This occurs because they are loading the 7 X 57 to lower pressure, because of original specifications.

You will see even more extreme examples such as the 416 Riby Vs the much smaller 416 Remington.

The most extreme examples are the old English Nitro rounds such as 470 Nitro and 505 Gibbs etc which have huge case capacities but reloads generally shown are very low velocities in relation tothe case size.

Mike

quote:

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Originally posted by I Need Guns:
That seems to be common sense, more stored energy, more power.
BUT: They shape of the case can cange things a lot. 300WSM will send a bullte faster that 300win mag in some bullet wights even though the wsm has less powder. Shorter cartiges genraly are more efishent. Also the test barrel for these loads may be diffrent.

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I can see your point but it doesn't seem to hold true with the 243 vs. 6mm Rem and they have the same contrast in case sizes. Why is it different for the 7mm bullet vs. the 6mm bullet? Strange.

Legal reasons for a start.

Secondly, it is always possible that a brass manufacture could make cases with only the lower pressures in mind.

I don't agree that case shape influences velcoty too much one way or the other. That was my experience with 6mm/06 and 6mm/284s.

There is a poster on these boards called Bob338 who has donealot with 338 Win and 338 WSMand his velocities have been in line with the powder capacities, that is, the 338 Win is a little bit faster.

Another consideration is how suitable available powders are for a given cartridge.

A 375 H&H isa good example. Without very heavily compressed loads or using Reloader 15, it is quite difficult to get the 375 to velocities that match its case capacity and bore size. In this case the powders around the 4064 burning rate are too fast and those around the 4350 are too slow.

This is one area where case shape could change things somewhat. My experience with the 6mm/06 and 6mm/284s was that the 6mm 284 needed slower powder.

So a short fat case with the same case cpacity as the 375 H&H, might do better with sday 4350 than the H&H and then have better velocity. But this still realtes to powder availability.

Mike

Venturi effect will produce higher velocities in smaller bores -- all else being equal. As gas moves from one "diameter" to a smaller diameter, its velocity increases.

Other variables in the load data can be barrel length, bullet diameter and land depth in the barrel, rifling twist, ambient temperature . . .

Two different chronos or two different metering set ups could provide variations in spec. I take it all with a grain of salt.

I've seen side by side data on the SAME caliber show lower velocity for a heavier load. It IS rocket science, but the mfg's are not giving us "rocket data."

quote:

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Originally posted by I Need Guns:
That seems to be common sense, more stored energy, more power.
BUT: They shape of the case can cange things a lot. 300WSM will send a bullte faster that 300win mag in some bullet wights even though the wsm has less powder. Shorter cartiges genraly are more efishent. Also the test barrel for these loads may be diffrent.

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300 WSM is loaded to higer pressure, the 300 Win mag will always win, if you use the same pressure.