Originally Posted by mrgeoff
Since nobody appears to have addressed this question, I’ll have a go.
If an airgun manufacturer orders 2000 mainsprings, 1000 ideal for .177” rifles, and 1000 for the more energy efficient .22”, the unit cost will be higher than ordering 2000 identical mainsprings, so it makes sound financial sense to order 2000 identical mainsprings and make them work in both calibres, which can be achieved in two ways.
The manufacturer could use two different amounts of spring preload, or two different piston weights (doubling as top hats). Both methods have pros and cons.
Using preload to set muzzle energy gives fractionally less, and we are talking a fraction of a millimetre, of primary (rearward) recoil, as well as shave a fraction of a millisecond off the compression stroke, and that’s my preferred method, but it does place the mainspring under greater stress. Using piston mass to set muzzle energy fractionally increases primary recoil, but the spring is less stressed, and that is the clincher for the manufacturer, because they want the rifle to perform satisfactorily for tens if not hundreds of thousands of shots, and not be returned for a warranty repair, or get a bad reputation when the rifles are out of warranty, because over-stressed mainspring creep (shortening) has lowered the muzzle energy.
Air Arms springs are top quality, and I have yet to have one suffer creep even after tens of thousands of shots, but then, I'm not a manufacturer concerned at the prospect of thousands of rifles being returned for warranty repairs, or having my reputation trashed because of rifles failing to perform just out of warranty.
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