Wsm's

[Jordan Smith]

check the Nosler manual for the .300 Winchester and .300 WSM data with R-22 and the 220 gr Partition. The WSM maximum load is compressed but holds 3 grs less than the maximum .300 Winchester load which is not compressed.

Again, this is not a matter of case shape, but simply that the .300WM has more powder capacity than the .300WSM. Check the water capacity of both cartridges, and you'll see why the .300WM can hold more powder without being compressed.

 

[Jordan Smith]

If the cartridges are ballistically equal, then their volume must be similar or there would be a disparity of velocity when the ammo is loaded to the same pressure. The smaller cartridge would not be able to produce the volume of gas necessary to match the volume of gas in the larger cartridge when fired in similar rifles. In the case of the .300 Winchester and the .300 WSM, the velocity only varies by 5 fps according to the Nosler manual, and 5 fps is meaningless in term of performance.

Rather than introducing ballistic gack, and trying to deduce the capacities based on the relative performance (never mind that they are being loaded to different pressures!), just simply check the water capacity of both cartridges, if you want to see how the relative powder capacity compares in both.

 

[Jordan Smith]

Magazine and throat length are what dictate the outcome of this argument, not case design.

HOWEVER, if you want to get into the minute details, you should compare neck lengths and shoulder angle, and factor that into the water capacity comparisons between the two cartridges. Ideally, if you had two cartridges that had identical water capacities when filled to the bottom of the neck, then you would have equal performance and load characteristics, regardless of case shape. As soon as the bullet protrudes below the bottom of the neck in our imaginary cartridges, you'll have a compressed load, whether you're looking at a long, skinny case, or a short, fat one.

 

[Jordan Smith]

From the Speer manual . . .
"The only limitation to the .300 WSM and its look-a-likes is that long bullets (200 grs and up) protrude into the case and take up powder space. Velocities with heavy bullets do not track with those of lighter bullets, and we elected to not show data for our 200 gr bullets. We screened some 200 gr loads and there was little gain over the .30/06."

That is 100% dependent on magazine and throat geometry.

 

[MiG25]

From the Speer manual . . .
"The only limitation to the .300 WSM and its look-a-likes is that long bullets (200 grs and up) protrude into the case and take up powder space. Velocities with heavy bullets do not track with those of lighter bullets, and we elected to not show data for our 200 gr bullets. We screened some 200 gr loads and there was little gain over the .30/06."

so if you seat a 200 grain bullet to the base of the neck in both cartridges, what would happen? yes i know that action length and OAL might work against actually doing this.

which case has more volume the WM or the WSM? is the real reason that the WSM can't keep up with heavier bullets is that it doesn't have the volume?

reloading manuals aren't the be all to end all as there are always errors.

 

[Boomer]

Rather than introducing ballistic gack, and trying to deduce the capacities based on the relative performance (never mind that they are being loaded to different pressures!), just simply check the water capacity of both cartridges if you want to see the relative powder capacity compares in both.

The volume of water that a cartridge holds only tells part of the story. It does not tell you how much volume is available to you once the shank of the bullet extends into the body of the case. Once that happens a percentage of the total powder volume is lost to you, there is simply no way to make use of it and that fact is acknowledged by the loading manuals as I've quoted with respect to the short fat cartridges. You are correct in that the shank's incursion into the body of the case does not reduce the volume of the case any more so than it does with the long cartridge, but it does reduce the useable volume of that case, if putting it that way works better for you.

Both the .300 Winchester and the .300 WSM are loaded to 65,000 psi or 54000 cup.

 

[Jordan Smith]

The .300WSM holds right around 10gr less water than does the .300WM. It can't keep up with heavy bullets because it doesn't hold as much powder. Much like the .308 can't keep up to the .30-06 with heavy bullets. It's not because of differing case shape, but simply because it doesn't have the displacement to keep up.

 

[Jordan Smith]

The volume of water that a cartridge holds only tells part of the story. It does not tell you how much volume is available to you once the shank of the bullet extends into the body of the case. Once that happens a percentage of the total powder volume is lost to you, there is simply no way to make use of it and that fact is acknowledged by the loading manuals as I've quoted with respect to the short fat cartridges. You are correct in that the shank's incursion into the body of the case does not reduce the volume of the case any more so than it does with the long cartridge, but it does reduce the useable volume of that case, if putting it that way works better for you.

Both the .300 Winchester and the .300 WSM are loaded to 65,000 psi or 54000 cup.

A case that is full of powder up to the base of the shoulder or neck, under a compressed load, is using all available case volume, regardless of the shape. If you have to resort to fast-burning powders that reduce fill volume because of load compression, then you should probably think about matching the rifle's mag and throat to your chosen bullet a little bit better.

I wasn't necessarily talking about SAAMI specs, but simply that the loads created by Speer for the .300WSM and .300WM are going to be loaded to different pressures, unless they specifically tailored loads to be identical in pressure.

 

[Boomer]

so if you seat a 200 grain bullet to the base of the neck in both cartridges, what would happen? yes i know that action length and OAL might work against actually doing this.

which case has more volume the WM or the WSM? is the real reason that the WSM can't keep up with heavier bullets is that it doesn't have the volume?

reloading manuals aren't the be all to end all as there are always errors.

I doubt if a 200 gr bullet is long enough to illustrate the problem, but 220 gr or 240 gr MK, a 240 gr Woodleigh, or a 210 gr VLD might make it clearer. The action length and the length of the lead becomes the limiting factors as you could otherwise seat the bullet out as far as you liked, but with very long bullets like these and a powder charge which fills the case up to the bottom of the neck, the result is an OAL that prevents you from closing the bolt. I can achieve .30/06 velocities with 210 gr VLDs in my long barrel .308 because I had that rifle built so that the base of the long bullets would never have to be seated below the shoulder of the case, thus I'm making a hair under 2700 fps with a 210 VLD. Keeping the cartridge within SAAMI COAL would cut the velocity back to 2400-2500 fps.

 

[Boomer]

A case that is full of powder up to the base of the shoulder or neck, under a compressed load, is using all available case volume, regardless of the shape. If you have to resort to fast-burning powders that reduce fill volume because of load compression, then you should probably think about matching the rifle's mag and throat to your chosen bullet a little bit better.

I wasn't necessarily talking about SAAMI specs, but simply that the loads created by Speer for the .300WSM and .300WM are going to be loaded to different pressures, unless they specifically tailored loads to be identical in pressure.

No, a compressed load is one in which the height of the powder charge prevents the bullet form being seated deeper without bulging the wall of the cartridge. There may indeed be airspace between the shank of the bullet and the wall of the cartridge at the shoulder or even slightly below it depending on the powder charge and the length of the shank.

If a faster powder is chosen to prevent the load from compressing, it might have to be so fast that maximum pressure is realized long before the optimum velocity can be reached. Heavy bullets almost always produce the best performance in bottle neck cases with slow burning powder. For example a safe load of IMR 3031 combined with a 220 gr bullet in the WSM might only result in 2300 fps, although I haven't run the numbers to be sure, so switching to a faster powder might not provide the solution you seek. Of course a 220 at 2300 is nothing to sneeze at if you are satisfied with .30/06 performance from your magnum. If it was me, the first thing I would attempt to do is to find a powder with a higher loading density such as a slow burning ball powder. If that didn't work I'd do what I should have done in the first place and go back to a bullet in the 165-180 gr range and save the long bullets for my full sized rifles.

 

[1899]

According to the Powley computer, a 220gr Partition seated to create an OAL of 2.860" in a .300 WSM will yield a net case capacity of 67.5gr (empty = 79.0gr). For the .300 Win Mag at 3.34" gives 76.8gr net vs 89.0gr empty.

So the .300 WSM loses 11.5gr and the .300 Win Mag loses 12.2gr. This represents a 14.6% loss for the WSM and a 13.7% loss for the .300 Win Mag.

That small increase in relative case capacity loss does not, in my mind, explain the increase in performance gap in the .300 Win Mags favour when using heavy bullets. Perhaps it is due to the more powder being beside the bullet in the WSM, whereas in the Win Mag most of the powder is behind the bullet.

With the 130gr TSX we see the average for all max loads:

.300 Win Mag 3502fps
.300 WSM 3492fps
.300 H&H 3455fps

200gr TSX
.300 Win Mag 2786fps
.300 WSM 2713fps
.300 H&H 2747fps

 

[Jordan Smith]

The .300WM holds more powder. That's why. Let's compare the .300WSM to the .30-06 and see how they stack up.

 

[1899]

The .300WM holds more powder. That's why. Let's compare the .300WSM to the .30-06 and see how they stack up.

Yes, but notice how with light bullets there is virtually no difference between the average of 10 max loads for the Win Mag and WSM? Yet when you go to the longer 200gr bullet the WSM lags noticeably.

Also the H&H, which is longer still, goes from lagging at light weight to surpassing at heavy weight. Why are the results not proportionate? Is it because the efficiency of the short cartidge decreases as bullet length increases? I think so.

 

[Whelen B]

"There's no replacement for displacement..." - good one.

Jordan Smith is laying it out for those with eyes to see and ears to hear - others always be "missing the point".

 

[1899]

Jordan Smith is laying it out for those with eyes to see and ears to hear - others always be "missing the point".

His answers don't address why, when the .300 H&H has about 1gr more capacity (and operates at a lower pressure) the WSM beats it with a light, short bullet, but not with a heavy, long bullet. The case capacity argument is moot, because they are virtually identical.

 

[Grizzlypeg]

So no shapes of cartridges are more efficient than others?

 

[MiG25]

His answers don't address why, when the .300 H&H has about 1gr more capacity (and operates at a lower pressure) the WSM beats it with a light, short bullet, but not with a heavy, long bullet. The case capacity argument is moot, because they are virtually identical.

you said it, less pressure.

 

[MiG25]

a few years back in either rifle or handloader, barsness published a test of the WSM vs the H&H with the same barrel (rechambered) with the same charge of various powders and bullets. pressure numbers and velocity where cited. the conclusion was that there is no difference, capacity being the same. it wasn't exhaustive by any means, but it was real data.

 

[1899]

you said it, less pressure.

Exactly, so you'd think the WSM would do better with heavier bullets too.

a few years back in either rifle or handloader, barsness published a test of the WSM vs the H&H with the same barrel (rechambered) with the same charge of various powders and bullets. pressure numbers and velocity where cited. the conclusion was that there is no difference, capacity being the same. it wasn't exhaustive by any means, but it was real data.

That is interesting. I don't suppose you have a link?

 

[Gatehouse]

My gawd there is alot of ballistic masturbation on this thread.

There isn't any real world difference between the 300WM and 300WSM, regardless of bullet. The difference between them using 200 and 220 grain bullets is less than 100 fps when you use the same powder in each of them. Sometimes it's less than 50fps difference.