Recently a friend and I started a discussion about which projectile would be better suited to my 6mm 284 for long range hunting applications. Neither of us are experienced long range shooters so as you can imagine there was a lot of “I dunno” comments.
One point that was brought up was whether lighter or heavier projectiles should be used. We both agreed that the light projectiles would shoot flatter, but then we started discussing whether the heavier projectiles with their better ballistic coefficiencies (BC) would “over take” the lighter projectiles even though they left the barrel at a slower velocity.
Of course there are other factors to take into account such as what the intended game would be and what the projectile construction consisted of. However I decided to over-look these points and focus purely on whether the better BC projectiles would eventually out-pace the lighter ones.
Using the 6mm 284 as an example, I entered some data into a ballistic program to see if I could make some sense of it all. I decided to use the extreme projectile variance of a 58gr Hornady V-Max and a 105gr Hornady A-Max.
The 58gr V-Max has a BC of 0.250 and the 105gr A-Max is listed at 0.500. So we can see straight up that the heavier A-Max has doubled the BC rating of the lighter V-Max.
Then we have the difference in velocity which is just as impressive. Using an average taken from two different reloading manuals, I entered the 58gr V-Max as leaving the barrel at 3850fps and the 105gr A-Max at 3050fps. That’s a difference of 800fps! I used a 250 yard (228m) zero which seemed realistic for the application.
The 58gr V-Max is 1.42 inches high at 100 yards, 1.37 inches high at 200 yards, zeroed at 250 yards, 2.44 inches low at 300 yards, 11.02 inches low at 400 yards and 25.93 inches low at 500 yards.
The 105gr A-max is 2.45 inches high at 100, 2.02 inches high at 200, zeroed at 250, 3.34 inches low at 300, 14.23 inches low at 400 and 31.71 inches low at 500 yards.
So at 500 yards (457m) the 105gr A-Max has nearly 6 inches more drop than the 58gr V-max even though the BC of the A-Max is more than double the 58gr V-Max.
However, if we extend the range even further we start to see the projectile BC at work. At 800 yards (731m) both projectiles have dropped almost the same and at 1000 yards (914m) the 58gr V-Max has dropped 48 inches further than the 105gr A-Max!
Retained velocity at this distance of the 58gr projectile is roughly 1047fps and the 105gr A-Max is 1513fps. Depending on altitude the V-Max is just under the speed of sound but the 105gr A-max is still well above it.
Just for fun I decided to look at the energy figures of both loads and this is probably what most hunters will be interested in. Right from the start the 105gr projectile has nearly 300ft/lbs more energy than the 58gr V-Max. As the distance increases, so does the advantage of the 105gr projectile. At 500 yards the difference is now 556ft/lbs, however at 1000 yards the difference has now dropped back to only a 393ft/lb advantage. We can now see that the heavier projectile does indeed deliver more energy at all practical ranges. Not everyone follows the energy idea but in any case it makes for an interesting exercise.
Wind factor is also something to consider when taking long range shots and the figures between the two projectiles were quite interesting. It’s often said that less flight time equals less wind drift so let’s see how true that statement is.
Using a 10 mph crosswind the 105gr A-Max has approximately 3.58 inches of drift at our 250 yard zero. The 58gr V-Max on the other hand has 5.51 inches at the same distance. That’s nearly an extra 2 inches of drift. At 500 yards the 105gr A-Max now has 10 inches less drift and at 1000 yards the difference is now over 70 inches. So at all ranges, our slower and heavier projectile is less affected by wind than the quicker starting 58gr V-Max. Interesting!
So, by using a ballistic program I’ve been able to answer some questions that I’ve been wondering about for some time. Whilst so many other factors come into play when making a long range shot, I can at least now understand the theory behind Ballistic coefficiency!