Cast versus machined versus forged mainsprings: does it make any difference?

[Eric Kettenburg]

Any spring can take a set.  The way that it is made has minimal bearing upon the issue, although possibly true metallurgists might argue that point.  I will say that there are a LOT of antique locks with forged springs (both main and frizzen) that have weakened over time and 'taken a set.'  Frankly, I've seen barely any of it in modern cast springs, assuming they were tempered properly.  They tend to simply snap like a cracker while many old forged springs may crack but continue to function.  Is it an age issue?  I don't know but I would say that many modern shooters are shooting and thus cycling locks much more frequently than a gun owner 200+ years ago likely did.  Individual shooting for fun is a lot more prevalent now than historically, I suspect.

[FlinterNick]

Any spring can take a set.  The way that it is made has minimal bearing upon the issue, although possibly true metallurgists might argue that point.  I will say that there are a LOT of antique locks with forged springs (both main and frizzen) that have weakened over time and 'taken a set.'  Frankly, I've seen barely any of it in modern cast springs, assuming they were tempered properly.  They tend to simply snap like a cracker while many old forged springs may crack but continue to function.  Is it an age issue?  I don't know but I would say that many modern shooters are shooting and thus cycling locks much more frequently than a gun owner 200+ years ago likely did.  Individual shooting for fun is a lot more prevalent now than historically, I suspect.

Depends on what they’re casted in. 1080 or 1095 cast springs are tricky same with 5160 cast springs, although you dont see them too often. They have to be tempered correctly or they will eventually shatter sitting in the lock.
I only use 6150 for my castings and ones I’ve purchased, i also use 6150 in billet for forgin, I’ve never broken one. The manganese content enables flexibity of the steel.

[rich pierce]

Though not in the business, I’ve heard tales of foundries using steel that was not specified when filling small orders of list wax casting. I suppose that could lead to some issues with cast springs that would not typically happen with forged or machined springs.

[mountainman]

"Taking a set" refers to when a spring is compressed, and doesn't return to its original "wanted" or "full spring" position. Thus it will be weakened permanently from the original intended power.

Thanks for that explanation! It all makes sense now what you're talking about.
when I think about what you guys are saying especially along with Eric Kettenburg's explanation as well, I think of the time that I had looked into some old CVA locks that some guys bring into the shop, their mainspring was working just fine, but the sear spring was just like you described, and also on some other locks the frizzen springs were also in the same condition, just too weak to come back to where it was.

[FlinterNick]

Though not in the business, I’ve heard tales of foundries using steel that was not specified when filling small orders of list wax casting. I suppose that could lead to some issues with cast springs that would not typically happen with forged or machined springs.

That’s certainly happened before with the rifle shoppe, sometimes they accidentally pour 4140 steel for the springs. One way to tell is to take a bluing pen and mark the spring, if it turns violet then it’s likely 4140.

[FlinterNick]

Any spring can take a set.  The way that it is made has minimal bearing upon the issue, although possibly true metallurgists might argue that point.  I will say that there are a LOT of antique locks with forged springs (both main and frizzen) that have weakened over time and 'taken a set.'  Frankly, I've seen barely any of it in modern cast springs, assuming they were tempered properly.  They tend to simply snap like a cracker while many old forged springs may crack but continue to function.  Is it an age issue?  I don't know but I would say that many modern shooters are shooting and thus cycling locks much more frequently than a gun owner 200+ years ago likely did.  Individual shooting for fun is a lot more prevalent now than historically, I suspect.

I see that often with springs that were not tempered correctly, usually they were tempered too high in a non controlled environment such as with a hand held torch and not a gauged device or oven. Torch tempering can be difficult, catching that second blue is critical, and iit happens quickly. John Bosh was color blind and relied on the slight color of red in complete darkness to get his springs tempered in complete darkness a slight red color is generally around 750-800, by slight i mean hardly noticeable to someone who is not color blind.

[Eric Kettenburg]

John Bosh was color blind and relied on the slight color of red in complete darkness to get his springs tempered in complete darkness a slight red color is generally around 750-800, by slight i mean hardly noticeable to someone who is not color blind.

I do mine the same way.  I know it sounds weird, but the 'slight red' is almost more "sensed" than actually seen.  If it's too easy to see, you've generally gone too far.

Kit Ravenshear told me about that method probably 30 years ago and I think he may have mentioned it or discussed it further in one of those little booklets he authored, but I don't have them so I'm can't be positive.