Author Topic: help with sight in yardage (Read 709 times)

PAINLESS · « **on:** November 21, 2003, 05:42:24 AM »

hello all i have a question about sighting in a rifle. i have in the past always sighted my .270, .308,.260 1 inch high at 100 yards. my 7mm rem mag and 300 win mag are sighted in 3 inches high at 100 yards. is this correct or is there a better way to do this. our lease is mostly bean fields with some logged out timber tracts throughout so shots range from 20 to 400 yards. the 300 and 7mm rem mag are primarily elk guns. so for the other guns is this what i should be sighting in at or is there an optimal range that would cover lets say 100 to 300 yards for a dead on hold. i hope that you can decifer these ramblings any help would be great........thanks

jhm · « **Reply #1 on:** November 21, 2003, 06:01:02 AM »

Painless: Without knowing the bullet and the vel. fir the various calibers mentioned its a shot in the dark but will give it a try: If I was setting my 270 to shoot the ranges you are refering to and using 130 gr, bullets going 3000 fps I would set it to zero at 300 yds that will give you a maximum point blank range of 360 yds, wqhich is 5 inches above and 5 in below line of sight. This info can be located in a sierra reloading manual just take the bullet you are using for that cal and the velo. and it will show you what your rifle is supposed to do.

JIM

longwinters · « **Reply #2 on:** November 21, 2003, 11:57:10 AM »

I tend not to shoot as far as you are talking about. In the past I always stuck with the 1"-100 yds. But I have started sighting in all my rifles at 2" high -100yds. and even when shooting my buck at 70 yds this fall it worked great. Like jhm says, you need to know your velocities and your bullet path window +-.

long

crow_feather · « **Reply #3 on:** November 22, 2003, 03:48:11 AM »

PAINLESS,

I figure out the height of the kill zone for the animal I'm hunting. Let's say it is 8 inches top to bottom. I sight my rifle in to be no higher than 4 inches at any range. I check on the range that the bullet drops below 4 inches. I know that out to this max range, I just need to aim dead center. Beyond that range problems begin. Always aim on fur, if you have to hold over the animal, get a Barret Light 50, or hold off on the shot.

My 2 one hundreths of a buck.

C F

Iowegan · « **Reply #4 on:** November 22, 2003, 12:12:58 PM »

What you were refering to is called max point blank range or sighting channel. It means taking a dead on aim at a target located any distance between X and Y yards and being assured of a hit within the size of the channel. The higher you set 100 yd zero, the farther your range is extended but the bigger the channel will be. As stated above, the channel size is the max kill zone on the type of game you are hunting.

Using a standard 270 Win with factory 120gr bullet, If you zero dead on at 100 yds, your channel would be + or - .7" from 25 to 145 yds. 1" high at 100 yds will have a channel + or - 1" from 12 to 200 yds. A zero for 1.5 " high at 100 yds, your channel will be + or - 1.5" from muzzle to 225 yds.

To complete the "formula", you must also consider your rifle's accuracy and wind. Lets say your rifle will shoot a 2" group at 100 yds. That would be 4" at 200 yds. Add the components together for your 1" high at 100 yds example and you get an oval that is 6" high and 4" wide. Add in a 10 mph cross wind and you are up to a 6" circle from muzzle to 200 yds.

Most shooters consider 1~1.5" high at 100 yds to be optimum for hunting.

crow_feather · « **Reply #5 on:** November 22, 2003, 03:49:18 PM »

Iowegan,

Iwoegan

The 270, a more traditional western rifle, needs to shoot as far as possible and still stay in the kill zone(the 2' shot placement error only affects the range if it shoots high or low instead of right or left). This is because in areas where shotguns are for ducks, the distant ranges can be under estimated. The 130 grain (NOT 120 grain) bullet should stay in the kill zone for as long as possible. The correct way is to chronograph your load at the temperature estimated during your hunt. Then use a computer program to assist in finding the maximum point blank range.

The other way is to aim 2.5 to 3 inches high at 100 yards and keep it simple.

C F

Iowegan · « **Reply #6 on:** November 22, 2003, 09:15:12 PM »

Crow-feather, Sorry for the confusion. The example I used was for explaination purposes. You can plug in any velocity, bullet weight, ballistic coefficient, wind direction & speed, uphill, downhill, temperature, humidity, and barometric pressure to the Ballistic Explorer program and see what your rifle will really do down range. I've used this program for many different rifle calibers with excellent results. When I chart a particular load then go to the range, it will track almost perfect.

The point blank or sighting channel concept only addresses the vertical component (rise or drop). Group size and wind affects the vertical and horizontal components. This technique works very well for shooters that don't want to calculate holdover or windage, they just put the crosshairs on the vital spot and shoot. If you try to extend the range too far, the technique doesn't work very well because the vital area gets too big. In the example that jhm posted, 5 inches above and below (10") with the 2" group size (6" @ 300 yds) and a 10 mph wind (8") factored in, would give a vital area oval about 16" vertical and 14" horizontal. For me, that would probably be too big for a deer sized animal.

What you described is basicly the same thing without the group size and wind factor. If your gun shoots a perfect one hole group and there is no wind, then your concept works fine. Believe me, your horizontal spread will increase dramatically the farther the distance.

I used this technique and killed deer and or elk 7 years in a row in Colorado. All but one was a one shot kill. I now use a Burris Ballistic-Mil-Dot scope and calibrated it to my rifle. Using my laser rangefinder, all I have to do is hold the correct dot on the target and squeeze. It's good out to 500 yds, not that I would take a shot that far. Technology is wonderful!

crow_feather · « **Reply #7 on:** November 23, 2003, 07:08:53 AM »

Iowegan,

I have shot a few elk out here, but of all the elk I have shot, I have never been able to use a range finder. I do talk about the ranges, but the truth is that I haven't busted an elk outside of a growth of trees, thus limiting my shot to less than 100 yards.

This year a friend of mine missed his elk at about 200 yds, the thing walked to within 50 yards of him and stopped - go figure.

May your shots be true, and you game never feel pain -

C F