This is a repeat message, edited from my first post in another board. It was pointed out that this may be a better place for the question, so here goes.

I am looking to create a fairly reliable ballistics / trajectory chart for my favorite load, the 150 grain Ballistic Sivertip. My gun eats the stuff up and shoots it pretty well at 200 meters. However, I am not experienced enough at using the Point Blank program (or any of the others I've tried) to figure out what the chart ought to look like. I have looked online and can't seem to find the data for the factory loads anywhere either. My estimates (below) for the ballistic coefficient and the factory load fps at my altitude are just that - estimates. I've thus far been unable to find the BC for the 150 grain Silvertip and I don't know the math for figuring the difference between the factory load at sea level and at 7000 feet. My data is as follows:

Temp: 59 degrees F
Altitude: 7000' ASL
Bullet Weight: 150 grain
Velocity (I don't know. All I have is the 180 grain stuff, but I think it's in the neighborhood of 3100 fps)
Ballistic Coefficient: I think it's about .508, but if anyone else knows for sure, I'd be much obliged.

I know it sounds like I'm a mouth breathing idiot for not being able to figure this out, and well...maybe I am. Still, I've learned a few things over the years. Among them? When in doubt, ask people who are smarter than you! You all seem to know your stuff, so please help a fella out. Thanks in advance! Also, any notes on sources for the info I've listed would be much appreciated.

Sine Pari!
Odyssey

Are you talking about the Combined Technology Ballistic Tips? What caliber are you asking about?

Blaine

Sorry. Winchester Ballistic Silvertips, .300 WSM, 150 grain bullets

B.C. is 0.418 here is the link to the Winchester site page:

www.winchester.com/pro...=5&type=13

Blaine

Gidday Odyessy, have a look at the question I asked. It will answer some of your query.

[Calculating BC

Like me, you are going to have to get a Chronograph to check velocity.

Good luck mate.

Cheers, Vince

Thanks to both of you. I appreciate the help.

Well, you need a cronograph to get the real world muzzle velocity. But, you will find that the figures on the factory websites are very close and do not make a gread deal of difference in the trajectory.
We have the factory muzzel velocity(3100fps), the bc (.507 - Nosler CT info), bullet diameter (.308) & weight (180). That is all you have to enter in the NEW LOAD info in point blank. Sometimes the factory test altitude is listed on the factory website. If it is enter that info in point blank also. So, if the factory test altitude is 1500 ft (used for example only) and you want to know the trajectory at 7000 feet just enter 7000 in point blank on the Ballistics Calculator page and click the recompute button. You will have the corrected figures for 7000 then. If you can't find the test altitude it is probably calibrated for sea level (0') at standard temperature (59.0f) at standard Barometric Pressure (29.53). Then do a quick check of how the round actually shoots at the range to see how close it is to the figures generated in Point Blank. Point Blank only runs one bullet profile (shape), the G1 profile, so there will be just a little varience in what you actually get from the program computations. You can adjust the BC up or down in Point Blank to more closely resemble the real drop figures you get on the range. You can play with the different temperature, altitude, and velocity imputs in Point Blank and you will see small changes in the outputs.