7 mm trajectory ?

azbow · Jan 25, 2008

I hope someone can help me on this one. I have a 7 mm Rem mag shooting 140 gr Nosler partitions through a 26" barrel with 65 grs of R22 . Not sure of the speed. I have B&C crosshairs and have the main crosshair is on at 200 yds, the second crosshair is on at 300 yds. The third crosshair is 7" high at 400 yds and I don't have a place to shoot it farther to see where the bullet will drop back down to this crosshair. Does anyone have a way to determine the distance where this would be?
(There is yet another crosshair in the scope but have no idea where it would also be zeroed.)

HuntElk4Fun_ · Jan 25, 2008

LAST EDITED ON Jan-25-08 AT 06:20PM (MST)[p]I contacted Leupold with all my information and my zero and they told me where each of my "crosshairs and posts" were in relation to yards with the B&C reticle. I would bet if you gave them your info, they could tell you. Better yet, get your load chrono'd, send the info and they will tell you each crosshair exact. It's awesome!

ODDNUT1
Kirt C.

mtmuley · Jan 25, 2008

First, I'm pretty sure your velocity is 3200 fps, give or take a few fps. Have you verified on paper that the main aiming point is spot on at 200 yards? Also, do you know your line of sight at 100? I can run Sierrra Infinity, but it helps to know where the bullet impacts at 100 yards. mtmuley

azbow · Jan 25, 2008

No, I don't know where it is at 100 yds. Never thought about contacting Leupold either. Thanks for your help.

completesportsman · Jan 26, 2008

Your owners manual will tell you how many MOA of drop for each crossbar with a 200 yd zero. Then if you know your velocity you can get mtmuley to run the infinty program for you or go to Hornady.com and use their ballistics calculator. Its pretty close too. It will tell you your MOA drop with a 200yd zero for every 100 additional yards.

canhunter · Jan 27, 2008

IMO your only guessing until you get a true chronographed speed. Get the true fps then start. I would run my Oehler also if you get me the fps.

SilenceBreaker · Jan 29, 2008

I have the scope and a 7mm. I just went out put a target up at 100 yards and sighted in at about 1.5 inches high. I then practiced at 200, 300, 400, 450, and 500 yards and adjusted my scope until I found a happy medium. Take a big peace of cardboard and a paper plate and figure out where its hitting. You may have to adjust your zero to achieve a decent average through out the ranges. I know you can call and get tech info that will speed up the process, and it is hard to find a place where you have enough room to do this. But I like to shoot and think its good practice.

azbow · Feb 1, 2008

OK , got the rest of the info.
140 gr nosler partition through a 26" tube.
3180 FPS at 40 degrees this morning(you were almost right on mtmuley)
100 yds it is 3" high of top crosshair
200 yds it is 1" low of top crosshair
300 yds is right on second crosshair
400 yds it is 7" high using third crosshair.
Again, at what distance will the bullet be zeroed at the 3rd and possibly the 4th crosshair?
Looks like a math homework assignment huh?

azbow · Feb 4, 2008

I called Luepold and didn't get what I was looking for. They said to start with the top crosshair at 300 yds and go through a differant procedure to get the crosshairs to fit the trajectory. I don't have the time or ammo loaded to start over, as I am leaving Monday for a hunt.
Hope someone can run their programs for me to get at least very close to where the 3rd crosshair will be on the mark.
Thanks

completesportsman · Feb 5, 2008

LAST EDITED ON Feb-05-08 AT 10:32AM (MST)[p]This should get you very close, I personally would load more ammo and check at all distances if I were going on a hunt, even if it meant staying up all night loading ammo, but thats up to you.

The cross bars in your scope are as follows according to the owners manual.
top cross = zero
2nd cross = -2.19moa
3rd cross = -4.80moa
4th cross = -6.26moa
top of post = -7.82moa

Your load should be as follows with a 300yd zero and a sight height of 1.5in (should be close if you have a 50mm scope) and at 40 degrees according to Hornadys ballistics calculator.
300yd = zero
400yd = -2.3moa
500yd = -4.9moa
550yd = -6.4moa
600yd = -7.9moa

Not dead nuts but really close. If I were you I would go back and zero your top cross at 300yds. It shouldn't take more than three or four shots to zero your gun again and you should be good to go holding each cross dead on at the given yardage on big game animals. Again I would want to check and be sure. In warmer temps you would have less drop at each distance and be closer to being dead nuts on.

If anyone sees anything wrong with my information please correct me, I don't want to be blamed for missing out on a chance at a trophy!
Just kidding, have a good hunt and good luck.