accuracy of 25 yard sight in at longer ranges

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hillbillyjake

New member
just got my scope on my stag AR .223 i bought a box of winchester 64 grain power points that i am going to try. my question is, can i sight this gun in at 25 yards and know the accuracy of this gun at longer ranges? the wind here is howling and its about 20 degrees but i have access to an indoor range. thanks for the help
 
yes and no.

sight it in about 1/2 to 1 inch low at 25 yards. IF you can drop 5 shots into ONE 38 caliber hole at 25 yards. You'll have good accuracy out to 100.
 
If you sight in at 25 yards, the only thing you can be assured of, is that at 25 yards, your dead on. Don't play that game, Ive heard its merits at the range by the old salts, but Ive witnessed how flawed it can be. Just shoot at 100 yards to be sure of a good sight in.
 
Something to remember: at 25 yards, the point of impact adjustment is different. ie- at 1/4" click increments, to move the POI 1" at 100 yards, it takes 4 clicks...but at 25 yards, it would take 16 clicks to get the same 1" POI adjustment.....Keep that in mind! This COULD lead to running out of adjustment on your scope. They claim you should never go more than 75 clicks on a scope, or you may run in to other issues.
Can't you just drop it off and have it boresighted right quick? I think that's what I would do, personally.
 
If you know the bullet weight, bullet diameter, bullets ballistic coefficient, and exact fps for your load you can plug all that info into a ballistic callculator and it is pretty darn close at given distances. That said, if any of those variables are off so is your bullet, do like ChileRojo suggested and shoot it at your zero yardage to be sure.
 
I use Oehler's Ballistic Explorer as my primary external ballistics program, and it does a very good job once you get the correct data fed into it...but, getting the correct data takes a little more effort than simply accepting the bullet manufacturer's assigned ballistic coefficient is correct.

BC's are not cast in stone, even when published. IME, most of the time they appear to be a little "optimistic".

When I want to work out a long-range comeups table for one of my pdog rigs, if I key in the data I've derived from chrono testing and simply accept the published BC, almost without exception my rounds (in .223 Rem with the 55 VMax) land between 3-4" lower at 300 yards than the program "computes". That's pretty bad, considering I do a lot of 450-500 pdog shooting with these rifles, and the discrepancy becomes even worse.

To avoid this, I fire a 5 shot group at 100 yards. Then I back the target out to 200 yards and fire another 5 shot group, using the same 100 yard aimpoint and making no scope adjustment. What I'm trying to find out is how much the bullet drops between 100 and 200 yards with no sight adjustment.

Once I've found out this drop, I can "tweak" the BC numbers in the Oehler program to make the computed results fit the trajectory I experienced at the range.

Using the "tweaked" BC numbers in the program, I wind up with a much, much more accurate comeups table than what I get by simply plugging in the manufacturer's published BC.

As to the original question, it is my honest opinion that using a 25 yard zero with the hope of it being "accurate" much past 100 yards is pretty wishful thinking.

Mike
 
It will get you on paper at 100. Like golf, long range shooting is a game of millimeters at the shooter and inches to feet on target. Poor mans bore sight is to find the longest run in your house, place a dot or object (I usually used a door knob before buying a boresighter), break open your AR and look thru the bore at the dot and secure it in that position. Then adjust the scope to the dot. Should have you on paper at 100. I shoot alot of one hole groups at 25 yards, but find it harder to do at 100 or 200, it requires adjustment.
 
1/2 inch low at 50 will put you close to zero at 100 depending on how your high your scope axis is above the bore axis. For 25yd sight in AND 100yd zero you're POI will be lower than POA should by slightly more than height of your scope above bore line. If that makes sense:)

A 25yd ZERO will put you roughly 3.5 inches high at 100 and depending on bullet and velocity back to ZERO around 275 yds.

all that said, a longer yardage zero (preferred) will show you alot more error than a short one.
 
Quote:
depending on how high your scope axis is above the bore axis.



That right there is the most important factor. Ballistic coefficient, minor velocity differences, those aren't going to show up going from 25 to 100 yards. Sight in dead on at 25, then you'll be fine in azimuth and on the paper at 100 or 200. 5 rounds at 100 yards and you'll be done. I do this everytime I start with a raw scope just so I don't eat ammo figuring out which side of the target I'm missing on.
I'd guess with an AR you want to be 1 inch low at 25 for a 200 yard zero.

Quote:
A 25yd ZERO will put you roughly 3.5 inches high at 100 and depending on bullet and velocity back to ZERO around 275 yds.



Listen to this guy, he's giving you good dope.
 
The biggest problem is that the slightest error at 25 yards gets magnified the further out you go, 1/4" is an inch at 100 yards. Best practice is that a 25 yard zero is better than nothing, and it should mean you will be on the paper at 100 yards, but quite frankly, that's really not good enough when shooting at a small target like a coyote.
 
Shoot one shot, after bore sighting, at 25 yds from a bag. Then re-sight on the aiming point and holding the rifle still, have a friend move the crosswires to the bullet hole. You'll be on the paper at 100 and should be sighted in in very few shot's. I use bolt actions so when I bore sight, I just set up on a protable shooting bench with bags in the house.

I'd never believe any rifle is sighted in after shooting only at 100yds. After that sight in at 250 and the clicks on a 1/4" @ 100 yds will be 5/8th" @ 250 or 3/4" at 300. The farther you can sight it in, the better off you are.
 
The 25 meter zero is the miliary M16 range way of doing business. Zero at 25 = zero at 250 and the ability to hit a man sized target anywhere out to 300 meters. The 25/250 distance are based on the ballistics of the round they use for the M16A1/A2. It will most like be flawed with any other round/barrel combination.
 
if you are going to shoot game at 100 200 300 or what ever range you need to shoot at these ranges to see what your gun and you can do.you owe the animal a quick and humane kill.i can give you a prime example of what i am talking about.i am working on loads for my new 308.the load i thought was right for it was shooting sub 1/4 groups at 100(5 shot groups).so i moved to the 200 yard target these loads opened up to 4 inch five shoot group.shot 4 groups with my 204 all where less than 1/2 inch 5 shot groups right after i shot the 308.if these 308 loads opened up to 4 inch at 200 they probably wouldnt even hit the target at 300.i have seen it too many times where a gun would shoot good at a 100 and go to crap at 200.you take a gun that shooting 4 in groups at 200 from a bench and put it on shooting sticks or by-pod then your talking about 7-8 inch groups.
 
thanks alot guys. i think i will just wait and til the weather breaks then do some range work with this gun before hunting. i had some doubt before i asked this question /ubbthreads/images/graemlins/confused.gif, and all doubt has been verified. /ubbthreads/images/graemlins/grinning-smiley-003.gif thanks again
 


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