Hello:
The following is in prior posts on our Forum:
ArmiSport/Chiappa/Taylors Spencer mainspring dimensions and tempers have varied over twenty-plus years of production. Best to contact the Chiappa Warranty Service Center in Dayton, OH.
Other seemingly identical mainsprings such as originals also vary in temper and geometry.
The same well fitting mainspring swapped between several gun locks will make a range of difference from none to a few pounds in pull weight. I have put properly fitting Shiloh's fine Sharps mainsprings in originals and Romano repro's, and found much less cocking effort with a rangeof zero to four pounds reduction in pull weight.
Original Spencer and Sharps mainsprings can have significant temper and geometry differences and may not be interchangeable with originals or Armisport's. There were/are still lots of original Spencer mainsprings that were condemned, per Marcot, and I have learned that those found their way to post-civil war surplus parts dealers and into current parts bins. Dealers have told me that some of the temper variation in original Spencer/Sharps mainsprings is due to being for cap fired vs primer fired use.
I have found originals with and without inspector marks, some with up to 1/8" length difference, large temper ranges and some that only fit poorly, if at all.
Before spending upwards of $40, try to test any originals first and NEVER use channel locks to compress the spring. Use a good mainspring vise and attach it with the thumbscrew sticking up to avoid slippage. Only compress enough to remove and attach.
Be careful:
Original Spencers used strong mainsprings with sear and hammer angles that were designed to work against themselves to create a "martial", 8# pull weight.
Original issue Spencers had no fly on the tumbler, which prevents the sear tip from bumping the half-cock notch. Armisport repro's do have a fly in the ones I have inspected. Nice.
Using a digital or coil spring trigger pull weight gauge allows the weight of pull to be INSTANTLY released and the sear tip to bump either the fly, which prevents half-cock contact or in those with no fly, eventual damage. A heavy pull weight with no fly, as on originals, and FINGER pull release force maintains enough pull weight to move the sear tip well away as the half-cock notch rotates.
Italian reproduction lock parts may not be through hardened so stoning sear and hammer cock notches cuts away the hard surfaces so re-hardening is needed for durability. I do not know anyone now who will attempt it because they cannot get anyone to tell them about the alloy that is used in Italian repro parts.
All the best,
El Supremo/Kevin Tinny
edited for typo's. VR/KT