Accuracy and MOA Question

[WalkAbout]

Hello all,

I've just gotten back from the range today and saved a couple of targets with 3 and 5 shot groups on them in order to check the accuracy of the rifles I was shooting. I'm quite happy with both of them as they were both able to shoot shotgun shells off a tree limb at 50+ yards, but now that I'm home I wanted tp get a it more technical with it.

I've measured the group sizes using digital calipers from the outside edge of the two holes furthest apart in the group. I've utilized a free MOA calculator I found via google,

http://www.indecorous.com/bullseye/moacalc.html

but I'm getting some answers I don't quite follow. For instance, I have a target here with a 3-shot grouping of .825" at 50 yards. According to the calculator, that is a .432 MOA group. It was my understanding that 1 MOA is equal to +/- 1" at 100 yards. Unless my math is completely off base, which is also entirely possible, that would make a group size double that (say 1.6" for simplicity's sake) 1 MOA at 100 yards, which is well above 1.04whatever.

So either I'm doing this completely wrong (likely), the calculator is doing something wrong (plausible), or I actually have no freaking clue what I'm talking about (highly likely.)

Somebody please set me straight. I'd really like to find some ballistics software for a Mac, but as of yet no luck. If it helps, I have the following groups:
3 shots at .825"
3 shots at 1.184"
5 shots at 1.503"
5 shots at 1.398"
5 shots at .828"

All at 50 yards.

Thanks in advance!

b

 

[deadeye1122]

I am not an expert in MOA and some Q&A on the forums are way over my head. Anyway I think you are correct in your 1.6" at 100 yds. Your 2 outermost rounds are traveling at a angle and going to 100 yds and farther in a wideing spread. I'm sure someone will set it straight.

 

[Welding Rod]

Double your group size at 50 yards, and then divide by 1.047.

 

[wanderinwalker]

You're on the right track, relatively, but you've somehow managed to run your math and get an opposite result. At 50 yards, 1-MOA is 1/2". At 25 yards, 1/4". At 100 yards, 1" (starting point).

What really annoys me is when somebody shoots a 1" group at 50-yards and then says "It's MOA at 50-yards!" WRONG! That's a 2-minute group.

Edit: And the "cone-of-fire" method works pretty well, but it isn't a precise relationship. Some ammunition shoots better MOA-wise as range extends, while others will shoot progressively worse. The 80gr bullets we use in .223 for shooting 600-yards are notorious for this phenomanon. My 600-yard ammo only shoots "OK" at 100 yards, but really hammers at 300-yards and shoots OK at 600. (Granted, at 600-yards the shooter is a much bigger limitation in this case.)

 

[GLShooter]

have the following groups:
3 shots at .825"
3 shots at 1.184"
5 shots at 1.503"
5 shots at 1.398"
5 shots at .828"

All at 50 yards.

Thanks in advance!

OK. Technically an MOA at 100 YARDS is 1.047. An MOA at 50 YARDS is 0.5235" I'll round up to 0.524

0.825/0.524 = 1.574 MOA
1.184.0.524 = 2.259 MOA
1.503/0.254 = 2.868 MOA
1.388/0.524 = 2.868 MOA
0.828/0.524 = 1.580 MOA

To find MOA measurement at any range take 1.047 and multiply that by range in yards/100.

Example: 225 yard target: Range in yards 225 divided by 100 = 2.25 so you multiple 1.047 X 2.25 = 2.355":for your MOA at 225 yards

Now lets do a 73 yard target: Range in yards 73 divided by 100 = 0.73 so you multiply 1.047 X 0.73 = 0.764" for your MOA at 73 yards

Once you have the inch measurement for the MOA at the given yardage you divide your measurement by the MOA factor in inches and that gives you what MOA that group is at that yardage.

So using the 73 yard factor above: A group of 1.749" divided by 0.764" (your inch measurement for MOA at 73 yards) yields an MOA for the group of 2.289 MOA

Piece of cake.

The magic number is 1.047

Greg

 

[WalkAbout]

Piece of cake.

The magic number is 1.047

And all this time I thought it was 42!

Thanks so much for the explanation. I was about to pull what little hair I have out last night trying to figure that out. If you can't tell, Math ain't my strong suit. I do have to admit I'm a bit discouraged by those numbers, but I suppose for .22's thats pretty good. I'll have to try some of those Wolf Match bullets and see if the groups tighten up any.

Thanks again!

b

 

[LKB3rd]

MOA= "minute of angle." If you divide one degree (like in a 90 degree angle, etc) into 60 parts you get a TINY angle, measured in "minutes".
So, once you get this, it should make sense that as you go further away, the same angle gets bigger on the far end. 1moa = approx 1" at 100, 2" at 200. 3" at 300 etc. which you already know.
Hope that helps. I am "big picture" learner. I have a hard time memorizing facts, but if I understand how things work, no memorizing is needed, it just makes sense

 

[Art Eatman]

If I understood the first post correctly: When you measure group size, it should be center-to-center. Measure outside-to-outside and then subtract one diameter of the bullet.

 

[NeuseRvrRat]

the term "MOA" is overused imo. every mall ninja on the internet is striving for a 1 MOA rifle.

just tell me the group size and the range and i'm much happier

 

[WalkAbout]

If I understood the first post correctly: When you measure group size, it should be center-to-center. Measure outside-to-outside and then subtract one diameter of the bullet.

Interesting. Having re-done the math now it still is a bit short of where I want it, but every little bit helps I suppose.

What's really frustrating at the moment is that the $100 pawn shop Marlin Model 60 with the mediocre trigger and fixed 4 power BSA $15 gun show scope in dove tail mounted rings is out shooting my new Savage MKII with a Bushnell Banner scope on it held on by a DNZ scope mount. I suspect at this point that it's all about the cheek weld. I can't get a good one on the Savage, but I can mount my head like a rock on the Marlin.

MOA= "minute of angle." If you divide one degree (like in a 90 degree angle, etc) into 60 parts you get a TINY angle, measured in "minutes".
So, once you get this, it should make sense that as you go further away, the same angle gets bigger on the far end. 1moa = approx 1" at 100, 2" at 200. 3" at 300 etc. which you already know.
Hope that helps. I am "big picture" learner. I have a hard time memorizing facts, but if I understand how things work, no memorizing is needed, it just makes sense

So it's basically referring to an angle with the barrel of the gun being one point, and the two farthest apart shots as the other two points? If thats the case then it actually does make a lot more sense now.

the term "MOA" is overused imo. every mall ninja on the internet is striving for a 1 MOA rifle.

LOL I hardly think my Marlin 60 with the wood stock qualifies for mall ninja status. Like I said, both of them are hitting shotgun shells at 50 yards consistently so I'm happy with them. Shrinking group size to 1 MOA is now a matter of increasing my skills rather than either of the rifles being ninja-esque. It's also a matter of pride as I spent a lot of time and money getting this Savage set up the way I want it and the Marlin is outshooting it. I still have plenty of types of ammo to go through and the cheek weld problem to deal with though. In the end I have faith the Savage will emerge the more accurate.

Thanks everyone for the replies!

b

 

[Caliper_Mi]

the term "MOA" is overused imo. every mall ninja on the internet is striving for a 1 MOA rifle.

just tell me the group size and the range and i'm much happier r

Knowing group size without range is worthless, IMO. Many people leave that off. MOA combines group size and range into a single easy number.

I will agree with the Mall Ninja comment. While a MOA rifle is quite obtainable, I'd still like to spend a day at the range with some of the people who claim to shoot that all day long. I figure it will be good entertainment watching the excuses roll out, or good times hanging with a good shooter...


bdubz0r: the reason the Marlin is out shooting the Savage is just because Marlin .22's rock! I've only recently discovered them, but after buying a '70's vintage Glenfield 60 (dept store Marlin) I'm hooked. That rifle shoots darn good just as Marlin made it. Like it so much, I picked up a 795 (box mag fed version of the 60) this past weekend. There's no way to beat a $105 rifle that shoots so nice with nothing other than a quick barrel floating job! ($25 Marlin rebate + $30 Dunhams sale)
Oh, and you're right - Marlin makes a stock to get a nice cheek weld on, too!

 

[Lovesbeer99]

Your groups are actually a little smaller. You should measure from the center of each shot not the far edges. Another way is to measure the 2 outside edges of the rounds like you did but then subtract the bullet diameter.

So if you are shooting a .22 and your group measures .85 on the outside edges you subtract .22 to get .63 and then calculate your MOA. This basically take 1/2 the diameter from each shot so that you can accurately messure the spread. Sometimes it hard figure where the center of the holes are when you have ragid edges or clover leafs.

Also don't forget to measure the outside edge of the lead ring around the whole and not just the whole.

 

[ghostwriter]

I think that FREE google located MOA calculator is out of whack.
I shot a 2.75" group at 557 yards the other day and it says thats something like 16.04 MOA... I don't think so.

 

[GLShooter]

I think that FREE google located MOA calculator is out of whack.
I shot a 2.75" group at 557 yards the other day and it says thats something like 16.04 MOA... I don't think so.

Like advice Google is sometimes worth what you pay for!!

Greg


PS: A NICE 0.470 MOA group there. Excellent shooting.

 

[Bonesinium]

I can shoot sub moa all day, with any firearm, at any range I can hit a target. But once I start shooting anything at or above 2 shot groups the drop off is substantial!

I am not sure why the usual standard is a 3 shot group. Give me a 10 shot moa group. That will prove accuracy and skill.

 

[NeuseRvrRat]

Knowing group size without range is worthless, IMO. Many people leave that off. MOA combines group size and range into a single easy number.

that's why i said "tell me the group size and the range"

the problem is, a rifle may shoot under 1" at 100 yds and get called a "1 MOA" rifle, but shoot well over 2" at 200 yds. further more, some long range shooters report poor groups at close ranges like 100 yds, but their groups shrink at long ranges after the projectiles "go to sleep". imo, measuring groups in "MOA" is pointless. like i said, i'd rather know the group size and range.

 

[benzy2]

MOA is a good unit of measure because it takes in both group size and distance, rather than one or the other. Assuming perfect conditions, 1MOA at 25 yards will be 1 MOA at 1000 yards. That never happens and with more distance 1MOA is a harder and harder accomplishment. But it is better than just saying I shot a 1" group today.

 

[Lovesbeer99]

1 last comment from me. You should take 5to10 5 shot groups and calculate your average like they do in gun tests. It's not really accurate to shoot four 3" groups and a fifth 1/2" group then claim your gun is a 1/2 moa gun. Technically 1/2 falls within 3 so it's within range but a single group is not representative.

 

[ghostwriter]

Just my 2c worth to jump in here briefly. I have some experience here with long range and some close range shooting with a .220 swift and my .300 Win Mag so from my experience...

I had a decent Leupold 3 x 9 vari-x scope on the swift. At 100 yards I could shoot a decent 1 MOA group all day long. At 300 yards, not so much. Then I invested in a 6.5 - 20 Nikon scope and my 1 MOA group was still there at 100 yards but the coolest part was I was still 1 MOA at 300 yards and all because I could see where I was aiming and was able to hold the mark much easier.

With the .300 Win Mag I use a Nightforce 12-42 x 56mm scope and let me tell you something... I can see the holes from those 200 gr SMK's at 550 yards! I couldn't shoot as well at any longer yardage without the magnification. You get people saying you can have "too much power" on a scope... well, my less than 3" group at 557 yards begs to disagree.
This is just an observation but your accuracy is very much dependant on your ability to see what you're shootin at.

 

[henschman]

Don't sweat all the decimal places and whatnot... for shooting and sighting purposes, all you need to know is that 1 MOA = 1 inch per 100 yards. You don't need a calculator or any of that crap to calculate MOA.

You asked what angle it is measuring. Well, if you are measuring group size, you are measuring the "cone of dispersion" of the group, or the angle within which your shots land on the target.

You can also use it to measure how far your point of impact is from your point of aim, for sighting purposes. In this case, you are measuring the angle of where your sights are pointed from where your bullets' trajectory is pointed. You are trying to correct this angle when sighting in a rifle.

But most bubbas don't know anything about this, so they just crank on their sights a little in the way they need to go and end up taking all afternoon sighting in the rifle, instead of actually measuring in inches, converting to MOA, converting to clicks, and making a single sight correction that should get them on target.

If you want to really learn this stuff, along with all kinds of other things about proper rifle marksmanship, you need to go to an Appleseed marksmanship clinic. www.appleseedinfo.org Bring your .22 and a brick of ammo, and you will learn more than you ever thought possible about rifle marksmanship. We throw a little Revolutionary War history in the mix too. It is a great time.

 

[GLShooter]

But most bubbas don't know anything about this, so they just crank on their sights a little in the way they need to go and end up taking all afternoon sighting in the rifle, instead of actually measuring in inches, converting to MOA, converting to clicks, and making a single sight correction that should get them on target.

Very well stated and there in lies the difference between the wannabees and the candos.

Greg

 

[snake284]

Everyone measures groups different it seems. When we have a club bench rest meet, we measure from center to center. There are measurement tools you can buy for that. But if you measure outside edge to outside edge, you can subtrack one caliber and come up with the correct size group.
I think you're overthinking this. Center to Center is the correct measurement for groups. So try what I said and this will be the group size you shot.

 

[snake284]

Art, that's the way I learned it in school. Just measure side to side and subtract one caliber. Simple as falling off a log into a bed of aligators.

 

[Lovesbeer99]

Quote:

But most bubbas don't know anything about this, so they just crank on their sights a little in the way they need to go and end up taking all afternoon sighting in the rifle, instead of actually measuring in inches, converting to MOA, converting to clicks, and making a single sight correction that should get them on target.

I don't think this is answered the question that was asked. Sound like a way to start advertising the Appleseeds. I guess it's that time of year.

 

[LKB3rd]

So it's basically referring to an angle with the barrel of the gun being one point, and the two farthest apart shots as the other two points? If thats the case then it actually does make a lot more sense now.

Yes, that's right.