Trajectory Help

[rkittine]

I should be able to figure this out as an Engineering Grad, but the answer is alluding me and I am new at using my Ballistic Calculator.

I rifle sighted in for distance, with usually be on target at two distances. One on the bullet rising and one on it falling through the second target.

Is I am shooting 90 Grain Scenar Lapua 6mmBR Norma factory ammo and hitting the target at 1,000 yards, what yardage should I hit an in line target as the bullet rises? I am trying to work out what inserts to use in my Burris Rings.

Thanks Bob

 

[Turbulent Turtle]

I'm not sure I completely understand your question, but for starters, JBM will show you the trajectory if you give it the proper information. For instance, I used the library's BC for the .243 90gr Scenar and put in 3000FPS for the muzzle velocity. You can set JBM to show you intermediate distances, and I set it to show me every 50 yards.

I get 16.5 inches high at 50 yards, then 34 at 100 and so on. The apogee is 127 inches right around 600 yards. Then at 950yards it's around 32 inches high and 0 at 1000 yards. So I would recommend you look at that.

If you're trying to set up the inserts, I think the easiest way is to figure out what MOA you need to get to 1000 yards, in the case I was using above that would be 36.4 according to JBM and then measure that on a thermometer-type target. That's what I do. I take a 4-5foot high cardboard, place an X at the bottom and then I draw a line from that X to the top of the cardboard. Then I measure feet from the bottom and when I get to 2 feet, I start filling in inches. Then I aim at the X at the bottom and look for my impacts to be at the elevation that I want on the perpendicular line. My .308 load needs to be at about 30 inches and that puts me on paper at 1000 yards.

With the Burris Signature rings, the Burris site has a nice table to help you with that. It's all based on the distance between the front and rear rings. You can also figure it out with a bit of trigonometry, look for arctangent.

 

[Mickey D]

I'm not sure I completely understand your question, but for starters, JBM will show you the trajectory if you give it the proper information. For instance, I used the library's BC for the .243 90gr Scenar and put in 3000FPS for the muzzle velocity. You can set JBM to show you intermediate distances, and I set it to show me every 50 yards.

I get 16.5 inches high at 50 yards, then 34 at 100 and so on. The apogee is 127 inches right around 600 yards. Then at 950yards it's around 32 inches high and 0 at 1000 yards. So I would recommend you look at that.

If you're trying to set up the inserts, I think the easiest way is to figure out what MOA you need to get to 1000 yards, in the case I was using above that would be 36.4 according to JBM and then measure that on a thermometer-type target. That's what I do. I take a 4-5foot high cardboard, place an X at the bottom and then I draw a line from that X to the top of the cardboard. Then I measure feet from the bottom and when I get to 2 feet, I start filling in inches. Then I aim at the X at the bottom and look for my impacts to be at the elevation that I want on the perpendicular line. My .308 load needs to be at about 30 inches and that puts me on paper at 1000 yards.

With the Burris Signature rings, the Burris site has a nice table to help you with that. It's all based on the distance between the front and rear rings. You can also figure it out with a bit of trigonometry, look for arctangent.

 

[Mickey D]

I shoot moa. Burger has a ballistic calculator that will help you get close. Type in the information it ask for the bullet you want to shoot. I use a 100yd zero. I use a 50yd distance so when I run the numbers I have a chart from 100 to 1000 at 50yds. Now the fun starts. I shoot a NF scope with a MOA reticule and my scope adjustment is in 1/4" incriminates.
I'm at 0 at 100yds. My chart says I will need 3 moa to be on at 300yds. I turn in 3"(a inch is close to a moa) and I shoot the target. A group may be at 3.25 on the target. Have a notebook and write down the exact number. Do this for every 100yds. At 850yds I put in 11.25 moa. At 1000
I put in 20.5 moa.
Then take your figures and print a range card and tape it to your stock on the side you rest your cheek on. Cover it with clear packing tape or your numbers will run.
I carry a Ziess range finder in my range bag so anytime I need to make a shot in the field I shoot the distance and put in the proper moa for that range.
I live in west central Alabama and have a friend who lets my shooting buddy and I put up our targets on his bean field after he gets his crops in. So we have the distance to shoot.
A good scope with a zero stop makes things simple.
I hope I explained this in a way you can understand. Once you get this down it's simple.

 

[rkittine]

Thanks Guys, I have the JBL app on my phone, so I have to look closer at that and maybe also on my computer so I have a larger screen to see. I will also look again on the Burris site and see if I can find the chart, which I have yet to come across.

Bob

 

[Turbulent Turtle]

Here is a link for the info at Burris:
http://www.burrisoptics.com/mounting-systems/rings/xtr-signature-rings

Once there, go to the Users Guide tab and download the XTR Signature Rings User Guide. There's a table at the bottom. It should work for all Signature rings; the suggest you measure from the middle of the ring. (You can probably also measure from front to front or back to back, just make sure it's the same place on both rings, but follow their instructions.)

You will note that 4.75 inches is the golden distance.