Ted - you know that I have the greatest respect for you and your vast knowledge, but we are talking about getting 5500 ft-lbs of energy out of a case that holds perhaps 91gr.
I am of the view that you don't get a free lunch.
You have "some" experience with the .358 Norma Mag. That case would have slightly less capacity, and the .358 STA would have almost 15% more case capacity. The .358 Norma would work hard to get a 250gr bullet to 2800 fps, and I think the STA might make 3000 with the same bullet.
So long throat ( a la Weatherby) or not, you are talking about a relatively small case making as much power as a .378 Wby Mag (factory 300gr loads listed at 2925 fps). I have faith that you won't hurt yourself, but we are talking about some pretty extreme loads here, aren't we?
One of you guys must have QuickLoad - I am curious to see what kind of pressures these loads might give.
1899, I appreciate your kind comments. The feeling is mutual.
Okay, let me put this all in a better perspective. Years ago we built, not one, but two 375s on the 300 Win Mag case, one on a SAKO, the other a Patter14 Enfield. Both rifles would get 270 gr bullets over 3000 fps.
Then we did a 358 on the 300 Win,.... lo and behold 250s went past 3000 fps.
Those were the Halcyon days when we used case life as a measure of loading safety.
Any load that did not expand primer pockets after five firings was considered a safe load for regular use. With this in mind, most of us loaded the 358 Norma Mag to well over 2800 fps with 250 gr bullets. Some loaded to 2900, although I never did myself, as I determined 2800 was plenty for big game, and was getting beat up enough at that velocity.
I got my first 358 Norma in 1969, a Husqvarna with a 23 3/4" barrel. I drove a lot of 250s out of it, and several others, at over 2800 without incident, killing several tons of game with aplomb, and to the best of my recollection
never losing a case due to expanded primer pockets.
We used Oehler chronographs that had screens with electrical circuits that we actually shot through, physically breaking the circuit to start and stop the timer. The elapsed time was determined by an intricate manipulation of dials and lights, the resultant number then being further interpolated from tables to render the velocity. In 1977 I got my first Oehler that had Sky Screens, the Model 33. We could shoot repeatedly without having to replace the screens! And, the velocity was a direct readout, along with average velocity and standard deviation. We were ballistic neophytes, but continued to learn more and more. Standard deviation, in particular, was a real eye opener, but that is another thread.
The magic number back then was IMR 4350. You could compress enough of it with the 250 Speer to reach 2800. IIRC the load in the Speer Manual was 2790 fps. There was no Re17, 22, etc, and most of us never dreamed we would have the variety of powders available to us we have today.
So, what does all this have to do with your concerns. There are no small number of us old farts who still believe that if primer pockets are still tight after five firings, that the load is safe. That's it in a nutshell. I have been loading since 1962, and still have all my fingers and my eyesight.
Have I blown up any guns? No. Have I loaded until I blew primers? A few times. What do I do when that happens? I reduce the load a full ten percent, call it good, and go to a slower powder.
While I did not do all the firing of the rifle in question, I did do some, and was there when the velocities were recorded. I did not personally load and fire five rounds from the same case, but know the man who did very well, and he is not only a very experienced handloader, but one of the most honest men I know. There is nothing in this for him to exaggerate velocities. In fact, he recently gave up on a 270 Wby because he could not get even close to factory velocities.
Yes, that is a lot of power being developed by the 300 Win case, and we were both quite surprised at the velocities. One thing I do know, WW 300 mag cases are about as strong as anything around. I routinely load 180s to over 3100 fps out of 24" barrels with good case life and no expanded primer pockets. There is at least one 300 Win Mag load in an older Speer Manual showing their 180 gr spitzer at 3200 fps using 4350. I actually loaded and shot that particular recipe quite a bit.
Taking this all one day at a time, and with patience, we will see if C-FBMI can shed any more light on this. He already has said he did not reach those velocities, and that speaks of his being forthright with all of us here.
My apologies for such a long post.
Ted