Striker riding sear causing light strikes?

[ssdrew]

A couple of weeks ago I ordered the new LE M&P9 with the new reset and PVD slide. I ordered at the same time a APEX sear and installed it before my first range trip. I was extremely pleased with the trigger. I had a couple hundred primed brass from the past spring i never loaded. So I loaded them up and took a box of Tula and FC with me to the range. Once i started shooting I couldn't believe how well I shot this gun compared to my Glocks, I was in heaven, for a moment. I don't remember the round count it started at, probably after 60 of my reloads I got a light strike, it fired the 2nd time. I ended up with 6 light strikes (all my reloads). The 100rnds of factory ammo functioned fine. I did some research online and read that sometimes primers that are not fully seated will cause light strikes, also I read that the striker contacting the sear as it fires can cause a light strike occasionally.I broke the gun down and there was a slight ridge on the striker that seemed like it was riding the sear. I took a polishing stone and slowly removed that slight ridge thinking that might have been the issue. I also made sure the striker tunnel was dry and oil free.

I loaded up 25rnds with noticeably high primers to test that theory. I also loaded 125 regular and made sure that each primer was fully seated at least flush. I picked up a 100rnd Federal pack and 50rnds of Brown Bear.

I went to the range and as I expected the high primers would not fire. With the Apex sear I had 1 light strike with fully seated.4 light strikes with the brown bear. Halfway through I swapped out the sear to the factory one and ended up with 1 light strike with the brown bear in 20rnds. I also took a sharpie and colored the factory sear surface to see if the striker was riding it. Sure enough there is a line down it. Not sure if this is normal. Also I have shot around 1k of my reloads out of my glocks and have never had one issue. I love the feel and how well I shoot the M&P, but the reliability is a problem. I am curious if anyone else has encountered this, or could verify if the rubbing is normal.

Striker that I stone polished the center ridge down

Factory Sear

Apex Sear

 

[Pilot172P]

My Shield 40 just starting doing the light primer strikes. About 1 in 10 rounds is a light strike now. Happened about 10 times now. Not sure what's causing it. They are all hand loads and the ones that failed, the primers looked fine and fired the second time. I have about 500 rounds through the gun. The first 400 or so had zero failures. This "was" my favorite carry gun, but now I can't trust it. I cleaned the striker and hole so will try it again soon with factory and hand loads.

 

[Neumann]

The striker will always ride on the sear. Stoning a critical part like that is madness unless you have a fixture and a microscope.

Factory loads work okay, but reloads have light strikes? Obviously it's a problem with the gun, LOL.

First, make sure you don't have high primers. Primers should be 0.005" below the base, which is easily seen using a straight edge and your unaided eye. Primer seating is all about technique. I've never found residue (other than tumbling media) that would keep a primer from completely seating.

Do a "plunk test" with your reloads, and check the OAL v factory loads. The shape of the ogive makes a difference in the maximum OAL that works. The cartridge must headspace on the lip of the case. The bullet should NOT engage the rifling. You can usually hear and feel the difference. Press the cartridge into the chamber with your thumb. It should drop free when the barrel is inverted, unless the bullet sticks in the rifling.

 

[ssdrew]

Well that is good to know that the striker is suppose to ride the sear. All i did was removed the edge from the part caused by the mold.

The first range trip it was only my reloads. Next range trip only 1 reload and 5 from factory Brown Bear ammo. I know it is a cheap ****ty brand. Maybe I am being over critical, but this gun seems way more picky on ammo than my Glocks.

I will try the plunk test and see what happens. Thanks for the tips.

 

[Rastoff]

Factory Sear

I don't believe the striker is "riding" the sear as you suspect. The mark you see is from the striker moving backward, with the slide under recoil, after the gun has fired.

How do you know this Rastoff? Well, if it were rubbing along the sear as it were fired, the portion rubbed off would be almost as long as the mark. In the pic we can see that the rubbed spot is well short of the full travel of the sear. So, the mark is being made after the trigger bar loop has been pushed out from under the sear, the sear has popped up and the striker tang drags along the sear as the slide moves backward.

I suspect the largest cause of your light strikes to be the primers not being seated properly. This can happen even with factory rounds, but is plainly obvious in your experimentation with your hand loads.

I had a similar problem, but to a much lesser extent. Now I push harder on the primer seating station of my press. No problems since.

 

[ssdrew]

Rastoff, your explanation of the mark on the sear makes perfect sense. I'm thinking maybe the M&p is just a hair more picky on primers. I would like to pick up a few more boxes of brown bear to run through my glocks to see if i get FTF. If I did, that would defiantly clear up the light primer strikes with the m&p. I defiantly gave all of my reloads a good firm primer seat, more than i usually do on the 2nd go around. I still had one light strike, but that is better than the first go around. I might have to start uniforming my primer pockets to ensure they are all even and slightly below flush.

 

[Rastoff]

A primer that is seated flush should be OK. Mine are and I haven't had any issues since I first learned that primer seating could cause light strikes.

The Glock striker...

...is different than the M&P striker...

Notice how the Glock is squared off and the M&P is a more traditional round protrusion where it strikes the primer. Therefore, I don't think it's an apt comparison.

 

[robkarrob]

Rastoff is 100% correct. The striker is not contacting the sear after the break, except on recoil the striker will push the sear down so that it will catch to the rear of the sear. There are a number of reasons for light hits, and reloads can be a major cause. Hard primers, high/low set primers, loose primers, etc. Then you can go to the gun. Striker spring weak/broken, striker partially contacting the striker blocker, debris in the striker bore, etc.

Bob

 

[Pilot172P]

My Shield 40 just starting doing the light primer strikes. About 1 in 10 rounds is a light strike now. Happened about 10 times now. Not sure what's causing it. They are all hand loads and the ones that failed, the primers looked fine and fired the second time. I have about 500 rounds through the gun. The first 400 or so had zero failures. This "was" my favorite carry gun, but now I can't trust it. I cleaned the striker and hole so will try it again soon with factory and hand loads.

Just a follow up on my Shield 40 failing to fire about 1 in 10 rounds, all hand loads. I removed the striker and cleaned it and have had zero failures since. The striker wasn't that dirty. I've shot over 100 hand loads from the same batch and no failures. Some other thought the hand loads were the issue, but it appears that cleaning the striker fixed the issue. I only had 500 rounds through the gun previously, so wouldn't think cleaning the striker was required.

 

[SWShootinDave]

Just a follow up on my Shield 40 failing to fire about 1 in 10 rounds, all hand loads. I removed the striker and cleaned it and have had zero failures since. The striker wasn't that dirty. I've shot over 100 hand loads from the same batch and no failures. Some other thought the hand loads were the issue, but it appears that cleaning the striker fixed the issue. I only had 500 rounds through the gun previously, so wouldn't think cleaning the striker was required.

It doesn't take much in the way of primer-shavings buildup in the striker channel to slow the striker enough to cause light strikes. That's why I clean my SW9F's and SW9VE's striker/channel after 300 rounds. It only takes a few minutes and those could save your life.

 

[Rastoff]

This thread is 4 years old. Pilot172P hasn't made a post in over a year. It's unlikely he'll see this.