I have a lot of misfires with reloaded ammo with a Taurus 837. Not a S&W but similar I guess. I think the cause is the weak tension of the main spring. The trigger pull is very light. How to change it? Below a picture of the spring.

For a "give it a shot and see if it works" you could stack up some small washers under the spring seal, effectively placing extra compression on the spring and see if that helps. Maybe check to see if Wolff make springs for it. Of course if it fires OK with factory ammo and only fails with reloads I would question your reloads.

The reloaded ammo that won't go off -- does it fire with a second hammer strike? If so, you or whoever is doing the reloading is failing to seat the primers fully. First hit seats the primer; second fires it.

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Pisgah

If it turns out that the spring needs to be changed --and it is always possible a previous owner shortened the spring to lighten the trigger pull, which can easily be overdone -- replacement is straightforward. Cock the hammer. This will expose a hole in the rod that the mainspring rides on. Put a paperclip or similar small item through the hole. Holding the hammer, pull the trigger and ease the hammer forward. This will compress the spring and allow you to remove the mainspring assembly.

Now -- BE CAUTIOUS FOR THIS NEXT STEP!! It is best to place the entire assembly inside a large Ziploc bag, or a cardboard box, because you are going to pull the paperclip out of the hole to allow the spring and the small cup it seats into to be removed from the rod. If you make a slip, that little cup will be launched in to infinity -- or your eye, or whatever is in line with it. Once things are apart, you put the new spring in place, then replace the retention cup and once again insert the paperclip in its hole -- easier said than done! That little cup is going to want to fly away until you have it pinned back in place, as the spring tension is substantial. But being cautious, and again, working inside a box or bag, you'll get 'er done.

Place the spring assembly back in to the action, cock the hammer again, remove the paperclip. You're done.

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Pisgah

1: incorrectly seated primers.
2: someone tried to "improve the trigger" on a gun that worked fine.
3: both of the above.
See how it does with factory ammo.

Yes the second strike does it. The primer is seated with a standard Lee primmer tool. The primers are very suspicious however, a no brand import. May be they do not have the full height to seat properly or are just too hard.

Anyway the hammer print on the primer is not that impressive be it on factory primers or on the cheap ones.

It's easy to short-seat with a Lee priming tool -- ask how I know! Try giving them just a bit of an extra nudge. The idea is to just slightly crush the primer cup, which "sensitizes" the priming compound and insures the hammer hits firmly against the primer anvil.

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Pisgah

Ok I will try it.

Minha Arma:

Welcome to the Forum. Just curious, but have you tried firing factory loaded (NOT reloaded ammo) out of your revolver? If so, what were the results? Also, it appears to me that there is an excessive amount of lubricant on the inner works of your revolver. Excessive lubrication won't necessarily "hurt" your piece, but it does have a tendency to hold and trap dirt and other contaminants. A very light coating of a good quality, light oil on the parts to protect from rust, and a small drop or two of oil on the bearing surfaces and pivot points to prevent or reduce friction is all that is needed.

Good luck,

Dave

It works fine with factory loaded ammo.

If that statement is not an absolutely clear cut indictment of the quality of the reloads...