Trajectory calculator that shows where a bullet first crosses the actual axis of the barrel

[tonyshooter]

Can anyone help me please.

I have a thermal sight on my rifle and I need to know the range at which the bullet first crosses the axis of the barrel ( possibly around 20m ), and not the second time it crosses the axis of the barrel at 100m which is the range at which it is zeroed.

This thermal sight virtually precludes me from shooting at taget cards to find the answer by convential methods !

 

Can anyone sugest a reloading where it can find / generate this data.

 

Thanks.

 

Tony

 

[SchmidtP3]

Play around with this calculator- 

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

You can adjust the range increments down to 1yd. Barrel length, sight height, bullet BC - it's all there.

[Kevgun]

You can do the same on Strelok pro, by putting in all your relevant details then go to the table settings and set for 5 yard increments, then just look at the table, this is how i setup my thermal, first zero 85 yards 2nd Zero 235 yards just over and 1 1/4 at it's highest point. this is for a 22.250 using 50 gr Vmax

[Arell]

On 2/10/2021 at 10:29 PM, tonyshooter said:

Can anyone help me please.

I have a thermal sight on my rifle and I need to know the range at which the bullet first crosses the axis of the barrel ( possibly around 20m ), and not the second time it crosses the axis of the barrel at 100m which is the range at which it is zeroed.

This thermal sight virtually precludes me from shooting at taget cards to find the answer by convential methods !

Can anyone sugest a reloading where it can find / generate this data.

Thanks.

Tony

 

 

Slap me for being pedantic... but... The bullet only 'crosses the axis of the barrel' as it travels along it. After exiting the barrel the bullet will only ever being falling away from that axis on an ever diminishing curve... assuming you hold your rifle the right way up and relatively level(!)

In this instance, the question relates to the curvature of the bullet's trajectory and the single point at which it becomes tangent to the constant of your scope's reticule - if successfully calculated / verified.

It's a good question. There will be a long list of variables to consider though - combining the curvature of your bullet's trajectory whilst factoring in the centreline of your scope from the centreline of the muzzle - especially with a NV/Thermal unit, potentially mounted relatively high. 

As others have mentioned a ballistics app will get you close. Hopefully close enough to then verify with stepped paper targets at 10yrd intervals out in the field before finalising your zero.

[phoenix]

http://www.shooterscalculator.com/point-blank-range.php

Plug in:

Bullet BC

Muzzle velocity

Sight height

Target size (only necessary to get the calculator to work)

The result will give near zero, far zero, minimum PBR, maximum PBR and POI at 100 yards

 

Cheers

 

Bruce

[Kevgun]

I use the same setup with Strelok pro on my Android Bruce, takes about 5 minutes to measure and input all the data, providing you don't enter rubbish , you get very accurate data out of it. I'm out on Sunday setting up a keepers NV for MBPR

My own Ward thermal is zeroed at 80 yards with a 2nd zero of 270yards, so point and shoot to 300 which is more than good enough.

 

[phoenix]

Use a hot hands bag as a target for your thermal scope.,

Stick one on a target board at 100 yards (or your preferred zeroing distance) and shoot at the centre of the hot spot

If you can put bullets into the bag you are within one inch of a perfect zero

Remember that you are zeroing a thermal scope, not a target scope, so forget about 1/2" groups, or even 1" groups.  

I also would not be trying to head shoot any animal with a thermal scope - aim for the middle of the heat blob!!

 

Cheers

 

Bruce

[Sherlock]

On 5/20/2021 at 4:45 PM, Kevgun said:

I use the same setup with Strelok pro on my Android Bruce, takes about 5 minutes to measure and input all the data, providing you don't enter rubbish , you get very accurate data out of it. I'm out on Sunday setting up a keepers NV for MBPR

My own Ward thermal is zeroed at 80 yards with a 2nd zero of 270yards, so point and shoot to 300 which is more than good enough.

 

Hi Buddy  - what rifle is that your shooting.

My 22.250  (zerod at 70yrds)  and shooting a 40 gn Nosler at 4050fps has a primary zero of only 180 yrds - I thought that was fast and flat. 😎    What are you shooting to give you a 2nd zero of 270 yrds  😘

 

S 

[Kevgun]

How high does your Scope sit above the bore line?  the higher the scope sits above the bore line then the further between the 2 zeros but seeing as most people are obsessed with the scope being as close to the bore line as possible then this would  reduce the distance between the 2 zeros 

So with a 40 grain Vmax doing 3800fps using my x15 Drone pro Zeroed  at 60yards and Scope height above bore line of 2.75 inches the 2nd Zero is 260 yard and 2.4 inches low @300 yards the highest point between the 2 zeros is 2.1 inches

I set mine up using the MPBR method, for instance if you zeroed your rifle nearer , say 60 yards, then the 2nd zero would be further out but your bullet would be higher between those 2 points , but as long as you know exactly what your bullet does at a given distance ( I do ) then using a rangefinder you can make a slight adjustment for the shot, In my case a Rabbit at 200 yards my bullet would be 1.8 inches high, so I would aim at at the bottom of its head, it's a tried and tested method  I have used for years, I'm out 3-4 times a week helping my mate who is a pest controller who specialises in Rabbit control, so we use all means to control them. 

[Sherlock]

HI Kev.  My scope (Thermion on my 22.250) is 1.7 inches from the bore.  I like my all my scopes mounted as  close to the barrel as i can get them.

Most of the foxes i shoot are between 150 and 200 yrds therefore I wouldn't want the highest part of the bullets trajectory curve  to be the distance where most of the action happens.   

But whatever paddles your canoe  👍  😎

[Kevgun]

Exactly, but I know I have to come down the Body a tad at 170 ish, but it works for me, I get quite a few across Valleys that are around the 250 -280 mark so, the Rifle was setup for that Job, got so used to it, If it works leave it alone, there is no wrong way as long as it's safe.