Measuring mainspring strength

[Navy Six]

I intend to conduct a series of tests on Colt style percussion pistols in regards to mainspring strength and its affect on percussion cap performance. I would like to accurately measure and compare a variety of mainsprings. I do have a trigger pull gauge and considered measuring that as I swapped out different mainsprings on the same gun. Is there a better way of doing this? I don't want my results to be based on "well, this spring feels heavier than that one". Any thoughts would be appreciated.

[Marshal Will]

The trigger pull might give a good enough reference of the springs in use. I can't think of another way to measure them unless you make a fixture to measure the pull on the hammer to full cock or how much force to bend the spring far enough to equal full cock. That could get expensive if you have to buy measuring equipment.

[45 Dragoon]

I've always measured from half cock. I hook my scale under the nose of the hammer and check the weight when it starts to move.  That's where the 4 lb hammer pull comes from. It's all repeatable numbers.
  In my experience,  they tend to run anywhere from 6 lbs  to 9lbs+  .  .  .  2nd Gen Colt's are all over the place. Just checked two 2nd Gens .  .  . '60 Army is 8 lbs, Walker is 7lbs.
 
Measuring just gives me an idea of how much "dressing " I'll need to do to get to 4lbs.

Mike

[Marshal Will]

I look forward to seeing your results. Are you going to include aftermarket ones like the Wolf Reduced Power main springs?

[Hawg]

I've always measured from half cock. I hook my scale under the nose of the hammer and check the weight when it starts to move.  That's where the 4 lb hammer pull comes from. It's all repeatable numbers.
  In my experience,  they tend to run anywhere from 6 lbs  to 9lbs+  .  .  .  2nd Gen Colt's are all over the place. Just checked two 2nd Gens .  .  . '60 Army is 8 lbs, Walker is 7lbs.
 
Measuring just gives me an idea of how much "dressing " I'll need to do to get to 4lbs.

Mike

Why half cock?

[45 Dragoon]

I've always measured from half cock. I hook my scale under the nose of the hammer and check the weight when it starts to move.  That's where the 4 lb hammer pull comes from. It's all repeatable numbers.
  In my experience,  they tend to run anywhere from 6 lbs  to 9lbs+  .  .  .  2nd Gen Colt's are all over the place. Just checked two 2nd Gens .  .  . '60 Army is 8 lbs, Walker is 7lbs.
 
Measuring just gives me an idea of how much "dressing " I'll need to do to get to 4lbs.

Mike

Why half cock?

Can't get the hook on with the hammer all the way down. 

Tension remains constant throughout the pull from half cock.

[Navy Six]

Thanks Mike. Your response sounds like a good solution. I will give it a try. I know what you mean about Colt mainsprings. I've replaced all my original Colt springs(tagged each one to what gun it came out of) and at one point in 3rd gen. Colt started using a tapered one. Worked on my friends un-altered early 1st gen and it had the heaviest mainspring I ever felt.
Marshal Will, I will probably use the Wolf springs as a starting point as many of my guns have them. Even the newer standard Uberti springs aren't much heavier.

[Marshal Will]

Thanks Mike. Your response sounds like a good solution. I will give it a try. I know what you mean about Colt mainsprings. I've replaced all my original Colt springs(tagged each one to what gun it came out of) and at one point in 3rd gen. Colt started using a tapered one. Worked on my friends un-altered early 1st gen and it had the heaviest mainspring I ever felt.
Marshal Will, I will probably use the Wolf springs as a starting point as many of my guns have them. Even the newer standard Uberti springs aren't much heavier.

Thanks, I wondered about those. I look forward to hearing what you find.

I saw an 1890 Colt SAA that had a leather shim under the mainspring to lighten it up some. That shim had been in there a long time. Obviously people thought they were too stiff even back then.

[Navy Six]

Marshal Will, I recently obtained a early 3rd gen. Colt SAA that was very lightly used. However,  the original owner had done that leather pad under the mainspring trick. I recall back in the 70's & 80's that was the recommendation in many gun magazines. I tried it back then and found very little difference. Anyway back to that recent purchase. The owner must have installed that leather pad when the gun was pretty new because on taking the grips off the whole area around the mainspring/backstrap/trigger guard was covered in rust. You would know better what type of leather would cause that. It cleaned up quickly though. Fortunately the rust didn't intrude any farther as this particular SAA was a full blue model with what looked like extra polishing, about what the older Pythons used to come with.

[Marshal Will]

The one I saw had been used a lot and the leather shim was soaked with oil so there was no appreciable rust around it. Glad yours cleaned up easily.

[45 Dragoon]

Marshal Will, I recently obtained a early 3rd gen. Colt SAA that was very lightly used. However,  the original owner had done that leather pad under the mainspring trick. I recall back in the 70's & 80's that was the recommendation in many gun magazines. I tried it back then and found very little difference. Anyway back to that recent purchase. The owner must have installed that leather pad when the gun was pretty new because on taking the grips off the whole area around the mainspring/backstrap/trigger guard was covered in rust. You would know better what type of leather would cause that. It cleaned up quickly though. Fortunately the rust didn't intrude any farther as this particular SAA was a full blue model with what looked like extra polishing, about what the older Pythons used to come with.

  Which is why "real gun tuners" ( Jim Martin) teach NOT to use a leather for that.  A steel washer is better.  I don't use washers anymore,  I'd rather get the main to the tension desired.
Mike

[Navy Six]

Well, just to satisfy myself that I wouldn't be wasting my time, this morning I did a brief preliminary test. A pair of Uberti mainsprings that came out of Cattleman(circa 1998 & 2000 and are definitely heavier than current production) were installed in my Uberti 51 Navy squarebacks. These two cap suck at the rate of 2/3 every 30 rounds or so despite everything done to them. After 60 total rounds I didn't have a single issue. No changes from usual other than the mainsprings. So I will hunt down more mainsprings of a similar weight as I intend to continue testing these two guns as well as a pair of 61 Navies and 60 Armies. I want to know about what weight mainspring is required to make these things work.

[Marshal Will]

Sounds like you're on the right track. Congrats.