Elevation adjustment on the 1902 rear sight

[Shawn Agne]

Are the notches on the 1902 rear sight calibrated to MOA?

[Dick Hosmer]

I do not believe so, though am not looking at the manual.

IIRC the preceding Buffington sight on the TD, and the following 1903 sight, were marked (for windage) in "points" an arbitrary graduation which may well be related to, or derived from, MOA, but is not a direct statement of same.

And then, CRS may be affecting my answer! :-)

[Dan Shapiro]

IIRC the windage markings on the '03 are in mils. Why the infantry would use an artillery measurement is another question.

[Shawn Agne]

Yeah I remember reading that the markings were 4 mills on the 1903 sight. Just wondering what the serrations or "clicks" on the 1902 rear sight are elevation wise. The rifle is zero'd for 200 yds and Perry but just kind of like to know.

[Dick Hosmer]

Oh - you meant elevation! For that, any graduations would have referred (more or less) to the service load. If yours differs from that trajectory, I would expect to have to use trial and error. Is the 200 yd. zero for your load right at the "2"? I don't know how you could be sure of going up or down any particular number of serrations with any real certainty. Best bet for quick repeatable changes would be some sort of micrometer accessory, I would think.

[Shawn Agne]

No with the tall blade the elevation is about a notch or two below 500 with the 125s. The 175gr load is printing about 2-2.5 MOA higher. Main reason is I'm thinking about shooting it in a full course match sometime using the 125s at 200 and the 175s at 300/600 so just wanting to know how much to adjust. I'll play around with it.

[Cosine26]

Military Rifle Sights.
In general most military rifles have rear sights for elevation that are marked in some linear measurements such as :yards (US & UK), meters (most European), other units such as "paces" (Russia).
Few if any military rifles make provisions for windage adjustments except the later US and some early SMLE's. The windage adjustment on SMLE and later variants were usually dispensed with during war years.
On US military rifles, the Krag and the M1903 the windage is marked in "points". On the Krag there are six minutes of angle per point while on the M1903 there are four minutes. These are minutes of angle not "mils".
Mil vs MOA is somewhat complicated.
MIL is short for miliradian. A circle has `6.28 radians, (2 X Pi) or 2 X3.14. The radian is a large measurement so the services usually use the miliradian or 1/1000 of a circle for finer measurements. This means that there are 6280 miliradians to the circle. Here we have to be careful, the naval ordnance community and the US infantry use the true mil (6280/1000). The US artillery, finding that 6280 was difficult to divide evenly, elected to arbitrarily use 6400 mils to the circle. I believe that in today's army, the decision has been made to adopt the artillery mil. The true mil was commonly used in infantry and naval ordnance.
A circle contains 3600 minutes. There are 60 seconds per minute, sixty minutes per circle so 60 x 60 = 3600 minutes of angle.
Most commercial sights are calibrated in MOA not mils. Most target shooters like the MOA for one MOA ~ one inch per hundred yards.
Hope this helps.

[psteinmayer]

Shawn, I use the 1902 on my Krag at Perry. If you are zeroed for 200 yards using the load you'll use with us at Perry, then you should be just fine. Sometimes, we'll have to use just a tough of Kentucky windage, but I think the notches on the slide allow for four between each graduation. There is a calculation for this, although I'm not sure what that is... and I'm not at home right now so I can't look that up either. There is a rare slide that has a very fine serration which allows for a much more accurate elevation adjustment... but that is a rare exception. If I've mis-spoke on this... someone please let me know.

[Parashooter]

Elevation adjustment on the 1902 rear sight.
Are the notches on the 1902 rear sight calibrated to MOA?

The answer is 'no', but understanding why takes some appreciation of how a tangent sight works.



Look at the leaf and you'll notice that the graduations (and serrations) and spaced equally over its length. However, moving the slide from one graduation/serration to the next doesn't have an equal effect on the vertical movement of the sighting notch. This is mainly because the slide gets closer to the leaf's pivot joint as it moves to the front, changing its mechanical advantage.

The curved surfaces on the base are shaped so the amount of vertical movement produced with each graduation changes in a manner that reflects the trajectory of the service round. Consequently, while moving the slide from 200 to 300 yards (marked 2 and 3) produces a vertical change of some 5.8 MOA, the same amount of slide movement from, for example, 9 to 10 yields a vertical change of about 14 MOA.

So, the real answer to the question is "it depends." If we apply the calculated values based on the service round trajectory (220 RN @ 2000 fps) and round off minor fractions, we can come up with a practical set of MOA equivalents -

From
2-3 = 6 MOA
3-4 = 7 MOA
4-5 = 8 MOA
5-6 = 9.5 MOA

(If your leaf has 4 serrations per graduation, divide the MOA values by 4 to give a usable value per serration.)

Ballistic calculation used for these values. Highlighted column has cumulative MOA elevation values -


1 MOA at 100 yards is actually 1.0473" - rounded here to 1.05" per "click". BC is from Woodleigh FMJ, probably close to service bullet.

If you have a slide caliper handy, you can check the values by measuring the amount of vertical change produced (at the notch) by moving the slide one graduation at various ranges. Just divide the vertical difference by .007" (~1 MOA at 24.5" sight radius) to give the approximate MOA value for that specific change. For example, moving the slide from 2 to 3 should give a vertical change of ~.041" (5.8 X .007").

Please feel free to point out any gross errors - math was never easy for me. Must . . stop . . . head . . . . hurts . . . . .

[madsenshooter]

And, to add further to your confusion, not all 1902 sights come with the same notches. I don't know if that info came along with the site upgrade or not. As a for instance, mine has very fine notches and would be half the value shown on this chart, if I was shooting a 220@2000fps. And there are some with a crosshatching on the side that allows for even finer adjustment.

[psteinmayer]

What does this all mean? Well, if you are using a 220 gr RN bullet at 2000 fps, which is what the Krag is designed to shoot... and you are zeroed so that you are on the 200 graduation at 200 yards, and hitting the bullseye... then I think you'll be just fine! LOL Fortunately, we only shoot at one distance in CMP competitions like Camp Perry. This is one of the reasons I don't like to shoot in CMP matches that use the SR-1 target at 100 yards (simulated 200 yards). Even though it is a simulated 200 yard sight picture, it's at 100 yards, and that requires me to recalibrate. Not a problem with a more modern rifle like a Garand, but I prefer to leave my Krag set for 200 yards and leave it alone.

Maybe I should get another 1902 sight, calibrate it for 100 yards... and switch sights for different distances. Hmmmmmm

[Shawn Agne]

Thank you that is what I was wondering. Now I need to see if I have the regular 4 notch or the fine notch sight. However seeing that makes me wish I kept the short blade in the front instead of the tall blade. Oh well. Did a 97-3 with 2 called 9s Friday, need to keep practicing.

[psteinmayer]

Shooting in the slow fire prone position should prove to be your most accurate string. Prone rapid should be just as accurate, but adding the cycling of the bolt, and reloading... all within 80 seconds can make one more than a little flustered, which can (and does) sometimes affect accuracy. My advice would be to practice the off hand (standing), which is for most of us the most challenging position. I word of advice: Turn your fore stock hand (left hand for right handed shooters, and vice versa for lefties) around so the thumb pointing towards the opposite arm. This will allow you to tuck your elbow in tighter to your rib cage, providing a little more steady support while standing.

Do you have any chargers for quick reloading? If not, send me a PM, as I still have a few available.

[Shawn Agne]

Hi Paul,

Yes I purchased a couple chargers from you a year or so ago. I'm a High Master in Long Range and Mid Range prone, one more match and I'll be there in Fullbore also. Last match if I didn't fire 2 6's and an 8 in offhand I would have shot a lot better than the 767 I did. Up until that match had been shooting low 180s in offhand. Just about to High Master in course. The 80 seconds seems like an eternity for me as usually my rapid prone is done in 60ish since I shoot space gun.

Thanks
Shawn

[psteinmayer]

Sorry... I do remember that you had gotten a couple now that I think of it. I didn't mean to mistake you for a newbie shooter either. I just assumed that you hadn't competed before with your Krag or at Camp Perry. I do look forward to meeting you this year and shooting side by side!