How to measure a MOA at the front or rear sight (sticky)

[polymerase2]

Thought I would transfer this info to the new forum
MOA stands for minute of arc (or angle). With a $10 harbor freight calipers you can make very fine adjustments to sights without spending a lot of trial and error time. I also have the MN sight tool that works on Mosins and Enfields. Paid $20 with shipping. The more tools you have the more Mosins you should buy. Each one gets easier!

Measure the distance from the front sight to the rear sight. On my 91/30 it is 24.5 inches.
Double that number 49 inches. This is the diameter of the circle that has the rear sight at the center and the front sight at the edge.
Multiply the diameter by 3.1412 (Pi) which gives you 154 inches. That is the circumference of the circle.
Here is where it gets easier. A circle is divided into 360 degrees, and each degree is divided into 60 minutes.
Divide 154 inches by 360, which is about .429 inches. Divide that by 60, which is around .007 inches. One MOA at the front sight is .007 inches. The front post of a globe sight is around .042 inches or 6 MOA.
If you do this calculation for 100 yards you will find that one MOA is around 1inch.
So when I drag out the ex-dragoon that is shooting 6 inches to the right at 50 yards, (one MOA at 50 yards is .5 inches) I know the sight has to be moved .084 inches to the right which moves the muzzle to the left.
The reason that rifle is so far off is the front globe and sight pin are off of the original witness mark and bent a little.
I'll make a new witness mark with a sharp pencil and move the sight (bought the tool) till the marks are around .084 inches apart That is where the cheap digital calipers come in.
I have done this with an Enfield and was spot on the first time. It shoots high and if I decide to buy a higher front post I will know how high to get it.
If you have a gun that is shooting high this can tell you how much to raise the front sights. Or how much to hold over, the width of a Mosin pin is 6 MOA or 6 inches at 100 yards.
If you want a spot on 100 yard sight, You can:
buy one of the replacement adjustable sights from the sponsor above or
slip a piece of 14 gauge wire insulation over the front sight and raise and lower it with a knife tip.

I'll continue this with pictures when I take the Ex-dragoon to the range.

[polymerase2]

Back to work on the ex dragoon. It was 6" to the right at 50yards. So I moved the front sight to the right by .083 inches. I think It will need to go over a smidge more. The range will tell.

[Junk Yard Dog]

Good job!

[polymerase2]

Here is the final result at 50 yards, I was facing the sun so I could be a little tighter. I had to move the front sight another half a turn to the left. I'm not sure why it shoots low at 50 yards. Since this was a dragoon at one time maybe the globe sight they replaced the original one with sucks! You can see how far I moved it in the preceeding picture. Further research and range trips are necessary.

[Rongo]

Great info.

[SA1911a1]

That is very handy information.

I have always been very good with figures.
Not so good with numbers.

[Hlavinka]

Great Post, Thanks

[millman]

I wish I could find one that shoots low.

[Ironnewt]

I wish I could find one that shoots low.

You are not the only one, but height adjustment will handle that (usually)

[WeldonHunter]

Very informative post. Thanks for taking the time to post this. Now I have another use for (Pi). The only time I ever used it my whole life was calculating total displacement on multi-cylinder motorcycle engines using only the bore, stroke and number of cylinders.

[firefighter5765]

I have my front post dialed in (close enough for 1.5" in the head of a silloette target @ 100 yrds) only problem I m having is the rear sight "creeps" up due to the recoil. Is there any way to tighten the rear sight so it will not move unless I want it to do so?

[Shawnc]

On that sight tool, have you calculated about how far to turn it for 1 moa? And do they make a sight post that's "pointy" that might help it dial in a little tighter?

[firefighter5765]

Just back from the range and what a great day, cool temps @ about 68 degrees light wind from the north (headwind) @ 3-4 mph. Got the sight tool out and according to my estamates 1 full turn on the sight tool give you 1" of movement. I had to go 1.5 turns and this is what I got...

[desdem12]

Nice shootin there.

[firefighter5765]

Well thank you sir, I used some of the advise above along with a little "kentucky windage" lol and the rear sight did not move at all so I guess flipping it over got it to lock into place. Now I have to find a longer range WOO HOO!

[polymerase2]

Nice shooting. This can get addictive.
The LT sight tool is approx 7 minutes with one full turn.
I will need to peen the sight on the ex dragoon. It is loose enough to move by hand.

[geoshaff57]

thanks for the info sir .i found this forum today while trying to find a way to adjust my 91/30 that is shooting 12"high and 6"right at 120 yards i especially liked the idea of the shrink rap on the front sight because modifying the gun is not an option for me thanks again guy.

[Shawnc]

Thanks. I just got my caliper toy...uh tool in and I'm waiting for my adjustment tool. Can't wait to dial my rifle in!

[mosinmike17]

Got 3 to dial in. Ordering a 91/30 and 38 tool from the sponsor above soon, and getting the caliper. I'm not going to complain, they're not too inaccurate as is, but this post makes me want to seek perfection.

My last target caught fire at 25 yards when I was using the 38 (I like to spend one live fire round shooting close range when I first arrive to adjust my eyes to the sights and get in the swing of things) Range master was not too happy about that and made me move back to 75. All it did was burn the paper, the frame didn't even catch. It's not my fault Ivan made me a 1942 musket.

[desdem12]

I had to laugh a little at that. I haven't burned nothing down yet. But it is a reminder to watch out for it. I would've liked to been there to see the faces on the peoples faces when you let 'er off though