... and there’s more!

Gary Wain sets the scene to an­swer the ul­ti­mate ques­tion

Airgun World - - Contents -

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.

START­ING HERE

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.

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