Need a little help. I took my brand 9mm CORE out today and experienced lite primer strikes on 9 out of 100 rounds fired. The rounds are my own reloads which consisted of precision delta 124gr HP, federal brass, CCI primers and 4.0 grains of Unique. OAL is 1.250 +\- .003. On top of the 9 lite strikes, I had about a dozen FTE/stove pipes. I'm stumped on these issues. Primer depth was set to flush...do I need more powder?

As a side note, I shot 25 rounds in my P226 and had no issues.

 

Also the mag springs were tough as hell...I'm guessing they'll loosen up, but I'd like some feedback on that as well.

I do not have an M&P but the same troubleshooting steps should apply.

1: inspect striker and ensure that there are no burrs, chips, etc on the outer edges which may restrict full travel.

2: clean off all lubrication from striker and ensure that new lube is thin. 

3: check for obstructions or poor fit of slide to frame. Ir may be that the slide is not locking fully because of some obstruction or friction with the frame.

You may have had light strikes on all rounds but only 9 failed to ignite. Your weak ejection may indicate that the slide is not achieving full lockup. Not familiar with Unique so I assume this is a tested load which should work.

4: check your recoil spring, it may be defective or broken, either would produce your symptoms.

5: check that the barrel and slide are in full lockup, without a round in the chamber and then, with a round in the chamber.

Primer depth should be just below flush.

 

Also, alliant load data says 1.125 oal and a charge of 5.8 for 1180 out of a 4" barrel. Coming down 2 grains and adding more than a tenth to oal probably has you going really slow.

 

 

My guess is high primers and the slide short stroking. Possibly with some help from the shooter, but my guess is you are down around 90pf. With my m&p .40, 115 is where things got sketchy with ejection and extraction. Anything resembling less than a rock solid grip and fte of some sort.

Thanks for the update and feedback guy. 

I appreciate it.  just so its out there, I also had a lite primer strike on 1 round from Freedom Munitions.   I'll give it a complete cleaning and up the load charge for the next 25 to see of that helps...

Primers should be a bit below flush, i'd aim for .006ish for your semi. Did you change out the springs for lighter ones, also CCI primers are pretty hard to set off on the sensitivity scale, try winchester or federal primers if you continue to have issues.