Looking for help with MOA

[drahthaar]

I have been reading about scopes. Adjustable turret 1/4 MOA, 1/2 MOA, 1 MOA.

Does anyone know a site or have a good link to how these scopes "work". Say I have a 1/4 MOA adjustable turret scope, say your rifle is sited in dead nuts at 100 yard zero.

Now you range a target at 300. How many "clicks" is that? I seriously can't find a good explanation to figure this out?

I am just lost on this? Obivously different calibers, bullets, etc will affect this.

Do you figure out how many clicks "at the range", then make yourself a card for your stock?

And yes, I know you can just get the CDS system with the actual yardage, but I want to know how the MOA system works.

So any good link would help. I just can't seem to find one.

 

[belly-deep]

1 MOA is a hair over 1 inch at 100 yards. And so a scope with 1/4 MOA turrets would move the crosshair 1/4 at 100 yards.

As distance gets longer, a MOA covers more space. For example, when distance doubles to 200 yards, the size of a MOA doubles as well, so now your 1/4 MOA turret would move a little over 1/2 inch per click.

To calculate drop at 300 yards with a 100 yard zero, you would first consult ballistics charts or a computerized ballistics calculator to find your bullet drop. Say its 12 inches. You would then convert it to MOA. Since 1 MOA is a bit over 3 inches at 300 yards, it would take 4 MOA of adjustment to put your crosshairs on the impact point. You would then adjust your 1/4 MOA scope accordingly, which would be 16 clicks.

Clear as mud?

 

[cowboy]

Probably the best way for you to start understanding "how many clicks" it takes, is to use one of the free ballistic programs on the internet. What you need to know is what your rifle/ammo combo velocity is, your altitude you are shooting at, bullet you are using etc. If you are not familiar with a ballistic program send me a PM and I'll get you a couple free web sites that have them.

You plug your data in and there is what comes up as a "drop chart". Look it over and it will tell you how many clicks you need sighted in at 100 and shooting at 300.

None of this is a one size fits all. Sight in at sea level and shoot at 6000 ft. and your old drop chart is no good.

If you can't figure it out send me a PM with the caliber, barrel length, type of ammo and the elevation you are going to be shooting at and I can run the numbers for you.

PS: Belly types faster than I do.

 

[jryoung]

Typically you need to determine your rifles ballistics for your load (velocity, BC, sight in height, avg temp, avg barometic presure, et. etc.) You can run these numbers through a ballistics calculator and it will give you the MOA at select intervals.

It could be
3 moa @300 (12 clicks, 1/4MOA = 4 clicks per MOA)
7.5moa @600 (30 clicks)

Make a cheat sheet and put it on your stock, then you'll know how many clicks based on your rifle and your load. Then go out and test it and confirm, once confirmed, test again.

 

[KRasmussen]

http://www.youtube.com/watch?v=VA2PZBD5Tjg

 

[Carl]

I'll pick an example so we have some numbers to work with.

Below are numbers for a 165gr Nosler Accubond at 2900 fps, standard atmospheric conditions except at 5000 ft elevation. (30-06 ish velocity, though the numbers will be the same as long as the velocity is the same, regardless of chambering)

I got these numbers from JBM's Ballistic Calculator: http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

Since the numbers are already in MOA, there is no need to convert from inches of drop to MOA. If you wanted to anyway, the formula should be MOA = ( drop in inches * ( 100 / range in yards ) ) / 1.047 unless my brain was feeling dyslexic today.

(can't seem to get them spaced nicely, but you get the idea)

Range MOA drop
100 0
125 -0.3
150 -0.6
175 -1
200 -1.5
225 -2
250 -2.5
275 -3.1
300 -3.7
325 -4.3
350 -4.9
375 -5.5
400 -6.2
425 -6.8
450 -7.5
475 -8.2
500 -8.9

Using a 1/4 MOA turret, I'd make myself a chart that I would tape to the stock in MOA, not clicks. All turrets I would use are marked in MOA on the turret, so zero the turret once the rifle is zero'd, then just spin to the correct number, no counting clicks. I've counted clicks (before I had a marked turret) and this system is easily 1000% better, maybe more.

The chart I'd tape to my stock would look like this (I just round to the nearest .25):

Range MOA
100 0
125 .25
150 .5
175 1
200 1.5
225 2
250 2.5
275 3
300 3.75
325 4.25
350 5
375 5.5
400 6.25
425 6.75
450 7.5
475 8.25
500 9


Just for conversations sake, with the aforementioned 1/4 MOA turret, to get the number of clicks you'd of course multiply the MOA value by 4. Also, the above chart could be used with any MOA scope (1/4 MOA, 1/2 MOA, etc) due to it not being in "clicks".

Now, setting it up myself I'd do a few things a little different. 1st, I'd probably zero at 200 yards, or 1.5 MOA high at 100. 2nd, I'd include some sort of windage reference on my drop chart for a 10 mph full value wind, on a stadard duplex usually referencing what % of the reticle the bullet will drift. I usually color my chart to indicate quickly how far out point blank range is, and I'd also extend it past 500 yards. Lastly, I'd test my system, starting with running the turret up at 100 yards and measuring how it moves the point of impact (many scopes vary from true MOA on this), and then shooting at lots of different ranges to confirm what the ballistics program tells me. I only make the chart I tape on my rifle AFTER I do this.

 

[Carl]

I hope that helps, let me know if you want clarification on anything. I could snap a few pictures when I get home tonight if need be.

 

[drahthaar]

OMG, exactly what I needed. I love this site.

I need to slow down and digest this info, so I can ask another dumb question. LOL.

Thanks a ton Carl. Belly, even muddy water clears up in time.

I sat for a couple hours this afternoon looking over websites, none of them put it like you guys just did.

Thanks.

 

[BuzzH]

drathaar,

I was in your exact boat about 20 months ago.

The others have given you a great rundown on MOA, in particular Carl. I think his advice is spot on.

Heres the site I used to determine my come-up chart:

http://www.biggameinfo.com/index.aspx?page=/balcalc.ascx

Just plug in the values, make sure they are SPOT on, in particular BC and Muzzle Velocity (need a chrony).

I second Carls advice to shoot a lot to make sure your shit is tracking correctly. When in the development stage of my chart, I used a MV of 3000 fps for my initial chart. My actual MV through a chrony was 2970...and that do make a difference and I found that out real quick while at the range.

I use a 250 yard zero and my chart looks like this, picture of my chart on my stock:

I hand wrote in the exact MOA comeups in minutes rather than clicks, which correlates to your turret hash-marks.

Heres a picture of the turrets dialed to my come-up at 350 yards. I shot my Montana bull from the ridgeline in the background at 350 yards, give or take, as I ranged a tree near the bull before he got there.

I also have wind charts for various windspeeds that I put in my pack, but to tell you the truth, the wind scares me to shoot in if its blowing very much at all. Bullet drop is pure physics providing you have the correct data. Doping wind is a more art than science and I'm still learning constantly on that front.

A picture from this afternoon...3 shot group at 550 yards (the 3 shiny silver spots). I could cover the 3 shots with the lid of my coffee cup.

Good luck...

 

[drahthaar]

More awesome stuff. Perfect. Thanks Buzz. Trying to put this all together.

The handwritten numbers. Did you get those from using the equation Carl wrote, MOA=.... in post 6? that is the chart he wrote rounded to nearest .25?

So you guys all bought a chronograph? Need to be very exact.

 

[BuzzH]

I just divided the comeup clicks by 4...the same as Carls chart. The far right numbers on my chart are the actual number of clicks. So in the example of the 350 yard shot, I need to correct 9 clicks, or 2.25 MOA, which is the value dialed on my scope in the picture.

Yes to the chronograph, you have to be as precise as possible with all your values.

I would talk with Carl if you have lots of specific questions, I know he's done a lot more of this stuff than I have. Its a pretty steep learning curve though, and the secret is to shoot...alot. You'll find any problems once you start shooting at ranges past 500.

On the other hand, its flat crazy how good a basically factory rifle will shoot out to 7-8 hundred.

 

[cowboy]

So you guys all bought a chronograph? Need to be very exact.

NO, Yes

No - you do not "HAVE" to buy a chrony but it I will say it makes it easier. You could get your velocity by backing it out on a ballistic calculator from field shot proven data. By this I mean you could get a large target and draw your bullseye close to the top of the paper. As an example you could sight in dead on at 200 yds, take same paper and move to 500 yds - do not change your scope setting from initial firing and shoot at the same bull from 500 yds. you will have a group much lower on the paper, you can take this same paper to say 800 yds and fire a new group. Measure the group drop from 2-5oo yds and from 2-800 yds. Take those drops back to a ballistic calculator and keep changing the velocity till your drops match that velocity. This method is more exact than using a chrony but takes more time to get things completed.

Chronographs can be a very good tool to get you started but DON'T BELIEVE that they are perfect. That is why you always need to verify whatever the data shows with a lot of trigger time. I once saw a guy shoot his lying no good chrony that he had believed in for years. I send mine back to factory to get re-calibrated every so often.

And once you are done with your data something always throws a wrench into what you have done. As an example - I have found very few different "lots" of powder from the same manufacturer that have the same burn rate. Some powders are worse then others, some are more heat sensitive so if you work things up at 30 degrees all hell breaks loose at 90 degrees. Primers and bullets are not the same either between different lot numbers. That is why when we find a combo that works I buy powder, bullets and primers to last me for a number of years all from the same lot number.

YES - it is best to be exact. I have found the 400 yd mark as the breaking point for needing everything to be exact. 400 yds and in and you can get buy with being a little less perfect.

 

[Drake4]

Draht-
Once you get your MOA figured out and a drop chart buit..you can make things even simpler. I print off yardage labels that I tape onto my turret. That way I can just dial directly to the yardage. It just eliminates one more step of looking at a drop chart on your rifle and dialing up the corresponding number of clicks.

If you range a deer at 375 yards..dial your turret to 375 yards. You don't have to worry about the extra step of making sure that 375 yards is 5.5 clicks according to your chart. It's definitely not necessary, but it just takes one less error out of the equation in my opinion. I can post a pic or two, of what my turret looks like if you are interested.

Nice shooting Buzz..doesn't get much better than that.

 

[BuzzH]

Drake4,

Post up some pics, I'd like to take a look at how you rigged that up.

 

[Drake4]

Here is what my setup looks like. Just a standard M1 turret.
I just figured the circumference of the turret so I knew how long to make the label. I have 1/4 MOA click values, so I marked each 25 yard increment. The only tricky part was matching the exact click values (distance between marks on paper) to the turret itself. Once I got that nailed down, it was a piece of cake.




200 yard zero..I get 775 yards out of one revolution, and then go to the top numbers for anything past 800 yards.


Dialed to 500 yards.


It has worked pretty slick for me. Piece of cake to change, and holds up surprisingly well. This same label has made it through 2 hunting seasons. I figure if I only have to change the label every year or so, it isn't so bad. A lot cheaper than ordering custom engraved turrets as well.

 

[drahthaar]

Pretty awesome Drake! Thanks.

 

[Randy49er]

You guys are amazing! Sure beats guessing how far over to hold the old crosshairs.

 

[BuzzH]

Drake4,

Thanks for the pics.

That looks like a slick set-up, has me thinking...

 

[Drake4]

Send me your drop chart if you want..I'll print you out a .pdf file with your customized labels to try out. I've got the template all setup and it will only take me a couple minutes to adjust to your data.
Clicks and height should be the same since you are running an M1.

 

[T Bone]

I'm about to go down the M1 road in the next few weeks. Very informative read.

Drake, that is a handy little label. What kind of paper/material is it printed on?