Thread: Long Range Shooting and TBR

Originally Posted by ebf

@Tui4Me, I suspect you simply forgot to remove the angle value when you entered the TBR. Remember that when you use a TBR value, the angle needs to be reset to 0

TBR is just simple trigonometry. You effectively have the hypotenuse, and want to calculate the length of the adjacent side. The formula is:

adjacent = cos(angle) x hypotenuse

There is a small difference between entering just the TBR into a ballistic solver, compared to entering the line-of-sight range and the angle. But it should not be more than 1 or 2 clicks, assuming your turrets are 1/4 MOA or 1/10 MRAD.

Using shooter I calculated the following:

650y (line of site) @ 15° angle = 70.4" of drop

628y (TBR) @ 0° angle = 67.2" of drop

Error in mm's = 81.28

650y (line of site) @ 20° angle = 68" of drop

611y (TBR) @ 0° angle = 62.5" of drop

Error in mm's = 140

This is now getting into 'missing deer territory' taking other field shooting factors into consideration as well.

Both the examples you have above show an error of less than 1 MOA.

It just illustrates the problem with ethical hunting at extended ranges...

Let's be honest, most guys with their hunting rigs struggle to hit a 2 MOA plate beyond 400 yds

A solid kill zone on a deer to me is about a 300mm diameter circle. Then work it backwards, if you can truthfully hit a 2.5 MOA sized target repeatedly and consistently (under stress and time pressure), then the max distance you should really be looking at hunting is around 450yds.

Originally Posted by ebf

Both the examples you have above show an error of less than 1 MOA.

It just illustrates the problem with ethical hunting at extended ranges...

Let's be honest, most guys with their hunting rigs struggle to hit a 2 MOA plate beyond 400 yds

A solid kill zone on a deer to me is about a 300mm diameter circle. Then work it backwards, if you can truthfully hit a 2.5 MOA sized target repeatedly and consistently (under stress and time pressure), then the max distance you should really be looking at hunting is around 450yds.

In fairness that’s probably for another post.

My guess is that those that are relying solely on their rangefinders TBR outputs to calculate an inclined shot aren’t shooting as steep or as far as they think they are.

Originally Posted by Gibo

Its got me bamboozled

Greeting Gibo,
Me too. In my minds eye I can see all this going on while the deer wanders out of sight and very likely dies of old age.
Regards Grandpamac.

Il stay under 400yds,still gota go and pick up the deer.Good luck with yr findings Tui4Me.

To be fair that if you don't under stand whats been talked about you shouldn't be shooting past 450m at the most.
I would go as far to say there is a hell of a lot of people taking shots at animals and can't work out why they are missing or fluke a good shot every now and again.
Yes I do know what I am talking about.

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Originally Posted by grandpamac

Greeting Gibo,
Me too. In my minds eye I can see all this going on while the deer wanders out of sight and very likely dies of old age.
Regards Grandpamac.

Mate in all honesty you’d be surprised at how quick and prepared you have to be especially with Sika. Often you may get two or three minutes if that.
I’m no stranger to bush hunting but to me there is nothing better than sitting back and watching how animals actually behave in their environment. It’s amazing what I’ve actually learnt about deer.

Originally Posted by Pommy

The way I've had it explained to me is that TBR doesn't account for the bullet having to push through the LOS distance of air. An uphill 600m shot might have a TBR of 550m but the bullet's still got to push through 600m of air, slowing (and dropping) accordingly.

Absolutely agree with this mate. Thanks.

Originally Posted by Tui4Me

Absolutely agree with this mate. Thanks.

Its gravity that is the effect tbr is compensating for not pushing through the air

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Originally Posted by andyanimal31

Its gravity that is the effect tbr is compensating for not pushing through the air

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Its the same thing, without gravity pushing through air is effortless.

Originally Posted by andyanimal31

To be fair that if you don't under stand whats been talked about you shouldn't be shooting past 450m at the most.
I would go as far to say there is a hell of a lot of people taking shots at animals and can't work out why they are missing or fluke a good shot every now and again.
Yes I do know what I am talking about.

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See quite a bit of that on youtube. Long range. Clean misses.

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Greetings All,
So to summarise, the use of true ballistic range to calculate drop allows for all of the drop due to gravity and most of the drop due to velocity loss What it does not allow for is the additional velocity loss due to the difference between TBR and line of sight range (the actual distance to the animal). This becomes significant as inclination and range increase and as ballistic coefficient decreases. The consensus also seems to be that this becomes important somewhere beyond 400 metres. From Tui4Me,s example above the error is around 0.5 MoA at 650yards (600 metres). Hard to hold that close in field conditions. Significant as this may be it seems small potatoes compared to allowing for wind deflection at these ranges. Something to think about.
Regards Grandpamac.

Originally Posted by Mauser308

The interesting bit is this is just one small sector of the LR art form.

Once you add in denisty/pressure variations, wind/air movement, sun position, and the biggie (elephant in the room) pockets of humidity in the path of where you are shooting TBR and angle errors are only a part of the fun. I've been in the butts on a day when fog blew in and while the range was still open as the fog settled (prior to RO calling it through lack of vis) we noted the hits from the good shooters that we were consistently indicating suddenly became misses or edgers and the poor shooters started to really give us the shits with stuff impacting at just over head in the butts. Not exciting at all...

Greetings Mauser308,
And target shooting is on a dead level range with targets at exact ranges. Plus you get sighters to correct for conditions. Went out with my son when he was shooting FTR at 1,000 yards one day. Boy those jokers can shoot. No targets as such you see where your shots go on your cell phone. Hard to see how that level of precision can reliably be achieved in field conditions with all the things you mention plus more. The lack of sighters would be critical.
Regards Grandpamac.

Spent this past weekend participating in a extra long range event on a central north island station.

After speaking to several of the other competitors, and doing some testing, I am starting to think @Tui4Me is onto something here.

I was also not correct in saying the flight time (in the software) for the 2 scenarios would be similar.

Taking the 1000m / 20 degree angle

940 @ 0 : 1.522 sec
1000 @ 20 : 1.622 sec

this is for something leaving the muzzle at 875 m/s, so it does make sense.

The actual flight time will be the longer value, gravity only works on the short leg of the triangle. Because the solver is time-of-flight based, you will get a more accurate value by entering the true LOS value and angle, as opposed to just the TBR value.