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Michael Csenger wrote:
> 
> -----Original Message-----
> From: Tim Mcmurray 
> 
> >Learn about why speed doesn't impress. Air resistance goes up at the
> >square of the velocity. Shoot for a projectal going max 850 and
> you'll
> >be headed pretty much in the right direction. Velocity means squat.
> >Retained energy is all.
> >
> 
> Is there a point at which velocity way above 850 fps actually pays
> off?
No. Our projectals are meant to go subsonic. The dynamics of supersonic
dictates a whole different design for ammo. They'de be longer, pointy,
and maybe even boattail. Check out supersonic firearm ammo to get a
clue.
 Out
> on the web I found specs for an airgun claiming 98 ft/lbs in .25 cal.
> 
> Ballistics software says that a 17 grain .25 Beeman Laser would leave
> the
> barrel at over 1600 fps.
Where did that fps and pellet come from? Let me guess. You assumed it.
More likely they are pushing a 55 grainer @ 900 than a 17 grainer @ 1600
to get the 98 ft. lbs. You are talking about a .25 cal. career more than
likely. That gun would destroy a 17 grainer B4 it ever even saw 1200
fps. You can't shoot extra light stuff like that in a PCP high power or
the projectal gets blown up. You need extra heavy stuff for these guns
to perform.
 Energy drops precipitously down to 27 ft/lb
> at 50
> yards, where velocity hits 850 fps. Then the curve mellows out, and
> you stop
> losing energy so fast.
That would be pretty close to the expected performance. Air Resistance
goes up at the square of the velocity. Do you know what that means? That
means double the velocity and the air resistance quads. Not worth it.
> 
> BUT. There's another ballistics program that claims to be better tuned
> for
> airgun pellets. It doesn't do energy graphs, but it does draw
> trajectory
> charts. So I input the same starting data to see what it would figure
> out.
> It paints a totally different trajectory. The one from above was a big
> fat
> downward loop, shedding speed all the way. This other software shows a
> nice
> flat trajectory, with lots of punch way out.
Ballistic programs are not rocket science. Most only are practical
within a narrow range of velocity. Airgun ballistics are assumed to be
subsonioc so the programs out there will be mostly garbage for what you
are trying to figure here. Remember. Garbage in/Garbage out. Also when
you are pilling on some of your own suspisions/assumptions you need to
state that fact. Like I assume that 98 ft. lbs. would be 1600 w/ a 17
grainer instead of stating it like it was gospel. When you know, share.
when your guessing, admit it. That way you won't lead anyone off on a
tangent that is a product of your imagination.
 
> 
> It's been my (limited, early) experience that my .22 trajectory is
> flatter
> than the books say it should be. It seems more in line with results
> that the second software predicts.
> 
> So I'm not arguing with Tim, but I ask if there's an effective
> compromise
> somewhere between 850 fps pellets and the sort of velocities that
> firegunners are used to...
> 
> -Michael
We have relatively little performance compared to powder burners so we
must use the most efficient projectals at the most efficient velocity to
have any long range capability. If we want to reach out we cannot afford
to be halving energy every 25 yards or worse. The hot tip is to shoot a
very good projectal like the kodiak at a reasonable velocity and the
downrange effect Vs. a poor projectal will be obvious. Now turn off the
computer and go out a prove it to yourself. Ballistic programs should
only be used for a starting point. The pellet shape gets changed
with evry gun we try it in. This means that the info you get in a
ballistic chart is mediocre at best cause the bc of a pellet will be
different out of every gun you shoot the pellet out of. Airguns do
strange things to pellets. Especially out of the ultra-high-power types.
Later  
Tim
-- 
MAC-1 Airgun Distr./McMurray & Son   Phone 310-327-3581 FAX 310-327-0238
http://www.mindspring.com/~airguns/  Hours-M,Tu,F,Sa 11:00AM-6:00PM PST
13974 Van Ness Ave.                  Tim McMurray
Gardena, CA 90249 USA                mac1@concentric.net
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