Drop Chart Questions

Skinny Shooter · #1 02-13-2003, 02:19 PM

This a great resource, thanks ya'll.
My passion is shooting skinnys (groundhogs). Out beyond 400 yards they start getting small, especially the jr. skinnys in Spring so knowing where thy bullet will impact is critical.
I have read that many of you use a computer program to generate your drop charts and are successful with it.
Had been using a Sierra program in the past to caculate drop for a 22-250.
How important is it to know humidity, altitude and temp for any caliber drop chart?
My .267BC 55gr BT at 3625fps would drop more at 400 yards than my chart indicated (20" which should be 5MOA from a 100yd Zero) and would have to spin the dial for a 500 yard setting to get near the target.
I was starting to give up on computer generated charts.
I downloaded PointBlank and thought I would try that.
This Spring I want to try out a new Starke bullet, the 150gr Red Prairie in my 308. It's supposed to have a BC of .400 but that seems very idealistic to me.
Thanx.

[ 02-13-2003: Message edited by: Skinny Shooter ]

Mysticplayer · #2 02-13-2003, 04:34 PM

Unfortunately, my experience mirrors yours. Computer drop charts don't work that well for simple reason that the parameters we enter are not correct. BC, scope height, and weather conditions will affect the data. Since most of these parameters vary from gun to gun, and day to day, there will always be some error.

I generate a computer chart so that I am in the ballpark then shoot to finalize. By using "my" drop chart, I shoot during different weather conditions to confirm. Usually am very close to my data (plus or minus a click or two).

At the ranges you are shooting, the weather conditions will not matter as much as temp. changes and its affect on muzzle vel and accuracy. Doing load development in the spring then shooting in the summer can give you different results. I avoid this by using Hodgdon Extreme powders. They are temp insensitive and seem to provide very consistent vel over a large temp change.

Get a good rangefinder (I like Leica) and work out your table. Enjoy the shooting.

Jerry

Skinny Shooter · #3 02-13-2003, 05:13 PM

Thanks Jerry. Varget is my main powder for the exact reason you specified. I won't be getting serious about load development till it warms up a bit more.
I joined the Green Hills Gun Club recently which has a 300yd range. That'll be good for my 223 TC. [img]images/icons/grin.gif[/img] The rest of the guns will have to be shot at a farm somewhere I believe for real-world results.