Have a Sd9ve. After having Apex put in I get about 2-3 light strikes on 50 rounds. Have about 600 total rounds through the gun .
Some people say it's ammo. others say it's the spring on the striker. If it's a spring would it happen all the time?

Ammo is Winchester white box and Remington green box.

Any thoughts?

Probably not the ammo. If you weren't getting light primer strikes before the Apex stuff then something with the Apex kit is causing your problem. Personally, I never go lighter than the factory spring on any of my striker fired guns.

I'm not familiar with the kit for the SD9 so I can't venture to guess exactly what the problem is but if you put a lighter striker spring in it then the reason you are getting intermittent light strikes could be that the spring force on the striker is marginal. In other words, the force that the striker is hitting the primers will set them off sometimes and sometimes it won't.

Like I said , I'm not familiar with your particular Apex kit but have seen other issues such as timing problems where the timing wasn't right and the striker was being released before the striker block was fully disengaged causing light strikes due to the striker dragging on the striker block.

My advice would be to drop the OEM striker spring back in it and see how it goes.

"Don't fix what ain't broke."

The striker gets it's impact strength solely from the
striker spring.

Your aftermarket striker spring is weaker than the OEM,
so your striker is hitting primers with less oomph.

Add in the variation of primer hardness/sensitivity, plus
accumulation of miscellaneous junk in striker channel
over time, and you've got the perfect set-up for misfires
and unreliability.

Your call: reliable pistol, or lighter trigger pull--pick one.

With the Sigma types, SW/SD, it is probably not the best idea to use a reduced-power striker spring, since there are many complaints about light strikes with them. IMHO, this is generally applicable to any striker fired handgun, which tend not to have much extra power reserve for the striker anyway.

__________________
Science plus Art

I am putting the stock spring back. Before I do I wanted to see if there was something else I was missing.
Outside of this handgun I've always had hammer fired handguns.

I'd leave the trigger spring and striker block spring from the Apex kit in, but use the factory striker spring.

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Had my gunsmith put an Apex kit in my Sigma 40F and have started having light primer strikes on my reloads using CCI primers. Works with some factory ammo however I like using my reloads so it's going back to the smith for a factory spring. Sounds like I am not the only one that has experienced this problem.

In some of the other forums people have said that Apex will send you a stiffer spring if you don't want to use or have the factory one.
Seems like others have been having the same problem.

I am of a notion that there is no way I could know more about my SD9ve than the great folks at S&W that designed & built it, so I just shoot it & clean it some times That has worked out for me for going on 7 years now.

Generally, that's case. However, in MA the triggers are extra stiff because of state gun laws. If I had a non MA trigger I would have left it alone.

But wait don't modifying the tripgger get you in trouble.

No. It's a big misconception. A dealer cannot sell it with a trigger modification. Once you own it you can do almost anything you want.

What the heck is the point then ?
I thought forks up there were smarter than that, do you have to do it yourself or can you have a gunsmith do it.