|
Post by 12ptdroptine on Jan 16, 2016 22:28:12 GMT -5
I know how to measure group size but forget how to calculate moa. Richard posted a link on anotherboard and I lost it. Richard ...could you post that again? Drop
|
|
|
Post by keith on Jan 16, 2016 22:31:13 GMT -5
Divide inches by 1.047 multiplied by range increment
|
|
|
Post by shane on Jan 16, 2016 22:37:09 GMT -5
Thats confusing.... ?.....multiply by 1.047? Im a little slow. . . . . . I always measured outside to outside of bullet holes at widest point in the group and subtracted the diameter of the projective, and Called it good. LOL If at 200 yards divided by 2 If 300 yards divided by 3 and so on.....
|
|
|
Post by 12ptdroptine on Jan 16, 2016 22:56:05 GMT -5
Keith .363÷1.047=.346×200=69.2 I am missing something Drop
|
|
|
Post by keith on Jan 16, 2016 22:58:34 GMT -5
Say you shoot .5" at 200yds:
(.5/(1.047×2))=MoA
|
|
|
Post by 12ptdroptine on Jan 16, 2016 23:07:03 GMT -5
So .363÷2.094=.173 moa at 200 yds? Drop
|
|
|
Post by keith on Jan 16, 2016 23:18:12 GMT -5
Yep
|
|
|
Post by mike on Jan 17, 2016 0:40:38 GMT -5
Thats confusing.... ?.....multiply by 1.047? Im a little slow. . . . . . I always measured outside to outside of bullet holes at widest point in the group and subtracted the diameter of the projective, and Called it good. LOL If at 200 yards divided by 2 If 300 yards divided by 3 and so on..... The actual linear distance, measured at 100 yards, of one minute of a degree equals 1.047 inches. Many, such as yourself, simply round it down to 1.00 inches. You're close enough.
|
|
|
Post by keith on Jan 17, 2016 7:58:40 GMT -5
Rounding down only works for short range.
|
|
|
Post by mike on Jan 17, 2016 10:14:41 GMT -5
Rounding down only works for short range. Yes, keith, you are correct. Not considering the .047" over 500 yards equals .236", just shy of 1/4".
|
|
|
Post by keith on Jan 17, 2016 10:39:04 GMT -5
If you consider it at 1 minute yes but it has the same effect as tolerance stacking. Dial on your data assuming 1" instead of 1MoA and it gets different fast. Scopes are different and if you had MOA instead of IPHY you can miss(and vice versa): let's say it takes you 40MoA to get to 1000yds and your scope is IPHY you miss by 18". I guess what I'm driving at is rifle loonies aren't rounders. If they were they'd zero at 25yds and guess at MPBR zeroes. He asked for the math and I gave it to him.
|
|
|
Post by shane on Jan 17, 2016 12:45:13 GMT -5
Well i dont have access to a range longer than 500 yards. Never even shot farther. Never competed. That 1.047" threw me off. Thanks for the info. Wish i had access and time to shoot with you guys.
|
|
|
Post by dannoboone on Jan 17, 2016 13:59:48 GMT -5
K. I. S. S.
This isn't the long range forum. Very, very few shots will be taken, even with these high performance SML's, over 500yds in which that .047 makes no more difference than 1/4". A calculation of wind drift is much more important than the technicality of using 1.047" over 1.000".
|
|
|
Post by Richard on Jan 17, 2016 16:29:32 GMT -5
You are 100% correct danno! For the everyday hunter/shooter, inches work out just fine. If I shoot a group at say ............300 yards that is 3" CTC? I just call it MOA
|
|
|
Post by 12ptdroptine on Jan 17, 2016 17:11:06 GMT -5
Truthfully 500yds for me will be few and VERY far between. Unless I can set up some kind of range out at the farm. Problem is , we're kind of on top of a knob. So in the essence of safety...keeping bullets on the property would be a major concern. All in the pursuit of accuracy. drop
|
|
|
Post by keith on Jan 17, 2016 17:40:04 GMT -5
Regardless, the questing was how do you calculate MoA. But, for a practical exercise: I shot a coyote at 505 yards tonight with my SML. I held 3 MRAD which is 10.5 MoA in elevation and 1 MRAD wind. Drop in inches was 55.1 which if you go of your rounded numbers comes up to 11.02 MoA-ish. That is .6 real MoA off which is 3.14". My coyote is 7" from withers to brisket so your estimation error reduced your hit probability to 50% because you are working on half the target. Introduce your inherent rifle precision and your hit probability gets cut in half again if you have a 1 MoA rifle.
|
|
|
Post by TheOldGuy on Jan 17, 2016 19:13:42 GMT -5
Regardless, the questing was how do you calculate MoA. But, for a practical exercise: I shot a coyote at 505 yards tonight with my SML. I held 3 MRAD which is 10.5 MoA in elevation and 1 MRAD wind. Drop in inches was 55.1 which if you go of your rounded numbers comes up to 11.02 MoA-ish. That is .6 real MoA off which is 3.14". My coyote is 7" from withers to brisket so your estimation error reduced your hit probability to 50% because you are working on half the target. Introduce your inherent rifle precision and your hit probability gets cut in half again if you have a 1 MoA rifle. Keith, I think that the original post had to do with determining group size in MOA. Most shooters when determining group size in inches measure the largest distance between the holes (outside to outside) and subtract (1) bullet diameter to obtain CTC distance of the group. To express this in MOA and not inches you have to, as you stated in a earlier post, take that result and divide it by 1.047 and multiply by range increment. I having difficulty understanding your latest post. Most shooters today utilize optics that adjust in MOA or MRAD and ballistic programs that provide the holdover required to hit a target, whether it be in MOA or Mrad. In you post above you stated at 505 yards you needed to hold 10.5 MOA in elevation which is 10.9935 inches. If I would equate (1) MOA to 1 inch then I would holdover 10.5 inches which is a .4935 error at 505 yards. If you could, please explain to me where the 3.14 inch error comes from. Stan
|
|
|
Post by keith on Jan 17, 2016 19:57:01 GMT -5
Yes, it was about group size but he asked how to calculate MoA. Calculating MoA never changes regardless of what you are trying to solve whether drops or group size. Since everyone has a phone with a calculator there is no reason not to do the math. If for no other reason than it actually makes your group look smaller and who doesn't feel better when your groups look smaller? I disagree with your statement about ballistic solvers and scopes. There are still lots of optics that are in IPHY and lots of guys don't know the difference. Owning a ballistic solver and putting it to good use are two different things. You put garbage in and you get garbage out. I'm not talking down to anyone because I work with guys who should know better and still can't seem to use a ballistic solver properly. Then there are the majority (based on working at a gun shop and range for more than a decade) who just buy ammo and go shoot it and have no idea what their limits are. So, to answer your question about error, lets say you are the guy who comes to the shop and buys ammo then goes to plug a deer at 600yds. You bought this: Your buddy tells you that 1 MoA is 1" at 100yds and 6" at 600yds. You divide 71" by 6" for your 600yds shot and get 11.83 and round up to 12 because your scope is in .25 increments. You dial it on your optic which is in MoA not IPHY so you actually get 75.38". I know you are saying it's only 4.38" but a deer has vitals that are 8-10" in diameter so you effectively lost 50% of your target assuming your drop on your box of ammo was accurate.
|
|
|
Post by mike on Jan 17, 2016 21:00:51 GMT -5
Keith, you are absolutely correct in what you are writing. One question from this newbie: what does the acronym "IPHY" stand for?
|
|
4buck
New Member
Posts: 49
|
Post by 4buck on Jan 17, 2016 21:14:01 GMT -5
So where does a person like myself learn to actually dial up on a scope like you guys are talking? I've always been the type of guy to "holdover" a target at long range, but would love to learn to be more accurate
|
|