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Benelli mp90s firing pin

Posted: Wed Sep 26, 2012 8:39 pm
by gusso
So I managed to break a firing pin tonight. I do have a spare but I'm not certain how to replace it. When looking down at the bolt I can see that the pin needs to seat in front of the leaf spring. The problem i'm having is that when I place the pin with the bevel down (not visible) , the pin doesn't stay put. When I try to place it with the bevel up (showing), I can't get it to slide all the way into place -- I don't want to force it. Any advice? Thanks

Posted: Wed Sep 26, 2012 9:36 pm
by jbshooter
I've broken three of them - too much dry firing without using plug. You have to remove leafspring by drifting out the crosspin. You need to do this while holding the return spring and retainer together or else the whole assembly inside will spring apart and you can lose parts. The leafspring has a swaged-on stud to guide and retain the spring retainer. The firing pin can only go in one way. If its a .32 then there will be a small return spring in front of the pin - don't drop it.

Posted: Wed Sep 26, 2012 10:04 pm
by gusso
Thanks so much. I'll see what I can do with your advice tomorrow. BTW, it is a .22.

Re: Benelli mp90s firing pin

Posted: Wed Sep 26, 2012 10:29 pm
by slofyr
Fwiw, Larry Carter has had new pins for the Benelli 90/95 made in the U.S. which are apparently less prone to breaking.

Re: Benelli mp90s firing pin

Posted: Thu Sep 27, 2012 4:53 am
by gusso
slofyr wrote:Fwiw, Larry Carter has had new pins for the Benelli 90/95 made in the U.S. which are apparently less prone to breaking.
That's where I got my replacement pin.

Posted: Thu Sep 27, 2012 6:29 pm
by gusso
I installed the new firing pin today. It was actually easy to do (even for a mechanically challenged person like myself). Thanks for the advice.

Posted: Fri Sep 28, 2012 9:59 pm
by gusso
Uh oh, this gun had been flawless for the last 6 months or so until breaking that firing pin. I thought everything was fine with the new pin BUT now there is suddenly a problem with jams. This can't be a coincidence. Could I have screwed something up with the extractor/ejector while installing the new firing pin? I'm starting to panic as BE starts next week. Suggestions please!!!

Posted: Sat Sep 29, 2012 8:03 am
by Gwhite
Did you find all the pieces of the firing pin? Sometimes the tip breaks off, and it can get jammed someplace. It's also remotely possible that the broken part did some damage somewhere.

If the extractor can hold onto a loaded round with the slide held horizontally, it's probably OK.

I'd start by giving the chamber a good cleaning with a bronze brush, and then clean & oil the sliding bits. If you can't dropped a round into the chamber until the bullet engages the rifling, that can slow things down enough to affect operation.

Posted: Sat Sep 29, 2012 10:26 am
by gusso
OK, I took a closer look at the problem this morning. It is not the extractor. In fact all of the jams have been because it's not feeding live rounds properly. It doesn't do it each time, but it happens every 5-10 shots. All of the jams are consistent -- the casings are getting squished with the bullet pointing up. Looking at the diagram -- is it possible that when the retaining pin was out that I didn't properly reinstall the spring guide screw, return spring, and return spring bushing (parts 3/17, 3/18, & 3/19)? Would that be an explanation? I'll have a friend take a look at this afternoon to see if he can do a better job of diagnosing the problem. And I did retrieve the entire broken pin. Thanks

Posted: Sat Sep 29, 2012 12:22 pm
by Gwhite
Still sounds like either a slide cycling issue, or a magazine problem. I think the busted firing pin is just a coincidence.

One other possibility is that the new firing pin is sticking out of the bolt face, and is interfering with the round sliding up & into place. However, your description makes it sound like the rim isn't getting picked up at all.

One thing to watch out for with the Benellis is to use a light oil. Thick oil or grease will slow things down too much. The factory oil is quite thin. Breakfree is OK, but a little thicker than the factory stuff. Rem Oil is thinner than the factory oil, so it tends to disappear faster, but a thin coating works pretty well.

Posted: Sat Sep 29, 2012 1:00 pm
by gusso
But it never had jamming issues until I replaced the broken firing pin. I must have put over 7500 rounds through her in the last 8 months or so. It had been flawless up until a few days ago. Also, I have 6 mags, it doesn't appear to be jamming mag specific.

Posted: Sat Sep 29, 2012 6:48 pm
by Gwhite
OK, if it isn't the magazine, the symptoms suggest something is adding drag to the slide so it isn't coming back far enough.

Check for a burr on the edge of the chamber from the busted pin. Also, take a look and see if there is any way the new pin could be rubbing on anything during recoil. Another possibility is that the cross pin is sticking out far enough to rub.

Posted: Sat Sep 29, 2012 10:49 pm
by Shooting Kiwi
Is the rubber buffer in the 'locking head' (Benelli's term, not mine - they mean the bit you pull out to let the slide back far enough for removal) breaking up?

Posted: Sun Sep 30, 2012 5:05 am
by gusso
The buffer is fine but I think I spotted the cause -- there are a few burrs on the part of the slide where the firing pin is. I'll try to address that issue and see where I'm at.

Posted: Sun Sep 30, 2012 5:18 pm
by gusso
I smoothed out the burrs but it is still misfeeding. I feel sick, this gun had been absolutely flawless until just a few days ago.

Posted: Sun Sep 30, 2012 7:29 pm
by Gwhite
Don't despair. With all the work you did on it, all it takes is a piece of dirt to get knocked loose & jammed in the wrong place.

Question: Does the slide go back far enough to get behind the rim of the round it is trying to feed? If not, something is slowing the slide down.

If it's picking up the rim of the round on the bolt face, then I'm not sure what the problem could be, but I suspect the new firing pin is preventing it from sliding into place. Some Benelli pins have very sharp edges on the end. I would stone those off a bit. Also, make sure the new firing pin floats freely in its channel. It should rattle back & forth freely. Unlike many pistols, there is no spring to keep the pin out of the way. It operates on its own inertia, and a burr or dirt could mess that up.

Posted: Sun Sep 30, 2012 8:10 pm
by gusso
Tomorrow I'm going to remove the pin and be doubly sure it is debris free in there. I appreciate all the suggestions.

Posted: Mon Oct 01, 2012 7:00 pm
by gusso
I'm pretty certain i may have incurred more damage than I originally suspected. A friend and I tore it apart today multiple times and shot quite a few rounds. We were able to duplicate the error by pulling the slide back partially. By doing so, we could see why some rounds weren't feeding properly. Some rounds are getting moved into position midway on the casing, forcing the round to get pushed upwards and then crushed by the slide. The problem appears to be in the trigger assembly. There is movement within, and you can feel "ticks" when you play around with it. I suspect that a small piece may have fallen in and caused havoc. I plan to contact LGI and see if I can just send the trigger assembly. I hope it can be repaired -- I'd rather not shell out $417 for a new one. I'm not feeling very happy at the moment...

Posted: Mon Oct 22, 2012 5:03 am
by gusso
Update --

I sent out the trigger group to LGI. He looked it over and it's fine. I put the gun back together and it was the same thing -- jams every 5-10 shots!!! Grasping at straws, I tried another firing pin and viola-- it has not misfired in over 200 rounds. Go figure...