Short Range Zero | Zeroing At Shorter Ranges

FEATURE Marcus O’Dean

Zeroing at shorter ranges

Marcus O’Dean explores achieving a maximum point-blank range hunting zero when shooting space is limited. 

At ANZAC Rifle Range in Sydney’s Eastern Suburbs, access to our magnificent facility is limited to one day a week, where National Rifle Association of Australia disciplines are shot at mostly longer ranges, from 300-800m for Fullbore Target Rifle and F Class (300-800m), while on the Service Classification Range, where I compete in Service Rifle most Saturdays, 100m competition occurs roughly one Saturday a month. Depending upon my volunteer responsibilities as coach or range officer, I sometimes have little opportunity to set up a discrete target to the side to accurately zero and chronograph centrefire hunting rifles 3-4 inches high to be effective in the field.

If you are unfamiliar with the concept of ‘maximum point-blank range’ (MPBR), for hunting it can be simply defined as ‘the distance at which the bullet will neither rise nor fall below the vital area of a target animal when aimed at the centre of the chest’.

Early personal experience

On one of my earliest fallow deer hunts I was fortunate to stumble upon a bachelor herd of fallow bucks after the rut. They were positioned at the end of a long valley which I ranged to be 316m. I had zeroed my rifle, a 6.5 x 55 Swedish Mauser, at 200m shooting a starting load (I had no chronograph then) with 120-grain Sierra ProHunter projectiles. I settled over a log and aimed at the backline of the most obvious deer and it went down.
 
Then the herd came running towards me back up the valley, where I shot a further two at 80m and 30m respectively, both one-shot kills. 

Walking down the valley to the first deer, he was sitting upright alive and was shot through the bottom of the brisket. I finished him there but was disappointed at the suffering I had caused and was surprised at the drop because it was a good shot. 

The following week at the range, I confirmed the drop at 300m as being 14 inches. How could that be with a 200m zero? It was then I bought a chronograph and learnt and applied the principle of the maximum point-blank range and, provided I did my bit, no pig, deer or goat was safe out to 300m.

Applying the MPBR principle

If we are talking of medium game animals, like fallow or chital deer for example, an eight-inch vital zone fills the bill. For larger red or rusa deer, we may consider a larger vital zone; say 10 inches. Why am I speaking in imperial measurements? Because shooters think in minutes of angle, one of which is easily visualised as one inch (actually 1.047 inch rounded off) at 100 yards. For the purposes of this article, let’s work with an eight-inch vital zone.

If your zero allows your bullet to rise no further than four inches above, nor fall more than four inches below your line of sight, you will be able to maximise the hunting range you engage while being able to aim at the centre of your game’s vital zone, i.e., the chest area. This gives you a good basis for all deer species (with the exception of hog deer) in Australia while giving you good ‘wriggle room’ for error for larger deer species.

Visualising MPBR

To visualise the principle of MPBR, imagine that you are shooting down a pipe with an inside diameter of eight inches with the muzzle at the centre. With the correct zero applied, you maximise the length of that pipe with the bullet reaching its elevation apex (just inside the top of the pipe) somewhere over halfway to your target. At ranges very close to the muzzle the bullet will print low and it will gradually rise, crossing your line of sight (a few inches above the bore line) until it reaches its apex and begins to fall again. With a slightly higher zero at 100 yards/metres of three-plus inches at 100 yds/m, with most high-velocity hunting centrefires these days, the bullet will hit its apex of four inches high at somewhere just short or beyond 150 yds/m, from which point it will start its descent back towards the line of sight. At about 200 yd/m the bullet will have only descended back to being close to three inches above line of sight and it will bottom out at four inches low, around 300-plus yards. 

Now to 50 yards/metres 

Using my shorter-range availability for discretionary shooting, mostly, my opportunities arise at 50m. If you are in a similar situation, then this solution could be for you.

Using a Sierra ballistic program, I asked it for data for the example .270 Winchester 130-grain load I used in this article.

The figures it yielded gave me a 1.35-inch-high zero at 50m. At 200m it was 3.3 inches high, at 300m it shot 2.85 inches low and at 325m was 5.5 inches low. One could reasonably assume 315m would be the resultant MPBR.

Some cautions 

I have found Sierra’s Infinity 6 program to be a very good predictor to apply to hunting ranges, providing most of your inputs are accurate. These include:

•    The bullet weight and design
•    The muzzle velocity of your load
•    The scope height above the bore line
•    Altitude of range

Zeroing at closer ranges necessitates you having to be more precise in landing your bullets pretty much spot on the height above line of sight and for windage. To that end, I design a target that suits my cartridge, projectile and muzzle velocity. I have included one in the images where I have zeroed a 6.5 Creedmoor shooting 140-grain soft point hunting rounds, which yielded a sight in height of 1.54 inches above point of aim at 50m. This yielded a MPBR of 285m.

Throughout this article I have chopped and changed between yards and metres and I hope that you are not confused. What you choose to use will depend very much on your local range or bush block. In my case, my access is to a metric range, so I tend to work stuff out at 50m through all applicable distances. Experience over years has built a little predictive calculator in my head, where I can visualise requirements by a chambering’s characteristics to an extent. 

Get your height above point of aim right at 50, 100 or whatever range you zero with a view to extending your ‘more certain hitting range’ in the field and it takes much guesswork and ‘hail marys’ out of the equation. Your field results will be more humane and certain. 

Whatever the case, zero your centrefire medium-big game rifle 3.5 inches high at 100 yards or metres (or 1.5 at 50) and you will be close to a MPBR zero by a useful rule of thumb.

Example of how zero affects MPBR

Using a .270 Winchester 130-grain spitzer bullet at 3100 feet per second as a ‘for instance’, a 3.1-inch-high zero at 100 yards (3.25 inches high at 100m) the bullet reaches its highest point at 154 yards, crosses the line of sight at 278 yards and has a maximum point-blank range of 326 yards, where the bullet has fallen four inches below line of sight. 

Now if you decided that a 200-yard zero was a better bet, think again. Remember the 3.1-inch high 100-yard zero in the example? Well, it would result in the bullet being roughly the same height above the line of sight at 200 yards.

With a 200-yard dead-on zero, you are 1.2 inches high at 100 yards. At 150 yards the bullet is 1.2 inches high. Go past the 200-yard zero and the bullet is now below the line of sight so that, at 260 yards you are at the bottom of the pipe; four inches low. So, 260 yards is the greatest distance you can hold dead-on to achieve a vital zone hit. At 300 yards your bullet has fallen 6.2 inches below line of sight. All other things being equal, you have a wounded animal. 

You have effectively lost 66 yards of maximum range for dead-on hold using the often-touted 200 yard zero. Those who tout it would likely never have shot beyond that distance, or if they had they wouldn’t probably tell you.