Which ELEY tenex air Head Size Should I Buy: 4.49, 4.50 or 4.51?

ELEY’s answer is to try them first: every firearm is different, so buy all three and test them in your own airgun. ELEY tenex air is offered in 4.49 mm, 4.50 mm and 4.51 mm head diameters precisely because airgun barrels differ from one another, and the correct head size is the one that suits your barrel’s bore, which is not something that can be recommended in the abstract. It is the same logic ELEY applies to batch testing in .22LR, where the best ammunition is always the production lot that performs best in your rifle.

Why Three Head Sizes Exist at All

ELEY’s research into pellet performance identified pellet profile, dimensional consistency and weight control as the key parameters influencing precision and repeatability. Head diameter sits squarely inside dimensional consistency, and it is the one dimension that has to be matched to something outside the pellet: the barrel.

Nominal 0.177 barrels are not all identical. Bore and groove dimensions vary between manufacturers, between models and between individual barrels, and they change as a barrel wears. The head is the surface that engages the rifling and centres the pellet in the bore, so a head that is marginally too small can sit slightly off-centre and take the rifling inconsistently, while a head that is marginally too large loads harder and can be deformed on the way in. Offering a single nominal size would mean accepting that the pellet is a compromise fit in most barrels; offering three means the shooter can find the size that genuinely fits.

The Same Logic ELEY Applies to .22LR

ELEY’s entire test range operation exists because of this principle. Because every barrel has its own unique characteristics, and each batch of ammunition performs differently, a thorough testing process is essential. What performs flawlessly in one barrel may not deliver the same results in another.

ELEY runs five batch testing centres, in the United Kingdom, Hungary, Germany, the United States and Canada, where up to 20 batches are fired through the shooter’s own barrel, ten shots at a time, with the best-performing batches shortlisted for a further 30 shots each. Hundreds of shooters, from club champions to Olympic medallists, go through that process every year rather than assume a product name is enough. Head size selection in an airgun is the same problem at a smaller scale, and it deserves the same method.

How to Test the Three Sizes

1. Get all three. Buy a tin of 4.49 mm, 4.50 mm and 4.51 mm.
2. Shoot from a rest, at your competition distance, in one session and in the same conditions, so barrel, weather and shooter are constant and head size is the only variable.
3. Shoot enough shots per size for the result to mean something. A five-shot group can be dominated by one flier.
4. Judge on the whole group, not on the single best group. Consistency across strings is what wins a card.
5. Re-test when things change: a new airgun, a rebarrel, or significant round count through the current barrel.

Keep a note of which head size won and by how much. If the result is close, shoot the comparison again on a different day before committing.

Two Practical Points

The rest of the pellet does not change across the three sizes: all are 0.177 flat-head pellets weighing 0.531 g / 8.2 grains, all carrying ELEY’s published weight control figure of 30 per cent superior to other brands. Head diameter is the only variable, which is what makes the comparison clean.

Treat the pellets carefully while you test. tenex air ships in damage-resistant, re-sealable packaging because a dented head or a bent skirt is a flier before it is ever loaded. Keep the tin sealed, and do not let a handling artefact tell you a head size does not suit your barrel when it does.

The Bottom Line

There is no universally correct answer between 4.49 mm, 4.50 mm and 4.51 mm, and ELEY does not offer one, because every firearm is different, which is exactly why all three sizes are made. Head size interacts with your barrel’s individual bore dimensions, so try them first: buy all three, shoot them side by side from a rest over enough shots to be meaningful, and let the target tell you which one your airgun prefers.

It is the same conclusion ELEY reaches for .22LR: the best ammunition is the one proved in your own barrel.