cartridge efficiency

[wolf300H&H]

heres something worth discussing. ive been working on a formula,im sure its/youve done it before.i usually go off my handloads,but go off reloading data in the manuels for calibres i dont have. efficiency tends to go with the bigger bullets. bullet wt x velocity /by gr of gunpowder. so far my 308 win is the top , 175x2700/44.6 . equls about 10400 or you could say 10.4 etc etc. also really high is a 22 Lr, 8 mm mauser , 308 R , . this doesnt take into account barrel length or type of powder cause for my 45 acp load its like 33000 or 33 pts. 230x760 / by 5. anybody got anything to add? or other really efficient cartridges? just thought it was something neat to discuss.

 

[ben hunchak]

I think you have a lot of extra time on your hands.

 

[Andy]

Your formula doesn't take pressure into account. "Expansion Ratio" is a much better measure of "Efficiency". Even so, so what? Use a cartridge that will do the job - if you want "Efficiency" buy a 22 Short and go hunt Grizzly.

 

[dan belisle]

In the old days this topic used to come up fairly regularly in all the gun writings. For reasons that I don't quite get, some folks would figure out how many rounds they could get from a pound of powder from whatever cartridge they were working with, or how many grains of powder it took to reach a certain velocity. I recall a formula the Ken Waters had used at some point (assuming my memory is working today, not always a safe assumption) that calculated for that very point. I still don't get why, but how isn't all that tough. still, if it makes you feel good and gets you more involved with the sport, have fun. - dan

 

[Glock4ever]

I consider a round efficient if it can burn all the powder that is in the case before the bullet leaves the barrel. Because of varying barrel lengths, it is possible to have a cartridge that is efficient in one rifle become inefficient in another rifle. Is this stuff really important - not really but it is pretty interesting. A good way to find out, how efficient your rifle/cartridge combo is - lay a white sheet on the ground and fire your rifle with the muzzle over it. You will see laying on the sheet a lot of unburnt powder - more = less efficient and less = more efficient.

 

[Obtunded]

Achieves the most with the least....

There is a performance curve with cartridge efficiency, but it is far flatter than you think. Beyond a critical mass of powder, it takes a very large increasing amount of slower buring powders to achieve even small gains in velocity.

For example, the 6mmBR takes roughly 31 grains of powder to push a 105 grain bullet to 2900. It takes 38-39 grains of powder in a 243 to achieve the same results.

One could argue the 6BR is more efficient than the 243

The 308 and the 30-06 produce nearly identical velocities with a 180 grain bullet, yet the 30-06 uses 7 grains more powder to do it.

 

[Dogleg]

I think a cartridge is efficient if it accomplishes its purpose without a lot of fuss and is in the best top few cartridges for that purpose. That could be shooting gophers all day without getting screaming hot. It could be flattening elephants with one shot. It could be making first round 1000 yard hits easy, while haveing enough power to disable machinery.

I think it was Elmer Keith that said "Efficiency be damned, I'm interested in results."