Stubblejumper,
4831 does produce good velocities in 7MM Remington Mags but not necessarily the best velocities. 4831 does usually produce the best velocities in the 280 Remington for instance. Modern factory loads in the 7mm Remington mag often don't even reach advertised 280 velocities. A 175 at 2750 is pitiful and close to 300fps slower than at the introduction.
MTM,
Since I am not a fool, I would have no reason to compare a 308 to a 300 mag. I will cheerfully admit the 300 mag will outperform the 308 Winchester. Let's look at the 308 for a second though. The 308 will, from a 26 inch barrel, achieve about 2650 to 2700 fps with a 180 grain bullet and 4350. Pressure is still quite low since the 308 lacks the capacity to get enough 4350 in there to get the pressure up but it's really a pretty decent load. This is a situation where more case capacity is in order if we want to do everything 4350 can do. By going up to 30/06 capacity, we have enough room that we can use all the 4350 possible and still operate within acceptable pressure limits. Our velocity will now be around 2850. If we go up to 300 H&H mag capacity, we can gain a bit with 4350 but, if we want to see maximum improvement we'll probably have to go to a slower powder like 4831. All cartridges behave this same way. If a given cartridge has sufficient capacity to hold all the powder necessary to reach maximum pressures, it will perform very well with that powder. Increased capacity will allow a certain amount of increase but not as much as if it was possible to move to a slower powder and still reach max pressures. So, in the case of the 7mm's, the 7 Rem Mag has sufficient capacity to reach maximum pressures with any of the commonly used powders and bullets of 160 grains or heavier. It will not hold enough of some of the slowest powders to reach max pressures using lighter bullets and this is where the STW has a chance to show some advantage.
3180 with a 160 is pretty hot. In fact it is an absolute maximum load using that powder. So is 3260 with the same bullet weight and using the same powder in the STW. Both cases still have room left so would probably work better with a slower powder (not probably; they will absolutely do better although the Remington has probably about topped out).
I'm not trying to quibble over a few feet here or there and I freely admit the STW is faster than the Rem Mag. I am just trying to point out that real, valid information comes from real, valid experimentation. If somebody wants to tell me about his 26 inch barreled STW that is way faster than his factory 24 inch barreled 7 Remington; I don't care. It's not a valid comparison. Even if both cartridges are tested in 26 inch barrels it's not valid. Only if tested in the SAME barrel is the test valid at all. Only if both cartridges are loaded with the optimum powder is the test wholly valid. Loading to the maximum load shown in the loading manual is meaningless. Both cartridges have to be loaded to the same pressure. Measuring brass expansion is apoor way of doing this but it's better than no way at all. The best way is using strain gauges which are available now if one wants to really know.
I don't care for cartridges like the STW simply because they are past the point of diminishing returns. If one wants more speed than he can get with a 7mm Remington or 7mm Weatherby ( regardless of what the books tell you, the Weatherby is always a little faster than the Remington. Maybe there is something to that venturified shoulder. Even with the same freebore and in the same barrel, the Weatherby is about 50fps faster), then the STW is as good a choice as any. Just don't expect the sort of big increase Layne Simpson told you about. Regards, Bill.
