.25 cal. Ballistics Coefficients

[rsterne]

The .25 cal RWS SuperDome looks (and weighs) like a rather poorly made H&N Baracuda.... This is not the case in the smaller calibers, it is very different....

Bob

[rsterne]

Here are the last two set of data.... The first approximates the BCs between 75-100 yards....



The second set of data approximates the BCs between 100-125 yards....



This is nearly the lowest power level I can achieve on my Hayabusa by simply adjusting the transfer port restriction.... It should be noted that the BC of the JSK Kings peaked at a velocity of about 700 fps, which is just about what I expected.... They are, after all, the lightest pellet in the test series.... All five of these pellets produced about dime sized groups shooting through the Chrony at 25 yards, and I wasn't exactly being very careful.... They all need to be assessed for accuracy at longer ranges in the summer when I have the opportunity.... Now to analyze the data to see how the BC varies with velocity....

Bob

[rsterne]

After compiling the raw data, I graphed the Ballistics Coefficient vs Velocity for the best pellets.... I did one extra data point for the H&N Baracudas with the gun set for maximum power, with the data collected over just 10 yards, to see if the BC rolled over at about 900 fps, and in fact it did, dropping from 0.039 down to 0.033.... Here is a plot of that data, including that additional data point....



I didn't have enough EunJin Pointed pellets to test at various velocities, so the only data point taken is shown.... You will see that several of the lines are "wavy", and perhaps the tendline should be smoothed (or maybe not).... I'll let you draw your own conclusions.... The JSB Kings did, in fact, exhibit the typical curve I have grown to expect of them, peaking at about 700 fps.... What that means, is that once they lose the initial 100 fps or so (in the first 25 yards), the BC is above 0.030, and continues to increase out to about 100 yards.... It probably isn't a good idea to push them much beyond 900 fps.... they are, after all, the lightest pellet in the group.... In my Hayabusa, they were noticably more accurate than any of the other pellets, at all the velocities tested.... and had the flattest trajectory....

Using the above graph, and using Chairgun, I then compiled a table showing as closely as possible what I could expect when shooting the various pellets out of my Hayabusa when set for ~53 FPE (the way I started the testing).... I used the muzzle velocities for each pellet recorded at that power setting, and then using Chairgun I calculated the velocity every 25 yards.... I used the BCs from the graph above for each calculation.... Here are the results....



The "Avg. BC/100" numbers are determined using ChairGun.... I input the muzzle velocity, and then changed the BC until I got a number that matched the 100 yard velocity in the table.... It represents a number you could use to determine the trajectory, velocity and energy at 100 yards without going through all the steps.... The ACTUAL trajectory would vary slightly from what ChairGun would predict using those numbers.... as an example, for the JSB Kings, the trajectory would be a bit more curved initially, and then actually flatter as you go out further (relative to ChairGun)....

You can see that from about 10 yards out, the H&N Baracudas have the most FPE.... They also have the highest average BC, and although the BC does start to drop off at velocities over 850 fps, they would be an excellent choice for any gun that can shoot them fast and accurately.... The EunJin Domes have good close in power, but their relatively low velocity and mediocre BC make them a poor choice at long range.... both for trajectory and wind drift.... It would appear that driving them over 700 fps costs significantly in terms of the BC, as you might expect with a relatively blunt pellet.... The Predator Polymags likewise have a drop in BC which hurts their performance over about 750 fps.... They were close behind the JSB Kings in terms of accuracy.... but their retained energy at 100 yards was under 20 FPE.... and the lower BC will make them sensitive to crosswinds.... The RWS SuperDomes simply weren't accurate enough in my Hayabusa to bother with.... In fact, it wasn't unusual to have to shoot 10 (or more) shots at 25 yards to get 5 that didn't produce an error or no velocity reading.... They did have a very good BC, however, so if your gun shoots them well they bear investigating.... The Benjamin Domes had a consistently high BC, significantly better than the JSB Kings at the higher velocities.... I didn't drive them fast enough to see the fall-off in the BC, but I'm betting it will start to drop at over 900 fps....

So after all this testing, I have four pellets on my short list.... The most accurate and flattest shooting were the JSB Kings, but in terms of ballistics the Benjamin Domes are very close, I'll have to see how the accuracy compares at long ranges.... I'd love to use the H&N Baracudas if they prove to be accurate enough, they certainly have the power.... The Predator Polymags are teasingly accurate, it will remain to be seen if that is enough to overcome the lack of energy and susceptability to wind drift at longer ranges....

Bob