Target Sports

TARGET RIFLE BASICS: A LEVEL PLAYING FIELD?

Created on 14th May 2009

CHRIS WHITE has some advice on cant for TR shooters

THROUGHOUT THIS series we have looked at similarities and differences between smallbore and fullbore shooting. Some of these differences are insignificant but we now come onto an area in which there is a major difference.

The rifle's sights are usually fixed over the centreline of the bore and the butt is placed into the shoulder. Unfortunately the right or left eye (depending on which shoulder you shoot from) is not directly above the appropriate shoulder. This, in theory, means that to get your eye directly behind the rearsight you need to tip your head over. It is difficult to raise a counter-argument to this, although I have to say I have never known it to cause a problem. Tipping the head is thought to be bad because it disturbs the balance mechanism in the inner ear and causes disorientation. It can also cause fatigue in the neck muscles. Be that as it may, you will see that almost all high-level smallbore shooters cant (lean from a vertical axis) their rifles and that‘Supermatch'-style butt assemblies have suitable adjustments to allow the rifle to be canted while the butt-plate remains upright in the shoulder. Having said that, three visits to my smallbore club failed to produce any evidence of cant worth photographing from the assembly of GB and A class shooters present!

If you are going to have the rifle permanently in your shoulder for 20 minutes these issues need to be considered. However, NRA rules require you to deliver your shot within 45 seconds of your target appearing - so even if you have shouldered your rifle well before your marker has re-presented your target, you are unlikely to have it in position for more than a minute at a time.

Canting the rifle has some very bad effects and despite popular belief the smallbore shooter is also affected by them. Imagine that your rifle is canted to the left as you look at it. This means that your rearsight elevation staff is tilted to the left. As you raise the rearsight the eyepiece will go to the left as well as upwards, thus causing a zero error as you increase elevation for longer distances. Similarly, since the wind arm is not level as you put left wind on the rifle you will reduce elevation, and as you put right wind on the rifle you will increase it. This ought to be obvious, but just in case it isn't Figure One should make it clear.

In his 1972 book Target Rifle Shooting (co-written by EGB Reynolds), Robin Fulton claims that a cant of 6° displaces the shot 54" sideways and 3" downwards at 1,000 yards. The theoretical explanation for this is shown in Figure Two (actually showing shot displacement to be 50" and 4" respectively).

What is important here is not how far you are from the target but how much vertical displacement there is between the bore line and the sight line. This is, of course, related to the ballistics of the ammunition - in the case of Robin's argument it's around 40 minutes.

Crudely, if you are shooting at 100yd with a smallbore rifle this figure is between 7½ and 8 minutes, or about a fifth of Robin's 40 minutes. Therefore the lateral displacement is about 10". Instinctively this sounds an awful lot: although I can find no grounds to dispute Robin's theoretical argument, the fatal ‘years of experience' syndrome kicks in. I decided to look into it further. Experimenting with a fullbore rifle is always dependent on range availability and wasn't an option, but outdoor smallbore was no problem. Canting the Anschütz would require radical alterations to the butt assembly settings, so I used the old BSA MkII.

The experiment was not entirely scientific but was conducted by shooting a group at 50m where every effort was made to overcome wind effects (not entirely successfully, as it proved. See figure three). I then fired a group with about 20° right cant on the rifle. This proved so uncomfortable and difficult that little heed was paid to wind conditions (see figure four). Nevertheless, the drastic effect of cant is quite apparent: the group has been displaced about 1½" to the right and about ½" low. QED, as my geometry teacher used to say!

Now if all you are going to do is shoot indoors at 25yd with a smallbore rifle this doesn't matter, provided you can maintain the same angle of cant. If you are determined to cant you can keep this angle consistent by using a spirit level attachment on the foresight. (Incidentally, of course, you can also ensure that the rifle is kept perfectly upright using the same device. See Target Sports May 2008 p72.) When you move from 25yd to 100yd or even 50m and elevate your sights you will also displace the group laterally. This does have an effect on how you deal with wind. While smallbore shooters will generally have difficulty seeing the relevance of this it is something they should at least think about. TR shooters certainly cannot afford to ignore this phenomenon and should adopt a coping strategy.

Canting causing havoc!

Having a different wind zero at every range other than the one at which you zeroed the rifle will cause havoc. So will making a big change in wind setting (a common event at 1,000yd) and finding you have lost a point because the shot has gone high or low.

The standard advice to TR shooters, therefore, is not to cant the rifle under any circumstances. If all ranges had perfectly flat, level firing points this would be relatively easy to achieve. Unfortunately we often have to perform under less than Utopian conditions. My personal attitude is that a small amount of cant is acceptable if it aids the delivery of a good shot - as opposed to forcing the rifle upright, adopting an unnatural position, inputting muscular effort and consequently letting off a bad shot. The operative word is ‘small'.

Most of what we have covered so far is the ‘mechanical side: shooting techniques which should be second nature. Next time we'll remind ourselves of the salient points as a prelude to getting our brains in gear.

TARGET RIFLE BASICS: A LEVEL PLAYING FIELD?

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TARGET RIFLE BASICS: A LEVEL PLAYING FIELD?

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