Benelli mp90s trigger unit maintenance

[Rudi]

Good day from the Netherlands, another questions regarding cleaning.

Can the trigger unit be pretty much left alone? I mean, my “new” old benelli (1991) came pretty grubby and I’m wondering if it’s fine to leave the trigger unit well alone.
Or indeed if you have some (any) basic tips to keeping things running smooth.
I don’t know the cleaning history of the pistol, so I can’t be sure it’s ever been touched.
My model has no safety lever if that makes a difference with the advice.
A club member mentioned ultra sonic cleaning but I’m almost certain that’s not a good idea for the trigger group.

Thanks again for putting up with the noob questions

[Rudi]

This is the one

[-TT-]

Definitely no ultrasonic baths. All that will do is drive dirt deep into the mechanisms and trigger plungers.

The only cleaning I do is to wipe off the top surfaces, and run a swab or cloth through the magazine channel, where carbon adheres.

I also wipe off the hammer surface, where it strikes the firing pin, and sear contact ridge, at the lower edge just in front of the trigger. I then give both these areas a tiny touch of TW25B gun grease.

[Rudi]

Perfect, this is what I suspected and what I'm doing, also since watching Mr White's great youtube playlist. Thanks!

[Gwhite]

The most important thing is not to store it in a cocked condition. That can weaken the hammer spring over time. In the MP95 triggers, the plastic housing can get brittle with age, and I know of two where the hammer spring broke out the bottom of the housing. Using the dry fire plug is fine if you have one that works (see below).

Generally, you just want to wipe off any fouling & powder residue. I also put a small dab of grease on top of the hammer to help keep the drag in the action down. If the trigger ever feels gritty, clean & lightly grease the mating surfaces of the sear & hammer.

Beyond that, a lot depends on the exact vintage. Benelli has used three different disconnector designs over the years. The original was just a single part (#098P). This allowed the pistol to fire "out of battery", and they added a long flat topped lever (#215P?) that holds the disconnector down until the bolt closes. That only allowed the pistol to fire with the bolt fully closed, but defeated the dry fire feature. Later, they modified the lever by cutting down the back a bit, leaving a bump in the front. That restored the dry fire capability.

If you have the lever (either style), you should lightly grease the top, and also get some grease in between the lever and the disconnector. This will also help reduce drag when the action cycles.

[Rudi]

fantastic!
thank you for your time and patience with these questions

[-TT-]

The most important thing is not to store it in a cocked condition. That can weaken the hammer spring over time. ... Using the dry fire plug is fine if you have one that works

I'm not sure I agree that this is accomplished when the dryfire plug is in place. When dry firing, the hammer only strikes the underside of the bolt, not the firing pin. This means the hammer spring/strut is only partially relaxed. Do you think this is enough?

[Gwhite]

If you are shooting regularly, I think it's fine. For long term storage, it's certainly safer to fully de-cock it.

[Gwhite]

Here is a photo that shows the two different disconnector levers:

The maintenance & lubrication is pretty much the same. Some of them are a bit rough on top, and polishing them can also help reduce drag. The place you need to get grease is in between the bottom front of the lever and the rounded top of the chrome disconnector.

The levers are hand fitted to make sure that the pistol can fire when it's supposed to, without being able to fire if the bolt isn't closed far enough to prevent a case rupture (~ 1 mm gap or less). The fitting process may leave the under side of the lever a bit rough where it pushes down on the disconnector. You can feel how smooth the action of the lever is just by pushing it down a few times. You can lightly polish that area of the lever, but you don't want to remove any significant metal.

One other word of caution: The cross pin the holds the lever in place is often not tight. They can drift sideways enough to make removing the trigger assembly difficult. In extreme cases, they can just fall out while you are cleaning the trigger assembly. I've had to use a "prick" punch to stake the material around the hole on both sides to keep them in place.

[Rudi]

Super information. Thanks so much

[nik365]

The levers are hand fitted to make sure that the pistol can fire when it's supposed to, without being able to fire if the bolt isn't closed far enough to prevent a case rupture (~ 1 mm gap or less).

Just to illustrate the Gwhite's detailed explanation, this is how the case rupture due to not fully closed bolt of MP95e looks like:

[Gwhite]

I was actually surprised to discover that a large number of highly regarded European target pistols can do this. US pistols tend to have the disconnector set up so they can only fire when the slide is closed. Early Benellis, Pardinis and MatchGun MG2's can all fire "out of battery", and I think I heard that Hammerlis can do it as well.

This case looks like what I've experienced several times with my MG2. An ejection failure leaves a case in the action crosswise, but the next round is picked up by the bolt OK. The bolt closes with the round in the chamber, but is stopped by the sideways case so about 5 or 6 mm of the back of the next round is unsupported. As long as the extractor has a good grip, the hammer can hit the firing pin hard enough to fire the round. Kaboom!

It's rare in the Pardini (and relatively safe) because of the way the inner contour of the bolt surrounds the breech area. It's hard for a case to get stuck just right in that small space, and the bolt serves as a shroud to keep any brass bits from flying around. The MG2 is more open, and can trap brass easily if the ejector/extractor aren't set up right. The top cover helps to contain the blast, and I haven't had even a slight scratch from 4 or 5 kabooms. The Benelli is completely open on top, and they may have decided to fix the disconnector because of the increased risk of injury from shrapnel.

It's not too hard to retrofit the new style lever in place of the older lever to reacquire the dry fire feature. The original style trigger housings would require some significant modification to install one of the levers.