100 yard zero @ 25 yards?

[CK_32]

Does anyone know the process to what they call "hunting or field" zero your rifle at 25 yards for 100?


I remember a WHILE back I quick read an article on the way to do this and I remember they had a supplied target with impact adjustments for 5.56 and 308 loads. But never thought of it because I've always just gone to the 100 yard range to zero. But I just got finished with my MK11/M110 LR308 build and this will be my comp gun and my local matches don't allow you to zero before the matches to make time.

I won't be able to make it to any 100 yard ranges before the next match and am limited to 25 yard indoor ranges. So does anyone know the process on doing this? Yea I know it's not 100% zero but it's on paper which is all I need till I can full zero this thing.


I've already ran my load work up through JBM ballistics. It's a 168gr pet load.

JBM says for a 100 yard zero:

25 yards - -1.8" or -.5 mil (for elevation scope adjustments)

100 yards - 0.0" or 0.0 mil

So does this mean at 25 yards I set an center point with a center dot 1.8" high or 1.8" low of my point of aim and have my POI be that? Cause I know 5.56 and 308 have different flight patterns from 25-100 and I'm just having a brain fart figuring out what I need to do for this.

 

[Handloader]

Set your impact LOWER than your point of aim (.5-1.5in depending on your zero) at 25 yards. I.e. you aim at the bullseye at 25 yards and the bullets hit lower than the bullseye.

 

[Graham]

100 yard zero @ 25 yards?

Set your impact LOWER than your point of aim (.5-1.5in depending on your zero) at 25 yards. I.e. you aim at the bullseye at 25 yards and the bullets hit lower than the bullseye.

Are you sure about that? If you are, can you explain why?

It sounds like you are saying to aim low, but you are actually saying to aim high. Which one is it and why?

Is there a reason you do not advocate dialing the appropriate amount of correction and setting POI to POA? Is it to set a 100 yard zero on the optic?

 

[Gunfighter14e2]

A scoped weapon (within reason) that is zeroed for 100yds will always shoot between 0.5-1.5" low at 25 yds,... mechanical off set. My off set knob setting for my 700 in .308 is 3.5IPHY, at 25 yds ... the 300with a 58mm USO is 4.5IPHY, same yardage.

 

[Graham]

A scoped weapon (within reason) that is zeroed for 100yds will always shoot between 0.5-1.5" low at 25 yds,... mechanical off set.

Then why am I dialing over 4 MOA?

 

[Gunfighter14e2]

Your 4 moa is ruffly 1" at 25 yds

 

[mosquitoshooter]

Are you sure about that? If you are, can you explain why or did you make it up?

It sounds like you are saying to aim low, but you are actually saying to aim high. Which one is it and why?

Is there a reason you do not advocate dialing the appropriate amount of correction and setting POI to POA? Is it to set a 100 yard zero on the optic?

It doesn't appear to me that handloader is saying either of what you are suggesting. He is correct in that if your point of aim or crosshairs are pointing on a bullseye at 25 yards, then the actual impact of the bullet should be low by about 1.8 inches "or so". So, at 100 yards once the bullet is higher in the arc it will be dead on at 100. The exact measurement varies by gun and how the optics are mounted, etc. remember the guns barrel is technically pointing up. And the intersection of the arc of the bullet and point of aim is 100 yards. Therefore, anything less than 100 yrds should shoot low.

Another way you can do it is just hit the bullseye at 25 yards and click the scope "down" 1.8".

 

[mosquitoshooter]

Then why am I dialing over 4 MOA?

4 moa seems about right. If you didnt click it down 4 moa and shot at a target at 100 yards, it would impact around 4 inches high. Thus 4 moa correction is needed

 

[Graham]

100 yard zero @ 25 yards?

I know the answers. I am looking for the explanations. Gunfighter had it right. Handloader is not wrong, but his directions are confusing without explanation.

 

[Handloader]

Graham,
The Arc of the bullet will pass through the crosshairs around mid-30 yards as the bullet climbs with respect to the scope. Then the bullet will cross through the crosshairs again around 100 yards on the down aside of the bullet flight arc.
Your 4 MOA moves your bullet about 4 inches at 100 yards, but as it is an angle, as you get closer to the point of origin the unit of measure gets smaller. So at 25 yards, 4MOA only moves the impact about 1inch


Sent from my DROID RAZR using Tapatalk

 

[Graham]

100 yard zero @ 25 yards?

Graham,
The Arc of the bullet will pass through the crosshairs around mid-30 yards as the bullet climbs with respect to the scope. Then the bullet will cross through the crosshairs again around 100 yards on the down aside of the bullet flight arc.

Handloader, you were correct the first time.

The 100 yard elevation zero is made up of two parts: Compensation for bullet drop from muzzle to 100 yards; and the mechanical offset of the line of sight over the line of bore.

With a .308 the bullet drop is about 2.7 inches. Assuming a sight height of 1 3/4 inches, at 100 yards that's about 1.7 MOA. Add them up: 4.3 MOA.

So, if you zero at 100 and then shoot at 25 you will have to hold 4.3 MOA high at 25 to make the POI equal the POA.

If you want to place a 100 yard zero on your rifle, but are accomplishing that at 25 yards, your POI at 25 yards should be 4.3 MOA (about 1.1") lower than your POA.

 

[Gunfighter14e2]

Cause I know 5.56 and 308 have different flight patterns from 25-100 and I'm just having a brain fart figuring out what I need to do for this.

Flight paths are about the same, both drop approx 4" from bore ctr line. Many folks get confused when the mechanical off set is taken into account, this is why on a 25yd M14/M16 BSZ target there are two impact areas indicated. One for the 14 with a low mechanical off set and one for the 16 which has high off set.

 

[Gunfighter14e2]

Graham,
The Arc of the bullet will pass through the crosshairs around mid-30 yards as the bullet climbs with respect to the scope. Then the bullet will cross through the crosshairs again around 100 yards on the down aside of the bullet flight arc.
Your 4 MOA moves your bullet about 4 inches at 100 yards, but as it is an angle, a you get coder to the point of origin the unit of measure gets smaller. So at 25 yards, 4MOA only moves the impact about 1inch


Sent from my DROID RAZR using Tapatalk

Must be my sticks operate differently. My .308(175smk) crosses at 76 yds and recrosses again at 123 yds. (+/- 0.050). At 50 yds I still have to dial 1.5 (0.75")with the .308

 

[Handloader]

The 100 yard elevation zero is made up of two parts: Compensation for bullet drop from muzzle to 100 yards; and the mechanical offset of the line of sight over the line of bore.

With a .308 the bullet drop is about 2.7 inches. Assuming a sight height of 1 3/4 inches, at 100 yards that's about 1.7 MOA. Add them up: 4.3 MOA.

So, if you zero at 100 and then shoot at 25 you will have to hold 4.3 MOA high at 25 to make the POI equal the POA.

If you want to place a 100 yard zero on your rifle, but are accomplishing that at 25 yards, your POI at 25 yards should be 4.3 MOA (about 1.1") lower than you POA.

So...using Graham's example, a quick field zero at 25 yards........when your crosshair is on the bullseye, and your bullets are hitting 1.075in lower you are darn close to a 100 yard zero.

 

[Graham]

100 yard zero @ 25 yards?

The problem is to accurately determine .1 inches at 25 yards when you are printing .308 caliber holes at that distance.

 

[Handloader]

The problem is how to accurately determine .075 inches at 25 yards when you are printing .308 caliber holes at that same distance.

Bottom line is....you can't (or I can't). I always go back to my 100 yard bench (I have my own range), and dial it in. I very rarely do a 25 yard zero. Truth be told, I only do a 25 yard zero if I am really low on bullets.

As for my semi 5.56, I keep them all at a 200 yard zero. The Bolt 223, I zero at 100 and dial from there,

 

[CK_32]

Thanks for the in-depth responses. So my thinking was correct that it should land 1.8" low.


For the guys wondering the MOA adjustments. 1 MOA is 1" @ 100 yards. So now that you are at 25 yards your at 1/4 the distance making your adjustments per click 1/4 the value. So 1 MOA adjustment is now 1/4 the value relative to the target. So your 4 MOA at 25 yards is equal to 1 MOA at 100. Same logic that 1 MOA @ 300 yards is 3" instead of 1".


Found this to help others understand how this works.

 

[Graham]

100 yard zero @ 25 yards?

Handloader,

Add scope adjustment issues, that 4 MOA at 25 yards with a scope that adjusts in 1/4 MOA adjustments is 64 adjustments, and it becomes very hard to place a 100 yard zero by shooting at 25 yards.

 

[Graham]

100 yard zero @ 25 yards?

For the guys wondering the MOA adjustments. 1 MOA is 1" @ 100 yards. So now that you are at 25 yards your at 1/4 the distance making your adjustments per click 1/4 the value. So 1 MOA adjustment is now 1/4 the value relative to the target. So your 4 MOA at 25 yards is equal to 1 MOA at 100. Same logic that 1 MOA @ 300 yards is 3" instead of]

That is incorrect. 1 MOA is 1.047" at 100 yards. You are off by 5%.

 

[CK_32]

That is incorrect. 1 MOA is 1.047" at 100 yards. You are off by 5%.

Ok ROUGHLY 1" @ 100 yards. I didn't think we were being exact.

 

[Graham]

100 yard zero @ 25 yards?

Ok ROUGHLY 1" @ 100 yards. I didn't think we were being exact.

You are posting on a precision shooting website..... about zeroing a rifle.

With a .308, the difference at 1000 yards between using MOA and IPHY adjustments is twenty inches. Even if you limit your effective range to 500 yards, if you ignore that difference you will miss your target.

 

[Gunfighter14e2]

off by 0.9551098376313276 the product of 1 divided by 1.047. Which in the math world I was taught would round to 4.5%. Odd down, Even up, hence down a 1/2 point. Won't make a big splash while shooting, but ranging is another thing.

 

[RobertB]

This is too complicated for the guy. OP make the bullet hit about an inch to 1.5" low at 100 from where your crosshairs are. If you don't have a 100 yd range you will NEVER be sure that it is right anyway. But that should get you close. Your scope is higher than your barrel so you need to make that about the same. That SHOULD put you on paper at 100. Maybe not ripping the center out of the bullseye but close.

Good luck. Keep us posted. There is NO shortcut with precision shooting. You have to confirm everything, your zero must be confirmend as well as your MV. Chronograghs will get you close but you need to verify with actual shooting at distance.

 

[Dave in Idaho]

My dope book lists my 25 yd zero as +2.25 MOA.
So if a situation dictated that I reset a 100 yard zero using a 25 yd zange I would do thus:
Fire and adjust until I had perfect hits at 25 yds. I would then reset my elevation knob to +2.25 MOA and call it good.
My 25 yd verification rounds and reset to 25 yd dope should put me very close to previous zero at a 100yds.
In every instance I would prefer to verify at a 100 with shooting, not previous data. But not always possible.
Dave

 

[HANDYMAN]

I find that with standard height sights (2.5" above bore) on my AR's that if my bullet impacts 1.25" low at 25yds I'm dead on at 100.

 

[CK_32]

I find that with standard height sights (2.5" above bore) on my AR's that if my bullet impacts 1.25" low at 25yds I'm dead on at 100.

What loads are you shooting? My scope center line is roughly 2.77 from the center of the bore.

I'm shooting 168 SMK and Amax's roughly 2550 FPS from an 18" 1:10 gas gun.

 

[HANDYMAN]

The info I listed for mine is for 5.56 but your load with the BC of SMK's should be damn close with in a couple inches. According to my Ballistic calc with the info you gave you want to be exactly 1.5" low at 25.

 

[azimutha]

The info I listed for mine is for 5.56 but your load with the BC of SMK's should be damn close with in a couple inches. According to my Ballistic calc with the info you gave you want to be exactly 1.5" low at 25.

Yeah, with that much sight height, that'd be about right.

 

[CK_32]

The info I listed for mine is for 5.56 but your load with the BC of SMK's should be damn close with in a couple inches. According to my Ballistic calc with the info you gave you want to be exactly 1.5" low at 25.

Yeah, with that much sight height, that'd be about right.

I imputed my loads specs into JBM ballistics at 60 and 95 F for my indoor range temp and when I shoot the desert and the data card it gave me was -1.7" POI and at 95 it said 1.7" POI. So yea about 1.5 to 1.7 should be expected. Im going to split the difference of your and JBM's data I got and aim for a 1.6" low POI. Hopefully should at least get me on paper at the match then let me make adjustments accordingly and run with it from there.

 

[samnev]

What loads are you shooting? My scope center line is roughly 2.77 from the center of the bore.

I'm shooting 168 SMK and Amax's roughly 2550 FPS from an 18" 1:10 gas gun.

My NF NXS 8-32X56 scope is about the same height above the bore axis. I also shoot 168 SMK @ ~ the same velocity. My AIAW shoots 1.5 " low at 25 yards and dead on @ 100 yards.

 

[tipper]

Does anyone know the process to what they call "hunting or field" zero your rifle at 25 yards for 100?


I remember a WHILE back I quick read an article on the way to do this and I remember they had a supplied target with impact adjustments for 5.56 and 308 loads. But never thought of it because I've always just gone to the 100 yard range to zero. But I just got finished with my MK11/M110 LR308 build and this will be my comp gun and my local matches don't allow you to zero before the matches to make time.

I won't be able to make it to any 100 yard ranges before the next match and am limited to 25 yard indoor ranges. So does anyone know the process on doing this? Yea I know it's not 100% zero but it's on paper which is all I need till I can full zero this thing.


I've already ran my load work up through JBM ballistics. It's a 168gr pet load.

JBM says for a 100 yard zero:

25 yards - -1.8" or -.5 mil (for elevation scope adjustments)

100 yards - 0.0" or 0.0 mil

So does this mean at 25 yards I set an center point with a center dot 1.8" high or 1.8" low of my point of aim and have my POI be that? Cause I know 5.56 and 308 have different flight patterns from 25-100 and I'm just having a brain fart figuring out what I need to do for this.

This is the truth, if you need to ask this question then you need more time on the range before you enter any comp matches, The End

 

[CK_32]

This is the truth, if you need to ask this question then you need more time on the range before you enter any comp matches, The End

You do realize competition isn't all about winning and being #1 seed right?


Your statement is like saying if your not over seas you don't need a firearm to begin with.

But I'll gladly post my seatings with my $2,500 308 set up against, $6,500 rigs shooting 6.5 just for you

 

[LtDan]

Handloader,

Add scope adjustment issues, that 4 MOA at 25 yards with a scope that adjusts in 1/4 MOA adjustments is 64 adjustments, and it becomes very hard to place a 100 yard zero by shooting at 25 yards.

64 adjustments on a scope with 1/4 MOA adjustments is 16 MOA of adjustment. 4 MOA at 25 yards is 16 "adjustments", same as 100, 500 and 1000 yards, but value of a MOA changes with the distance.

Using 25 yards to obtain a 100 yard zero (rough zero) is a viable tool, we use it often and it is very simple. Law officer magazine did a nice write up on it and have a down load AR-15/M-16 Sight In Target for getting a 100 yard zero on a 25 yard range.
Long Gun Zero - Tactics and Weapons - LawOfficer.com

 

[Graham]

100 yard zero @ 25 yards?

64 adjustments on a scope with 1/4 MOA adjustments is 44 MOA of adjustment. 4 MOA at 25 yards is 16 "adjustments", same as 100, 500 and 1000 yards, but value of a MOA changes with the distance.

With apologies to Gertrude Stein: An MOA is an MOA is an MOA.

And I am not familiar with the term 'rough zero'.

 

[vinsonr]

Using 25 yards to obtain a 100 yard zero (rough zero) is a viable tool, we use it often and it is very simple. Law officer magazine did a nice write up on it and have a down load AR-15/M-16 Sight In Target for getting a 100 yard zero on a 25 yard range.
Long Gun Zero - Tactics and Weapons - LawOfficer.com

With iron sights or using standard CCO type optics and known mount heights and ammo. Nobody's data will be exactly like OP's for his weapon/sight/ammo combo.

 

[LtDan]

From the article I referenced:

0 3,000 -2.5
25 2,901 -1.47
50 2,805 -0.7
75 2,712 -0.2
100 2,620 0
125 2,530 -0.12
150 2,441 -0.57
175 2,353 -1.39
200 2,264 -2.6
250 2,093 -6.33
300 1,930 -12.05
*assumes a .223 caliber, 55 grain, full-metal jacket bullet

 

[vinsonr]

From the article I referenced:

0 3,000 -2.5
25 2,901 -1.47
50 2,805 -0.7
75 2,712 -0.2
100 2,620 0
125 2,530 -0.12
150 2,441 -0.57
175 2,353 -1.39
200 2,264 -2.6
250 2,093 -6.33
300 1,930 -12.05
*assumes a .223 caliber, 55 grain, full-metal jacket bullet

Yeah, OP is shooting .308. My semi-auto .308 is 7.1MOA up for hits at 25 yards with a 100 yard zero.

 

[LtDan]

Vinsonr, Truth.

The target and data available for download assumes 2.5 inch bore to sight differential. Data is easily adjusted if you know what your particular situation is. And it's good for a rough 100 yard zero even if you don't know exactly what your bore-scope/sight difference is to an exact degree.

 

[LtDan]

Yeah, OP is shooting .308. My semi-auto .308 is 7.1MOA up for hits at 25 yards with a 100 yard zero.

7.1 MOA at 25 yards is 1.775 inches, not very far off from the 1.47 referenced in the 223 data table.
The target on the article I referenced would get you a good rough zero at 100 with your 308, definitely "minute of deer".

 

[Rob01]

Wow this thread went totally sideways for a very simple question. LOL

 

[Graham]

100 yard zero @ 25 yards?

The target on the article I referenced would get you a good rough zero at 100 with your 308, definitely "minute of deer".

Is that the same as roughly 44 minutes of duck?

 

[CK_32]

Wow this thread went totally sideways for a very simple question. LOL

Welcome to Internet forums.


90% of the time, it happens a everytime.

 

[Rob01]

Welcome to Internet forums.


90% of the time, it happens a everytime.

Thanks. I'm new to these places

 

[LtDan]

And I am not familiar with the term 'rough zero'.

Gets you on paper at 100, close to a precise zero. I'm sure you guessed that.

 

[Graham]

100 yard zero @ 25 yards?

Gets you on paper at 100, close to a precise zero. I'm sure you guessed that.

'On paper' is not a zero. Not even close.

 

[LtDan]

Never said it was. Didn't mean to upset you by pointing out 66 adjustments was not 4 MOA at 25 yards. That would NOT put you on paper at 100. No need to spend a lot of keyboard time trying to Graham it up my ass.


"I won't be able to make it to any 100 yard ranges before the next match and am limited to 25 yard indoor ranges. So does anyone know the process on doing this? Yea I know it's not 100% zero but it's on paper which is all I need till I can full zero this thing."

I was simply trying to assist the OP.

 

[Graham]

100 yard zero @ 25 yards?

Didn't mean to upset you by pointing out 66 adjustments was not 4 MOA at 25 yards. That would NOT put you on paper at 100. No need to spend a lot of keyboard time trying to Graham it up my ass.

No worries. I'm not upset. No need to call names.

I retread what I posted and I was mistaken: 4 MOA is 4x4 adjustments. I think I posted 64, not 66, but I was using a linear unit of 4" at 25. Didn't proofread. Sorry.

However, the value of an MOA does not change with distance, which is what you posted. On a scope that has 1/4 MOA adjustments, four adjustments equal one MOA. One MOA is one MOA. That doesn't change with distance.

And 64 adjustments would, even with my math error, only put him about 2" away from where he wanted to be, which would have been 'off the paper' only if the paper was very, very small... Because MOA doesn't change with distance.

 

[LtDan]

This is really going off in the weeds.
The value (measurement) of 1 MOA does change with distance. The number of "adjustments" required to change one MOA does not.
4 MOA at 25 yards is 16 "adjustments" on a 1/4 moa turret. You stated it was 64. That is 16 MOA, not 4 and if you set a rough, field, hunting (not precise) zero 11 MOA at 25 yards you are more than off the paper at 100.
Your "linear unit at 4 inches" reference?

If you reread, it's all there. Not interested in derailing the thread any further, you made a simple mistake, just let it go.

 

[Graham]

100 yard zero @ 25 yards?

And it would have been off the paper at 200, and 300... Except that he was shooting at 25 yards.

I admitted and explained my mistake. No need to try to capitalize on it and make it more than it was.

MOAs don't change. The linear value of one MOA increases at distance because an MOA is an angular measurement.

I remain unfamiliar familiar with the term 'rough, field, hunting' zero.

 

[RobertB]

Rough zero means it aint as good as it should be, and it always should be as good as it can be, and it can always be better than it was, and it was better than it is, and it is better than it could be, and it could be better than me, but it aint.