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Old 17th September 2015, 01:32 PM
skires skires is offline
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Join Date: Apr 2009
Posts: 950

Quote from that thread ...

Due to constraints on time and botheration the chrono tests were a bit half-arsed - 10 shots through the F1 chrono at 1m from the muzzle, then another 10 shots through the chrono 26m from the muzzle.

8.45gn Batch 20000012 JSB Exact 4.52s gave a BC of 0.0205 - very similar to the 0.0202 I got through the same gun with the same batch last year (using two chronos), between the extremes of 0.020 and 0.024 I've measured with these pellets and nicely inkeeping with published values.

10.34gn Batch 30000012 Daystate FT Heavies gave a BC 0.0260 - somewhat down from the figure I recorded last year of 0.0278 for the same pellets. The published BC values for these pellets seem to vary wildly (typically 0.23 - 0.30) - I suspect due to velocity and twist rate variations between tests affecting their stability (lots of the higher BC figures seem to originate in America; where they will be fired at significantly higher velocites than we can use legally over here).

By comparison the 8.46gn (as weighed) H&N Snipers managed a BC of 0.0260 - the same as the heavies on this occasion and (IME) an unprecedented high for a pellet of this mass. To put it another way, the Snipers generated the same drag force as the Heavies (actually very slightly less) despite travelling over 10% faster; illustrating that the shape of the H&N pellets generates significantly less aero drag.

This can be seen by comparing the drag coefficient of each pellet - the Heavy managed a Cd of 0.363, while the Sniper gave 0.296 (the lowest of any pellet I've ever tested); illustrating that the H&N will generate around 20% less drag at a given velocity.

I was just reading comments by HECTOR J MEDINA GOMEZ.

A few of his comments ...

H&N has been a long time supporter of FT and was kind enough to send some of the first samples to come out of the Sniper line. They admit that the line is not running as smoothly as they like (some skirts are "wavy"), and the offerings are, for now, limited to the 4.50 head diameter. In the future, the Sniper line will also offer the 4.52 mm's head diameter for those of us that shoot non-Match barrels.

Center of gravity will be as forward as can be, given the weight of the pellets (7.5, 8.5 and 15 grains respectively). This emphasizes the "shuttle-cock" effect and adds stability to the pellet.

Center of pressure will be a little bit in front of geometrical center, which should make these pellets less susceptible to vertical deflection with side winds.

Because of the "Column" shape, they will exit the barrel pretty much as they went in. Preserving the BC. And the relatively thin skirt affords a good seal at any pressure above 80 BAR's.

Last edited by skires; 17th September 2015 at 01:51 PM.
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