If you have read our introduction, you have learned that our standard systems come in sets of three cards, one for cold, one for moderate, and one for hot seasonal conditions. They are color-coded for quick and easy identification and also have the temperature range listed on each card. This makes the system more accurate than standard ballistics data which are normally calculated at only 59o F. Very informative instructions and tips are included with each set of Ballisticards®.
Q: What brands of ammunition are Ballisticards® available for?
A: Most Ballisticards® are specially calculated for use with FEDERAL ammunition and matching handloads. However, most of our systems are cross-referenced for use with other brands of ammunition, so you are not limited to only one load.
Q: What barrel lengths are Ballisticards® calculated for?
A: Most Ballisticards® are calculated for 24 inch barrels (custom calculations are available) because it is a common length and falls between 22 and 26 inches. A difference in barrel length of 2 inches, up or down, will not affect velocities as much as you might think. Published SAAMI guidelines are as follows:
|Centerfire Rifle Velocity vs. Barrel Length|
|Muzzle Velocity Range
(feet per second)
|Approximate Change in Muzzle Velocity Per One Inch Change in Barrel Length|
|2000-2500 fps||10 fps|
|2500-3000 fps||20 fps|
|3000-3500 fps||30 fps|
|3500-4000 fps||40 fps|
If we use these criteria as guidelines, we see points of impact changing as follows, when going from a 24 inch barrel to a 26 inch barrel (calculations based on a 200 yard zero):
|Cartridge||Bullet||Point of Impact Change|
|.223||55gr. SBT||0.3" @ 300 yds / 2.1" @ 500 yds|
|.308||168gr. HPBT||0.3" @ 300 yds / 1.9" @ 500 yds|
|.300 Win. Mag.||200 gr. SBT||0.2" @ 300 yds / 1.2" @ 500 yds|
As you can see, even at 500 yards the difference is relatively insignificant. Allowing that most hunting shots are well under 400 yards, the 24 inch barrel calculations we normally provide will work well for most situations. For a worst case scenario, if you were to chronograph your ammunition, in your rifle, under your hunting conditions, and found that instead of a 30 to 40 fps per inch change in average velocity (10 shot minimum - please), that there was a 50 fps per inch change (100 fps total), you could simply move up or down to a "hotter" or "colder" card - Note: velocities are listed at the top of each card.
Q: What about altitude? Standard Ballisticards® are calculated for sea level and I hunt at 5,000 ft?
A: Ballisticards® are very versatile! A recent question came from a hunter in Canada. He was going on an Ibex hunt in Siberia. The weather was to be well below freezing and the altitude between 7,000 and 8,000 ft. When we ran his 30-06 load through the computer, with that criteria, we found that by shifting up, from the blue card to the green card for reference, that his actual theoretical point of impact would be within 2 inches of the point of impact indicated on the green card, at 500 yards! At 5,000 feet above sea level, the numbers were within a fraction of an inch! One magnum load we checked came within 0.1" @ 5000 ft. by using this method. When hunting at higher altitudes the air is less dense, providing for flatter trajectories. Above 5,000 feet, you may do well to simply move up to the next hotter card. If you want to get fanatical about it, at around 2,500 feet, you could split the difference between two cards, etc. For long-range tactical shooters this could be valuable information! Note: Your actual point of impact at different altitudes should always be tested and verified, in your actual shooting conditions, prior to relying on this method of compensation.
Q: What about humidity and barometric pressure?
A: These variables have minimal effect out to 500 yards. A good solid shooting position is far more important!
Q: Do I have to change my sights seasonally?
A: You should always re-zero in the conditions that you anticipate hunting in. You may not notice much difference at 100 yards, but at longer ranges you will. Keep all ammo out of direct sunlight and allow it's temperature to stabilize to ambient conditions. Let your barrel cool between shots and don't leave a round sitting in a hot chamber any longer than necessary. Otherwise, it will raise the cartridge temperature, and can change the velocity and subsequent point of impact. A "cold barrel zero" (at least five minutes between shots - or cool to the touch) is advisable.
Q: What if I'm not into it that much and really want to keep things as simple as possible?
A: Get a good solid zero, limit your shots to within 400 yards, and use the green card year round.
Q: So what's the bottom line?
A: Nothing is perfect! But we're getting closer. We can't control nature, but we can adapt in a way never available before, by using this three-card system. Remember the days when we felt confident with a small scrap of paper taped to our stock? Look at what is available now! When you see all the information on these three little cards and learn how truly versatile they are, you'll never want to go back to guessing or trusting to luck!