Zeroing

[MinnesotaHunter]

As for the equivalence of the expedient zeros. 25m equals a 250 or 275m zero (depending on the version M16A1, M16A2, M4A1, BUIS). the Marine 36m zero is equivalent to a 300m zero.

Rob, See above for the equivalent zeros with 5.56 ball ammo.

 

[RobG]

Bullets do not rise after they leave the barrel. They start straight and then start dropping. You are talking about inches above or below the line of sight. It is impossible for bullets to rise, due a small issue called gravity.

Breaking out my inner nerd, the scope is pointed slightly downward relative to the barrel so when you put the crosshairs on target the barrel is pointing slightly upward. Thus the bullet does rise after it leaves the barrel due to a small issue called launch angle

 

[Gunner46]

Yes, and No. Yes, the barrel is inclined at an upward angle, (Launch Angle) in relation to your sight plane. This allows the bullet to travel in an arc through the 1st sight plane (the distance between the barrel exit point and your sights) and then fall back into the 2nd intersection of your sight plane. That would be the range that the rifle is Zeroed in on, whatever range that may be.

No, the bullet never really rises once it leaves the barrel, per say. It's pointed up and only travels in the direction it's pointed. If the barrel were held at absolute level, the bullet would immediately begin to drop the instant it left the barrel. Gravity, Physics.

Drop a ping pong ball off of X height and launch another one straight out, from the same height, regardless of speed, and they will both hit terra firma at the same time.

Does that help?

 

[Deleted member 20812]

Breaking out my inner nerd, the scope is pointed slightly downward relative to the barrel so when you put the crosshairs on target the barrel is pointing slightly upward. Thus the bullet does rise after it leaves the barrel due to a small issue called launch angle

Yes, but it never rises relative to the axis of the bore.

 

[Deleted member 20812]

Just for the record to avoid confusion, the first time you said it results in a 100 yd zero, but I think you meant 200yd.

I was taught the 25 yd rule, but it seems like the second zero point would vary a lot depending on ammo and caliber. As a practical matter how much variation can you expect?

It also varies with the rifle in question. An M16A1 has a different sight offset than an M14.

 

[Gunner46]

Wait just a sec JWH. I'm a little late to catch this tid-bit, but you stated you were 'drawing' your data from a 270WSM. Just what are you really looking at shooting ? It has a Tad influence on our answers.

 

[sbhooper]

Breaking out my inner nerd, the scope is pointed slightly downward relative to the barrel so when you put the crosshairs on target the barrel is pointing slightly upward. Thus the bullet does rise after it leaves the barrel due to a small issue called launch angle

Negative. The bullet can only fly straight and drop. The barrel is angled up, the bullet does not rise.

 

[noharleyyet]

Rocket science...it sorta is.

POA compensates for gravity. Speed and mass mitigates rate of pill drop.



....no phd,

 

[mtmuley]

Sierra Infinity is a great tool to mess around with various zeros before shooting any ammo. Has a maximum point blank range feature and some other neat tools. I've found it to be pretty dang accurate. mtmuley

 

[zachthebowhunter]

I don't really know what my "zero" distance is, but I bet is over 300. I sight in 3" high at 100. 0-350 I hold center of chest cavity. 400 I hold the horizontal crosshairs on the top of the back. 400+ I get closer. This method has served me well for and works great when shots happen fast. I think a 270 WSM would be similar to a 150 grain bullet out of a 300 win.

This is what i have sighted my rifles in at for years and my dad before me. It seems to work out well for us! My girlfriends 7mm-08 was sighted in 3" high at 100 and she held on the hump of her cow this year at 388 yards and hit center of chest double lung.

 

[RobG]

Negative. The bullet can only fly straight and drop. The barrel is angled up, the bullet does not rise.

We are saying the same thing it is just that you are saying it wrong (I agree with JLS)

 

[jwh525]

Gunner,
The original post had incorrect information. Some of the data was for a 270WSM and some was for 338win mag. I was toying around with taking my 270wsm on an elk hunt this fall, but after talking to some buddies who are from the area they recommended I bring my 338. The country we'll be hunting in is a mix of forested and high county open areas.

 

[Igor]

I have always used a 200 yard zero. Out to 300 or so you just aim at the center and launch the bullet.

 

[Rooster52]

Got my new rifles zero at 100 yards the otherday.Tommorrow going back to zero at 200 and then they will be ready for Wyoming and Colorado next month.The cooler temps will help .

 

[danr55]

If you run ballistics programs on most modern cartidges, you'll find that zeroing a rifle at 100 yards with a 3 inch high point of impact with give you a 10 inch point blank range to about 325 yards. That should be good enough for most big game hunting in the west if you plan on shooting from less than 300 yards. If you are a long range hunter, then you should be able to run the balistics program on your specific load and know exactly what the deviation is depending on your zero POI.