Been all over the web looking for an @ BC value on the new JSB Heavy in .20 cal finding nothing.
Thanks if you can help,
Scott S
Thanks if you can help,
Scott S
Anyone know ... What the BC value is running on JSB .20 15.89 HEAVY pellets ?
- Thread starter Motorhead
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Motorhead, from my Az tuned rapid shooting them @ 900 fps mv I get a bc of .044. target @ 85 yds. 
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That's believable since the former best 20 caliber 14.3gr CROSMAN PREMIERS (RIP) were .040.
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This inquire was to get some idea from others if or not the heavier 15.89 would likely show an improved BC over the 13.7 grain .20 cal ?
In my testing and getting chairgun data to follow actual field ballistics of the original JSB Exact 13.7 when shot at @ 800 fps, found time & time again the BC value needed to be raised to @ .040 for lower elevation and .044 when at @ 5000' * BC corrected from the IIRC @ .032 default BC value provide by chairgun.
Doing so the DATA produced by chairgun is Dead Nuts accurate !!
To stay under 20 FPE for Field target work with the 15.89 grain, velocity will need to be @750 fps and no faster. This speed reduction from a previous 800 I'm sure will shift the BC value some as well ???
In my testing and getting chairgun data to follow actual field ballistics of the original JSB Exact 13.7 when shot at @ 800 fps, found time & time again the BC value needed to be raised to @ .040 for lower elevation and .044 when at @ 5000' * BC corrected from the IIRC @ .032 default BC value provide by chairgun.
Doing so the DATA produced by chairgun is Dead Nuts accurate !!
To stay under 20 FPE for Field target work with the 15.89 grain, velocity will need to be @750 fps and no faster. This speed reduction from a previous 800 I'm sure will shift the BC value some as well ???
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Try going below 700fps or not much over 700fps you'll probably get a significant BC boost. At that 800fps mark and up the speed naturally tends to slow down quicker than 700fps and below thus head scratching BC theories. Tried it a long time ago and baffled the hell outa me.
Strange that at 5000ft elevation+ gets better BC than at sea level. Especially when shooting at normal 850-890fps speeds. Usually trends the opposite way the higher elevation you go.
Strange that at 5000ft elevation+ gets better BC than at sea level. Especially when shooting at normal 850-890fps speeds. Usually trends the opposite way the higher elevation you go.
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I’ve experienced the opposite from Yo with regards to BC and altitude. I shoot two places, one at 430 ft and another at 3500 ft elevation. The BC from ALL pellets and slugs in ALL guns tested goes up at the higher elevation.
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Same here. BC improves (increases) with elevation.
I live at 5600 feet above sea level and shoot field target matches at 1700, 7200, and 8600. More rainbow at the 1700 than at my house (mostly affects the shots past 45 yards though). Unbelievably flat trajectory at 8600.
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ABOVE ... Only applies to a Spring piston or Pump or SSP pneumatic air gun .... NOT a PCP
Yo be wrong ... sorry
Yo be wrong ... sorry
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You know what?
I've heard you jabber about the .20 for a couple years now Scott, and pretty much thought it was just a way of being different.
THEN, I bought a Steyr 110 Hunter in .20 a month or so back.........
Yeah, I get it now!
I will no longer dismiss the .20 as an aberration or throwback. You were right, and I am a new convert to the dark corner of the darkside.
I've heard you jabber about the .20 for a couple years now Scott, and pretty much thought it was just a way of being different.
THEN, I bought a Steyr 110 Hunter in .20 a month or so back.........
Yeah, I get it now!
I will no longer dismiss the .20 as an aberration or throwback. You were right, and I am a new convert to the dark corner of the darkside.
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Yup .... One generally only see this with having RELATIVITY of shooting a .177 FT rig along side a .20 rig ... in some wind, targets that are split prone to not fall etc ...
The .20's while harder to D.O.P.E. indeed pay dividends when you can and figure out good dope data.
My Partner Jim C shoots an AZ prepped LG-100 in .20 and it is a seriously tough combo to beat !!
Enjoy that 110 in lowly .20 cal !!! Nice gun I'm sure !!
Scott S
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I actually have 2 AZ prepped Steyr 110s, a .177 full on FT rig and the 110 Hunter in .20.
Totally unquantifiable, but while the .177 is spot on (when I do my part) the. 20 is almost too easy to stack pellets with at 50 yds. The .177 punishes me for poor form, while the .20 seems to not care as long as its pointed somewhere near the target.
It does not care for the 13.73s but with the 15.89s it gave me that giggly warm feeling that I got the first time that I shot a RAW and the tiny hole in the target just got a little raggedy at the edges.
Anyways, keep on preaching man, you brought me to the light!
Totally unquantifiable, but while the .177 is spot on (when I do my part) the. 20 is almost too easy to stack pellets with at 50 yds. The .177 punishes me for poor form, while the .20 seems to not care as long as its pointed somewhere near the target.
It does not care for the 13.73s but with the 15.89s it gave me that giggly warm feeling that I got the first time that I shot a RAW and the tiny hole in the target just got a little raggedy at the edges.
Anyways, keep on preaching man, you brought me to the light!
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At high altitude the atmosphere is less dense,thus less friction to slow a projectile. That is why the baseball carries so well in Denver and breaking balls don't want to break. T.S. Eliot,
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Goodness gracious, Yo! There are a LOT of rocket scientists in this thread.
Motorhead The BC numbers shambozzie gave you agree closely with what I got on my 40 yard range at about 25 feet ASL with MV around 835 fps.
The biggest problem with .20 is the dearth of pellet choices. It would be very nice to see some heavier pellet choices than the JSB Heavies.
Motorhead The BC numbers shambozzie gave you agree closely with what I got on my 40 yard range at about 25 feet ASL with MV around 835 fps.
The biggest problem with .20 is the dearth of pellet choices. It would be very nice to see some heavier pellet choices than the JSB Heavies.
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