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Cartridge Efficiency

As another year is closing, I’m looking back over the advancements in my industry.  New bullets, powders, and cartridges are always out there.  But, as I sit here thinking about it all, I began to question what is a tangible gain in cartridge design.  There are more cartridges and firearms competing for your hard earned dollars everyday.  Sometimes it just feels good to feel like you’re on the frontline of tech, having the newest caliber and rifle.  I love that feeling as well, but there are so many calibers to choose from, it begs the question of where to start.  

I wanted to take all the hype and clever marketing out of the equation and solely look at a calibers’ performance based on the numbers.  I will be honest here, I only used one reference manual, Hornady’s No 10, and didn’t look at the very newest ones such as the 7mm PRC.  However, I feel that I have narrowed the search down to a few categories and a fair way to see who is really on top strictly based on the numbers.  

First, I wanted to know what was the most efficient long range cartridge.  I had to qualify the cartridges in some way.  So, I wanted to only look at cartridges that would have a bullet with a BC of .500 or higher and could be driven to a velocity of 3,000 fps.  That weeds out anything under 6.5 caliber.  I want to be clear about this entire article.  It’s not saying that some calibers kill better, go faster, or shouldn’t be considered excellent hunting rifles.  I hunted with 25-06, 257 Roberts, and the 257 Weatherby for a long time.  I love those cartridges dearly, however, none of those made the list.  The BC of the .257” bullets simply isn’t high enough to qualify.  

I qualified the “Efficiency” of the cartridge very simply by taking the bullet weight with the qualifying BC and dividing it by the powder charge required to get it to 3,000 fps.  It just generates a simple ratio that we can now take and use to see what cartridges push those high bc bullets to over 3,000 fps with the least amount of powder.  Why would this even matter, you might be thinking to yourself.  It matters, because those calibers will give the longest barrel life and lightest recoil for the round.  Without getting deep into this, let’s just talk about the calibers and not all the semantics of what bullet, weight, and powder charge.  If I go down that road, we’ll be here all day.  I drew a hard line in the sand at an efficiency ratio of 2.5 or higher to make the most efficient round list.  Some of the calibers are predictable and others, you would never think of.  For this ratio the higher the number, the better.  They are as follows:

6.5 Creedmoor –   123gr SST –       2.53 Ratio

6.5-06 –                 135gr A-Tip –     2.523 Ratio

6.5 Rem Mag –      153 A-Tip –        2.615 Ratio

6.5 PRC –       147gr ELD-M –  2.512 Ratio

300 SAUM –          168gr ELD-M –   2.560 Ratio

300 WSM –            178gr ELD-M –   2.557 Ratio

300 PRC –              200gr ELD-X –   2.554 Ratio  

I have personally shot everything on the list with the exception of the 6.5-06.  Of those I like the 30 calibers over the 6.5 simply due to the heavier bullets and greater choices of bullet construction.  I really like the design of the 300 PRC.  It really shines with heavier bullets and long barrels.  The 300 WSM is a standout with a 24” barrel and short action.  For a hunting rifles I don’t know that you could pick a better caliber.  Long barrel life, manageable recoil and light muzzle blast are all considerations as I get older.  I would feel confident that any of those calibers on the list are among the best on the market today.  I would even give the 6.5-06 a chance on a long magazine box and improving the cartridge to a sharp 40 degree shoulder.  However, that gets us away from the goal of the best commercially available calibers.  

We aren’t done twisting your brain around just yet.  I wanted to go a step further and look at the most efficient for the highest BC.  Basically this gives you the longer range you are looking for without just putting lots of powder behind little bullets and watching them eat up your barrels.  Here, I took the BC of the bullet and divided by the efficiency ratio I came up with earlier.  This puts you to a different category of ballistics, because the focus becomes more on the BC and less on the powder charge to drive it above the 3,000 FPS number we are looking for.  Here we are looking for a lower number.  I drew the line at a number of 2.4 or lower.  Those calibers are as follows:

6.5 Creedmoor –    123gr SST –          .2015 Ratio

270 Win –       145gr ELD-X –       .2214 Ratio

270 WSM –           150gr Interlock –   .2268 Ratio

280 Ackley Improved – 150gr ELD-X –      .2353 Ratio

7mm SAUM –         150gr ELD-X –      .2042 Ratio

300 SAUM –          168gr ELD-M –     .2042 Ratio

300 WSM –             178gr ELD-M –     .2139 Ratio

300 PRC –                200gr ELD-X –      .2337 Ratio

Now you can begin to see a pattern forming of the most efficient cartridges driving the highest BC bullets over 3,000 FPS.  What I wanted to see here was which cartridges appeared on both lists.  Which ones were actually efficient while still delivering the highest BC projectile possible over that speed.  There are 4.  The 6.5 Creedmoor, 300 SAUM, 300 WSM, and the 300 PRC.  At the turn of the century when the short fat power columns were the latest in cartridge design, they got a lot of things really right.  They created the most efficient rounds in 30 caliber that can be put on a short action.  While I will never pick a 6.5 Creedmoor to be my go to caliber for anything other than punching paper, it does a nice job with that lighter weight bullet.  Some of you maybe asking why 3,000 FPS.  I can tell you that bullets do the best when driven at the higher velocity as long as you picked the proper bullet construction. (Insert shameless Fox Cartridge copper plug).  It’s just magic when you kill an animal.  I could get into fluid dynamics and energy transfer but as my grandfather said, they just don’t take a step.  That’s why I’m pushing for that target velocity.   

While I was in the numbers on all this, I just wanted to see what calibers could push the highest BC bullets the fastest.  Forget efficiency here, this is all about raw flat shooting, muzzle blasting, powder burning horse power.  This is not the easiest to shoot, or the longest lasting barrels, but if you want to reach out and touch something a long way out, these would be the go to calibers.  Here, the BC of the bullet had to be .685 or higher and be pushed over 3,000 FPS.  So we are looking at long and heavy for caliber bullets.  The ratio is the efficiency just for comparison.

6.5 Rem Mag – 153gr A-Tip – .704 BC 2.615 Ratio

264 Win Mag –  153gr A-Tip – .704 BC 2.227 Ratio

6.5 PRC- 153gr A-Tip .704 BC 2.512 Ratio

7mm WBY Mag- 175gr ELD-M .796 BC 2.299 Ratio

28 Nosler- 190gr A-TIP .838 BC 2.054 Ratio

7mm STW 190gr A-TIP .838 BC 2.154 Ratio

7mm Ultra Mag 190gr A-Tip .838 BC 2.186 Ratio

300 WBY Mag 208gr ELD-M .690 BC 2.399 Ratio

It’s strange to me how you see where the high BC bullets truly fall.  The 7mm caliber has the highest BC, but you have to put so much powder behind them, that they turn into fire breathing monsters.  They loose any sort longevity in the rifle.  That does beg the question, “Does it Matter on a Hunting Rifle?”  You will run close to 80 rounds in load development and barrel break in if you reload.  Barrel should last for 400 rounds regardless of the caliber.  So, you’ve got a barrel working life of about 300 rounds give or take.  That should be at least 100 animals, for most people, that’s close to a lifetime of hunting.  But as I said, the older I get, the less I like the blast and raw power from a cartridge.  I’m looking for efficient, well balanced rounds that take game cleanly and quickly out to 500 yards.  That’s where the .500 BC and 3,000 fps come from.  I want minimal drop and retention of energy at that distance.  I know there will be so many comments about the bullets and my method of comparison.  One that comes to mind is some of the bullets with the highest BC’s aren’t really good hunting projectiles.  Well, maybe.  But, the cartridge still has to have the potential to hit the numbers.  So if it isn’t on the list, then there isn’t a bullet that Hornady makes to meet the standard. However, the potential of the cartridge to do so remains the same.  I’d like to look at this with Berger, Nosler, and Fox Cartridge bullets as well, but the time it takes is big.  Take the formulas and do the math.  See what other caliber pops up.  I’m willing to bet it’s not going to be much different from the list I’ve complied.  If you want the most efficient round the 6.5 Rem Mag actually takes the medal, but you need to build a rifle on a long barrel with a high twist to get those numbers.  The 6.5 PRC does it with rifles and ammunition you purchase off the shelf.  If you want the highest BC and not have your bell rung when you fire the rifle, you need to look at the 300 WSM.  The Remington SAUM was a little better, but again, long term availability of brass needs to be considered.  I also don’t know anyone chambering for that round at the time of this writing. Lastly, if I’m buying a round for flat-out hard hitting, noise making, barrel burning fun, hands down the 28 Nosler.  It’s the most fun I’ve had on the range in a long time.  I can also attest to the sound of striking a steel gong at 500 yards with it compared to everything else.  You can hear the difference.  While the cartridge still very loud, just make sure to use a good muzzle break and you’ll be set.  Recoil is very manageable with a quality break and a good rifle.  

Everyday we continue to learn and have new cartridges hitting the shelves, but I feel that hype needs to be dampened and math applied in a manner to compare these cartridges.  I still hunt with a 308 win and 300 win mag almost exclusively anymore.  You pair those cartridges with the right bullet and you won’t be disappointed.  But, if I’m buying something new for me to shoot in the field, you can bet I’m going back to my list and picking one of the top performers mentioned today.  There is nothing wrong with raw horse power when it’s used judiciously.