be an exercise in mental gymnastics, and I think a lot of guys are more pre-occupied with pole-vaulting over mouse turds, theorizing, collecting a safe full of rifles that all do pretty much the same thing, and punching paper than they are hunting.

Case in point, for the last 12 years I've used the 300 Win. Mag. more than any other cartridge in a score of states and eight foreign countries, and on a great many big game animals of all sizes, up to 2,000 lbs. in weight, and at ranges up to just over 500 yds. Yet, if you listen to a lot of the chatter, the short neck, belt, case length, powder efficiency ratio, etc., all make the 300 Win. Mag. some sort of a dinosauer that's not supposed to work just quite right.

Even so, I've never had a feeding problem, an accuracy problem, or a reloading problem with this cartridge. Nor have I been alarmed with or have given a rusty about recoil or if maybe its powder consumtion ratio isn't quite optimum. However, despite all of those purported drawbacks and potential hassles that haven't yet seemed to have manifest themselves or gotten in the way of terminal performance, it's just-plain worked for me anyway -- that's all I know.

Maybe I've been doing something wrong and and have been plagued with problems after all, and I'm just too dumb to know it!

AD

.....and here I was scrolling through and reading this thread with my own response about how all is naught if it doesn't go through the gun right come hell or high water...........and there just is nothing like one of those sleek H&Hs to do that, never mind all the theoretical advantages to the likes of the new beltless stuff and so on. And at that point, who actually gives a rip if it requires more or less powder to "get there." I won't even touch the accuracy thing since both the 300 as well as the 375 have an accuracy track record of some repute. Any difference for their normally used purposes is pretty much nil.

(And though I differ on cartridges- not so much because of appearance- I do have to agree with you on the human shoulders thing. I can't imagine us shaping ourselves as was considered attractive 200 years ago with corsets, etc to get a certain long-necked look....not sure that some of the presently popular human sculpting is any better though.........)

Unfortunately, living overseas at the moment, I can't get my hands on that article. The short fat cases do have a slight advantage in general. For a fixed barrel length, they get a bit longer bullet run. That means a greater expansion ratio, and that is well proven to up your efficiency. As others have pointed out, though, higher pressure increases efficiency as well, and I wouldn't be surprised if this old trick is being used to improve their efficiency claims. That 10% increase in fps means 20% more efficiency, which sounds pretty iffy. In my copy of Cartridges of the World, there is a picture of one of McPherson's cartridge. It sure looks to me it will enjoy some of the advantages of frontal ignition, the case body being shorter than it is wide. Still, I'm not convinced there's quite that much to pick up from the effect, though.

It is no doubt equal pressure will do only an equal amount of work. That is a given.

Can case design give more pressure with less powder? That is Cartridge Efficiency.

As far as the elliptical sholders go, once the powder has burn down to expose the sholders the show is all but over. If the powder is in an elliptical shape it would be a differant story.

All this talk about catridge efficiency - hell boys just fill it up! <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" />

Yea. Just give me a bullet with a BC around .440. Moving around 2680-3000 fps and I'm happy. Oh yea, Less then MOA too.

I know I'm jumping in kinda late on this one, but here's one that always burned me up. Have you ever been to Fred Z's Z-Hat website. In the old days, he had this write up on how the Z-Hat cartridge were so "efficient" and had some total BS explanation for it. I see he has updated this explanation to make it more plausable, but I still don't buy it.

http://www.z-hat.com/Efficiency%20of%20the%20300%20Hawk.htm

This particular graph I find ludicrous:



You really think there is something "magic" about blowing out the '06 case to hold maybe 8% more powder and all of a sudden it becomes more efficient than the '06 AND the .308 Win. C'mon Fred, get real!!! What he's really doing is comparing selected reloading manual velocities with his amped up handloaded velocities.

MM

Damn. All this and not a single mention of the "point of
dimishiing returns"? <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />

I notice the article you linked emphasizes "kinetic energy" as a comparison point. Since the kinetic energy calculation uses the square of the velocity, any difference in velocity causes an amplified difference in kinetic energy. Plus, like MuskegMan said, the comparison uses average velocities and is not a true apples-to-apples comparison with factors like pressure, energy content of the powders used, etc. controlled. There was, obviously, no controlled experiment run. Junk science.

As I read this I can't help wonder, if having the same case pressure to achieve a certain velocity is such a big deal, why do we bother with bottle neck cartridges? Then what was so bad about the cases like the .375HH, .30WCF and the .22Hornet.

The only thing is,the .30-30 could achieve higher pressures then what came before it. The .300savage had higher pressure then the .30-30.

As modern metallurgy improves and modern gun power improves, pressures go up. It's a fact. Face it. Move on.

Loaded to the same presures, black power will do the same job as modern gun powders. At least that is what I see in this topic. Or am I wrong?

So I say; if case shape didn't matter, all cartridges would have straight shoulders. Or, no two would look alike.

If the firearm can take that pressure, use that pressure. That is were pressure is most important.

Until there is a viable and reputable study done where the case capacity is constant, but the shape is changed and all other variables held constant, I will hang on to my belief that the .284 Win case will match the 280 Rem and use a couple less grains of the same powder to do it.
I am talking about using the same barrel, etc. ie: all things constant except the case shape.
Yes I know the 284 has slightly less capacity than the 280, but it is my belief that if the capacity was identical the shape of the 284 would cause it to out perform the 280 (higher velocity)-----ie truly be more efficient with all the variables held constant.
I have to believe that if you vary the powders used, but load to achieve the same pressure, the velocity will show some variation depending on the shapes of the different pressure curves
Just my $.02 worth. but some would say I am not up to that value.
mrk

Gentlemen, efficiency is primarily a function of the pressure limit and the expansion ratio.

Neither alone is the figure of merit. A .300 Wea in a 6 inch barrel is far less efficient than a .30-30 carbine. A .44-40 rifle is less efficient than a .44 Mag revolver.

It's the ratio of KE to charge weight that is the measure of efficiency (more or less -- some powders carry more energy per grain). Whether you care if you're burning a little extra powder is another matter.

You talking to me? <img src="/ubbthreads/images/graemlins/confused.gif" alt="" /> <img src="/ubbthreads/images/graemlins/confused.gif" alt="" /> <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />

I think many are missing the point of the article. The "plug" of powder not reached by the initial primer blast follows the bullet unburned and the elliptical shoulders cause an epiphany to be as yet understood, although the author tackled it as best as he could for laymen. It has been proven with sub 30 and now will have to wait until someone builds the 30 caliber model. That may not happen because it is so unconventional. Does that sound familiar? Think out of the box. Maybe progress has been waiting for 100 years but we missed it.
For hundreds of years, it never dawned on scientists that a different shape other than round ball might result in better ballistics downrange.