Against the grain

Bruce Potts highlights problems he has identified when converting from lead to non-lead bullets in a rimfire and outlines his concerns about this

- Bruce Potts

Lead-free ammunition for centrefire rounds is becoming far more prevalent. But what of the .22 rimfire? To convert a conventional lead .22 calibre bullet to lead-free involves a substitution to the tin or zinc mixture.

This is counter-intuitive, as it means that for a bullet to be the same dimensions – which is the length needed to stabilise in a traditional one-in-16in rifling twist rate – it means that the weight is nearly half that of the original lead .22 rimfire projectile if it’s non-lead. That’s why the only available .22LR lead-free ammunition have bullet weights from 24 to 26 grains (gr).

This brings up another issue. The velocities for such light projectiles increase past 1,500 feet per second (fps), making them hyper-velocity bullets well above the speed of sound. This negates its use as a quiet pest control round with a sound moderator, and has a detrimental effect on ballistics for both consistent velocities, accuracy and downrange energy retention.

Another problem that affects accuracy is lubrication down the bore. This affects fouling and fouling build-up in the rifling grooves of the chamber area, and is worsened by non-lead alternatives. You have to condition the bore when you switch ammunition types. It’s like when you clean a rimfire’s bore – you have to shoot it back in to condition the bore to that type of ammo to achieve best accuracy.

That said, it is pretty much inevitable that lead-free rimfire ammunition is on the cards, and I have three brands to look at to see how they shoot – RWS, Norma and Winchester.