Thread: Short fatties vs long slender ones...

One of the members just posted this: "short magnums in general,... don't mind a short barrel due to their short powder column".
Now I know that the case capacity to bore ratio allows a cartridge to be more efficient (less case capacity/powder to bore size = more efficient).
But what if you had a long cartridge and a short, fat cartridge that both had the same case capacity ie 6.5x55 and 6.5 Creedmoor or 284 Winchester and 280 Remington (close enough for our example).

Does a short, fat case design help to reach full-potential in shorter length barrels compared to a longer case design of the same amount of powder?... or doesn't it matter?

NOTE: this is only taking into account the case design NOT that the shorter cartridge allows say 1" shorter barrels due to the shorter action required.

Greetings Hermitage,
There was an excellent test of this in Handloader. A .30 calibre barrel was chambered for .300 H&H, loads worked up and then set back and rechambered for .300 WSM. A short length of barrel was fitted to the muzzle of the barrel at this point so that both cartridges had the same barrel length. Loads were then worked up again. While the results were not absolutely identical there was no significant difference between the two. .300 H&H was used as the capacity was near identical to the WSM. Generally same capacity and same powder charge and same velocity means same pressure. There are minor variations but overall results will be much the same.
Regards Grandpamac.

I was getting to the point of thinking this was a question that nobody on the NZHS forum could answer so thanks for clearing that up for me @grandpamac.

Long and thin goes too far in, short and thick does the trick...

Originally Posted by Hermitage

I was getting to the point of thinking this was a question that nobody on the NZHS forum could answer so thanks for clearing that up for me @grandpamac.

John Barsness, one of the two carrying out the test, also came up with a number of rules one of which is:
"Possible velocity increases at one quarter of available case capacity"
I used this rule to calculate probable top velocity in my 6.5 x 55. I worked up from the .260 Rem and down from the 6.5 - 284 and got a velocity for the 129 grain SST of 2,850 fps both ways. This velocity was achieved with 46 grains of current manufacture AR2209. This is in line with the 2,750 fps I got chronographing Norma 140 grain factory loads years ago.
Regards Grandpamac.

I found the old Handloader Magazine that Grandpamac mentioned about the .300 WSM vs .300 H&H Holland. It's the February 2007, No 245 on pages 95, 96 and 97.
The 300 H&H and 300 WSM have virtually the same case capacity. Both chambers were given the same amount of throat.

Using the 180 grain Nosler Partition:
.300 WSM RL-19 at 67.0 grains gave 2,918 fps at 56,064 psi Velocity spread 13 fps.

.300 H&H Rl-19 at 67.0 grains gave 2,914 fps at 57,177 psi, Velocity spread 9 fps."

So the 'short and fat' 300WSM has no velocity difference over the 'long and slender' 300 H&H.

Another test:
"A series of tests were described in 'The American Rifleman' 1981. Three cases were tested, all of the same capacity, and all necked to take identical .22 caliber bullets.
1st case - conventional body taper and a long 14-degree shoulder.
2nd case - very long body taper and a 35-degree shoulder.
3rd case - little body taper and a concave radius shoulder.

Velocities and pressures were measured by both electronic-transducer and copper-crusher methods.
It was reported that the performance was almost identical, within the expected error. This very carefully controlled laboratory experiment found no difference in ballistic performance.

So this confirms that 'short fatties vs long and slender' case shape has no effect on velocity.

I thought the short and fat is where its at was more to do with consistant powder ignition/burn for better accuracy?

Pretty much every modern popular chambering for competition shooting has this design.

Originally Posted by veitnamcam

I thought the short and fat is where its at was more to do with consistant powder ignition/burn for better accuracy?

Pretty much every modern popular chambering for competition shooting has this design.

Agreed. The short powder column centers more of the powder closer to the primer flash for potentially more efficient ignition and burning. Apparently.

Originally Posted by veitnamcam

I thought the short and fat is where its at was more to do with consistant powder ignition/burn for better accuracy?

Pretty much every modern popular chambering for competition shooting has this design.

Yeah PPC inspired designs (short n fat), are indeed more accurate than longer cases holding similar amounts of powder due to less velocity spread (SD over Chrono). But it generally takes a very accurate rifle to prove it out and the short fatties give no increase in velocity over long and slender.

Originally Posted by veitnamcam

I thought the short and fat is where its at was more to do with consistant powder ignition/burn for better accuracy?

Pretty much every modern popular chambering for competition shooting has this design.

Yep, and drag out the theories on gas turbulence and try and understand them. Although shoulder design probably has more influence here.
And then there is brass flow to theorise on as well.

So velocity only may be a one dimensional answer.

The original question re barrel length probably wasn't answered.
Nope, I don't have the answer.

so the good old 22hp savage rimmed cartridge would be awesome in a single break open if given a fast twist 224 barrel it wouldnt be giving buggerall away to the modern flash cartridges with similar case size...and be heaps easier to extract....
one day when win lotto....reminds me must get around to buying a ticket one day LOL

Originally Posted by grandpamac

Greetings Hermitage,
There was an excellent test of this in Handloader. A .30 calibre barrel was chambered for .300 H&H, loads worked up and then set back and rechambered for .300 WSM. A short length of barrel was fitted to the muzzle of the barrel at this point so that both cartridges had the same barrel length. Loads were then worked up again. While the results were not absolutely identical there was no significant difference between the two. .300 H&H was used as the capacity was near identical to the WSM. Generally same capacity and same powder charge and same velocity means same pressure. There are minor variations but overall results will be much the same.
Regards Grandpamac.

Out of interest how was barrel added?

Originally Posted by Hermitage

Yeah PPC inspired designs (short n fat), are indeed more accurate than longer cases holding similar amounts of powder due to less velocity spread (SD over Chrono). But it generally takes a very accurate rifle to prove it out and the short fatties give no increase in velocity over long and slender.

or longer ranges (much longer) where velocity spread has a bigger effect.

Originally Posted by veitnamcam

I thought the short and fat is where its at was more to do with consistant powder ignition/burn for better accuracy?

Pretty much every modern popular chambering for competition shooting has this design.

No sure why the writer of the article chose 300 H & H except of course for comparable capacity with the WSM.
THE 300 H & H certainly meets the long and thin criteria but it's design was such to allow early days loading of cordite strands.

I was recently offered a .300WM as a replacement for my .300WSM after comparing the ballistics there was a very minor difference between the two across velocity etc.
So stuck with the wsm.

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