... and there’s more!
Gary Wain sets the scene to answer the ultimate question
Gary Wain sets out his stall for future questions on ballistics
After a year’s worth of research into the ballistic characteristics of air rifle pellets, it’s fair to say that I thought I’d pretty much delved as deep into the subject as possible – that was until two things happened. The first was when I got my hands on a couple of R2A chronographs from Blackpool Airguns. They beckoned me toward all manner of other ballistic examinations I would be able to undertake. The second event was a letter from Airgun World reader, Robin Lambert, who challenged me to look at the variances between .177 and .22; not just in general, but with specific regard to the changes in energy levels at varying ranges.
In previous testing, I’d skimmed the surface of this battle royale, so I’d learned and demonstrated some of the differences. In doing so, I’d upset a few previously held misconceptions, not least of which was that the larger .22 pellet, by virtue of its greater size and mass, does more damage, whereas the lighter, faster moving .177 pellet will overpenetrate without doing much damage to the prey. As we’ve seen, this commonly held belief is total poppycock.
BOTH .177 AND .22
I want to look at both calibres to determine how much of a difference the distance to target makes. I want to see not only the amount of velocity and energy retained, but also the amount of energy the pellet is then able to deposit into the target; which calibre will lose more energy, and how quickly. Will there be a distinguishable relationship between the two calibres? Will there be a sweet spot for .177, and will it be different for .22? To get down to brass tacks, I also plan to graph the results so that we can see what the velocity and energy loss looks like. Will we see a linear drop off, or a curved relationship? Will the relationship vary massively between .177 and .22?
The one thing I learned from last year’s research was that as much as I think I know what’s going on, and that the answers are obvious, I genuinely can’t predict what they will be.
So, to methodology; as ever, things are never simple. In order to minimise power discrepancies between calibres I have to thank the team at Daystate for the loan of a .22 Pulsar, tested to have the same output as my own .177 Pulsar.
I will be starting with the .177 and then moving to the .22, and I’ll commence testing at muzzle and then 1m, shooting the pellets through the R2As and recording the results. I will then move up to 2m, 3m, and so forth, all
the way up to 30m. This will give the base-line data I need before I move to the next round, which will be to look at the amount of energy deposited into the ballistic material. To do this, I will be placing a chronograph immediately in front of the ballistic clay, and one immediately behind it. If all goes as planned, I should see a variance in the readings between entry and exit energies and velocities, and the difference will determine the amount of energy that has been deposited.
In previous testing, I’ve used clay blocks of about 80mm deep because my aim was to try to capture the pellet, which would then enable me to take a cast of the entire wound track. However, as my aim here is to allow the pellet to exit the material, it might not be possible to make such good casts.
There are also a couple of other variables to be determined, and locked down as much as possible. I’ve already discovered that the temperature of the clay makes a huge difference to its ballistic penetration properties, so I’ll be breaking out the meat thermometer again. I’ll also need to determine the optimum thickness for the slabs, and ensure that they are all cut to the same dimensions. The third, and potentially more troublesome variable is the potential for small particles of the clay to leave the exit hole with the pellet, and potentially to skew the results.
DO NO HARM
The last thing I needed to do was to ensure that no harm came to the chronographs. Had I just been testing at a short distance, I wouldn’t have been too worried, but as I was going to be testing at range, and with material in between them that could potentially divert the path of the pellet, I thought it prudent to take measures to protect them. This protection comes in the form of a pair of guards, whipped up by my good friend, Jim Brown. The guards are simplicity itself; each one made from a single sheet of steel, cut and formed in just the right way to protect the chronograph whilst allowing the pellet to pass through, and at the same time allowing access to the buttons and the read out.
So, I’ve certainly got my work cut out over the coming months. What do you think the results will be? Will the large wound cavities we’ve seen from lightweight .177 pellets be backed up by the data from the chronographs? Or will we see everything turned on its head? Let us know what you think, and if there’s anything you think I’ve missed, or other variables you’d like to see me tackle and test, then do let me know.
I’ve a feeling I’m going to be spending many more happy hours with this set-up.
I needed some guards to protect the R2A chronographs - my good friend, Jim Brown, was just the chap.
One in .177, the other in .22, otherwise everything, including the scopes is identical.
Can you see my thinking here?
Will the results from the chrono’ testing support the finding of the core castings?
Best get the terracotta wax heating up again.