I took some reloads out today and two of my revolvers did not set off the rounds. Not too long ago I lightened the trigger pull by backing off the tension of the grip spring by slightly backing off the screw in the grip. Would this lighten the force of the hammer strike?

Hey Dutch,

I'd say that you probably loosened the strain screw a little too much to ignite CCI primers. They do tend to the be hardest ones, so it may still work with other primers like Federals. I recently had a similar thread that may give you some more insight.
Brad
CCI Primers...Great for Flinching

Switch to federals.

Winchesters work on my lightened actions where CCI's will not.

tighten that strain screw back up a little. While it is true that CCI primers are a bit harder than some and Federals are the softest of all, a good gun should be able to pop any primer in my opinion. I just developed loads for someone else's 28 with the same problem.... I tightened the strain screw. His gun still has a great trigger but now it is reliable.

The strain screw should be fully tightened or it will just continue to back off more creating even lighter strikes. If you want to remove tension from the main spring using the strain screw, but a few spare screws and file them down. Federal primers are the key.

DEG is correct, if you don't keep the strain screw fully snugged down it will shoot looser and cause misfires. I've been making shims to adjust my mainspring tension and it's a method that allows me to do some experimenting. What I've found is that Federal, CCI, and Winchester primers will run reliably in my 625 with the trigger set up for an 8 lbs. DA weight. The Remington UMC is the ammo that requires a harder strike, for that ammo I've had to increase the mainspring tension enough to produce a DA weight of 8.5 lbs. Since 1/2 lbs. of weight really doesn't have much effect on how well I shoot I've retuned all my triggers to 8.5 lbs. so than I can shoot the UMC bulk packs if that's all that's available.

You can use a fired primer for a shim. Place it over the screw end and than tighten the screw all the way down.

The strain screw is not an adjustment. Tighten it all the way, and leave it that way. Problem solved.

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Pisgah

There are better ways to lighten the pull instead of loosening the strain screw.

+1 This ^^^

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Life is good!

With a lightened DA trigger pull you will only obtaib reliable ignition with Federal primers. CCI primers have the hardest cups, Federal the softest and Winchester is in between.

As PISGAH stated the screw is not a trigger job. It is not intended to lighten trigger pull. You can actually buy a lighter hammer (main) spring and rebound springs. The rebound springs make more of a difference in trigger pull than the hammer spring. The lightened hammer spring is only .5 (1/2) pound difference.

The primers are not the problem.

Revolver Springs for Customized Hammers & Triggers - Charter Arms, Colt, Smith & Wesson

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Still Running Against the Wind

Thank you for all of the advice. I've tightened my screws and will be trying my reloads shortly.

I noticed in Jerry Miculek's, Trigger Job, DVD he made the comment
that, at that time, CCI had just softened their primers and made
"the sweet spot" a little bigger, or something along those lines.

Based on that, CCI primers must have really been hard back in the 1990's.

I usually don't shoot Blazer ammo but always keep some .38 SPL around
for reliabilty testing after installing reduced weight mainsprings. Too date,
the only light primer strikes I've had were with Blazer & Remington ammo
so my experience dovetails with the other comments made in this thread.

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Ogy

1+. CCI DID in fact increase the 'sensitivity" of their primers, though I've not had any issue with them ( started reloading in the 90's, and didn't know "not to buy CCI" and was quietly amused to hear of how they were too hard to use! THEN I learned of ultra light trigger jobs that were SO ammo ( primer) selective as to be worthless off of a target range ( some of them were too light to be reliable ON a target range )- the AMMO always took the blame!
FACT IS, people will do what they want. I have ONE old PPC gun that is "iffy" with MAGTECH primed ammo ( bought some of theirs to try when things got tight after the last election ), but lights Federal. Didn't have any Winchester or CCI to try in that one. My other revolvers in small primer calibers will all light Wolf small pistol magnum primers, for reliability. For me, if the gun in question may have to do more than play, it has to light ANY appropriate defensive ammo it might see. For me, the less picky, the better for something that is not a "target only" gun. Just my 0.02