Flat Wire Coil Springs

[LubeckTech]

I have just been reading about flat wire coil springs and how they don't exibit "stacking" the way round or "piano wire" springs do. If that is the case wouldn't they produce a superior DA trigger pull on guns like the Speed/Service/Security-Six and GP series gun? Is there a reason ti is impossible or impractical to use them??

 

[DGW1949]

The very-early M1 Garand used one as a recoil spring, as-did a few years of Browning's Auto-5 shotgun. The round wire spring was considered an improvemet.

That's all I know about that.

DGW

 

[WOB]

All uniform springs, flat, round wire, or square wire obey Hooke's Law F=-kx where F is the force applied to the spring in compression or tension, x is the distance of compression or extension, k is the spring constant. There is no "stacking" which would imply a nonlinear force change with distance as long as the spring is not coil bound or stretched beyond the elastic limit.

Square wire allows the spring designer to increase "k" for a given wire OD and coil pitch over what a round wire spring would provide because there is more metal being deformed. In the real world, I would suggest that a square wire spring would have a potentially shorter life because the corners would be more highly stressed and thus be subject to stress cracking due to microscopic defects.

WOB

 

[Carry_Up]

Thanks, WOB. Exactly right. Perhaps the OP could point out the articles he mentions that make claims about stacking, or non-linear behavior, etc. We have to keep in mind that spring makers and aftermarket parts companies are trying to sell springs and not necessarily trying to provide you with correct science.

To get a better picture of the effect of any coil spring, you have to step back and examine the mechanism that uses it. As triggers and hammers move relative to each other, angles are constantly changing and with them the "mechanical advantage" of one part in relation to another. "Stacking" is really a result of changing mechanical advantage, and not due to the linear forces of springs.

One good example of a mechanism that relieves the feel of trigger pull stacking is the GP100 style double action trigger, with a 2-step design similar to the S&W.

Carry_up