sight in question...I should know this

[born to hunt]

Sighting in 300 WSM using barnes 168TTSX at a muzzle velocity of 3080 fps. The rifle is a Tikka T3 stainless with a Leopould VX3 4.5-14 scope. How do I know where the "zero" is on the rifle? I'm trying to get correct ballistics info.

Here's what I have now: My point of impact is 3.7 inches high at 100 yards, (sub MOA, as a 5 shot group is .75"). How do I calculate what it will do at 200-500 yards? Some ballistic calculators say the slug is still travelling upwards at 200 yards, (I assume they base that on rifle angle?)

Just looking for the best way to figure out point of impact at various ranges given being over 3" high at 100 yards.

Thanks!

 

[primalmu]

Why do you assume those ballistics programs use any sort of angle?

I think what you are really asking is how to figure out what range your POA = POI when you are hitting 3.7" high at 100 yards. Your "zero" is really dependent on where you set your scope. Are you wanting to zero your scope at the apex of the bullet's flight path? If so you will have only one zero point. If you want to zero at, say, 100 yards, you'll actually have 2 zeros where your POA = POI.

 

[Float Pilot]

Your rifle is currently zeroed at around 320 yards.

 

[born to hunt]

Primal MU- I assume that because the program states the bullet is still travelling upward at 200 yards, and that cannot happen unless the rifle is "angled" upwards. You bring up a great point...Thank you for phrasing my question better than I did. It would be nice to know how to deterine the Apex of my bullet's path. AND...make sure the rifle is not a POS.

Good luck with vet school!

 

[Art Eatman]

What I've come to, through the years, is to sight in for around two inches high at 100 yards. Your rifle, that ought to be dead on around 225 to maybe 250. I'd guess maybe right at four inches low at 300 or a tad beyond that.

 

[readyeddy]

If you want your Maximum Point Blank Range (MPBR), then sight in 2.74" high at 100 yards. This will place you +2.91" at 130 yards and -2.56" at 280 yards.

If you want to verify, do a search on "ballistic calculator" and input your data. Sight in at 240 yards and the ballistic coefficient for your bullet is 0.470.

 

[adelbridge]

How tall are your scope rings? Altitude and temp are going to be factors past 300 yards as well.

 

[born to hunt]

The reticle is about 1.5" above the muzzle....roughly.

 

[Resist Evil]

As you already are aware, every launched bullet travels in an arc. I zero my scope to 200 yards which roughly translates to two inches high at 100 yards. This means that when I hold the crosshairs on the target's center placed 100yds away and shoot carefully, my bullet will make a hole nearly two inches above where I was aiming. This translates to hitting dead on center while aiming on center, if I'm doing my part, at the desired 200 yard distance.

Now you might think you are shooting flat, but the scope/sight to barrel relationship is rarely parallel. Also, part of the relationship between scope and barrel is influenced by the power of the cartridge and the weight and shape of the bullet.

 

[born to hunt]

Well, my reload is where I want it in terms of velocity and MOA. I'm gonna leave mine zeroed at 300, which is 3.5" high at 100, zero at 300 and 10" down at 400. That's easy math for me and should work with my reticle set up.

Now I just need to keep in powder and primers. Hope an elk walks out at 20 yards...

 

[Geno]

born to hunt:

Here is a fantastic, easy-to-use website that will tell you the trajectory, velocity remaining, energy, drift, etc. for wherever you set your zero. Handloads (dot) com, Ballistic Calculator:

http://handloads.com/calc/index.html

Just enter the caliber as .308, and the other requested info. Per your info, you are zeroed at about 320 yards.

When I input your indicated data, it also shows, that this load's impact is 5.18 inches high around 180 yards. From what I was taught, that's excessive. I was taught to keep the bullet rise above the point of zero to less than 4 inches. You could achieve this either by increasing the load's velocity, or by backing the zero down to 290 yards. It also indicates that the load at 350 yards is 2,424 FPS, and impact is -2.49 inches. The data indicate the following at 400 yards: 2,339 FPS and impact is -7.84 inches.

Tinker with the website. There are other sites that are far more comprehensive, but I like the simplicity of this site.

Geno

 

[born to hunt]

Geno-

Thanks for the heads up. It's a good website. I just need to learn a lot and shoot more. Theory is fine to me, but I've only put about 200 rounds through the rifle, 300 yards max. I'll validate what the website says with real data.