.243 drop rate and trajectory

[alan j]

Sighted my 243 in at 1 inch high at 100 yards with winchester 80gr factory loads (silver pack). I was surprised when it dropped 3.5 inches at 200 yards. The pack says should be 0 drop at 200. Is this a normal amount of drop for a .243 at 200yd ?

[Wm.Traynor]

This site might be of help

www.shooterscalculator.com

[RDobber]

What rifle are you shooting them in, Alan?

Check the pack, does it say what barrel length the ammo is benchmarked from? Shorter or longer barrel effects the velocity and will change the result a little.

[alan j]

Rifle is a Tikka hunter blued. Im new to centrefires and thought this drop may have been a bit excessive.

[SendIt]

Sighted my 243 in at 1 inch high at 100 yards with winchester 80gr factory loads (silver pack). I was surprised when it dropped 3.5 inches at 200 yards. The pack says should be 0 drop at 200. Is this a normal amount of drop for a .243 at 200yd ?

Silver box, are we talking about Winchester Super-X here?

Assuming that's right, their site says 3,350fps muzzle velocity and 0.255 BC so trajectory calculator based on that says....

100m +1"
200m -2.4"
300m -10.4"

Muzzle velocity chances a little with barrel length like RDobber says but that's the neighbourhood you're talking about. What you've experienced seems right looking at the calculator.

I didn't see a ballistics table on the Winchester site, where did you get the info that +1" at 100y is 0" at 200y with this ammo?

If I looked up the wrong ammo let me know the specific one and I'll put it through the calculator again for you.

[alan j]

i just checked the box of super x it has a ballistics table on the back.. 3350 muzzle 100yd +1.3 gives a 200 yd 0 so my mistake i thought it was +1 inch at 100 for a 200 zero. However the drop was 3.5 inch in a tight group of 5. So based on your calculator this would be acceptable. ?

[Apollo]

Here is one of the best ballistics calculators going around if you give it the best input you can.

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

I use this all the time, especially for competition shooting with different ranges around and with data for the location to be used it comes out pretty close. If I sight in at home and adjust the distance I'm on target first shot at a match.

You may perhaps find that you are not achieving the stated velocity which is quite on the cards. Unless you can check your own velocity with a Chrony then you really are guessing.

I load 80gr Bullets for a mate's .243W Tikka Varmint for competition and the velocity is around 3,200fps perhaps 3,100fps. I don't have the last chrony figures to hand. I would think the stated factory velocity is a bit over rated and if I was to try and come close with hand loads I would say they would be a very hot load and something I would not consider trying.

Running the figures as per the factory loads does come out pretty close for a 200 yard zero, 1.1" high at 100 yards but it all depends on your own rifle. I'd say you aren't getting close to the factory stated velocity. Many factors will influence your own results.

I shoot 300 metre competition using 90gr Berger Boat Tails and they are pretty accurate.

You might also find different results on a day with different weather conditions.

Don't believe what factory specifications are supposed to be, how they were obtained is the big question.

[Fujix]

i just checked the box of super x it has a ballistics table on the back.. 3350 muzzle 100yd +1.3 gives a 200 yd 0 so my mistake i thought it was +1 inch at 100 for a 200 zero. However the drop was 3.5 inch in a tight group of 5. So based on your calculator this would be acceptable. ?

It sounds about right, tough to say much more than that as we're guessing a few factors here.

It won't be a perfect match to what's on the box.

1. They doen't say what barrel it was shot it.

2. Whatever they shot it in will be a little different to your barrel.

3. Without testing it's possible there figures are a bit "generous"

Rule of thumb on barrel length and velocity is you lose 30 feet per second muzzle velocity for every 1 inch shorter that the barrel is.

The only way to get a really accurate table is chronograph the load from your rifle then you can put it in the calculator and get the rise/drop at any distance you like.

When you're at the range keep an eye out for someone running a crony and ask if you can put 10 rounds through it. Record all the velocities and get the average, then you could work it out pretty well from that.

[Apollo]

The other thing that has an influence of velocity figures is the actual bore size. Even in the best custom made barrels and depending on how they rifle the bore is they can be a tight or loose dimension.

Using a chronograph is a start to at least get a better idea of what any round will do in your rifle. Foul the bore first then shoot a couple of groups is a basic test.

Really, if you are going to shoot exactly the same ammo all the time, all from the same batch then just use the figures you get and stay with them until you make a change.

If you sight in to be 1.0" high at 100 yards and it's 3.5" low at 200 yards then fiddle with the velocity figures in a ballistics program until you match your results. Then you will have all the drop points for virtually any distance.

[Chronos]

My guess would also agree with others here and the factory velocities quoted are "generous"

A quick play with "ballistic" shows you might be down about 200fps on those figures but that's not a big deal, no goat will be able to tell the difference

If it's grouping well as you said I'd be tempted to just click it up 1/2 a MOA and go hunting. That should give you a max point blank range of around 250m for a 4" target and that's good in anyone's language.

Chronos

[RDobber]

If it's grouping well as you said I'd be tempted to just click it up 1/2 a MOA and go hunting. That should give you a max point blank range of around 250m for a 4" target and that's good in anyone's language.

Chronos knows what to do

[brett1868]

I've never really understood the whole 1" high at 100 thing, what's the point of it? Zero @ 100 and work the drops out from there. If a round drops 3" from 100 - 200 then aim 3" higher. Otherwise you have to -1" for whatever the ballistic table tells you the drop is out past 100.

[Apollo]

I've never really understood the whole 1" high at 100 thing, what's the point of it?

In my view and use. Not many scopes have reticles that show elevation settings, mostly just plain cross hair perhaps a centre dot.

Think PBR (Point Blank Range) where the trajectory will hit a target within a certain hit zone. The hit zone being say 100mm (4") as in the case of a lot of calibres that 1" high at 100 yards will give you a PBR range over 200-250 yards so anywhere from your location to the target will be a hit in the vital zone.

To use this the average Joe will find it a lot easier to see and place shots for settings at 100 yards (metres) than trying to set a zero at 200 or so if he can actually see his shots.

If you zero at 100 yards then as you mentioned it's 3" low at 200 yards. First you need to establish that the range is indeed 200 yards and then work out some way of judging 3" aim high point at that distance.

It's something I have used for many years hunting/varminting, especially long range varminting.

Nick Harvey also uses this system and has written quite a long article on it in his reloading manuals.

Most all people I know that go varminting use this system. The height at 100 yards varies of course depending on the calibre's ballistics.

Target shooting is a completely different kettle of fish as the zero range is also your target range but not always like using a zero spot that is not target centre so you don't shoot out your aiming spot.

Just a few thoughts....

[Wobble]

I've never really understood the whole 1" high at 100 thing, what's the point of it? Zero @ 100 and work the drops out from there. If a round drops 3" from 100 - 200 then aim 3" higher. Otherwise you have to -1" for whatever the ballistic table tells you the drop is out past 100.

Useful for hunting, especially on game with reasonably large vital areas.

Lets you just aim and fire and if you're target is 100 - 300 you'll hit it.

Instead of seeing it, guessing the distance, trying to remember the drop and then compensate for it all while the deer is noticing you and flexing the legs to bolt.