Do you get additional speed from WSM or WSSM cases?

[retiredcpo]

All I can add to this is
my 300 WSM gets 2862FPS with a SD of 9.66
My buddies 300 WM gets 2688 FPS with a SD of 8.23
Not the same exact load his case holds more than mine
but both are middle of the road loads for the caliber. So the are about the same really and should get the same but mine is slightly faster
but the slight differance do not make mine a better round
retiredcpo

 

[4xforfun]

I've been pouring over reloading manuals. I might have come across a free lunch, if I'm reading things right. The 25 WSSm is a smaller case than the 25-06 and with considerably less of the same powder can attain the exact same speeds.

But i have always had a distrust of reloading manual specs and only use them as a rough guide. Even for the same bullet they have discrepancies of velocities with different types of powders. It's like the editor didn't even proof read the work before publishing.

BUT....at considerably higher pressures!!

 

[INTJ1]

I've been pouring over reloading manuals. I might have come across a free lunch, if I'm reading things right. The 25 WSSm is a smaller case than the 25-06 and with considerably less of the same powder can attain the exact same speeds.

But i have always had a distrust of reloading manual specs and only use them as a rough guide. Even for the same bullet they have discrepancies of velocities with different types of powders. It's like the editor didn't even proof read the work before publishing.

I too have found mistakes in loading manuals. I'll look up 25 WSSM info in my various manuals tonight and post what I find here on this site. I do know of a couple of 1K BR shooters that necked up a 25 WSSM to make a 6.5 WSSM. They shot a little slower than a 6.5 x 284.

I have good case capacity data for a lot of chamberings, but not for the WSMs and WSSMs. I can measure the 300 WSM. The others I'll have to search for.

 

[LongBomber]

The easiest comparison is a 300wsm and a 300 H&H. That is likely the closest case capacity comparison. A 7wsm and a 280 AI would also be a fair comparison.

The larger the case capacity the faster the MV given the other variable stay constant.

You could chamber a rifle in 300H&H and test it, then chamber to 300wsm. You could set it up to only move the neck/shoulder a couple thou forward, trim off and thread the barrel again. Then you could test the wsm with the exact same barrel. The barrel length would be the same, and the same action can be used for the testing. That is about as close as you are going to get to a useful test comparison.

 

[INTJ1]

Posted on another site:

"Found the old Handloader Magazine that I mentioned back on page 2, .300 WSM vs .300 H&H Holland. It's the February 2007, No 245 on pages 95, 96 and 97.

Both chambers were given the same amount of throat. Lilja 1.2" diameter barrel.

With 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."

 

[budlight]

Posted on another site:

"Found the old Handloader Magazine that I mentioned back on page 2, .300 WSM vs .300 H&H Holland. It's the February 2007, No 245 on pages 95, 96 and 97.

Both chambers were given the same amount of throat. Lilja 1.2" diameter barrel.

With 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."

Now that is a good comparison. I'd like to hear about smaller volume WSM VS larger mags with the same powder............................ I never ask about pressure difference. I don't care. I'm interested in efficiency caused by case shape. If it is not any difference...... fine at least I would know the truth.

 

[INTJ1]

I haven't had the time to look up the info on the 25 WSSM this weekend. However, I did measure the capacities for a 300 WSM and a 300 H&H. I got 80 grains of water for the WSM and 84 grains for the H&H. Based on the difference in capacity and the old 1/4 of capaity for velocity rule, the H&H should give 35 fps more velocity when loaded with 4 grains more powder, if all else was equal.

In the test above, thanks to Bobo7mmmag on the 'nest, we see the opposite of what we expected.

".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."

The WSM should generate more pressure and shoot faster than the 300 H&H at any powder charge level until the case capacity of the WSM is reached. At that point, the added capacity of the H&H should allow a little more velocity.

If smaller cases are able to produce more velocity per grain of powder, then in the test above the 300 WSM should have been signficantly faster at the same powder charge. As it was the WSM achieved 2918 fps at 84% of case capacity, while the 300 H&H achieved 2914 fps at 80% of case capacity. In this test, the H&H was more efficient than the WSM which goes against my theory of smaller cases being more efficient per grain of powder.

The most apples-to-apples data I could find comes from the 2009 Hodgdon loading manual. In comparing the 300 WSM vs the 300 H&H, the only time they had data fpr the same bullet was with 220 grain Hornady RNs, both fired form 24" barrels. The only common powders were H4350 and H4831.

WSM with H4350 shows 58.0 grains and 2602 fps at 63,300 PSI
WSM with H4831 shows 64.3 grains and 2646 fps at 63,500 PSI

H&H with H4350 shows 64.0 grains and 2717 fps. Pressure not listed.
H&H with H4831 shows 70.0 grains and 2714 fps. Pressure not listed.

The data above shows the WSM getting 45 fps per grain with H4350 and 41 fps per grain with H4831. The H&H gets 42.5 fps per grain with H4350 and 39 fps per grain with H4831. The data shows the results we typically see.

With both Supreme 780 and and Hybrid 100V, the WSM exceeded 2700 fps with that bullet. Of course, they didn't test the H&H with those powders.

So far, everything I've come across seems to confirm that that case capacity is a bigger determiner of velocity than case shape. A good test would be the 7mm Rem Mag vs the 7mm WSM. Their respective case capacities are with .2 grains of each other.