Ballistic coefficient of AA Express pellets

Ballistic coefficient of AA Express pellets

Postby Cantankerous One » Sat Jun 24, 2017 5:07 pm

Anyone know the BC of AA Diablo Express pellets please?

Thanks
S400F Classic .177
HW110 .177
HW100S .177
HW97KT .177
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Re: Ballistic coefficient of AA Express pellets

Postby gary martin » Sun Jun 25, 2017 8:32 pm

these pellets are rebadged JSB Express, Chairgun gives them the same BC as the regular 8.44g but these published values are really just a guide. The same pellet shot from a different barrel can give a different value. to get a true value you would need to work it out yourself. you will need two chronos, one at the muzzle and the other at a known distance, from the two readings it is then possible to get the true value.
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Re: Ballistic coefficient of AA Express pellets

Postby Archer50 » Mon Jun 26, 2017 9:12 am

I don't know how accurate you need the figures to be, but if you want to calculate the true BC for your gun and can't get hold of two chronos, you can get a useful approximation by measuring your POI at a longer distance - say 60 yards, and using ChairGun. I don't know about AA Express, but I have tested AA Field 8.4's and JSB Exacts with my S400 and HFT 500 and found that the AA pellets had roughly the quoted BC (0.021), but the JSB's had a much lower rating - around 0.016, so you can't assume that AA Express = JSB Express for BC.

Here are some figures averaged from 20 shot strings from my S400 off a bench rest indoors, with a Combro on the gun, a Caldwell 35yards down range and a paper target at 45 yards. 45 yards wasn't really enough for the POI drop to give accurate figures, but you'll see what I mean. The most interesting thing for me, was that the test confirmed what I had already found from ordinary shooting. Although the AA pellet left the gun significantly slower than the JSB, it was travelling faster down range, with the difference being noticeable in real life from about 40 yards on.

AA Field
Nominal BC = 0.0210
Velocity at muzzle = 748 fps
Velocity @ 35 yards = 605 fps (81%)
BC calculated from velocity = 0.0206
POI @ 45 yd = -2.40 inch
BC calculated from POI = 0.0203

JSB Exact (batch 44)
Nominal BC = 0.0210
Velocity at muzzle = 774 fps
Velocity @ 35 yards = 593 fps (77%)
BC calculated from velocity = 0.0163
POI @ 45 yd = -2.48 inch
BC calculated from POI = 0.0156

Of course, for most purposes you can just scrounge a few pellets and see how you get on with them ;)

Hope this helps.

Alan
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Re: Ballistic coefficient of AA Express pellets

Postby Cantankerous One » Mon Jun 26, 2017 1:07 pm

Thanks Archer and gary for the info and advice.

KRs
Tony
S400F Classic .177
HW110 .177
HW100S .177
HW97KT .177
Cantankerous One
 
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