Muzzle velocity sea level vs 9000 feet and its impact on shooting tables

1

17freak

New member
Over the years I have found the different tables or programs not very accurate when dealing with large variations in altitude. This summer I had the opportunity to shoot pdogs that haven't been shot so was able to deploy 22lr rifles. None of the numbers were valid in terns of holdovers or deflection.
My question then is two fold. Should I measure the muzzle velocity where I'm going to shoot and then at 100 yds and compare that to where I live. If there are differences and I suspect there is what should I do to refine the solutions from the ballistic programs. Never tried altering the muzzle velocities spit out by the programs other than at the muzzle.
Thanks
 
Velocity isn't going to vary much given a reasonable swing in temperatures. What you need is JBM and plug your parameters of altitude in with your bullet and BC. This will give you a CLOSE approximation of the drop difference. Of course parameters of humidity and pressure can enter in to it but for most of us non-professionals it doesn't make much difference.

Here you go. Plug and play.
http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

Greg
 
Thanks for the quick reply. I live outside New Orleans so Temp and Humidity are definitely different from most places that I hunt especially in late fall and early winter. My weather system is telling me that right now its 89 degrees, relative humidity is 78% and heat index is 107. This why I asked he question.
 
Originally Posted By: wormydog1724Use DA and get a kestrel. Once zeroed at any DA, can shoot at any DA.

thumbup1.gif
 
What has worked for me, I use my muzzle velocity and bullets bc and the expected altitude, temperature and humidity. This will give a ballistic curve that for hunting or prairie dogs is very close. I have used this for my 30tc and 338wm for elk and 17 rem,223,204,22-250 on prairie dogs. At common shooting distances(under 500 yards)on soft targets I can't see much error. I leave for Montana Wed(archery elk) I will take a target and my 17 rem with I will shoot my 960' elevation sight setting at 3000' and note the difference at 300 yards.
 
Back
Top