A cartridge reborn

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Producing a new concept in clay pigeon cartridges can be problematic, especially when the existing components are designed for other things and less than ideal for the new task at hand.

Bearing this in mind, out of necessity, the first batches of 21-gram 12-bore cartridges were made up at the reloading bench in 2002 using once-fired empty cartridge cases, to establish whether there was actually going to be any mileage in the concept.

This was achieved by utilising modified components that were readily available, together with spacers to take up the excess space within the wad, which was necessary when employing the light 21-gram shot charge.

24-gram plastic wads designed for Trap loads in 70mm cases worked well in 65mm cases with 21 grams of shot

24-gram plastic wads designed for Trap loads in 70mm cases worked well in 65mm cases with 21 grams of shot

After some general pattern testing and practical shooting, at a mixed variety of clay pigeon layouts, it became clear that the ultimate proof needed to encourage commercial production would be to assemble some 21-gram cartridges, using new components that were generally available in the UK.

The first experimental batch of commercially viable, 21-gram cartridges were assembled in 2003. They used an unusual pick-and-mix combination of standard components that were commercially available.

After careful internal volumetric measurement and a general study of the various wads and cases to hand, the plastic wads chosen were designed for 70mm-cased 24gm Trap loads, but the cases were 65mm plastic and the powder was of the fastest burning type, designed specifically for 24-gram loads.

This was because the shorter shot column of the 21-gram load took up less space inside the wad than the intended 24-gram version (in its 70mm case), 21 grams of shot just filled the shot cup sufficiently in a 65mm case.

Deep crimps were needed initially, to allow the proper combustion of the powder but the use of a slightly heavier powder charge changed this.

Using the same barrel of the test gun used in all the previous cartridge testing (12-bore over-and-under with a slight overbore to .733inch, extended tapered chamber cones and a 19thou fixed choke constriction at the muzzle), the velocities obtained with these first loads were around 1180 feet per second at 2.5 metres, well within the range of speeds recorded for typical club 28-gram fibre-wadded clay pigeon loadings.

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The felt recoil of these loads was extraordinarily low, but there was room for improvement in the overall design. Going to an increased powder charge (which was eventually plus 14 per cent from the original) gave a clean powder burn and eliminated the need for a deep crimp.

This was done in two stages and it pushed the velocities up to 1200fps at 2.5 metres, then to a relatively sprightly 1225 feet per second at 2.5 metres. Interestingly, the felt recoil was not much different with the faster versions, being only slightly greater than the first one.

Deep crimps were initially used, but this was found to be unnecessary

Deep crimps were initially used,
but this was found to be unnecessary

So here was the resting place of the first viable MK1 version, with its very low felt recoil, useful velocity and relatively cheap production. At this point the lead shot price had not risen to its now relatively high levels.

Some felt clay pigeon shooters would shun such a light load and that the only practical purpose of this low recoiling 21-gram load was as a budget cartridge for teaching new shooters, without the attendant recoil problems of some of the existing heavier 24- and 28-gram cartridges.

The main drawback for more serious penetration of the market by these MK1 type commercial loadings, was the universal use of a plastic wad, which greatly simplified production but also limited the sales potential of these loads to shooting schools and or grounds that permitted the use of plastic wads.

The 21-gram plastic wadded loading would also need an edge over the MK1 versions if it was to garner greater appeal among more experienced clay pigeon shooters.

The lack of a fibre wad version was no small consideration, as at local club level, probably more than 85 per cent of small clay clubs have fibre wad only rulings. Clearly fibre equivalents of the MK1 loads were required, before any general uptake of the concept could be realised.

Tim Woodhouse

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