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#1




8,4g vs 10,3g ballistic
Why FT shooter use 8.4g pellets and not heavy 10,3 g?
The standard answer is that the 8,4g pellets have much flatter ballistic curve, which is true. But this reasoning seems not justified. Let me explain: I take my Anschutz 8002 for example: 15.5 joules, zeroed at 25m, scope height 75 mm. 1) Exemple: with 8.4 grains jsb exact, zeroed at 25m, 15.5 joules  A range of 50 m needs 39 clicks (69,2mm) If I do an range finding error about 2 meters: 48 m estimated instead of 50m, this error correspond to 5 clicks, so I shoot 11.8 mm too low If I do a range finding error about +2 meters, 52 m instead of 50m this error correspond to 6 clicks, so I shoot 13.1 mm too high. 2) Exemple: with 10.3 grains jsb heavy, zero to 25m, 15.5 joules  A range of 50 m needs a correction of 50 clicks (88.3 mm) If I do a range finding error about 2 meters: 48m instead of 50m, this error correspond to 6 clicks, so I shoot 13.9 mm too low. If I do a range finding error about +2 meters: 52m instead of 50m error is 6 clicks, so I shoot 14.9 mm too high. In summary: for a range finding error about 2 m there is no significant différence of the correction between 10.3's and 8.4's. 11.8 to 13.9 mm = 2 mm for an estimate of 48m instead off 50m 14.9 to 13.1 = 1.8 mm for an estimated 52m instead of 50m. I find that a range finding error of 2 m at 50m whatsoever with "jsb exact" or "Heavy jsb" leads to the same error (approximately 2 mm). Now look at the wind drift for these two pellets weights: 1) For a wind of 5km/h at 90 ° The drift is 35 mm with "heavy" so what is 49 mm with jsb exact 2) For a wind of 10 km/h at 90 ° The drift is 70 mm with "heavy" so what is 94 mm with jsb exact If I summarize, the JSB Exact derived from 14 mm more than the Heavy under the influence of a wind 5km / h (24 mm for a wind speed of 10 km / h). For a wind from 0 to 5 km/ h if I do not correct my sight the target fall, while this is not right with the "Exact". So JSB EXACT 8.4g or HEAVY 10.3 g ? That is the question. Last edited by flyfisher; 4th November 2014 at 08:27 PM. 
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#2




interesting

#3




I like shooting ...........
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#4




Interesting.
Is your findings from real world observations or ballistic software programmes?
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#5




Of course, you're assuming that the BC for both pellets is the quoted average BC for that pellet in your gun.
There are around 50 different die's of JSB Exact 8.4's in 3 different quoted head size  some perform much better than others, I don't know how many die's of 10.3 or how many head sizes they come in? For an example  I have a batch of 8.4's that give a BC of 0.0265 in my rifle at 50m (measured with a chrono) Try your comparison again, but this time  compare an 8.4 pellet with better than average BC against an 10.3 with worse than average BC. Of course, if you can find a batch of 10.3's that give a better than their quoted average BC in your barrel and they group well and remain stable in flight out to 50m then I think you're onto something. But that might be part of the reason  it's easier to find a better than average 8.4 than it is to find a better than average 10.3 There's an added complication for spring guns too  the fine balance between slam/bounce and pellet weight/fit 
#6




Just did a little search and found a few different quoted BC's for the 10.3  0.023 being about the lowest over on the Yellow/Green forum  Chairgun quotes 0.031 which is quite a big difference.
Compare a 10.3 grain pellet with a BC of 0.023 against an 8.4 with a BC of 0.026 running at the same muzzle velocity and tell me which one has the better trajectory and takes less wind Last edited by Brian.Samson; 4th November 2014 at 06:37 PM. Reason: Did a bit more digging for the BC of a JSB Heavy 
#7




??
Lost me at 'hello!'
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#8




I used Bisley Match (10.3gr) for years for FT, with very satisfying results.
I liked that they didnt incur that slight 'drift' in a very gentle breeze, and less than lighter pellets in a stronger wind 
#9




Quote:
Hi Conor, These results are purely theoretical. I've calculated ithem by myself (I am an engineer and ballistics interested me). I took BC = 0.021for Exact and 0.031 for Heavy (values determined on the field with my Anschutz). Brian, if the BC of a pellet is dramatically lower from its average this means it has a major manufacturing flaw. Failure to geometry or weight distribution (disymmetry in terms of mass). its center of gravity away from its axis of symmetry.y. In my question I do not take care of exeptions . 
#10




It doesn't mean that at all.

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