The larger the bore, the faster the bullet?

[d2wing]

Interesting. My 7-08 seems to be pretty efficient.

 

[Newtosavage]

This weekend did NOT go as expected - a puking 5yr old, missing a wedding, and suddenly owning a stray pig saw a lot more of my time being occupied than anticipated...

BUT... I did pull together some data, largely from Hodgdon's data, tabulating the case capacity and powder efficiencies of a handful of 7mm cartridges using the 139grn pills. I was not surprised to see the 7BR case make the most out of the powder, but I'm wondering if this table really illustrates the 139's as a bad fit for the larger 7mm magnums - otherwise I can't explain why 7-30 and 7 mauser did so well in efficiency compared to some of the other cases near them in the list - 7WSM, for example. I didn't hold this to just 55kpsi cartridges to punt in a short timeline this evening. Packing tonight to leave for Mexico in the morning, so I know I won't have access to manuals for the rest of the week...View attachment 830511

I did sort these by powder efficiency, but the case capacity data is there too.

Thanks for the effort and enjoy your trip!

I knew I liked the idea of that 7 BR. But I'll have to settle for 2nd best, with my 7mm-08's

I wonder if there would be any value in looking at recoil vs. muzzle energy, or if the math would work out the same.

 

[TN Outlaw]

Not sure if this will help Newtosavage, but here's some data from "Chuck Hawks recoil table" applied with some of the info Varminterror provided to connect somewhat the recoil vs muzzle energy.

Some chamberings don't show recoil with 139gr pills, the rifles are different weights, and some cartridges were not on the chart altogether but here's what I found.

7-30 Waters 120gr@2700fps=10lbs of recoil in a 7lb rifle. (No 139-140gr listed) Varminterror listed 139gr@2472fps with 1886ftlbs of energy. Recoil?

7x57 139gr@2700fps=11.7lbs of recoil in a 8.75lb rifle. Has approx 2280ftlbs of energy.

7mm-08 140gr@2860fps=12.6lbs of recoil in an 8lb rifle. Has approx 2560ftlbs of energy.

.284 win 150gr@2860fps=17.4lbs of recoil in a 7.5lb rifle. (No 139-140gr listed) Varminterror listed the 139gr@3079fps with 2926ftlbs of energy. Recoil?

280 Rem 140gr@3000fps=17.2lbs of recoil in an 8lb rifle. Has approx 2750ftlbs of energy.

7wsm 140gr@3200fps=20.7lbs of recoil in an 8lb rifle. Has approx 3036ftlbs of energy.

7 rem mag 139gr@3100fps=19.3lbs of recoil in a 9lb rifle. Has approx 2190ftlbs of energy.

7wby mag 140gr@3300fps=19.5lbs of recoil in a 9.25lb rifle. Had approx 3300ftlbs of energy.

 

[someguy2800]

These are the results I got when I did the math on this the other day. In each case I used the powder that gave the best muzzle velocity per grain of powder, which was generally one of the faster powders listed. Listed from worst to best.

280 Nosler = 43
7mm magnum = 47.8
284 winchester = 57.6
7-08 = 59.92
7mm Valkarie = 62.2
7mm TCU = 65.7
7mm Raptor = 71.2 (approximate)

Here are some other cartridges from my stable that I ran the numbers for out of curiosity. These are my actual loads and results.

25-06 = 45.2 (120 gr Speer, 53 gr RL19, 3006 fps)
7.62x39 = 61.4 (125 gr nosler, 31 gr CFE BLK, 2620 fps)
45-70 = 63.9 (350 gr cast, 19 gr trailboss, 1250 fps)
357 maximum = 68.6 (180 gr XTP, 24gr win 296, 2030 fps, 13" barrel)
9mm Luger = 71.3 (124 gr FMJ, 5.2gr power pistol, 1160 fps, 10" barrel)
444 Marlin = 76.4 (320 gr cast, 45 gr RL7, 2200 fps)
300 blackout = 84.1 (125 gr hp, 19 gr win296, 2400 fps)

 

[Llama Bob]

These are the results I got when I did the math on this the other day. In each case I used the powder that gave the best muzzle velocity per grain of powder, which was generally one of the faster powders listed. Listed from worst to best.

This doesn't make much sense. Powder is a source of energy. Velocity is proportional to the square root of energy. If you compare the velocities attained to the square root of the grains of powder, you will get at something about efficiency (namely energy density and Sebert's factor). You will also notice the fast powders are not necessarily the winners any more. As it is, you haven't really discovered anything of interest.

 

[someguy2800]

This doesn't make much sense. Powder is a source of energy. Velocity is proportional to the square root of energy. If you compare the velocities attained to the square root of the grains of powder, you will get at something about efficiency (namely energy density and Sebert's factor). You will also notice the fast powders are not necessarily the winners any more. As it is, you haven't really discovered anything of interest.

I don’t follow you but I’ll await your results.

 

[Varminterror]

@Newtosavage - I’m not sure I believe the data I tabulated is a fair representation of the trends, as we’re talking about a specific bullet weight which is extremely light for the large magnums assessed there, but rather ideal for the smaller cases. This would explain why a long, skinny, slope shoulder 7-30 waters scored so highly. The trend of energy per case capacity wasn’t as clear, so I expect we have compounding factors here: aka, a huge case isn’t as efficient with a tiny bullet as it is with a huge bullet, as well as the fact we’re talking about 24” barrel data in almost all of these (from Hodgdon) - if a case holds 2-3x more powder or is 2-3x larger, it’s reasonable to expect it might need more barrel to reach the same powder utilization... more than the 2” we assign as proper for most magnums.

I’ll spend a little more time on this data this wknd, I have a few hours on the plane coming home to peek and poke around.

ETA: while powder is indeed a source of potential energy, I’ve never been a believer that “energy is energy”. Highly dynamic systems can have very different efficiencies, so even given the same energy in, we don’t always see the same energy out.