A while back I picked up a Ruger Old Army to replace the one I sent down the road years before. It's got a lovely, light action - but does not reliably set off the caps, unlike my first ROA with which I never had a failure to fire due to cap issues.

My understanding is that the Ruger Old Army uses the same mainspring as the Blackhawk and Vaquero. Is this correct? Where would someone find such a spring in today's market? Jack First has ROA springs, at $12 a pop... that seems a bit salty to me - but haven't had occasion to shop springs in quite a while. Brownells is sold out of Blackhawk mainsprings. Not sure where else to look.

I believe they're a few pounds heavier than the Blackhawk spring.

Wolff springs sells them for about 4 1/2 bucks.

Under single action springs they show...
"Factory Standard..: 23 Lb. (Reference Only)
Extra Power.........: 24, 25, 26 and 28 Lb."

I wonder if the spring can be seated in the wrong place. Also the stock configuration would allow you to shim the spring with washers or something similar to increase the force on the hammer.

Lovely "LIGHT" action would make one suspect lighter that required mainspring.
Another thought, is it random or always the same chamber?
If the same chamber(s) the nipple could be peened and not allowing the cap to fully seat until being struck more than once by the hammer.

I once installed a reduced mainspring in a SRH. Worked fine all summer but introduced misfires as the weather turned cold. . . . Lesson learned.

If I recall correctly Ruger Old Army springs average about 27#. Some longer range shooters with good trigger work used to swap them into Blackhawks to slightly reduce lock time.

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AKA zzr7ky