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Wednesday, 23 December 2015

Zero Tolerance - tools of the trade!

With Christmas being a season where we often indulge in good food we thought it would be a good time to teach you just how to make sure your rifle is shooting strait so you can put something tasty on the festive table.

Speaking of tasty things for the table keep your eyes peeled over the next few days for a game pate recipe and a report on the venison steak and kidney pie that Geoff accidentally made using the puff pastry his wife had set aside ready to make sausage rolls with.  

A hunting firearm is, of course, completely useless without a sighting system that will allow you to put a bullet precisely where you want it to achieve a humane kill. In simple terms, as a deer manager, I need to be able to hit a tennis ball at a 100 yards, every time and a golf ball is better!

Getting ready for a couple of zeroing shots on misty morning with my Browning X-bolt chambered in 6.5 x 55 mm
I'm sure that I could write a small book on the subject and I'm sure others have, so I'm going to keep this simple. I need the point of aim and the point of impact to coincide at my chosen range or at the very least, to have a known point of impact with reference to my aiming point. For my deer rifle, I have chosen to have my bullet strike the target one inch above my aiming point at 100 yards and that means that it's one and a half low at 200. So I can shoot at any range from 25 yards to 200 without having to worry too much about adjustments, the same point of aim at any of those ranges will have the bullet strike that same lethal, palm sized target area.

Adjusting sights to achieve this is called zeroing and it will be required when a new sight is fitted or if the existing one takes a knock or just drifts off under constant use and handling, a change of ammunition will also require a check to ensure zero is maintained.

Today of course, most people use a telescopic sight but the same principle existed in bygone days when open or 'iron sights' needed to do the same thing, deliver a bullet exactly where required to do the job. Almost 40 years ago,  I regularly shot at targets at 600 yards with open sights and people still do that at targets but hunting with a rifle at any range nowadays is almost invariably achieved with a telescopic sight.
M1911 Hausse.JPG
Adjustable rear 'iron sights' on an old rifle, iron sights normally consist of a rear 'notch' and a front 'post' which must be aligned with the target. They are normally a permanent part of the firearm unlike a telescopic sight which can be removed.
"M1911 Hausse" by Bouterolle - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons.

I am fastidious in attaching a 'scope, with screws tightened sequentially and in small increments at each turn so as not to have everything biased toward the first screw which you tightened so darned tight. Once it is firmly attached, you can secure the rifle and check that the scope and the bore are pointing at the same target, you can make adjustments even at this stage if you are confident enough and if you are inclined to, you can buy a small laser device to chamber like a bullet and that takes out some of the estimating out of the process.

Now there is no option but to fire a couple of rounds at a target after you have ensured the safety of the target area and it's back stop of course. I tend to use squared or good old graph paper to make the corrections easier to calculate and have a 1 inch 'bull' at its centre. For this process you can fire groups of 3 shots to establish a mean point of impact or you can fire single shots and use those for corrections.

My process would be to fire a shot and use the squares to establish that it was 'x' inches right of my required impact point and 'y' inches above (or below) my desired impact point. The adjustments on the sight will typically 'move' the impact point by a quarter of an inch (at a hundred yards) per click, so convert the required adjustment from inches to clicks, make that adjustment and fire again to see if you got it right first time or not, repeat the exercise until you get it 'spot on'.

Here I'm firing a zeroing shot from a prone position off a bipod, it's important when zeroing to do so from as stable as position a possible so as to take as much human error as possible out of the process. 

The acid test is then in the field and in the event that you miss or hit the target somewhere other than where you were aiming, you need to check zero and get it spot on, there can be very little tolerance to achieve what is required, we owe it to the target species to get this right.

Take care in the field!

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