Here is a abreviation thats bugging me. In this ballistic software there is a place to enter Group size (MOA). It does not really seem to an important field to fill in, but I keep looking at the brackets and cannot get my brain to figure out what they stand for. Probably something obvious but I'm blank.
6 replies [Last post]
Sat, 2006-09-30 14:23
Sat, 2006-09-30 14:36#1
MOA stands for "Minute Of Angle". MOA is used to measure windage and elevation deviations at any given distance and MOA changes (increases) the farther out your target is. This is measured as a line from muzzle to target at a given distance. At 100 yards 1 MOA equals approx 1 inch, basically meaning that it is 1/2 inch on each side of centerline of the vertical cross hair, and 1/2 inch on each side of centerline of the horizontal cross hair, on the target.
A good hunting rifle should be able to group 3 to 5 bullets of the same ammunition into an area that measures 1 inch to 2.5 inch circle or square at 100 yrds. (of course that's with a bit of human error involved). In fact most factory production rifles are capable of far better accuracy that most hunters are.
Competition shooters won't even qualify and Varmit shooters aren't happy unless their rifle and themself are capable of shooting sub MOA at 100 yrds. That's usually .25 to .50 inches at 100 yrds. So grouping shots would mean in this example that all of their bullets are placed into an area on a paper target that measures .25 to .50 inches.
Sat, 2006-09-30 17:48#2
Thank you. Not anything like I expected but you did a great job of explaining. I am still not sure why they have the field in the program as I see no reaction from changing it. Unless just to record what a certain load managed to perform.
Sun, 2006-10-01 21:35#3
What are you using that softwear to do?
Sun, 2006-10-01 23:27#4
Not much but was just checking out different gr and velocity scenerios, only to find out what I thought about certain bullets and weights is not true. I thought my 223 would shoot way flatter then then 30-06 or 270 but is not really the case. The big thing is finding that zero range that is right for the game your after. We now have that 270 shooting in a 8" vital zone out to 300yd and my son did it today. It was nice to know where to set it in at 50yds to do this. He put 3 holes touching about an 1" high at fifty then tried it a hundred which he was 3 in high but a bit more spread left to right. He then shot the gong at 300 4 times in a row. I was pretty proud of him for the small amount of shooting he has done. Now I only hope I can get him in to with 200yds of a deer.
Mon, 2006-10-02 01:52#5
As you do your research. You'll find that all of the popular big game rounds will have a point blank range (4" high to 4" low) of 280 yds to 320yds. Depending on cartridge. Most will be at the 290 to 300 yd maximum range.
Another thing you'll discover in your research is. At normal hunting ranges. Sectional density is more important than ballistic coefficient. There is only about an inch different in trajectory between a flat base spitzer and a boattail spitzer bullet, of the same weight and caliber, out to 250 yds. In many designs the flat base style is a sturdier bullet.
The middle of the road bullet weight, in the caliber of choice, are typically the best choice. 140gr in .277, 150gr in .284, 180gr in .308 and so on. There are exceptions to these. I personally prefer the new Hornady 130gr interbond in my 270 wsm but, I also load up a few 140gr Speer TBBC's for a good solid close range (under 150yds on heavier game) stopper, if needed.
Tue, 2006-10-03 22:38#6
If your softwear doesn't tell you where to zero with an 8" target, let me know and I'll run it thru mine. I'd need the bullet or better the B.C. and the muzzle velocity. If you haven't measured it or it's factory I can fudge and ou'll still be awful close.