Several years ago my 3rd Generation 1861 Colt Navy had one of the flat spring arms of the Trigger & Stop Spring break.
That is one of the weaknesses of the Colt design, but when Old Sam Colt designed the pistol, ONLY flat springs were available.
So, I ordered several of what Wolff Springs calls their "Sear/Bolt Wire Type Springs" for the Colt Single Action Army Revolver. [they don't list replacement springs for the replica percussion revolvers.]
The "Dirty Little Secret" is those Music Wire Springs are a great improvement over the old, 19th Century Flat Springs and last a lot, lot longer! Being by nature a "Pack Rat" I ordered several of the Wolff "Wire Type Springs" [Stock Number 32294-32296 Springs]
Well, I installed one in my '61 Navy and it immediately improved the smoothness of the action and also lightened the trigger pull a tad,
So, try this "trick" I think you will be pleasantly surprised how much that Music Wire Spring improves the action of your replica Colt!