Miscellaneous
Selecting Cartridge and Caliber
Long Range Cartridge/Caliber Selection
by Lucas Beitner
Trying new cartridges is one of the most interesting aspects of shooting. Most every cartridge has its application or “place”. It seems many are confused when it comes to selecting a cartridge and caliber. Questions like “what’s the best caliber?” are very common. No one likes to have their questons answered by another question (specifically “what are you using it for?”) but, there is no “best” caliber or cartridge. Application is the key. Here’s how I decide what caliber I want next (I say “next” because given enough time I’d no doubt have them all ). I’m lucky enough to be able to reload my own ammo, If you can’t, the selection process is different. Those who don’t reload must take into accout ammo availability as well as cost. Cartridges like the 308 and 223 are very good when restricted to using factory ammo due to lower costs and availability of high quallity ammo. I’ve also noticed the 308 generally comes from the factory with fast enough twist for fairly high BC bullets one would choose for long range shooting. If you do re-load, this is the basics of how I select what cartridge I want, specifically, with long range application.
Step 1) select a bullet.
I’d first decide how heavy a bullet you want to shoot, for vital shots on Elk 1200ft/lbs of engergy would be nice. 600ft/lbs is a good minimum for deer (These energy figures I read in the book “Hunter’s Guide to Long Range Shooting” by Wayne Van Zwoll, a fellow I trust to give accurate information). A ballistic calculator can give you a good idea of the engergy available at a given distance. If you’re just punching paper this isn’t a factor. For long range, BC is paramount. For example if you want a 130gr bullet it would be foolish to use a 7mm .395 BC, when a 130 gr 6.5mm has a BC of .595. If these were fired at the same MV the 6.5mm would have greater energy at long range,not to mention superior ballistics and wind bucking ability. For my personal use I go with the following (these will change with new bullets becoming available all the time):
6mm (.243″) up to 115gr
6.5mm (.264″) from 130gr to 140gr
7mm (.284″) 140gr up to 180gr
7.62mm (.308″)175gr up to 240gr
8.58mm (.338″) from 250gr to 300gr
Step 2) select a cartridge
You should now decide the ballistics/energy required for your application. Cartridge selection should be based on speed, and bullet BC’s. If you’re only shooting out to 500yds it may not be wise to sacrafice too much speed to shoot a bullet with a higher BC. At 1000yds BC is extremely critical and one may be well suited to choose a higer BC even if it requires you to sacrafice considerable speed. Spend time checking the possiblities with a ballistic caluclator. Be realistic with your expectations of muzzle velocity. It’s easy to come up with increadable results on a ballistic calculator. Check the recorded MV’s of more than one source. You may be able to match the results you read about, but your brass may become fatigued quickly doing so. It may also be advisable to select cartridges that are common in competition as info on accurate load data, and quality components will be more abundant. If you’re using a high quality hand-lapped barrel (especially the Benchmark Barrel’s 3 grooves I use) you are within in your rights to expect some decent MV’s.
Step 3) Compromise
Now that you’ve found the “perfect” cartridge/caliber for your application (no doubt a super magnum) you need to compromise with…
1) Expected barrel life
2) Recoil you’re willing to tollerate
3) Weight (large magnums reqire longer barrels to explot their potential, and also subject you to carrying heavier ammo).
4) Novelty factor (there are many ways to get a desired result; in reality the 338 RUM gives up little compared with a 338 Lapua magnum. It’s the novelty of the Lapua that makes it desirable to so many.)
5) Cost (100gr of powder per shot down range will empty your savings quick if you do much shooting.
Let me know if you find a good deal on .338″ 300gr SMK’s).
6) Availability of reloading components (no matter how good the cartridge, you’ll be up a creek if you can’t find brass anywhere).
Other things to keep in mind…
Make sure your barrel has a fast enough twist to stablize the bullets you plan to shoot. This is often the limiting factor in factory rifles for long range use. If you’re building a custom rifle you can really exploit a caliber’s long range potential by getting the proper twist. In my experience some bullet makers don’t recomend a fast enough twist. Check what others are using to stablize specific bullets. Some cartridges require a longer barrel to exploit their capacity. If your barrel is too short for your cartridge, you may be simply wasting powder. If a short barrel/rifle weight is a priority for you selecty your cartridge accordingly. For example the WSM’s have been reported to give good MV with shorter barrels compared to the standard magnums wich often sacrafice a great deal of MV if the barrel is not at an ideal length.
I believe the process outlined above is in a logical order, however, you may have a factory rifle or already have a rifle built. If this is the case check your twist rate and test bullets that will work with your twist and give you favorable ballistics for your application. You may have to compromise quite a bit, but when it’s time to replace that barrel get it right. When investing money into a rifle build, do the research necessary to get it right. Keep in mind, new cartridges will often be hyped a great deal (some rightly so) especially on the internet. Don’t be tricked so easily. There is no “magic” giving a cartridge supernatural performance. If a cartridge has a higher opperating pressure it may give excellent performance per/grain of powder. If a cartridge neither withstands higher pressure, nor holds more powder than another, how can it give substantially higher performance? I won’t say it’s not possibe, but use common sense. I could find information on the internet to back any rediculous claim I’d want to make, but this doesn’t make me correct.There are some cartridges (with factory loads) that use powders not yet available to the public wich yeild excellent performance. You would not be able to duplicate this performance with your handloads.
Things will change. New bullets and cartridges are becoming available all the time. Recently the 6.8mm (.277″) has recieved a boost due to new high BC bullets available from Berger (likely in response to new cartridges like the 270WSM and 6.8 SPC. Previously there was little intrest in this caliber for long range use, due specifically to bullet selection.
I’m not claiming this is the only or best way to go about cartridge selection. This simply outlines important factors that should be considered by anyone deciding on a cartridge for practical long range use.
Discussion