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The Sigma's sear rides in a slot in a pivoting arm. The trigger bar pushes rearward on this arm which causes it to pivot, driving the sear against the sear block. This pushes the sear backwards, which pulls the striker back to firing position and then down, releasing the striker. There are three springs that return it to the rest position.
Two push the sear to the end of the arm, this will push the sear to the rest position by sliding back against the sear block. One is on the pivot pin and pushes it back to its rest position directly.
The two that push are nested inside each other.
If you delete the smaller, inner, spring; there's nothing to hold the outer spring in place.
If you delete the larger, outer, spring; and drop the slide from slide lock, the sear doesn't catch the striker.
This is bad.
The spring on the arm axis doesn't appear to affect if the sear can catch the striker. Its sole purpose appears to be to make the trigger pull more "New York," which was the style at the time for plastic fantastics.
Compared to the two other Sigmas here, the trigger bar on the 9mm gun does not pull the sear all the way down to its stops. But the other two both have Apex triggers in them, that might be all the difference in the word.
The lack of movement might also explain why the previous owner had been grinding on the sear stud.
With many guns, this is less of a problem. You just order a replacement from the vast stocks of spares made to service the guns over their decades of production or the extensive aftermarket support base.
Um... About that. There isn't such a supply.
So if we find that the sear won't reset under actual firing conditions, this pistol is a paperweight. With the trigger's refusal to actually trip the sear when I bought it, it was a paperweight before too.
Which is a bummer, but it's been fun seeing if I can fix it.
I'm not blaming the gun shop. They really can't test fire every gun that comes in the door and the Sigma is famous for a shitty trigger.
I wouldn't give up just yet, there is always the possibility that someone, somewhere has a spare part sitting gathering dust in a drawer. Or possibly a donor gun with some other problem. I know, probably not very likely, but you never know.
ReplyDeleteDid anyone ever make 3rd party triggers for these? Given all the grumbling back in the day about them, you'd think that might have been a possibility.
How feasible would it be to fab a new part from scratch? Any pistol with a similar part that could be modified to work.
The juice might not be worth the squeeze, but it seems a shame to waste an otherwise functional pistol.
Apex Tactical makes a replacement trigger; but that utilizes the stock trigger bar and sear. Midway has printed a label for the kit I've ordered.
DeleteIt doesn't appear that anyone made an upgraded striker, but there's a couple of places with an improved sear.
Gunbroker has a grand total of one Sigma striker listed, and I've bid on it.
Numrich and Apex Gun Parts have trigger bars, so I might be able to go back to stock if I need to.
Eyes crossed that this ends up a good pistol instead of a paperweight. Hell, if it runs as is, it's a victory.
I looked on eBay and saw a striker assembly for an S&W om there, but I wasn't sure if it was the same model as yours. I don't know enough about S&W part numbers to tell.
ReplyDeleteThe SW9V and SW9F strikers interchange.
DeleteI don't know if the SW9VE strikers do, but they look identical.
SD9 strikers look very similar.
Small dimensional differences matter a lot.
V and VE trigger and bar assemblies are the same part, so the striker might interchange.
These parts look beat to crap but the innards to the slide look like they are there.
ReplyDeletehttps://www.ebay.com/itm/SMITH-WESSON-MODEL-SIGMA-SW-9-IN-9-MM-3-1-4-GUN-PARTS-LOT-ITEM-19-922/383300053562