Using ball ammo for airguns
Airgun owners had been using round lead ball ammo in their airguns for hundreds of years. Real muskets and pistols used this ammunition, so initially the very first large bore airguns did so likewise. Even after the arrival of what we know today as the traditional airgun pellet, many late Victorian and Edwardian airguns were still fed on lead ball ammo in the standard three airgun calibres. Modern steel BB's developed more in the US but as everyone knows, although tough and resilient, they also bounce on target for the same reasons and are disliked by many shooters.
Despite the popularity of ever better pellets, lead ball ammo survived and is still available in some of our most popular calibres. Obviously .177 or 4.5mm immediately come to mind. Lead balls don’t bounce on impact unlike BB's and it's been a very long time indeed since steel BB's were run through any airgun in this collection. As for the other calibres, ball ammo can still be found – just. With the current interest for large lozenge shaped slugs for air rifles people have overlooked the simple effective round lead ball.
With pellets, the skirt is gripped by the lands and is given a twist as it flies up the barrel to the muzzle. It’s always been a personal concern that if a pellet is too tight in the bore this results in severe damage to the pellet. If recovered later the skirts can look like they have been chewed by a critter with very sharp teeth, and that's surely not going to aid accuracy. In the worst cases this must surely affect the pellet's flight at anything over shorter airgun distances. Sizing down your pellets in a purpose-made sizer, or choosing a different pellet altogether can help minimise this. With modern choices a pellet with a different head size may be all that's needed; allowing it to fly with less restriction and damage whilst still allowing the lands to spin it for better accuracy.
A round ball fired out the barrel is given the same spin inside the barrel, but if too tight this could be even more detrimental. A round sphere surface that’s scored dramatically by the rifling must surely affect accuracy even more. On the cricket field using saliva to help assist a smooth flight or deliberately scoring a ball with a fingernail are two examples of how a smooth round projectile can be made to fly better or not at all.
Fine tuning therefore starts with determining what the bore is to try and match it to individual ball ammo sizes still available and is no different to testing with a selection of pellets. With .177 balls this is thankfully more simple. The continued use of round ball ammo in and around 4.5mm is still continued in places like Germany with the many Ball Repeaters still used there in clubs and shooting associations. However whilst here we may only find Gamo 4.5mm ball, on the Continent numerous options are or were once widely available. The smallest so far seen has been 4.30mm, rising to a more common 4.4mm for use in many pre-War German military trainers, rising to the very common 4.5mm, then to 4.95mm, this being the largest once seen in this calibre. If a selection can be obtained in those sizes still available, testing a chosen airgun should arrive at a good compromise whether in a rifle such as the rare Podium 286 lead ball repeater or the many recent BB pistols. These latter are seen everywhere today, some of which now claim 4.46mm as their calibre instead of 4.5mm. Steel BB's can withstand harsh treatment inside an airgun's mechanism but sometimes at the cost of accuracy. With some designs such as the iconic Makarov MP-654k there may be a trade-off when swapping to better lead ball as the softer material may not be robust enough, unless the pistol is tuned before use.
With .177 so popular it stands to reason that there’s more choice in this calibre. For .22 calibre or 5.5mm choice is more limited but still worth investigating. Here Gamo 5.5mm ball ammo can be found without much difficulty, but elsewhere there are a number of other manufacturers still supplying this calibre in lead ball. The average ball is 15g in weight which isn’t that far off from many common mid-weight pellets in this calibre. However as a solid projectile, impact and penetration will be far greater.
Going up a notch to .25 calibre is a tad more difficult today unfortunately. Until recently in relative terms that is, H&N made this ball ammo size which was more accurately 6.33mm. They later sold this in two versions with either a graphite coating or copper coating. So maybe that’s where the idea came from for their current copper coated .177 lead balls which have been winning many fans who use them in their Co2 air pistols. At just under 24grains one of these belted out of a tuned sub 12ft/lb springer can certainly give surprising performance. Unfortunately production appears to have been halted by H&N some time ago but new/old stock surfaces on occasion and is highly prized.
Sourcing lead balls in sizes bigger than .177 therefore can be time consuming but will reward the user with some interesting shooting experiences. Within shooting sports custom mould fabrication and hand casting is still undertaken especially by black powder fans. Measuring the barrel's bore accurately with test firing into a cloth backstop or pushing a selection of ball ammo through the barrel for recovery and examination later, will give a far better indication of the exact bore size to then work to if making a mould. Doing this for airgun ammo may appear to be a little out there but the resulting mould and the cast ammo can then be perfectly matched to it. That is not as crazy as it sounds, witness how many different head-sizes are available for pellets in both .22 and .177 now which allows considerable fine tuning for a perfect pellet to barrel match.
This may be too much for occasional airgunners but once upon a time to make things slightly easier you could buy off the shelf airgun ammo moulds and casting kits. Made by LEM in Blackpool these slug and ball moulds from the 70s were once popular and today they are worth their weight in gold for this purpose when they appear for sale. However the option still exists to ask a hobby engineer or airgunsmith to make a small bespoke mould in any chosen calibre opening the door to some interesting shooting experiences with ball ammo.