Point of Impact at 25 yards for a 100 yard Zero

[Old Tanker]

I have a Ruger Pricision in 6.5 Creedmoor. I’m shooting 142g SMK at 2700 fps. The factory barrel groups between .5 and .75 inches at 100 and I was able to shoot just over MOA at 1000 a couple of years ago, using a Nikon Black fx scope. On impulse, I bought a used Arken 5c 5-25x56 and thought I would give it a try. I like to start at 25, then refine at 100. The 20 MOA rail makes me think too much. What should the initial point of impact be at 25 in order to be POI = POA at 100? The scope is MOA.

 

[Rocketvapor]

To be ON @ 100 your scope axis will be pointed down by the height above bore plus bullet drop @ 100.
Lets say 1.7" above bore plus about an inch drop @ 100.

At the muzzle impact will be the height above bore of sight LOW (assume no drop), or 1.7" low.

Now, @ 25 yards; with your scope pointed down to your 100 yard zero, your impact will a quarter of the height above bore LOW (about 0.425") plus 1/4 of the drop @ 100.
A good guess would be hitting 0.7" low @ 25yds.

The JBM calculator says 0.8" low @ 25yds (3.1 MOA low) for a 100 zero.

JBM - Calculations - Trajectory (Simplified)

jbmballistics.com

OR, 25yd zero, hits 3.1 MOA HIGH @ 100.

 

[dthomas]

On most cartridges 1" low at 25 yards will have you real close at 100.

 

[SSL]

The above posts are correct. You are getting confused because of your mount. The scope adjustments and POI at 25 and 100 will remain the same. Because of its angle, the rail only gives you additional adjustment at distance. Your standard practice of adjusting at 25 and refining at 100 will work fine.

 

[p5200]

I sited my Tikka T3X Lite 6.5 creedmoor for dead on at around 23 yards. According to Hornady 10th edition the velocity should be 2600-2650. I'm shooting Lapua brass Hornady ELD-X 143gr over 40.5gr. of H4350. Should I be ok out to 100 yards also? I doubt I will get a shot near 100 yards where I will be hunting. Thanks! Target is 1" dot sighted dead center.

 

[MSS]

Cool website!

 

[SSL]

I sited my Tikka T3X Lite 6.5 creedmoor for dead on at around 23 yards. According to Hornady 10th edition the velocity should be 2600-2650. I'm shooting Lapua brass Hornady ELD-X 143gr over 40.5gr. of H4350. Should I be ok out to 100 yards also? I doubt I will get a shot near 100 yards where I will be hunting. Thanks! Target is 1" dot sighted dead center.

You probably would be fine, but I would hesitate to take shots at any distance where I hadn't tested loads to at least understand where to hold.

 

[p5200]

I think I can find a spot in the woods for 75-80 yard sight in I might try that. Thanka!

 

[Coyotefurharvester]

Zero at 23 yards impact will be HIGH at 100 yards. 3-3.5 inches depending on scope height above center of bore. Next sight/bullet intersection 240 ish yards.

 

[Link]

The above posts are correct. You are getting confused because of your mount. The scope adjustments and POI at 25 and 100 will remain the same. Because of its angle, the rail only gives you additional adjustment at distance. Your standard practice of adjusting at 25 and refining at 100 will work fine.

So would you be .5'' high at 25 to be 2'' high at 100?

 

[6MMsteve]

I have a Ruger Pricision in 6.5 Creedmoor. I’m shooting 142g SMK at 2700 fps. The factory barrel groups between .5 and .75 inches at 100 and I was able to shoot just over MOA at 1000 a couple of years ago, using a Nikon Black fx scope. On impulse, I bought a used Arken 5c 5-25x56 and thought I would give it a try. I like to start at 25, then refine at 100. The 20 MOA rail makes me think too much. What should the initial point of impact be at 25 in order to be POI = POA at 100? The scope is MOA.

inch or so low bullet impact at 25 will be close at 100, it's better to zero at 100 if you can but 25 will work and get you close

 

[p5200]

I'm guessing any shots I may get will be between 50-75 yards. Really don't need any more than I brush gun lol! Unfortunately I don't have one. I may try to get to the woods tomorrow where I think there's a spot where I can check my sighting that's between 50-75 yards. Thanks folks!

 

[p5200]

inch or so low bullet impact at 25 will be close at 100, it's better to zero at 100 if you can but 25 will work and get you close

I wonder if I should just adjust the elevation down a few clicks? It's 1/4" per click at 100 yards on this Nikon Monarch 3 4x16x42.

 

[SSL]

So would you be .5'' high at 25 to be 2'' high at 100?

All depends on load and etc. The idea is to use 25 yards to get it sighted close enough to get on paper, that's all. Then physically refine your settings at 100 yards. No guessing...actual shooting and adjusting. No shortcuts to getting it right.

 

[6MMsteve]

I wonder if I should just adjust the elevation down a few clicks? It's 1/4" per click at 100 yards on this Nikon Monarch 3 4x16x42.

If hunting I would setup targets and know where impacts are, but you have a few inches of leeway on deer.... most of all just know what the impacts are so you can have confidence when you want to make a shot

 

[Bill Norris]

So would you be .5'' high at 25 to be 2'' high at 100?

You will need to be around 1 inch low at 25 yds. in order to be pretty close zero at 100 yds. At least that is what I have seen with my rifles according to the load/speed.

 

[Rocketvapor]

Taking the JBM calculator for a ride, try the 142 SMK with about 0.6 inches LOW @ 25 yds at any velocity between 2500 and 2900fps. Sort of equates to a 50 yd zero.
There will be some variation due to environment and height above bore, but WHY is this so difficult?
Try it with YOUR bullet, and estimated velocity.
One issue with using a short range to set your scope is you need tiny little groups.

First post from middle of JUNE

 

[Ned Ludd]

For those attempting to sight in at 25 yd, just remember that the click values of the scope do not remain constant at distances of less than 100 yd. In fact, they decrease proportionally, such that a 1/4 MOA turret adjustment at 100 yd will only change the bullet impact by 1/8 MOA at 50 yd, and 1/16 MOA at 25 yd. That means you will have to twirl the turrets a lot more at distances of less than 100 yd than might be expected.

At one particular range, I used to have to sight in rifles at 25 yd to be "approved" to use the indoor 100 yd range. The shooter had to have a proof target at 25 yards for every rifle used on the 100 yd range, which required putting 3 rounds in something like a 3 or 4 inch square at 25 yd. This was not as easy at it might seem, given shooting the rifle off a narrow (front-to-back) pistol rest/table and the [large] scope turret adjustments necessary for the reduced distance of 25 yd. I eventually got smart and simply put out a 12" Shoot-N-C target, fired a couple shots, reeled the target carrier back in and then pasted up the test square target directly over the bullet holes and used the original point of aim to shoot the test target. The reduction in turret adjustment (click) value at distances less than 100 yd can mess with your head if you're not aware of it.

 

[whatsupdoc]

For those attempting to sight in at 25 yd, just remember that the click values of the scope do not remain constant at distances of less than 100 yd. In fact, they decrease proportionally, such that a 1/4 MOA turret adjustment at 100 yd will only change the bullet impact by 1/8 MOA at 50 yd, and 1/16 MOA at 25 yd. That means you will have to twirl the turrets a lot more at distances of less than 100 yd than might be expected.

At one particular range, I used to have to sight in rifles at 25 yd to be "approved" to use the indoor 100 yd range. The shooter had to have a proof target at 25 yards for every rifle used on the 100 yd range, which required putting 3 rounds in something like a 3 or 4 inch square at 25 yd. This was not as easy at it might seem, given shooting the rifle off a narrow (front-to-back) pistol rest/table and the [large] scope turret adjustments necessary for the reduced distance of 25 yd. I eventually got smart and simply put out a 12" Shoot-N-C target, fired a couple shots, reeled the target carrier back in and then pasted up the test square target directly over the bullet holes and used the original point of aim to shoot the test target. The reduction in turret adjustment (click) value at distances less than 100 yd can mess with your head if you're not aware of it.

That is not correct 1 MOA is the same angular measurement at 100, 50 or 25 the problem is you are thinking
it is a linear measurement.

 

[Ned Ludd]

That is not correct 1 MOA is the same angular measurement at 100, 50 or 25 the problem is you are thinking
it is a linear measurement.

I get that. But you might be surprised how many shooters do not have that solid a good grasp on angular measurements versus linear measurements. My suggestions was for those folks because the number of "clicks", in other words, the amount of linear distance at the target face, changes as the distance decreases below or above 100 yards. So what I stated is spot on. Not everyone that might try to sight in at shorter distances may know or recall that one MOA subtends an arc of 1.0472" at 100 yd, but only 0.5236" at 50 yd, and 0.2618" at 25 yd. My point was that moving the POI a given linear distance on the target face at 50 yards requires twice the number of "clicks" it would at 100 yd, and at 25 yd would require four times the number of "clicks" necessary at 100 yd.