Sunday, July 9, 2017
A bit of explanation on leaf springs compared to coil springs utilized in fine firearms.
Is there an advantage or disadvantage to one type over the other? Not really, as long as good materials are used, proper workmanship is employed, proper maintenance is implemented. But, you should understand some basic fundamentals as there are differences and there is some misinformation out there.
First, a bit of history. Leaf spring use in firearms goes back centuries. In the past, the technology was available to produce leaf springs. This was not the case with coil springs. Some people like their fine firearm that may have a historical tie to fine pieces of the past.
Leaf springs were used, and are still used, in some of the finest firearms such as Holland & Holland, Westley Richards, and James Purdey and Sons to single out a few. The trigger groups above are from another fine firearms maker, Perazzi.
Lets take a moment to look at a few points worth thought.
Some people state that a leaf spring will maintain the same tension until it breaks, this being it's advantage over coil springs. Simply stated, this is not true. We can dive into metallurgy to show this is not true but we can also set up a simple example which you can do at home to disprove this yourself. Take a simple steel paperclip and bend it partially, back and forth, as you sit in front of television. You may find it breaks before the show is over.
Coil springs are utilized in many modern firearm designs. They are also used in automotive engines and internal combustion engines in general.
Imagine a cheap car, using the cheapest steels, and imagine driving down the road as your tachometer reads 1,500 RPM. In a four cycle engine, the intake valve(s) are being opened and closed 750 times per minute, in a four cycle gasoline engine. That is 45,000 times per hour. The cheapest Yugo using the cheapest steels available will generally run for more than an hour. Let's imagine that we drive that car for one hour a day for a year. That would be over 16 million cycles of the coil spring. How many cars have you seen on the side of the road non-operational due to a broken valve spring? Fine flintlock and percussion lock guns were not generally fired 45,000 times in their lifetime (remember the Yogo above that drove for one hour). I believe, but may be incorrect, that Perazzi expects the life of their leaf springs to be about 40,000 rounds.
Drop lock and side lock guns that utilize leaf springs which are expected to break. This is the primary reason which why the locks in many cases are hand detachable. The springs can be quickly and easily replaced.
Leaf springs work great. They feel great as do many coil spring powered hammer actions. In both cases metal fatigues over time and use but leaf springs concentrate the force into one small stress spot while coil springs do not have a focused stress spot. This is not good or bad, this is just simple design and metallurgy science. The belief that leaf springs maintain the same force and lock time over their entire lifespan until they fail is false as well. You prove this yourself with the paperclip, or you can ask a metallurgist or physicist.
As a side note, some fine gun makers such as Perazzi give you a choice as they offer both leaf and coil spring models. If you love history and removable locks float your proverbial boat you can go one route. If you want a more modern and technological approach you have that option as well.