have the mp 2.0 in 9mm, fullsize, about a year, totally love the gun, never had any problems, last month started having occasional light primer strikes, about 6 out of 100, happened in a match, very aggravating!!! anyway, this is what I have done to fix the problem:
1. cleaned the striker, channel, and the gun in general.
2. replaced the striker with a new one from brownells.
3. double checked my press, (Square Deal B), cleaned everything, rechecked the specs on the machine, ran it thru tech support at Dillion. Nothing has changed with my reloads component wise, Have used the "search" function on here to research any possible solutions. use the press to "prime" the brass, I am pressing so hard, am afraid it will damage the press.My reloads all sit "flush" on a flat surface, actually slightly lower than the bottom of the brass. Am using CCI primers, never had a problem before but am at my wit's end.

2 questions:

Should I try a different primer? see if that makes a difference

Does cold, damp weather affect primers that much? reload in the garage, never had a problem before, but now.

Appreciate any help at all, not trying to "bash" a product at all. Love the gun, can't carry it if it is not "reliable"

CCI would be one of the "hardest" primers I believe. I wouldn't think the primer you are using would matter though if the gun is OEM. Perhaps there has been a minor change somewhere with respect to case re-sizing, casing length or OAL?? Strange

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Ret. LE, FA Instr, S&W Armorer

Federal makes the "softest" primer. Federal ammo is the only brand i use in BodyGuard. a search on the net will confirm the Federal primers as "softest".

Have you tried a thorough, detailed cleaning of the gun?

warren seems a fairly thorough cleaning was conducted.

I would isolate: change primers, if you see any decrease in the 6% from that modification keep on keepin on

I haven't loaded with CCI primers for a good 20 years, but have not had any problems using Speer factory ammo that is loaded with them.

Last year I had a hard batch of Winchester primers, the brand I normally use, in .45 Colt. My Ruger Flattop was only setting off maybe 1 or 2 out of every 10 rounds.
I didn't suspect primers at first, but ended up trying a different hammer, heavier hammer spring, etc. Firing pin was hardly making a tiny mark on the primer. My 1892 lever gun shot the hard primers fine.
I opened a new pack of primers and loaded with them, every single one went off in the Ruger with a nice normal deep indentation.
I have since switched over to Federal primers for my pistol shooting.

Shooting Winchester 124 grain Nato FMJ out of my 5 inch MP9, I usually get one or two rounds out of each box that won't go off, when I look at the primer, there is the faintest dent in it. If you've changed out your striker, your firing pin isn't chipped on the tip, and your brass is the correct length ( not too short), I'd do as the others suggested and try a primer switch. Federal's are among the softest.

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U. S. Army Veteran

I am not a reloader, but I am a Range Safety Officer, and I get to talk to a lot of shooters about problems with their firearms.

One thing that I have learned is that when a firearm has a problem, and that firearm is always shot with reloads, then the problem should be confirmed with factory ammo. This is not a criticism of the OP, or of any other reloader, but using factory ammo just removes a lot of variables. It is worth the cost of one or two hundred rounds of factory ammo to confirm more info about the issue. Usually this testing will give you a very good idea whether the problem is with the gun or the ammo. Also, if you want to return the gun on warranty, you should confirm with factory ammo before doing that.

Coincidentally, I recently helped a friend with a similar problem. He has reloaded for years, but he started getting misfires in his revolver. I looked at the revolver, and I was pretty confident that the hammer was hitting hard. It turned out that his press had worn so that his primers were not seated quite deep enough, and that was enough to cause issues.

Regarding the suggestion to switch to Federal primers, that would not be my first choice. There are many competition revolvers that are set up to only use Federal primers. That is perfectly acceptable for a competition gun, but for an M&P, I think it should have a firm strike that works with any ammo.

Federal commercial ammo also uses pretty soft primers, so if you buy a little factory ammo for testing, I would suggest to choose any ammo except Federal. If you are having problems with CCI primers, then CCI factory ammo might be a good choice.

Good luck with this issue. Sometimes these problems are frustrating, but they do eventually get solved.

Agreed 100%. Hopefully this isn't too far off topic but I was having a light strike issue with my Ruger Security 9 and it was driving me crazy. I am also a reloader and wondered if the problem was with my ammo, even though my two M&P's had no problems at all running those same reloads. I had just decided to run some factory ammo to see if that made a difference when I found the problem.

I assume this is not your problem but I'd like to add the post I made for a Ruger forum about my findings as it does show that by process of elimination you should be able to isolate what the problem actually is:

really thought I had it figured out, read here from another person's reply how if the brass doesn't quite fit in the chamber, it could cause the slide to "close" and fire the trigger, but the tiny amount of space from the primer and the firing pin would only push the round firmly into the chamber, a second try would fire the round. Well, I got out the 9mm case gauge, sure enough, some of the 9mm wouldn't fit the gauge. Took 41 rounds out today, all fit the case gauge perfect, got thru 28 rounds and had 6 light primer strikes. So, that is not the issue. really want to carry the 9mm, but it is just not reliable, went back to my 45acp, btw, it is also the m and p 2.0 in full size. Don't think I have ever had a light primer strike with it, not that I can remember. yes, the gun does the same even when cleaned, I also removed the extractor, cleaned it, no more gunk than normal, made no difference. Am so frustrated!!! What am I missing?

All CCW classes advise NOT to carry reloaded ammo. It can go bad in two ways:

1) It doesn't go bang when needed

2) It does go bang, and some gung ho attorney convinces a civil jury that you reload "man killers".

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Release the Kraken

^^^ Can you cite any evidence of 2) ever occurring?

Its probably your reloads. Do you plunk test or have a chamber gauge? the other obvious thing would be primers that are not fully seated. They should actually be slightly below flush with the bottom of your brass. At lot of guys don't trim their brass or clean out the primer pockets, which is fine if you want to make quick blasting ammo but the more steps and final QC you skip, the more problems you will have.

It can happen to anyone, I had a couple 45acp round that just would not fire in my 1955, I ran the couple I had through 3-4 times. They sat here for a few years then one day I was working up loads for a HK USP 45T, so I loaded those up and they finally went off without a problem even though the primers were already severely dented.

Nope, but every CCW class my buddies and I have attended brings it up, and none of us want to be first.

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Release the Kraken

Lots of great info above. I would say that first you need to verify whether the problem is gun or ammo-related. Based on what you have done with cleaning and striker replacement I would suspect the latter, however ruling out the gun is pretty easy to do.

If you have not already done so, purchase a couple boxes of factory ammo and see if you experience any light strikes. A Speer product like Blazer brass likely uses CCI primers so that should be a reasonably close comparison to your handloads.

If malfunctions continue with factory ammo I'd recommend contacting S&W and let them fix the problem on their dime.

If the gun functions properly with the factory ammo I would then look at primer seating (discussed above) as well as storage conditions of your components. You asked about storage, it is recommended to store primers and powder in a cool and dry location. Storage in a damp location subject to extreme temp swings, such as a garage, will hasten deterioration. Depending on the age and storage condition of your primers it is possible that moisture may be affecting them. I'd try a box of newly purchased primers and see if reliability improves.

Regarding those rounds that had light strikes: assuming you tried to shoot them a second time, did they ignite on the second strike? If so, in my experience this does point to primers not being fully seated. Frequently in this case the primer indent looks very light. This is not due to a weak hit but from the force of the firing pin/striker pushing the primer forward to the bottom of the pocket.

If the round did not fire on the second (and subsequent if any) attempt, then either the primer is truly a dud or it may have been damaged during the seating process.

I have a Dillon Square Deal I've owned since the late '80s. This press does not have the same seating primer seating leverage as their larger presses. It takes noticeably more effort to seat CCI primers than others. Over the years using this press I've had the occasional problem with a high seated primer. Now days I do the bulk of my loading on a Dillon 550 which has much better seating leverage.

Dillion Square Deal B ? Check you primer seating unit for wear or adjustment . If using mixed brass , pocket depths can vary and primers must be seated all the way into the pocket until they bottom out .
This can be a weak spot with a progressive that has some use/wear on it .
Gary

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Certified Cajun
NRA Member

when I mentioned carrying the 9MM, I didn't mean daily carrying with reloads always carry factory loads, the reloads are for practice, not my first rodeo!!
am going to get some Federal primers today, see if they make a difference, rechecked the press again, replaced the shell plate bolt, maybe it is cracked? press is clean and ready to go, also checked the press handle for any cracks which would weaken it, not providing enough pressure
/force to seat the primer, will try to send some pics

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well, just finished loading up 100 9mm with the Federal primers, using press with new shell plate bolt, really concentrated on firmly seating the primer, will try to run these through the gun tomorrow, if still have problems, don't know what to do

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^^^ Houston, we have a problem...

Take a look at those messed up primers. There is your problem.

Yeah, I noticed that too, some of the cups look distorted, some of them look like they have already been hit with a firing pin.
Check the face of the ram that seats the primers, it's probably not very flat.

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U. S. Army Veteran

Wow, I agree with previous 2 posts. Most of your primers look dented/damaged from your primer seating plug. Almost surprised some of them didn't go off during seating! As mentioned, check your primer seating plug for flatness, or make sure there is no debris on the plug. Hope you get this sorted out. :-)

I don't reload, but that picture had me in WTH mode. Is it newly reloaded rounds or the rounds with light strikes. If the latter OK. If the former, the H becomes an F.

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Release the Kraken

Funny how new reloaders "accept" obvious problems
Oh well, I probably did something similar when I started reloading.

the primer cup stem had a little bit of debris, seasoned reloaders will recognize that, obviously I as m applying enough pressure to seat the primers, will test them this afternoon, remember, these are the Federal primers, much softer, not the CCI primers, the problem is with the CCI, not the Federal, these are loaded in response to the problem of the CCI, have not shot these yet

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You are fixing the wrong problem. CCI primers are NOT the problem here. Going to Federal will not make anything better.

Find out what is deforming your primer cups. Once that is resolved your ammo should be reliable.

With all due respect, Warren Sear, you're wrong. the 100 primed with the Federal primers ran 100%, not one light primer strike, the striker indention on the Federal primers are significantly more deeper and pronounced, will have a pic to show that, CCI primers on the left, Federal on the right

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Have loaded up 200 rounds for the IDPA match tomorrow, we will see how they do

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well, am considering the problem solved, ran the entire match with 0 light primer strikes, ammo and gun ran great, thanks to all who contributed to this thread

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I'm glad you aren't having ignition problems anymore, but your primers still look like dog doo-doo. I zoomed in on the pic above of the 100 loaded rounds, and many of them look dented and deformed.
I've reloaded for 40 years, and never had primers look like that.

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U. S. Army Veteran

You may consider your problem solved, but I can guarantee you that unless the pictures that you posted are deceiving, and the marks appearing on the primers in the pictures don't exist on your actual cartridge primers, you do have a problem with your priming operation ! ! !

Well, I guess I've been put in my place.

There's a lot going on here. Your primers should never have that "dished" look at the end of the reloading process. If they do, you have a problem. Sometimes debris can get on the priming stem and cause a dimple or dent on your seated primer or your stem could be damaged. The dent can cause the priming compound to migrate away from under the anvil and desensitize the primer causing misfires. It doesn't happen with every dented primer but it happens way more with the dented ones than the properly seated ones. Your priming process needs to be addressed. In the photos of the fired rounds, the elongated primer strike is caused by the slide cycling faster than the firing pin can retract. This could be caused by an over pressure round, weak recoil spring, weak striker spring or a combination of these things, assuming that the rest of the gun is within spec. 40's are notorious for the primer wipe marks but that is more of a design thing with a round that has a sharp pressure curve than a sign of a problem. I would start with reviewing your reloading processes, especially your primer seating and the load you are using. I would also invest in some factory ammo and see how that performs. That gun should be able to shoot with any type of primer in a properly loaded round.

appreciate everyone's help, like the song say "let it go", see ya

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good job of de-fusing this....it could have escalated into a war. well done.

I think that's "Let it be".. (unless you're a Frozen fan and not a Beatles fan).

Yeah, Frozen, not Beatles, kids

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Better???

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Dillon's do that, probably any press, if you really put
effort into seating primers. It's nothing to worry about.

Thanks Steve!!!
like I said "a seasoned reloader would recognize that issue",
Like you said nothing to worry about, they shoot great, have a good one!

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