NEARLY all rifles suffer a loss of accuracy at some stage.

Consequently, facing and fixing accuracy problems is a normal part of a rifle shooter's life.

Because the first step is to find the problem's cause, we must look at possible explanations.

Admittedly, the field of possibilities is vast, for the laws of several sciences govern the way rifles work.

That is, rifles call on branches of physics, chemistry and, believe it or not, biology.

So where do we start? How do we avoid wasting lots of time? Answer: when a rifle becomes inaccurate, it is time for the "p" word.

That word is parsimony.

In the sciences, parsimony refers to possible explanations.

One possibility is more parsimonious than another if it needs fewer logical steps and makes fewer untested assumptions.

Guesswork is minimised or, better still, eliminated.

In short, parsimony is good.

If a suggestion is strongly parsimonious, it's more likely to be right.

Fortunately, the most parsimonious responses to accuracy loss are already known.

Let's dip into them now, starting with some common problems:

We've changed the ammunition and the bullets are no longer hitting the right place.

That is, the rifle has lost its zero.

Switching from one brand or type of cartridge to another changes the barrel's vibration pattern, so the point of impact often alters too.

Remedy: sight-in the rifle to suit the new ammunition.

Re-zeroing deserves to be part of every ammo change.

The ammunition is of good quality but does not group well - that is, the clusters of bullet holes on target are loose rather than tight.

All rifles behave as individuals, and some show strong ammunition preferences, so the ammunition may not suit this particular rifle.

With factory rounds, try another brand or type.

If the cartridges are handloaded, a change in the powder charge or the bullet seating depth may be enough to fix things.

One or more of the ring screws or base screws securing a telescopic sight may be loose.

Tighten them.

If this doesn't work and no other cause can be found, there are two possibilities.

Either the scope rings are not aligned with each other or the scope's internal adjustments are faulty.

Test by fitting a different scope - if accuracy improves, the fault was inside the original unit.

If sighting-in adjustments have been based on the points of impact of single bullets instead of the centre of a group of at least 3 shots, the rifle may seem unable to hold its zero.

In fact, it could be holding its zero well but that zero is not where the shooter thinks it is - in which case, the problem is the single-shot zeroing method, not in the rifle.

We haven't finished yet.

In the meantime, practise parsimony.

It pays.