Mossberg 500 light primer strikes?


chris in va
November 1, 2007, 12:57 AM
I posted this on TFL, thought I'd ask here too.

The other day I was shooting some hand thrown clays at my range. One shot went click, and found the primer to be barely dented. The next cycle it went off.

The rest of the session saw about 4 more misfires. When I got home I hosed out the bolt with Powder Blast, and frankly it wasn't that dirty, just average junk coming off.

So what would cause this?

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Dave McCracken
November 1, 2007, 09:36 AM
It doesn't take a lot of grunge in the wrong places to mess up the strike. I'd blow it out with gun scrubber,then air, repeat and lube lightly.

November 1, 2007, 09:53 AM
I have only seen that once before in a Mossy, and Mr. McCracken has it right...

There was just enough gunk in the bolt assembly to keep the firing pin from hitting full force. Rounds that did fire had only marginally deeper dimples..

Took apart the Mossy, and soaked the bolt in Min-Spir for a while, rinsed, carb cleaner spray next, rinsed, Hoppes #9 soak next, rinse, dry very lightly oil, reassemble. Problem solved.

chris in va
November 1, 2007, 04:53 PM
Thanks guys, I figured as much. One thing I noticed about the firing pin spring, it's REALLY strong! I've never seen one that stiff before. The hammer must have to hit it hard for a good dent.

November 1, 2007, 04:59 PM
It could also misfire if it's not quite going into battery. Sounds like it's past due to strip and clean.

November 1, 2007, 05:25 PM
I have assisted a friend with this problem with his Mossberg. The way we fixed this problem was to change the firing pin spring. It was so strong that it wouldn't allow the firing pin to go forward enough to ignite the primer. It would only do this with Remington loads. It was a new gun that had only used Federal and Estate loads. The first time he used Remington shells the hard primers would not ignite. I went online to one of these forums and someone kindly assisted me.

Remington shells have very hard primers that will FTF sometimes, according to what they told me. I gathered different brands and shot them in the gun. The Remington barely had an indent on the primer. Changing out the firing pin spring solved the problem. FWIW, I have never had any problem with Remington loads, but have noticed that the indentations are very light, maybe to the hard metal in the primers.

Hope this helps.

November 1, 2007, 05:30 PM
Like other mentioned, you might just need to clean it out.
Second option would be to change the firing pin spring (though it should work with the factory one)

Third option, look at the ammo.
What ammo are you using?
I used to have a Charles Daly maxi-mag pump.
With cheap Winchester (100 round pack), it had many failure to fires with light primer strikes.
I used calipers to measure the rims and the rims are just a tiny bit smaller than other shells.
The chamber of the Daly could have been out of spec too with the rim recess cut too deep (too much head space).
The combination resulted in light strikes that weren't due to the firing mechanism.

chris in va
November 1, 2007, 05:39 PM
I was in fact using Remington shells as they have worked best for me in the past. Maybe I could switch to Federal as they're cheaper anyway. So where can I get a different firing pin spring?

November 1, 2007, 07:32 PM
Cut one coil off the spring and try that. If you need a new one contact Numrich's Gun Parts.

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