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.

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.

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 Stocky

Out of interest how was barrel added?

Greetings Stocky,
Somehow I managed to get this test scrambled with a previous test comparing the .30-06 and .30-06AI. In this test the barrel section was attached with locating pins and bolts. They also wrapped the join in tape to detect any gas leakage, there was none. I think the extension may have been smooth bored. The idea of the extension was to test 24 and 26 inch barrels. The result of the test showed the extra velocity was minimal, as would be expected for the small capacity increase.
Getting back to the .300 H&H .300 WSM test the same throat was used but the barrel from breech face would have been .75 inches shorter, perhaps a 20 fps velocity difference. Interesting point in John and Charlies limited tests although the H&H showed higher pressure differences on average the ES was largely the same. The accuracy from the H&H was better than the WSM.
Regards Grandpamac.

Originally Posted by grandpamac

Greetings Stocky,
Somehow I managed to get this test scrambled with a previous test comparing the .30-06 and .30-06AI. In this test the barrel section was attached with locating pins and bolts. They also wrapped the join in tape to detect any gas leakage, there was none. I think the extension may have been smooth bored. The idea of the extension was to test 24 and 26 inch barrels. The result of the test showed the extra velocity was minimal, as would be expected for the small capacity increase.
Getting back to the .300 H&H .300 WSM test the same throat was used but the barrel from breech face would have been .75 inches shorter, perhaps a 20 fps velocity difference. Interesting point in John and Charlies limited tests although the H&H showed higher pressure differences on average the ES was largely the same. The accuracy from the H&H was better than the WSM.
Regards Grandpamac.

Very cool. Some ingenious buggers out there.

Originally Posted by Stocky

Out of interest how was barrel added?

Greetings stocky and Others,
I dug out the article on the .30-06 v .30-06AI in Handloader No 123 September October 1987 written by Gil Sengel. The rifle had a 24 inch barrel fitted to a Winchester Hi Wall action. The muzzle was drilled, threaded and reamed to take three each locating pins and bolts. The barrel was 1.25 inches in dia so there was plenty of room. The barrel was then shortened to 22 inches with a parting tool and a spacer made up the same thickness as the tool and reamed in the centre to bore dia. Thus there was only a very short section un rifled. Loads were worked up in Remington cases using measurements of the solid head of the case to keep pressures equal. 150,165,180 and 220 grain projectiles were used with 5 powders. Mostly the velocity increase for the AI was between 3 and 85 fps, hardly worth rechambering for. This was with the 22 inch barrel. The 24 inch barrel produced a maximum of 60 fps extra velocity over the shorter barrel but only with the slower powders and heavy projectiles. Mostly it was less than half of that
Regards Grandpamac.

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

Originally Posted by dvk-kp

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

long and fat, the wife likes that

Originally Posted by dvk-kp

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

Or,

Long and thin goes all the way in, short and fat, cant do much with that.

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.