zero-height-zero-offset-featured

Ballistic Performance Evaluation – Part Two

In Blog by Rich0 Comments

So this is the follow up from last week’s article on evaluating the ballistic performance of projectiles. Specifically, we’ve been looking at the differences between the 105gr Berger Hybrids and the 115gr DTACs. In general, the heavier the bullet the better the performance. That isn’t always the case and just because one bullet is bigger doesn’t mean it will have better ballistic performance. If the bullet has a poor design it can just be bigger and heavier without necessarily having better ballistics. Why would you want that? Well, Hunters are concerned with good terminal ballistic performance at closer ranges a lot of times. Some guys hunt long range but even still the average is probably around 650 yards. If you aren’t shooting as far, you can afford to use a bullet that’s a little less slippery as far as ballistic performance. The tradeoff being it knocks down the animal you’re hunting. For the rest of us interested in competitive and recreational shooting at longer ranges, the BC numbers tend to be pretty important. In this case it’s a difference of almost a full tenth of a point. The Bergers are currently rated at around 0.53 and the DTACs are pulling 0.62. Last time we looked at some of the numbers on paper, this time…we’ll see how the DTACs did in the real world!

Ballistic Performance Live Fire

So when evaluating the ballistic performance of a bullet in the real world there’s a few things to look at. For starters most people look at group size. How tight are the shots winding up both at 100 yards and farther out? As you can see above, these DTACs group really well. The Shoot-N-C target on the bottom was me zeroing the rifle for the DTACs. The first round was a touch low and left. I made a quick adjustment and put the next four into one ragged hole. It may not win me a medal in a Benchrest competition but that’s more than tight enough for a tactical application. For the record the group size was under a quarter inch at 100 yards. So that’s a pretty good start. Really good to be honest. I’d be happy with anything measuring under a half inch. The question becomes how well it does at distance though. Is that performance indicative of downrange results?

ballistic performance at 840

This is the target with 4 out of 5 hits at 840 yards. You can see where I changed my wind hold after the first shot to center the group, the wind shifted at one point and I missed a shot

ballistic performance group at 840

3 rounds (fired with the same wind hold) in under 2.5″ at 840 yards so it’s holding almost a quarter MOA accuracy to almost 850 yards

 

ballistic performance vertical group at 840

This wound up being around 1.5″ of vertical spread at 840 yards which we can attribute to consistent performance of the hand load and the AccuracyTech reloading method

Ballistic Performance Considerations

So it’s shooting well close up, and at distance. If you want to know what the line is for it’s just like a water line on a ship or a pier at the beach. The idea is to give yourself a good consistent point of aim for your horizontal crosshair. It also allows you to check and dial in whether or not the muzzle velocity or ballistic coefficient is accurate (Thanks Frank!). By shooting with the horizontal crosshair lined up with the line on the target you have a very fine point of aim to measure where the bullets are impacting. Wind is the great equalizer but the math for the drop is pretty straightforward. You should be able to get your impacts pretty close to or on top of the water line given the right information is fed to your ballistics software.

ballistic performance 640

Two rounds fired up top, made a 1/10th MIL adjustment down and fired three more. This is what we want to see, target was at 640 yards for this photo.

So here you can see the first two rounds were a touch high. Why? There can be several reasons for this. The ballistic coefficient can actually be HIGHER than advertised meaning the bullet is dropping less than anticipated. The muzzle velocity can be higher than we think so the bullet is arriving faster and giving gravity less time to take effect. Range error is a possibility and would mean the target was actually closer than we thought. The scope may not be tracking properly and actually moved the POA (Point of Aim) up more than we wanted it to. There could also be parallax error present. Lastly, the zero may be off a touch. To know which is likely you have to consider all the variables. I think David Tubb’s BC is probably pretty close so I doubt he under published the number. I’m quite confident of the muzzle velocity as reported by the Magnetospeed. Range error is unlikely as this is my home range and I verified it was at the distance expected with a quality laser range finder. I don’t believe the scope to be tracking improperly but could test it to verify. I’m also pretty confident of the zero. So which is most likely? Let’s come back to that.

ballistic performance at 1k

Here’s the target at 1040 yards, four hits out of 6 fired…what do you notice?

Here on the 1040 yard target we’re hitting high again. As the distance increases, any error present is magnified. I actually made a headshot on the target by mistake. The other three hits are pretty consistent in terms of vertical dispersion. The center of that 3 round group wound up being a little over 3.5 inches high at 1040 yards. That’s also coincidentally right around one click of elevation at that range. So we seem to be consistently about 1/10th of a MIL high across the ranges we shot at. I will have to test and see whether the zero is off or perhaps the scope isn’t tracking. I’ll have to drop my zero 1/10th of a MIL at the next outing and see where that puts my group at 100 yards. If I can still center it up on the bullseye then that’s likely my issue. If that moves the group below the bullseye my guess is that Parallax error is the issue. Likely at 100 yards, I may have zeroed without checking the parallax when I did it so the zero is just a touch off.

Wrapping Up

Moving the group down 1/10th of a MIL at 1040 yards would present a target similar to the 840 yard target where the rounds would be impacting slightly high in all likelihood. Remember there are many factors involved here. Including me as the shooter. If I’m being inconsistent with my fundamentals that’s easily enough to throw things off a touch. If I can head out and verify the zero and get the impacts to land within 1/10th of a MIL (3.6″ at 1000 yards) I’m going to call that good. If I moved the impacts by 2/10ths I’d likely be shifting the POI (Point of Impact) of the rounds down below the water line. The goal is to try and get within a tenth at distance.

There are two many variables to try and hash out as to why they aren’t landing exactly on the line at 1000+ yards. For the purposes of the ballistic performance evaluation it looks like the advertised BC on these DTACs is quite accurate. They don’t seem to be sensitive to seating depth and are grouping well both at 100 yards and much farther down range. I’ll likely do one more article in this series with some final confirmation and hopefully video that comes out clear next time! Have a question or something to add? Please do so below!

Owner and Proprietor of AccuracyTech, LLC. Rich is a Firearms Enthusiast, Precision Rifle Competitor, and Writer. He is committed to bringing readers quality reviews and articles related to the Precision Shooting Sports. If you have any questions for him, please use the contact form on the site.