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PostPosted: Sun Nov 11, 2012 7:38 am 
Blackhawk

Joined: Tue Dec 23, 2008 11:18 am
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Location: Denver
Why is a coil spring better than a flat spring for the main hammer spring? Or is it? I see that Freedom uses a flat spring in their model 97's. I don't think they cut any corners building that one.


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PostPosted: Sun Nov 11, 2012 7:52 am 
Hunter
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I've always been told that coiled springs are less likely to break.


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PostPosted: Sun Nov 11, 2012 11:05 am 
Hawkeye
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IMHO, the issues with flat springs are hugely exaggerated and the result of Ruger's marketing more than anything. I've been shooting traditional single actions with flat springs for 26yrs and have only ever had one spring break. That was the hand spring in my pard's Colt Frontier Scout two years ago, which is a high mileage sixgun with untold tens of thousands of rounds downrange.

The most common failure reported with the SAA's and replicas is the trigger/bolt spring, which is easily replaced with a music wire spring. I've never seen or heard of a hammer spring breaking.

S&W has always used flat springs, ever hear of one actually breaking?

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PostPosted: Sun Nov 11, 2012 7:03 pm 
Hawkeye
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It really depends on the quality of the spring. A poor quality spring of either type will break and a high quality one will not. The only spring I ever had break on any firearm was the little two pronged trigger/cylinder pin spring on an early Italian made SAA clone.


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PostPosted: Sun Nov 11, 2012 7:23 pm 
Single-Sixer

Joined: Thu Jan 05, 2012 9:03 pm
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Location: Seymour, CT
Speaking from the engineering side of myself, coil springs are MUCH less likely to break, and MUCH more resistant to weakening over time. For one thing, a coil spring spreads the load over the entire length of the spring, while a flat spring (like in an early revolver design) concentrates the force mostly at the anchor point, or at at the "V" , if of that shape. Given a choice, I would never choose a gun with flat springs, of any type.
From a historical point of view, use what was originally in the gun; as if one had a choice, in that case.


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PostPosted: Sun Nov 11, 2012 7:56 pm 
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Call Bob at Freedom Arms and ask him how prone to breakage the flat springs are! The percentage is VERY, VERY LOW!!!!!

JMHO,

flatgate


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PostPosted: Sun Nov 11, 2012 9:02 pm 
Hawkeye

Joined: Fri Apr 03, 2009 7:01 pm
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Location: People's Republik of Kalifornia
The only breakage of a flat main spring that I've ever experienced in 45 years of shooting is when someone ground down the sides of the leaf spring cross wise to lighten the tension but did not polish out the grind marks. The grind marks set up fracture lines and the spring eventually fails.
The someone in the case of spring failure that I observed was in a Bob Munden tuned Colt, not touched by anyone else after tuning.

I've seen many, many Colt style flat bolt/trigger springs and hand springs break. Coil springs are far superior for those.

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Last edited by Hondo44 on Mon Nov 12, 2012 3:39 pm, edited 1 time in total.

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PostPosted: Sun Nov 11, 2012 10:44 pm 
Buckeye
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Quote:
Speaking from the engineering side of myself, coil springs are MUCH less likely to break, and MUCH more resistant to weakening over time. For one thing, a coil spring spreads the load over the entire length of the spring, while a flat spring (like in an early revolver design) concentrates the force mostly at the anchor point, or at at the "V" , if of that shape. Given a choice, I would never choose a gun with flat springs, of any type.
From a historical point of view, use what was originally in the gun; as if one had a choice, in that case.



And that folks, is the correct answer. With a coil spring, each coil only flexes a fraction of the total amount. So the stress imparted to any particular section of the spring is very low. With a flat type spring, the entire spring flexes, and the flex is usually concentrated in one spot.

Here is a photo of two broken springs from my Colts. The split trigger/bolt spring at the top of the photo is probably the most common spring to break in a Colt type action. Notice where the spring broke, right at the base of one of the legs. This is absolutely typical of a broken trigger/bolt spring, this is where the spring flexes the most.


Image

There is something else at play here. It is called Stress Risers. The comment about grinding marks creating fractures is spot on. Such marks cause what is known as a Stress Riser. A Stress Riser is any feature that allows a micro fracture to start. Poorly smoothed over horizontal grinding marks are a perfect example of Stress Risers. What happens is, as the spring flexes over and over again, tiny micro fractures start at the bottom of the 'v' left behind by the grinding marks. Here are a couple of typical Uberti mainsprings for their replica of the 1873 rifle. Notice the grinding marks left on the face of the spring. Those make perfect stress risers, and yes, I once had a spring just like this snap in half in one of my rifles. Right on one of the grinding marks.Frankly, I'm surprised Uberti rifle springs don't break more often than they do, given the extremely poor finish they have when they leave the factory. When I tune an Uberti mainspring, I always grind along the length of the spring, never across the width. A spring that flexes along its length is not affected by grinding marks also going along the length, only across the direction of flex. And I always finish up with very fine sandpaper to smooth the surface to a mirror finish so no irregularities will be left for micro fractures to start.

Image

Going back to the broken Colt spring, notice the break starts right at the tight radius between the two legs. Another perfect Stress Riser. The other broken part in this photo is a bolt. Not a very common failure, but it does happen. With a Colt style bolt, one leg flexes every time the hammer falls, as the leg rubs over the cam on the hammer. This one gave way right at the weakest point, right at the hole for the screw it pivots on.

Image


Why don't the hammer springs in a S&W or a Colt snap? Because S&W and Colt do a good job of finishing the springs and not giving micro fractures a place to start.

Yes, Ruger coil springs are indeed more durable than the old style flat springs in the traditional Colt type lockwork. I ain't saying they are going to break right away, but they are more likely to break. I love shooting my Colts, but a pair of Rugers always comes along as back ups. In the last ten years of Cowboy Action Shooting, in addition to the broken rifle spring, I have had to use one of my Ruger backups twice, and you are looking at the reason for each instance.


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PostPosted: Sun Nov 11, 2012 11:20 pm 
Hawkeye
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Interesting topic! My 3rd Gen. Colt New Frontier .44 Special had a mainspring that took 2 men and a boy to cock. I put in a "Gunslinger" mainspring/ trigger spring. It took me a few outings and some bending of the mainspring to its max. strength before it became reliable. Am I asking for trouble?

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PostPosted: Mon Nov 12, 2012 3:19 pm 
Hawkeye

Joined: Thu Jun 24, 2004 1:01 am
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Location: Memphis, TN USA
For whatever its worth, I had an old Colt New Service, which has the "V" type mainspring, originally a .455, converted to .45 Colt, converted to .44 Special. After the last conversion, I cleaned the gun one day after a range session, then dry fired it one time. The mainspring broke.

Now I'd removed and replaced Colt mainsprings before, and could have done this myself, but on a whim, took it to a neighborhood gunsmith. While in the gunsmith's shop, my gun was stolen along with several others left for repair.

The gunsmith made my loss good, or as good as he could make it, but I sort of had a phobia against flat or "V" mainsprings for awhile.

However, I do believe flat springs give a little more "snap" to the revolver's action than coil springs do. But the type of mainspring has never been the deciding factor for me.

Bob Wright


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PostPosted: Sat Oct 31, 2015 1:05 pm 
Newly Registered

Joined: Sat Oct 31, 2015 12:57 pm
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Driftwood has it pretty much right , in my opinion, as a retired Metallurgist who has investigated many metal failures....but not on guns. The problem really begins with the fact that flat springs get mechanically punched out of strip stock and getting the cut edges smooth...and free of stress risers....is not easy. Fatigue failures often begin at stress risers.


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PostPosted: Sat Oct 31, 2015 1:32 pm 
Hunter

Joined: Sat Mar 20, 2010 9:11 pm
Posts: 3230
Location: Ridgefield WA
A flat spring is easier to make on a forge with anvil and hammer the way they were made hundreds of years ago. Coil springs are relitivly new compared to flat springs.
You will find flat springs in the best and most expensive shotguns not only due to the fact that they are traditional but they are "faster" as claimed by many professional gun makers. Coil springs are slower but much more dependable.


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PostPosted: Sat Oct 31, 2015 2:24 pm 
Hawkeye

Joined: Fri Apr 03, 2009 7:01 pm
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Location: People's Republik of Kalifornia
One of the most common action job measures, at least by me, to significantly increase the longevity of the cyl bolt is to reduce by half the height of the bolt cam on the hammer base. This in turn, reduces the flexing of the cyl bolt arm by half each and every time the hammer goes down.

Also polishing out all tool marks on the bolt.

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PostPosted: Sat Oct 31, 2015 3:10 pm 
Hunter

Joined: Tue Apr 03, 2012 12:12 pm
Posts: 3857
I've had people tell me that just using a pair of pliers to install a flat spring can create a stress riser.

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PostPosted: Sat Oct 31, 2015 5:14 pm 
Hunter

Joined: Sat Dec 08, 2001 2:01 am
Posts: 3275
Location: Pittsburgh, PA, USA
One minor point also in favor of coil springs is if they do break they continue to work, usually adequately if not perfectly, until they can be replaced. A broken flat spring completely disables the gun. S&W does use flat springs in their K,L and N frame revolvers but these aren't V-springs and have proven very durable.


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