Fat bottom gurls....

Im a fan of fat bottom girls but mine is a little slimer than yours.
i have a 6.5x284 that is cool and i like but my mate got a 284 at the same time and his is wicked. These little cases really punch outside there size and i think its because of there wider bottom than other med bolt face cartridges. id love to know the reason why short fat cases work better than long thin cases

 

You should love the 300 and 338 Norma Magnums. The ultimate "fat bottom" civilian cartridge is the McMillan " Fat Mac". It's a 50 caliber cartridge with 406 grains case capacity but only 2.630" case length.

 

I have an addiction to fatties with slow powders, the 270 WSM is my girl I must have some of the new Norma Mag stuff but it keeps getting on the back burner

 

That's awesome. I'm a 300. WSM kind of guy. Few years back I wanted something that would take game out to 500-600 easily without going to big, and I was going choose either a 300. Win mag or 300. WSM and everyone rippled up the WSM but anyone who owned on takes so highly of it. I picked one
Up and love it!!

 

I love the 300 WSM. My best 1K BR rifle was in 300 WSM and it dominated the competition. I currently have a 7.75 lb w/scope M-70 Classic/Benchmark/Edge in 300 WSM that is amazingly accurate.

However, there is no way a 300 WSM can shoot as fast as a 300 Winny. It is all about case capacity, and the shape between these two cases doesn't have a huge effect on velocity. Further, comparing the numbers we get with our handloads in a couple of rifles really doesn't tell us much other than what we can get those rifles to do.

The biggest question mark when we work up handloads is knowing pressure. I have personal knowledge of no less than five guys who have used Oehler 43s to test pressure. One of these fellows was an ballistics consultant for the US Army. They all agreed there really isn't a reliable way to tell when we are at maximum pressures. All of the conventional pressure signs: flattened primer, sticky bolt lift, case head expansion, etc; only tell us when we are well over maximum pressures. One particular lot of Remington brass tested to 80,000 PSI without showing and signs of pressure.

That leaves us with the data the bullet and powder makers publish as our best reference for velocities obtainable for a given bullet/power/barrel length combination. This data has been scientifically obtained using high-end pressure equipment, and enough shots are fired to get statistically meaningful data.

The 5th edition Sierra manual shows a 300 WSM with 190 and 200 grain bullets at 2900 FPS from a 24" barrel. It shows the 300 Winny shooting the same bullets at 3000 fps from a 26" barrel. We can add 50 fps to the shorter barrel, but the WSM is still falling short of the Winny. They don't show any data for a 240 grainer in the WSM, but they do show the 300 Winny getting 2800 FPS with a 240 grainer in a long throated rifle. There are many reasons why your own 300 Winny may have shot so slow, but it wasn't the norm.

A general rule of thumb is to take the 1/4 of the difference in case capacity to get the increase in velocity. A 300 WSM holds 80 grains of water, a 300 Winny holds 90 grains of water. That is a 11% increase, and 1/4 of that is 2.78% At a MV of 3000 fps, 2.8% equals 84 fps. Now the 300 WSM will effectively have 1/2" more barrel length than a 300 Winny in the same length barrel, and that is worth nominally 25 fps. We are again at a 50 fps advantage to the 300 Winny.

That is a 50 fps gain for the Winny in the Sierra manual, a 50 fps gain in standard calculations, and even a 50 fps gain with 240 grain SMKs in long throated rifles.

Now without question we get more velocity per grain of powder with the WSM over the Winny, but that is true almost every time we downsize case capacities, and the converse is true when we add case capacity. Regardless, when a 300 WSM and a 300 Winny are both throated relatively the same, shot in the same length barrels with ammo loaded to the same pressures, the 300 Winny will be a little faster.

 

I am not trying to be contentious, I just see it completely differently.

I get what you are saying about case shape, I just don't agree that it is as big of a factor as you seem to think it is. Case capacity is the primary factor in determining velocity.

I think you are getting higher velocities from your WSM because you are loading it to higher pressures than you are your winny. Been there, done that myself.

 

After trashing a 7mm STW barrel in short order I am building a 7mm SAUM as we speak! It's the PPC syndrome. "They make the rockin' world go round"

 

I too love the girls with big bottoms. I have a 270 wsm that has taken Pronghorn, and many deer. Haven't had a chance to soot elk, but would pull the trigger in a heartbeat. I have just picked up a 300 wsm and look forward to my first kill with it.

 

The 338 norma magnum and the wild cats made from this case lives buy the same rules as the Short magnums you got to love them.

 

I don't care , 100fps either way will make so little difference on target you would be better served practicing instead of arguing , it's hit's that count not kit!

having said that i still read the whole thread (chuckling to myself!)