Need help figuring out ZERO distance

[deerassassin22]

Okay I'm not a precision rifle shooter but have a question regarding Zeroing. In the Army some guy came up with the 37.5 meter zero being used in CARTC which is more accurate then the 25m zero to get your center mass at 300 anyhow. I have a SCAR 17 .308cal and want to zero my aimpoint using this same method how do I figure out the distance? I have my data below.

Scar 17 COAL 2.800 using RL15 45grs. AVG Velocity 10ft from chronograph 2457fps ELEV 560ft.

Same data as above but fired THROUGH my chronograph at 100yards AVG VELocity 2328 ELEV 560ft TEMP was 66F Humidity 90% Pressure 29.84

Any assistance would be much appreciated.

[Amerflyer48]

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

set for your current zero and keep playing with intermediate points until you get what you are looking for distance wise then reset zero to new distance and you will have your +/- for your current distance which once reset should give you the new zero basically you are pushing the trajectory curve further away so you should be low @ 25m to zero at 37.5m as you should still be rising from bore line to line of sight.

of course you should shoot it at the new zero distance to verify

[a.roberts]

Easiest way is to use JBM, then click the box for "Zero at Max. Point Blank Range."

It'll spit out the distance you should zero at.

[KTKlaus]

Zeroing really depends on both the rifle and loads. I also beleive its not about accuracy but more or less DOPE, effective zone, apexes and/or holdovers (as link below explains a few). I also have a belief that no one zero is better than the other (much like in the video). For example; depending on my rifle and loads, it depends if I will use the 36yard/300yard Marine Corps zero on my more tactical rifles (my backgorund as an FMF Corpsman) or a 50/200 yard zero on my competition rifles (for my AR15 and AR10 platforms). A ballistic app/software does aid in this as well. (I have a andriod phone), I have the Strelok+ ap which has been very accurate. On my computer I us the JB applications and aids as mentioned above. Do not just trust those apps and calculators entirely though, always go out to the range and confirm it.

Your load data that you have given us is missing a few things. Weight of bullet, style of bullet, ballistic coefficient, height of scope over bore, angle of mount (if it have one like a 20MOA built in), etc.

Granted I came from a military background, I found this video pretty helpful when it came down to all my rifles zeros:

http://www.youtube.com/watch?v=2Nzv8unkmJo

Edited August 20, 2013 by KTKlaus

[Pinecone]

What are you trying to accomplish?

How do you plan on using the rifle?

What are you using it for?

What scope reticle? (can you easily use hold over/under)

[jaredr]

What are you trying to accomplish?

How do you plan on using the rifle?

What are you using it for?

What scope reticle? (can you easily use hold over/under)

believe these are the questions you want to ask first, and then you can determine what is the optimal zero for your rifle based (in large part) on what range(s) you expect to be shooting at and the external ballistics of the rifle and ammo.

For example, if you're going to be taking your SCAR to a carbine course or other course of fire where your targets will be 25-100 yards, you mght do well with a 50 meter zero which puts you more or less dead on from 0 to 150 yards (actually 1.8" down at 150 but that's beyond my level of precision from field positions).

Now you can shoot 50 - 100 yard targets with a 400 meter zero, but remembering to constantly hold 3 mils over every target is (for me, anyway) a bit of a challenge. might be worth using one of the online ballistic calculators and playing around a bit to see what kind of holdovers you have from zeroing at different ranges.

[Pinecone]

Exactly.

JBM calculator allows you to put in a vital zone and then as mentioned, will give you the zero range and the maximum point blank range.

That means for that for a given size target, if you zero at the specified range, the bullet will hit the target out to the maximum point blank range (if you do your part).

So for my .308 load (bolt gun, 175 SMK at 2600 FPS), for a 10" diameter target, I would zero at 275 yards and the bullet would hit within 5" of my point of aim (higher closer than 275, low longer) out to 325 yards. Based on the data, if I had only a 100 yard range, I would set the scope to shoot 4.1" high at 100 yards.

With a good reticle, I could hold over or under if needed.

[Hello]

That was a great video!

Thank you,