Mossberg 500- Problem/Question

[crashguy]

I am having fail to fire in a Mossberg 500 (about 20 percent) using Federal, Remington, Independence and Winchester. The examination of the primers of all manufactures showed a similar slight indentation. On a second attempt to fire the shell most would fire , however, on occasion a shell will take several strikes to ignite, fewer take 4 - 5 hits without ignition at all. I have indeed thoroughly cleaned the firearm and changed the mainspring without improvement .
I would like some help with this as it is very frustrating. I would like to start with some specs. It would be helpful if someone could provide the specs on the over all length of firing pin as well as acceptable positive firing pin protrusion . Any other suggestions or guidance would also be appreciated.

[Mk42gunner]

Sounds like an excessive headspace issue, to me. Check the locking block and the surface it mates with for wear or peening.

Does the firing pin pass through the bolt freely?

It has been several years since I had a Mossberg apart, they aren't the easiest to reassemble.

Robert

[Chicken Thief]

Just measured my spare bolt and the pin protrudes @.051" max.
And the bolt cant be dismantled easily.

[crashguy]

Mk42gunner- no significant wear at the mating of barrel and locking lug. firing pin seems good as well, I had it apart and buffed the channel and the firing pin. Suggestions on a way for me to check head space? I have access to a unused barrel for comparison if that might help.

Chicken Thief- mine measured @.058, so that appears correct. Thanks for helping me check that off the list.

[John 242]

What if...
What if the bolt isn't closing all the way (just a tiny bit out of battery) or the rim isn't fully seated against the chamber mouth when the misfires occur. The firing pin would drive the round forward a fraction of an inch, absorbing some of the pin's striking power and a light primer strike results. Once the rim is fully seated, the gun fires, usually on the second or third strike.
Seems like I've seen this before, but I don't remember where. CRS is hell.
PS... Try the other barrel!

[ratboy]

i had the same problem with my 590. unfortunately i never did figure out why. i took it apart and couldnt find any thing wrong. i put it back together and it wouldnt duplicate the problem. this may not really help you but i thought i would share. i figured it was the gun equivalent of turn it off and turn it back on.

[imashooter2]

Are you operating the action briskly to ensure good lockup?

[crashguy]

This is what I have been able to do so far. I was able to get another model 500 ( a new than mine mode with little wearl) for comparison. From what I could tell it was in spec but found that mossberg changed the firing pin and firing pin spring design. I concentrated on that area. Additionally my bolt locking lug was stiffer and actually rubbing on the inside portion on the bolt face and if not completely locked would prevent the the firing pin full positive motion, so suggestions by members to check that area now seam very credible. So I eased the locking lug face to clear the bolt then polished the firing pin and channel. So now I'm ready to test it out .. but here on Long Island they frown upon shooting a box or 2 of 12 ga in your own backyard, so an update will be forthcoming.
Thanks all for the input and support it's a lonely feeling when everybody else's gun is going bang and yours goes click.

[Goatwhiskers]

Just an idea: make sure the barrel is fully seated into the receiver. Saw it happen once, causes the same symptoms. Goat

[Fixxah]

Also keep in mind that the primer compound crumbles when it fails to fire. Second strike ignition is fifty/fifty, after that you could use a hammer and it probably won't light.

[crashguy]

Goat- checked
Fixxah- good point, I never even considered that.

Range report - Well I'm still gonna hafta shoot in the " Tactical Club" category for now, as I still had FT Fires at the range. I swapped Barrel, bolt, and trigger assembly variety of ammo --no improvement. side note- Not a wasted trip though, my latest 9mm boolit recipe was eating the black... yea, that was nice.
Maybe a little thick headed but I feel a firearm should do what it was designed to do and I'm just not ready to give up.

[Chicken Thief]

Seems like the "only" thing left is the forestock.
It has to move freely in order for the bolt to close 100% and if it "sticks" or hits the barrel stub then misfire.

[crashguy]

Seems like the "only" thing left is the forestock.
It has to move freely in order for the bolt to close 100% and if it "sticks" or hits the barrel stub then misfire.

I will swap that out next. Man oh man it would be nice if that is the problem.

[JIMinPHX]

I had a similar problem on a Charles Daley pump a while back. The problem that I eventually found was not something that I had expected. Perhaps some of what I went through might give you food for thought - castboolits.gunloads.com/showthread.php?t=90256

[John 242]

Might want to let another shooter fire a box or two, just to rule out operator error. That may sound... rude, but I don't mean it that way. Just one more thing to cross off the list of possibilities.

I wonder if your receiver might somehow be out of spec. IF the barrel is not seated as deep into the receiver as it should be and the extractors are holding the rim slightly out of complete battery, the pin would be driving the shell forward and the resulting loss of momentum could case light primer strikes.
I wonder if a 12GA no-go gauge would tell you anything?
If I had one, or knew someone with one, I'd drop it in and see what happens.
(Yeah, I'm really reaching with this post, but my wife works at a Holiday Inn, so....)