Comparing cartridges & loads — Howell's short method

[Ken Howell]

Muzzle velocity alone certainly is no way to rate, relate, or compare cartridges' down-range performance. Here's a simple "quick and dirty" method of roughly comparing the down-range performance of two cartridges or two loads with different bullets in the same cartridge. This technique doesn't give you any details of retained velocity, retained energy, drop below aim, time of flight, or wind deflection. It sort of lumps all these specific performance details into one rough figure that's easy to compare with the parallel figure for another cartridge or load.

Multiply the muzzle velocity by the ballistic coefficient.

Hn = mv × bc

The higher result implies the "better" cartridge or load. Call it anything you like — Howell number (Hn), performance index (pi), relative performance index (rpi), whatever. It has no units, so it's just a number.

For a general comparison of two cartridges with different calibers and weights of bullets,
• calculate the Hn of each typical load in each cartridge
• calculate the average Hn of these loads in each cartridge
and you'll have a single figure for each cartridge, making it easier to compare two or more cartridges succinctly.

For specific performance details for any cartridge, you'll have to go the long math route.

 

[danr55]

Hey Ken, I would suggest that possibly you should restrict this kind of comparison to rounds of the same caliber and different bullets rather than trying to cross check calibers with it. For instance, Try comparing 264 Winchester, 140 grain partition, 3205 fps; 7mm Weatherby 140 grain partition, 3350 fps, 140 grain partition; 338 Win Mag, 200 grain Partition, 2850 fps. The results indicate that the best choice is largley dependent on what you intend to do.

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Dan AZ www.huntandlodge.com

 

[Slamfire]

Now all you have to do is devise a constant to describe bullet construction, then we'll have a real comparison of cartridges.

 

[Ken Howell]

Dan, I always assume that my average reader is at least as intelligent as I am and that a lot of my readers are much more intelligent than I am. So I assume that none of them is likely to have trouble deciding whether a .14 Flea or a 1.25 Barker-Butler Bear-Thumper is better for his purposes.

I've been getting a lot of requests to compare, for example, Cartridge A and Cartridge B (two .224s, a .224 and a .243, a .270 and a .280, a .338 and a .358, etc) with bullets of the same weight, or with bullets of the same BC, or with the "best" bullet in each cartridge, etc. Shooters who request these comparisons already know, I'm sure, that using only the muzzle velocities in these comparisons is totally inadequate and often misleading.

Yet they either don't know how to make the long, complex comparisons or for some good reason don't want to make 'em themselves. So I offered this quick-and-dirty so they can make their own rough and general comparisons.

 

[danr55]

Well Ken, if you can get eye to eye with folks, that's a pretty good assumption. Around here there are a lot of folks that will read what you right and interpret it literally. It's my experience that you have to be pretty exacting when passing along information that is not necessarily available anywhere else. I agree with your quick method regarding comparisons, and us a similar method myself. I just don't want anyone to get confused with what you were trying to offer. No slight intended to you or to anyone else.

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Dan AZ www.huntandlodge.com

 

[Ken Howell]

How could I have made it any plainer, Dan?

I thought "Muzzle velocity alone certainly is no way to rate, relate, or compare cartridges' down-range performance" clearly established what my simple, rough method is intended to replace.

Also thought "Here's a simple 'quick and dirty' method of roughly comparing the down-range performance of two cartridges or two loads with different bullets in the same cartridge" pretty literally carried the point that it isn't a completely detailed comparison. That's what I meant by "quick and dirty" and "roughly comparing."

Then I really thought that adding "This technique doesn't give you any details of retained velocity, retained energy, drop below aim, time of flight, or wind deflection" and "It sort of lumps all these specific performance details into one rough figure that's easy to compare with the parallel figure for another cartridge or load" further emphasized the acknowledged limitations of this method.

Then, after I gave the details of the ROUGH method, I added this further caveat:

"For specific performance details for any cartridge, you'll have to go the long math route."

Please show me specifically where any of this taken literally can possibly lead anyone to think the opposite of what it says. I'd love to know how to make it clearer, immune from misinterpretation by anything other than careless and incomplete reading.