We’ve received a lot of positive feedback for the extensive new HAM database of pellet BCs.
Of course, there also have been some questions, so we’ve put together this piece to answer some of these.
Question 1. Why did you use the FX Impact air rifle for the pellet Ballistic Coefficient testing?
That’s an easy one to answer! Apart from being a wonderful, high quality air rifle that’s a pleasure to shoot, the Impact has an unique feature set that makes it the ideal choice for our testing.
Firstly, it’s a regulated PCP. This means that the Muzzle Velocity is very consistent for every shot. There’s no need to be concerned with any “shot curve” issues as would be the case if we had used an unregulated PCP air rifle.
Secondly, the Impact is available with a range of different calibers. And we used them all!
So, we were able to determine pellet BCs for .177 cal, .22 caliber, .25 cal and .30 all with the same airgun. All we had to do was to change the barrel and bolts as appropriate.
This was another huge factor in attaining consistency and comparability between the full range of BCs that we have produced.
Question 2. Are the HAM pellet BCs applicable only to the FX Impact?
No, they’re not. The HAM pellet BCs are “typical BCs” that are generally applicable as a starting point for many air rifles shooting at similar Muzzle Velocities.
But because pellet BCs vary between different airguns, this means that they are specifically accurate for the Impact.
Question 3. Why didn’t you use a springer to generate the HAM pellet BCs?
Well, firstly, we couldn’t find a single springer that gives the ability to fire four different caliber pellets, as does the FX Impact.
Secondly, the need to break the barrel of a springer every time it’s fired makes it much more difficult to ensure that the gun is in EXACTLY the same position relative the the Labradar system for every shot. Again, this is a consistency issue.
With the Impact, the gun stays in exactly the same position for every shot in the string for a particular pellet, due to the smooth side lever action.
And thirdly, there was a whole lot less effort for the shooter – HAM tester Doug Wall – using the Impact than had we used a springer!
Question 4. Why do the HAM pellet BCs only cover the range to 30 Yards?
In experimental testing prior to producing the HAM pellet BC database. we did record velocities out to 50 Yards using the Labradar system. However, the difference in velocity between different individual pellets of the same type became significantly different beyond about 30 Yards. This made it very difficult to attribute a meaningful average velocity to the pellets at beyond 30 Yards.
This is shown by some data we generated in an earlier experimental test…
In this test, we had used a .177 caliber QB79 regulated PCP. Five shots were fired, each with 8.64 Grain H&N Field Target Trophy pellets.
As you can see from the following table and chart, the extreme spread of Muzzle Velocities for the five pellets was just 8 FPS. At 10 Yards, the extreme spread was still 8 FPS. This had opened a little to 9 FPS at 20 Yards range. Still very close and consistent!
At 30 Yards range, the extreme spread had opened to 17 FPS. Still pretty close. But at 40 Yards, the extreme spread had become 33 FPS and by 50 Yards it was 62 FPS. And these results were much closer than for many of the other pellets we tried!
| Shot | MUZZLE FPS | 10 YARDS FPS | 20 YARDS FPS | 30 YARDS FPS | 40 YARDS FPS | 50 YARDS FPS |
|---|---|---|---|---|---|---|
| 1 | 758 FPS | 720 FPS | 679 FPS | 636 FPS | 591 FPS | 543 FPS |
| 2 | 758 FPS | 723 FPS | 687 FPS | 653 FPS | 624 FPS | 588 FPS |
| 3 | 750 FPS | 715 FPS | 678 FPS | 643 FPS | 620 FPS | 575 FPS |
| 4 | 753 FPS | 719 FPS | 685 FPS | 651 FPS | 615 FPS | 588 FPS |
| 5 | 755 FPS | 719 FPS | 682 FPS | 645 FPS | 609 FPS | 605 FPS |
| FPS SPREAD | 8 FPS | 8 FPS | 9 FPS | 17 FPS | 33 FPS | 62 FPS |
So, pellet-to-pellet variation in velocity increases with range – as we might expect. Beyond 30 Yards, our experiments proved that the variation was such that it was not possible to derive a meaningful average velocity. So the pellet BCs determined at these longer ranges would have been less accurate, consistent and reliable.
Question 5. Where are the BCs for alloy pellets in .177 caliber?
While Labradar happily captured the velocities of .22 caliber and .25 caliber alloy pellets, we were not able to record .177 alloy pellet data at all. We’re not sure why this is and will try some further experiments to see if we can overcome the issue…
Question 6. I need the Ballistic Coefficient for 30 cal Polymags. Where is it?
Unfortunately .30 caliber Polymags would not fit into the magazine of the Impact. So we couldn’t shoot them. This also applied to a couple of other very long pellets such as the Eunjin heavies in .22 and .25 caliber.
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