More Hodgdon Reloading Data Centre Anomalies

[Andy]

Look at these two 7mm cartridges with the same powder and same bullet:


7X57 - approx 55.0 grs capacity

- 175 gr Nosler Partition
- 3.025" OAL
- H4831
- 40.0 grs gives 45.7 CUP


7mm-08 - approx 52.0 grs capacity

- 175 gr Nosler Partition
- 2.800" OAL
- H4831
- 49.0 (c) grs gives 49.4 CUP


A third cartridge, same powder, but different bullet:


280 Remington - approx 68.0 grs capacity

- 175 gr Hornady Soft Point
- 3.300" OAL
- H4831
- 51.0 grs gives 49.8 CUP



The 7mm-08 data does not seem to "fit". The slightly larger 7X57 shows just a bit lower pressure with 9.0 grs less powder, while the much larger 280 Rem comes out almost the same pressure with just 2.0 grs more powder.

Extrapolating the 7mm-08 data, one would expect closer 45.0 grs of powder for the 7X57 to exhibit the slightly lower pressure, and 60.0+ (even with a different bullet) for the 280 Rem to exhibit the same as the 7mm-08.

 

[*MALICE*]

It probably cuz it's a weekend and I turned my thinkin' cap off....but I'm not seeing what you're getting at.

Different cartridges have different case capacities and it doesn't say what length barrel any of those were shot out of. Pressure isn't linear.

Although I've probably missed something spectacularly obvious and everyone is now going to laugh at me

 

[Pathfinder]

send an email..see what they have to say for themselves.

Hpchelp@HODGDON.com

 

[Kelly Timoffee]

Maybe they used old data on one and new on the other??? Just a guess.

 

[snomad]

I think it relates to case capacity in that with the loads stated each case is filled to a different percentage of the case capacity. The pressures and velocities are not linear as you might hope. (And that is not considering the variables in rifles.) If you look at the velocities stated for those loads; 2201, 2516 and 2477 respectively, they make sense for the charge for the most part. H4831 is the best choice of powder for the 7mm-08 but a much poorer choice for the other two. Why? Case capacity? Bullet weight chosen?
Another way to look at this is to take the same powder and bullet and look at the pressure and velocity stated in the book (Lee for example) for 243, 250 Savage and 25-06. If you think that is skewed, substitute or ad in 257 Roberts and 257 WM. Just looking at 250S and 25-06 illustrates this very well. Then if you start comparing light weight and heavy weight bullets you can see that the case capacity really affects the cartridges "efficiency", especially with a range of different bullet weights.
It often appears that the smaller cases are more efficient than the big ones: 250S vs 25-06,
308 vs 30-06, 7mm-08 vs 7x57 or 280. The bigger cases often seem to offer more velocity gain potential at the light and heavy bullet ends of the spectrum if you choose the best powder.
If it were that easy to extrapolate it all I don't think all the wildcatting of the last 70 years or so would have taken place.

 

[Lodi]

It's possible they used different test fixtures, just like the manuals.

 

[Fracture]

Re: Snomad
H4831 is a better choice in the 280, compared to the 7x57 and 7mm-08. I think a 4350 burn rate would be better in all 3, with a faster powder like varget being an even better choice for the 7-08 or 7mm mauser. I am talking about 140 gr bullets though, I think 175's are too heavy for all 3 cartridges.