IMC is simple, yet causes confusion often, due to the innermixing of words and lack of critical thinking.
IMC stands for "Inches, Minutes, Clicks", and is a simple yet misunderstood way of zeroing your rifle.
Inches:
Inches is the simple distance measurement of your shot group, either in size, or in distance to center of your target.
Size is measured from center to center of your furthest two holes. This is where being able to "call your shot" is important, as a shot you called out of the group would not count.
Distance is the measurement of the center of your group to the center of your target.
Minutes:
Minutes are a measurement of a degree. There are 60 minutes in a degree. A minute at 100 yards is one inch, a minute at 200 yards is 2 inches. This is due to a degree (60 minutes) being a circular measurement. This makes a cone that is ever growing in size as it leaves the starting point. This gives us the resulting ever growing Minutes of Angle, MOA, that give us our accuracy gauge of a rifle.
The further away a target is, the wider this cone is when it intersects with the target.
MOA is measured as an INCH per 100 Yards. The cone widens away from this point and narrows before this point, so while an MOA at 300 yards is 3 inches, at 50 an MOA is 1/2, or .5, inches.
Here are the 1 MOA measurements out to 500 yards
25 yards = .25 inch = 1MOA
50 yards = .50 inch = 1MOA
100 yards = 1.0 inch = 1MOA
200 yards = 2.0 inch = 1MOA
300 yards = 3.0 inch = 1MOA
400 yards = 4.0 inch = 1MOA
500 yards = 5.0 inch = 1MOA
See a pattern here? Simple.
Also assume that bullet drop is as follows for unknown rifle/ammo combos. This is not precise, but a rough "rule of thumb" to get you started.
3 MOA from 100 to 200 yards
3 MOA from 200 to 300 yards
4 MOA from 300 to 400 yards
4 MOA from 400 to 500 yards.
Bullet drop then from 200 to 300 yards is 12 inches (300 yards equals 4 MOA drop, 1 MOA equals 3 inches at 300 yards, 4 MOA x 3 inches is a total of 12).
Drop from 300 to 400 is 16 inches (400 yards equals 4 MOA drop, 1 MOA equals 4 inches at 400 yards, 4 MOA x 4 inches is a total of 16)
Clicks:
Clicks are the measured adjustment of sights. Each "click" will adjust the sights an amount of MOA at distance. The distance moved per click depends on the distance from the target. If you adjust 1 click on an 1 MOA per click rifle at 200 yards, the Point Of Impact will shift 2 inches, or 1 MOA.
So a standard M1A, the open sights are 1 MOA clicks. Which means that one "click" of adjustment is equal to a 1 MOA shift at 100 yards. A 1 MOA shift at 100 yards equals 1 inch.
In Appleseed you will find that most of your sighting in is at 25 meters (yards for MOA purpouses). Thus, on the mentioned M1A, one "click" of adjustment will shift the sights 1 MOA, which is equal to .25 (1/4) inches at 25 yards.
Application on IMC will ease sight adjustment greatly for you in the future, and save you ammo. To help your understanding, here are some helpfull hints.
If you are shooting a rifle that you don't know what shift a "click" will give you, assume it will be 1 MOA. Adjust, then fire another group. If it did not put the group in center, take a measurement of the distance the group moved, divided by the "clicks" you adjusted. If I moved sights 5 clicks at 100 yards, and my group shifted 2.5 inches, I have 0.5 MOA adjustment per "click".
Examples,
I am shooting an AR that has been assembled from parts. I have no idea what the clicks are on this thing. I shoot a 5 round group, and the center is 5 inches to the right of center at 100 yards.
So I adjust the sights 5 clicks left, and reshoot. The group is now dead center. I have thus established my clicks to be 1 MOA windage.
I am shooting with a scope, that has 1/4 MOA clicks. I am 3 inches high and 2 inches right at 25 yards. I need my adjustment.
3 inches is 12 MOA at 25 yards (3 / .25 = 12). 3 is my inches, my distance is 25 yards. An MOA is .25 at 25 yards.
Using the same measurements, I determine that I also need 8 MOA adjustment left. 2 inches is 8 MOA (2 / .25 = 8).
My scope will need to be adjusted 48 clicks down (12 MOA / .25 moa per click) and 32 left (8 moa / .25 moa per click).
I am shooting a Nagant with ladder type sights. I am shooting 6 inches low at 200 yards. I am on the 200 yard setting. Roughly assuming that 1 "click" (200 to the 300) yard setting will move me 3 MOA (300 yards equals 3 MOA of bullet drop), the 300 yard sight setting should get me on (200 yards is 2 inches per MOA. 200 to 300 adjustment is 3 MOA. 2 inches x 3 MOA will result in a total change of 6 inches).
Here is an easy quiz question to start us off:
My rifle is hitting 2 inches right at 100 yards. I assume I have 1 MOA clicks, so I adjust 2 clicks left. This gives me a total change of 1.5 inches left leaving me 0.5 inches to the right of my target, still not to center. What are my windage "clicks" equal to?
Bonus question, do I go any more clicks, or do I leave the sights where they are?
PM your message to The Guy, and look for more quizes here. The correct answer will be given in three days, with the next quiz.
Enjoy!
[Disclaimer -- not all adjustable sights are set up for MOA; IIRC metric FAL sights changes are 1cm at 100m.]
[Other disclaimer, Know your rifle, know your ammo. Your rifle/ammo combo will work out different in the real world. This exercise is only to get you to think, not to be hard fast rules for any rifle mentioned.]
(edited for spelling, but mainly because I wish I was as cool as The Guy -- Reaper)
TheGuy,
Your table would be easier to understand if it was labled correctly.
One minute of angle out to 500 yards
25 yards = .25"
50 yards = .50"
100 yards = 1.00"
200 yards = 2.00"
300 yards = 3.00"
400 yards = 4.00"
500 yards = 5.00"
Sorry, didn't mean to butt in.
Doug in Virginia
Folks, when you really get this, you'll be looking at your target and be thinking in clicks from the start, as in "I've got to go X clicks up and Y clicks right". It takes time to get that way, but, keep thinking it out, and it will happen eventually.
Doug, good catch. This was on the Instructor board and we all missed that before posting...
Something I learned from Luckyman at Evansville was this:
If you want to find the size of a MOA at any distance, just adjust by 2 decimal points to the range.
If the target was at 75 yards, the MOA size would be .75 inches.
If it was at 475 yards, the MOA size would be 4.75 inches.
At 1279 yards? 12.79 inches per MOA.
A good way to teach it.
450 -> 4.75 inches only works when shooting into the Bermuda Triangle. ;D
Funny thing was, I was thinking 475 yards....
Oooops.
The Guy needs to read his PM's more often.........
Inches, minutes and clicks, don't wait to try and learn them at an appleseed or at an RBC. Do it now, in the comfort of your own home. In your pajamas. With air conditioning. ;D
Here is an easy quiz question to start us off:
My rifle is hitting 2 inches right at 100 yards. I assume I have 1 MOA clicks, so I adjust 2 clicks left. This gives me a total change of 1.5 inches left leaving me 0.5 inches to the right of my target, still not to center. What are my windage "clicks" equal to?
Bonus question, do I go any more clicks, or do I leave the sights where they are?
>>>>I didn't see an answer so here are my thoughts.
At 100 yards 1 MOA = 1 inch so 1.5 inches = 1.5 MOA / 2 clicks = 0.75 MOA per click.
If each click moves you 0.75 inches to the left, one more click should put you 0.25 inches left of center and that's a little closer than 0.5 inches to the right. ???
Looks like your understanding of how MOA = inches needs a refresher. For practical (shooting) purposes 1 MOA = 1 inch at 100 yds.
Your choice whether you go 1 click or 2 clicks as either puts you 1/2 inch off the center of the target. Again, for practical (shooting) purposes not many rifles of the type used by Appleseeders will see the difference at 100 yds. between 1/2" left or right of center. That is 1/2 MOA and the generally accepted belief is that most rack grade rifles with issue ammunition will do good to shoot a 3 to 4 MOA group (3 to 4 inches at 100 yds) with a rifleman firing them.
If it was me I'd shoot my rifle at a longer range (say 200 and 400 yds.) and see if the group was enough left or right to affect my group placement at those ranges and then make an adjustment to center the group at the longer range. Any change at 400 yds. should be 1/4 of that change back on the 100 yd. target. This last paragraph is just for my curiosity as again, for practical (rifle) shooting a 1/2" left/right difference at 100 yds. calculates out to a 2" difference at 400 yds. For most targets you'll shoot at at the 400 yd. mark with a service rifle 2" off your point of aim will get you the desired results. The wind and improper range estimation will have more of an effect on your group size and placement on the target.
I know, I know, too many words again. I'll go stand in the corner till it's time to go home.
Being 1/2 MOA off while shooting a 4 MOA rifle, then making an adjustment is pretty much being hasty. I would leave it, and watch the trend over a few more rounds, before adjusting that situation any further. If you have to make more adjustment, then your sights truly are not 1 MOA click sights.
Folks, if you work with this long enough, the inches and the minutes will eventually disappear, and you will look at the target and start thinking clicks right off. Hard for you to believe now, but once it happens to you, then you'll believe me.
Unless your rifle has high dollar target sights it probably doesn't track 'true' as you adjust your sights. If you start shooting off a rest at 100 yards and move your sight 1 click each shot you should have a row of bullet holes one inch apart if you have one minute sights. Almost no one has sights that are that precise unless they paid big bucks for them.
What most people have is a sight that moves one half minute, then one minute, then nothing, then two minutes and on an on and the next time you adjust the sight through the same area the movement will be different. If you seem to be hanging a half minute to one side try adjusting one click and then adjust it back. That might move you the half minute you need. Or you could drop five or six hundred on a good sight.
VAshooter
VA shooter
I do not seem to have that problem with my m-1 garand it seams to track true(the sights) is that just cuzz the m-1 is a good rifle ?or did I just get lucky with the one I bought?
Wade
;D ;D
Well, the M-1 is a very good rifle, and you also apparently got lucky that your sight's internal parts aren't very worn, and aren't full of gummy 50-year-old oil.
If the sights on your M-1 /M-1A are somewhat variable on clicks as mentioned above, where sometimes you get 1 min click movement and sometimes closer to 2, then something else, etc. You can minimise this and even out your clicks. The variable movement is likely due to wear and the tolerances neccessary in mass produced and assembled parts. This leaves small gaps in the fitting of threads and gears to each other and is called 'backlash". To even out the "slop" all you have to do is go 1 click past where you want to go and then come back that same click. For instance, you need to go 2 minutes right. You dial the windage knob 3 clicks right and then come back left 1 click, giving you a net movement of 2 clicks. You may not get exactly 1 min clicks but it will even out your sight changes. The second thing you can do is once a year or so diassemble your rear sight, clean all the gunk out of it and reassemble it, putting a little grease (not oil) on the threads, gear teeth, and the top side of the apperature gear where it rubs on the sight cover spring. If these 2 things don't improve your situation its time to replace parts.
Oh, and this is dependent on you using reasonably consistent ammo. If you are using mix-master leftovers all bets are off. ;D
On expensive match sights, you send them back to the manufacturer and bitch like hell! ;)