Zeroing

.243Ady

Well-Known Member
I usually use .243 remington core lokt 100grn soft point for deer and .243 remi accutip v 75grn ballistic for fox.
My rifle is zeroed in using the accutip 75grn to shoot 1.5" high @ 100yrds, about 3/4" group, barrel cold.
I don't charge my scope settings when using the core lokt just allow for drop.
I ran out of the core lokt 100grn and so had my gunsmith, but I managed to get hold of a box of federal 100grn soft point.
As I hadn't used these before I decided to check them out on a target @ 100yds to see how they performed.
I started off with the remi accutip 75grn and fired 3 shots and they grouped 3/4" at 1.5" high of centre (Spot on)
I then switched to the federal 100grn and fire 3 shots and they grouped 3/4" at 1/2" high of centre. (which is as expected)
This is the point when I should have packed it in, but no I decided to shoot 4 more rounds using the federals (barrel warm,weather warm)
The first shot hit the centre, the second 1" low, the third 2" low, the fourth grouped at 2" low.
I then decided to use the accutip 75grn because I know these usually shoot 1.5" high, 2 shots grouped at 3" high.
Now I know its to do with the barrel temp and I should have let things cool down, deer stalking/foxing is all about that first cold shot.
But why if the federal 100grn started to drop lower didn't the accutip do the same, they actually shot 1.5" higher.
I then waited 30 mins with my gun in the shaded with bolt open then shot 2 shots using the accutip 75grn and they grouped 1.5" high.
Luckily I never touched my scope settings at any time, just a bit strange. ( I'm fairly new to rifles so go easy):D
 
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Andy, my guess is your barrel is not floated and you are getting movement of the barrel against a pressure point or the barrel channel as it heats and expands. The group does not always move as you think it should.
 
It's quite simple and the difference is all to do with at what point in the barrels "swing" the bullet exits the muzzle. The Federal was obviously exiting on the low node the Remington on a high node.

Try it once more with barrel cool.

As to whether you take the advice or not is entirely up to you of course.
 
Even if I just stick to one ammo say 100grn , doesn't explain why bullet drops when barrels start to warm up.
 
Thanks Brithunter , advice most welcome.
Yes tried rifle again with barrels cold, shoots group 1.5" high @ 100yds with 75gn accutip.(spot on)
Might just slide strip of paper between barrel and stock when warm to see if anything touches mountainstalker.
 
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It's quite simple and the difference is all to do with at what point in the barrels "swing" the bullet exits the muzzle. The Federal was obviously exiting on the low node the Remington on a high node.

Try it once more with barrel cool.

As to whether you take the advice or not is entirely up to you of course.

spot on:tiphat: all about the muzzle flip and let's say as the barrel heated up it became a bit 'softer' therefore it might spend more time flexing 'downwards' and if the federal exits on the 'down' trend, the warmer the barrel gets, the further south it will shoot. and the opposite is true with your other round...but BH's reply says enough
 
Thanks alot guys I knew somone would know the answer, makes a lot of sense when explained so well.
Just glad I just hunt with my rifle and don't do any range shooting.:D
 
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Can someone answer me the question why people zero high at 100yds, to be on at say 150yds, I just zero on at 100 and elevate for extra distance, I may be wrong but it has worked for the last 30yrs. If there is another reason I am willing to learn.
 
I can't say why others do it but I do it to allow for mistakes in range estimation. I've found that under some circumstances such as looking down a thickly wooded forest ride it is very hard indeed to get a good sense of perspective to help estimate the range. I've found that deer that are a long way away usually look small when I see them in the scope and for me this effect usually starts at about 250 yards or so. So, although I do my best to estimate the range out to that distance any big mistake still leaves me with a dead deer that is well hit.
 
Can someone answer me the question why people zero high at 100yds, to be on at say 150yds, I just zero on at 100 and elevate for extra distance, I may be wrong but it has worked for the last 30yrs. If there is another reason I am willing to learn.

Each to their own I suppose; so long as you know your trajectory it doesn't matter. I zero at 200 which equates to over 2inchs high at 100.
 
Taff

Try a search on "Maximum Point Blank Range".

I am sure someone will come up with a perfect explanation, but basically you are zeroing so that you are maximising the range at which you don't have to hold under/over for the bullet to go into the desired kill zone.

willie_gunn
 
As Willie says, it's about your point blank range. PBR is not, as the papers would have you believe, where the muzzle is touching, or almost touching, the target. Point blank range is the range of distances over which a desired size of target (for deer a 4" circle is assumed for the kill zone) will be hit without any aiming off.

As you know, the trajectory is an arc. For most practical purposes you will zero your rifle so that the bullet starts off at a slightly upward trajectory. (Note that it never goes above the line of the barrel as some people think. It leaves the barrel in line with the bore, and the trajectory starts to drop away immediately.) As the distance from the muzzle increases, departure from the initial line of travel increases, giving you an arc.

The point blank range is measured from the first instance the bullet passes through the bottom of that 4" circle, right through to when it drops out of the bottom of the circle. Of course sometimes there will be a section in the middle where the bullet is out of the top of the circle. This is where zeroing 1" high at 100 yards comes in for the .243.

The .243 trajectory is such that, if you zero dead on at 100 yards, your final pbr (where the bullet drops out of the circle) is fairly close. This reduces the range of distances where you can "point and shoot" without estimating range and then estimating the bullet drop. If you zero 1" high at 100 yards, you get the best maximum pbr, so from the muzzle (if your scope centre line is less than 2" above bore centre line, otherwise a short distance from the muzzle) right out to around 200 yards you can put the cross hairs on the chest and know for certain that you will deliver the bullet into the area that will give a quick, humane kill.

Of course, there are those that are sufficiently skilled and experienced to accurately judge distance, and know the trajectory of the bullet well enough to adjust, indeed some do it instinctively, but the 1" high (ok, it varies for different bullet weights and mv's, but 1" high is a good start point) gives you that little bit of extra "safety margin".

Edited to add, I just found a great explanation HERE
 
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Right lads thanks for that, I suppose as most of my stalking is in dense woodland at less than 100 yds I get away with it. As all of you have explained I may rezero my 243
 
Can someone answer me the question why people zero high at 100yds, to be on at say 150yds, I just zero on at 100 and elevate for extra distance, I may be wrong but it has worked for the last 30yrs. If there is another reason I am willing to learn.

What ever works for you, I zero 1 inch high at 100 yards, puts the bullet in the kill area from 0 to 200 yards so no need think about aiming high.
 
Taff, as I said, it's an edge for those who need it, but if you're used to estimating range accurately and judging the trajectory then there's no need to change. I do it because that's what I've been brought up with, others don't, it's a personal thing.
 
Right lads thanks for that, I suppose as most of my stalking is in dense woodland at less than 100 yds I get away with it. As all of you have explained I may rezero my 243

Taff. One thing to consider, is that your sight picture will change slightly. You've spent thirty years working with your current sight picture and got good results. I have spent 45+ years shooting rifles based on a 1 inch high at 100yds sight picture. I did try to change to shooting dead on at 100yds, didn't like the results and changed back. For deer out to 180yds, I just aim at the chest and fire, I don't make any allowances for elevation changes.

Good luck. JCS
 
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