50gr JSB BC??
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Measure it. If you have Strelok you can calculate BC with bullet drop, or use your chrony at say 50m and calculate it that way. I know that my BC is very different from the suggested BC of Chairgun, measured with Air chrony first at muzzle then at 50m (not 50gr though)
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Seems low until you go out and measure. Go measure for yourself and you tell me what you get
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I calculated the BC (using the POI method) of the JSB Match Diabolo Exact .30 cal. 50.15 gr pellets (wasp style) shot out of an FX Impact .30 (MAX power) at an avg velocity of 832.6 fps (based on 40 shot string). Zeroed @ 25 yds; 4.53 in. drop @ 65 yds. I got a BC of 0.022 as well. I then field ranged using this BC as input in Chairgun. The numbers were spot-on out to 120 yards (Hawke Sidewinder 4-16x 50).
I hear that JSB has a Match Diabolo Exact 50.15 gr .30 cal. pellet (cone style) w/a BC of 0.042, which would give me 30 more yds range on my scope w/ 11.4 more ft# than 120 yds (20 ft#) out to 150 yds (31.4 ft#). I am really disappointed with the pellet choices for the .30 caliber. My Impact .30 mag will not accept the Predator Polymags and the Baracuda Hunter Extremes do not come in .30 cal. I hear that the new FX Crown mag will accept the .30 cal. Polymags; I hope that's not just a rumor! God, I love that round; and I love the FX platform!
I hear that JSB has a Match Diabolo Exact 50.15 gr .30 cal. pellet (cone style) w/a BC of 0.042, which would give me 30 more yds range on my scope w/ 11.4 more ft# than 120 yds (20 ft#) out to 150 yds (31.4 ft#). I am really disappointed with the pellet choices for the .30 caliber. My Impact .30 mag will not accept the Predator Polymags and the Baracuda Hunter Extremes do not come in .30 cal. I hear that the new FX Crown mag will accept the .30 cal. Polymags; I hope that's not just a rumor! God, I love that round; and I love the FX platform!
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I think assigning one BC number to any pellet is sub optimal at best. In my last big project, I attempted to assign a BC to the korean 24 grain .20 cal. Recorded velocity at muzzle (duh) 25, 50, 75, 100 yards on the same day, same tin. After doing the math, I ended up with FOUR different BC numbers!
Seems that BC "evolves" or is dynamic depending on the duration of the flight. Further, you can NEVER assume that your BC # will be the same from a different rifle.
In my case, I took an average of the 4 numbers (.032) and it's been spot on. Took an entire day, but I've shot with that data for years!
Another variable to consider besides all the usual ones (temp, pressure, elevation, blah blah) is what's called "pancaking". What?
Pancaking is more prevalent in thin skirted pellets fired out of higher powered pcp's. The sudden air blast actually shortens the overall length of the pellet! There was discussion on this topic on the Yellow Forum years ago when pcp's started to really get serious (back when 40fpe was a BFD). Everyone was wondering why their BC data was so far off in their new rifle (me for example, shooting 16gb JSB out of a new Air Ranger)
I guess the moral is that BC numbers should be taken with a grain of salt. Unless it was derived from the same rifle, same power setting, same conditions, it'll only get you in the neighborhood (not even ballpark)
Just wanted to share some hard learned lessons with the group. Might be old news for some.
Brian
Seems that BC "evolves" or is dynamic depending on the duration of the flight. Further, you can NEVER assume that your BC # will be the same from a different rifle.
In my case, I took an average of the 4 numbers (.032) and it's been spot on. Took an entire day, but I've shot with that data for years!
Another variable to consider besides all the usual ones (temp, pressure, elevation, blah blah) is what's called "pancaking". What?
Pancaking is more prevalent in thin skirted pellets fired out of higher powered pcp's. The sudden air blast actually shortens the overall length of the pellet! There was discussion on this topic on the Yellow Forum years ago when pcp's started to really get serious (back when 40fpe was a BFD). Everyone was wondering why their BC data was so far off in their new rifle (me for example, shooting 16gb JSB out of a new Air Ranger)
I guess the moral is that BC numbers should be taken with a grain of salt. Unless it was derived from the same rifle, same power setting, same conditions, it'll only get you in the neighborhood (not even ballpark)
Just wanted to share some hard learned lessons with the group. Might be old news for some.
Brian
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Brian, that is sound advice. This is why I always field range to verify numbers I get from Chairgun. Your point is well taken; the BC metric is tricky at best with pellets.
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