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PostPosted: Mon Jan 01, 2018 8:54 pm 
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Location: Massachusetts
Curious if other Benelli MP90S .22LR owners see a similar "gap" between the extractor and the rim of the shell as seen in this photo of mine.

The extractor functions well enough, but as you may imagine it doesn't hold the round very tightly. I've recently had some FTE's. Replacing the extractor didn't change the gap, although replacing the plunger (with Larry's upgraded in-house design - recommended!) and spring helped retain the shell quite a bit and improved the situation.

The gun has always thrown shells in a somewhat random direction, they may go forward, backward, sometimes straight back at me. The gap makes sense as a cause. I'm wondering if the pivot hole in my gun's bolt is slightly too far forward.

Any info appreciated!

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PostPosted: Tue Jan 02, 2018 8:52 am 
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I have tons of notes on Benelli extractors, but they need organizing. The gap is somewhat normal, although yours may be a bit excessive. It's probably OK if you can pull a fired case straight forward and still have the extractor prevent the round part of the rim on the opposite side from popping off the bolt face. I recently measured the gap on a Pardini SP at about 0.010", but the pocket on the Pardini bolt face is deeper than on the Benellis. The rim pocket on a typical Benelli is about 0.036" deep. The rim on a fired case is going to be at least 0.042" thick, so the center of the round edge is ~ 0.021" from the back of the case. That says the gap under the extractor hook to the bolt face should be less than ~ 0.015", or you might start to have problems. I have a small feeler gauge set that can fit under the hook to check this.

Benellis regularly throw brass around a lot. The first round tends to go one way, the next three will be more consistent, and the last one will go a different way. I'm not sure what's up with the first round, but the last one doesn't have a round in the magazine to interact with. My personal Benelli will announce its desire for a cleaning by bouncing brass off my head...

A couple other things to check:

The hole for the extractor spring & pin may have burrs. The shank of a #38 drill should slide in smoothly.

The nose of the extractor should be sharp, but the angle is also critical. The extractor should hold a case UP against the pocket in the bolt face. This requires that the angle of the extractor nose be tilted slightly to the left when viewed from the front. It also needs to be radiused on the bottom so a round can slide up the bolt pocket face and push the extractor to the side.

I'll work on cleaning up my notes, but it may be a while. I'm also in the middle of debugging some extractor issues with a Pardini and a Benelli that will add to the knowledge base. I'm pretty certain I know what's up with the Pardini, but I'm not sure about the Benelli. I have to check the serial number, but I think I did a complete extractor overhaul on this pistol a while back, and it was fine until suddenly it wasn't. It feels like the extractor spring is weak, and I want to compare the tension with a good one before I take it apart.


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PostPosted: Tue Jan 02, 2018 12:03 pm 
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Great info, and yes mine bounces brass off my forehead from time to time. I never found it related to needing a cleaning, maybe I'll watch for that. If not at me, it then bugs the guy in the next lane, which is maybe an advantage! :-)

Your <0.015" observation is almost exactly what mine measures, right around 0.013" to the front surface of the bolt. I'll have to pop it out to measure the setback where the rim nestles. In my photo, you can just see a couple mils of the rim standing proud of the line (this was a fired round in the photo btw). The plunger/spring hole is quite clean but I'll check it with a #38. The extractor has plenty of lateral oompf now that I installed Larry's new 046P/047P, much smoother and stronger than before. I haven't messed with the factory extractor angles you describe.

Gwhite wrote:
It's probably OK if you can pull a fired case straight forward and still have the extractor prevent the round part of the rim on the opposite side from popping off the bolt face.


Definitely not. The round barely stays put and the slightest nudge sends it off on its merry way. This is what I think causes the FTEs and also the random eject direction.

One other question while I've got the floor. For some reason, these factory extractors are nickel plated, and the plating starts to fail almost immediately (two so far). The falling flakes bind up in the slot, preventing a smooth pivot. I've had to hone the top and bottom surfaces to remove it, and keep the flakes from jamming up the works. Is this your experience?


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PostPosted: Tue Jan 02, 2018 7:32 pm 
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-TT- wrote:
One other question while I've got the floor. For some reason, these factory extractors are nickel plated, and the plating starts to fail almost immediately (two so far). The falling flakes bind up in the slot, preventing a smooth pivot. I've had to hone the top and bottom surfaces to remove it, and keep the flakes from jamming up the works. Is this your experience?

I've only seen plating issues on a couple over the years. Certainly never enough to flake & bind things up. I think they must have had a bad batch.

The older pistols were blued, and had extractors to match. The newer ones are plated, starting with just the bolts at some point. The team I help coach has over 20 Benellis, dating back to the early 1980's. We have quite a range of design variations, including a number that pre-date Larry Carter's importing them.


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PostPosted: Tue Jan 02, 2018 8:22 pm 
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Gwhite wrote:
must have had a bad batch.


I purchased my MP90S last year, and replaced the extractor with a newly-purchased part this summer, so the parts certainly came from different batches. Both are plated and the "new" one started to fail in weeks. Here's a photo of the part after a month or two in service - the bronze tone is an artifact of the flash lighting, the part is a uniform silver. Note the flaking "around the corner" of the part, disappointing.

Well, it's easily corrected with a stone, and if it's "rare" so much the better. And I've proved to myself it's not the source of the FTEs. Just wondering.

Attachment:
BenelliExtractor.jpg
BenelliExtractor.jpg [ 28.93 KiB | Viewed 366 times ]


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PostPosted: Thu Jan 04, 2018 7:44 pm 
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I took some time while waiting for today's blizzard to pass and did some measurements. I have two Benellis, and the bolt from one of the team pistols. I measured the gap under the extractor and the bolt face pocket depth on all three:

My Benelli: Extractor gap was 0.015", and the bolt face pocket was 0.034" deep.

My Daughter's Benelli: Extractor gap was 0.013", and the bolt face pocket was 0.036" deep.

Team Benelli: Extractor gap was 0.015", and the bolt face pocket was 0.034" deep.

The team pistol has extraction issues, but I think it's a combination of a weak spring and a slightly rough chamber. I'm going to replace the spring and polish the chamber with an expanding lap.

If anything, I would have expected my Benelli to be marginal, but it will happily go 500 rounds between cleanings without a hiccup. That's when it starts bouncing brass off my head.

While studying how to lap the chamber of the team pistol, I measured the chambers on my two pistols, and compared the results against the factory specs for a S&W Model 41. The chamber diameters vary by about 0.001" at both front & rear between the two Benellis. One has close to 100K rounds through it, and some of the difference may just be wear. What I found interesting is that the taper of the Benelli chamber is less than half that of a Model 41. That might explain why the Benellis tend to be a little fussy about extraction...


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PostPosted: Thu Jan 04, 2018 10:22 pm 
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Thanks! I haven't had a chance yet to measure the pocket but i'm betting mine will be about the same. Either way it confirms the gap is pretty much normal and by design. Very interesting.

I had to take an alibi last night because of an unejected empty. So I'm still on the quest to figure this out.


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PostPosted: Fri Jan 05, 2018 6:12 pm 
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I have continued my research...

The team's Benelli bolt that is acting up had a complete extractor overhaul about a year ago, and worked fine ever since. Suddenly in early December, it started failing to extract reliably. The change was quite dramatic. It all looks OK, but the spring tension feels a little light just pushing on it with my thumb, but it's hard to tell. I swapped a spare bolt onto the pistol and the malfunctions continued, but the pistol was pretty dirty by then, so it's hard to tell what was going on. It's been cleaned, and the problems persist with the original bolt.

I wanted to find a way to reliably to measure extractor tension rather than relying on a "calibrated" thumb. I have a Lyman digital trigger pull gauge (highly recommended!), and using a small loop of monofilament line, I used it to pull on the extractors of several pistols. The 10 pound test line I have is about 0.011" in diameter, so it will fit nicely into the typical extractor "gap." Because the force depends a bit on how far you move the extractors, I settled on pulling them until the nose would be about where it would sit on a case. On a Benelli, there is lots over-travel designed in. I'm also debugging a Pardini SP, and this one in particular has ZERO over-travel, so I measured it when I could just see the extractor beginning to move. One nice thing about this test is that you don't need to even take the pistol apart to do it.

My Benelli: 1 pound 12.7 ounces

My Daughter's Benelli: 1 pound 8 ounces

Team Benelli: 1 pound 1.6 ounces

Out of curiosity, I also tested:

Team Pardini: 1 pound 14.5 ounces

High Standard "Victor": 12.9 ounces

The High Standard has a deep bolt face pocket (0.047"). and a very sharp extractor hook. Somehow it works just fine with less than half the tension of the European pistols.

In any event, it appears that the spring tension in the team's Benelli is a good bit lower than my two, which both work fine. I know I replaced the spring in the team pistol last February. It may have taken a "set", broken, or is one of the older factory springs rather than the new ones from Larry's Guns. The team has a bag full of extractor parts, and I didn't realize there were old & new springs, so they are jumbled together. I need to see if I can identify a way to sort them apart. Given that it failed rather abruptly, I'm guessing it broke or got compressed due to a heat treating problem. Now that I've documented its behavior carefully, I will take it apart & see what I find.


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PostPosted: Fri Jan 05, 2018 7:34 pm 
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More good info, thanks. I'll have to borrow my friend's Lyman. Spring tension on mine is pretty tight though, and swing-action quite smooth. Your #38 bit shank test is spot-on.

Measured my gaps today:
Extractor to bolt face: .014"
Bolt face to bolt pocket: .037"

Interestingly, at least .002" extra clearance from yours. Unfortunately, I don't see any way to correct it. The only way to bring the beak "in" would be to shim the pivot end, which is just not practical. I wonder if I can sacrifice the part and simply compress it in a machinist vise and see what I can do. At this point, it may be worth it, since I have at least one (used) spare.


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PostPosted: Fri Jan 05, 2018 9:38 pm 
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I'd hold off on desperate measures. It sounds like the "gap" on yours is better than most.

The first thing I would do is take a close look at exactly how the extractor holds a case in the bolt face. Because the Benelli extractor is at an angle, the nose has to be ground at an angle, otherwise it wants to push the round down off the bolt face. They also need a radius on the lower corner so that the extractor gets pushed aside as the case slides up the bolt face.

I've examined a dozen or so brand new extractors, and there is quite a bit of variation in how the nose is shaped. On some, the angle is almost non-existent, and others the radius is too large.

Rather than mess with uploading pictures someplace I can link to, I popped them into a PDF with some explanation. Hope this helps.


Attachments:
Benelli MP90-MP95 Extractor Tuning Info.pdf [832.24 KiB]
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PostPosted: Fri Jan 05, 2018 10:12 pm 
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I inspected both my extractors very closely and they are nearly identical in every way, including dimensions, radius and bevel you describe. I will look some more at the angles and compare to your excellent photos.

I know it seems drastic, but at this point I believe I have eliminated the other issues. The chamber is spit-clean and rounds pass the plop test 100%. The extractor and recoil springs are new, the bolt slides slick as snot. But the brass still rattles around the breech. The good news is, the gun holds pinky-tip-sized groups and I'm shooting it as well as I ever have. Except for those dratted alibis.

[edit]
Ok, I've re-examined the two extractor nose edges and I believe they're similar to your "so-so" example. The original extractor completely fails to hold the brass, the replacement one holds it only weakly. I'm going to alter the angle and sharpen the better one as you suggest before attempting to alter the gap.
[/edit]

Quote:
Rather than mess with uploading pictures someplace I can link to,

BTW, the forum accepts picture uploads, and once uploaded you can use the "Place inline" button to show them. That's how I posted the ones I took earlier anyway! But I'm not going to discourage you from creating the excellent pdf's. ;-)


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PostPosted: Sat Jan 06, 2018 8:21 am 
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-TT- wrote:
Quote:
Rather than mess with uploading pictures someplace I can link to,

BTW, the forum accepts picture uploads, and once uploaded you can use the "Place inline" button to show them. That's how I posted the ones I took earlier anyway! But I'm not going to discourage you from creating the excellent pdf's. ;-)

Thanks! I've always FTP'd images to my web site (which is almost full) and linked to them. I hadn't realized (obviously) that the file upload worked for images as well as documents. I shall have to experiment...

Back to the topic at hand: I really don't think your "gap" is the issue. It sounds like a little careful tuning of the extractor nose will solve the problem. It's also possible the hole in your bolt is a little extra deep, and you don't have quite as much tension as is ideal. If you find that the Lyman gauge is giving you low readings, you can put a tiny plug in the bottom of the hole. Just make sure you can still compress the pin far enough to get the extractor in & out easily.

One thing I've never quite figured out is how the magazines get into the act. I know there is an interaction, because failures to extract are frequently "round-specific". For example, the most common time for an extraction failure is the first round, because that is when the upward force of the remaining rounds is maximum. That actually points to a slide drag/lubrication problem. The Pardini I'm working on always fails to eject on the 4th round, which is really weird... It's a good idea to mark your magazines, and keep track of which ones are involved when you have problems. It may be random, but maybe not.

When I first started working with the team, there were some pistols that would ONLY work with a specific magazine. We had about 20 spares which included a few notes about this one or that one not working in so-and-so's pistol. I took them all home one summer and rebuilt them. Unfortunately, I didn't think to test them in my Benelli first, so I'm not sure how many were actually "bad". In any event, by the time I was done, all 20 worked flawlessly in my pistol. Other than varying amounts of grime, I didn't find much that I would consider "wrong" with any of them. There were a few instances where the spring took a funny set, and in some cases, a loop would try to pop out of the magazine catch slot:

Attachment:
Spring in Catch Hole sm.jpg
Spring in Catch Hole sm.jpg [ 93.2 KiB | Viewed 248 times ]

The springs don't have a well defined "top" or :"bottom", and often flipping them end for end will fix the way they compress inside the body. There can also be burrs in the slot the button rides in. New Pardini magazines are really awful in this regard, and manually cycling them up & down 20 times will usually smooth them up considerably.

I eventually found that the problem with the Benellis was usually with the pistols, and I've been trying hard to find and fix the subtle issues (like the extractor nose shapes), but some of them still prefer some magazines over others. Given that the "ejector" is part of the magazine, there's always a possibility something is amiss there.

I also had to deal with several different vintages of magazines, included both 5 & 6 round mags, which have dramatically different feed lip designs:

Attachment:
5 & 6 Rnd Mags.jpg
5 & 6 Rnd Mags.jpg [ 80.84 KiB | Viewed 248 times ]

The one on the right is (I believe) the newer design, and the extra metal in the middle helps to guide the rim of the round up at the right time in the cycle.
I have found that some feeding issues are magazine related, but I also found that is usually still the pistol that is at fault. I had one where the firing pin tip broke, and the broken part raised a tiny burr on the slide face where the round slides up. That was enough to cause jams...

You say your slide cycles smoothly. Doing this with an empty pistol is often misleading. If you have some dummy rounds, try it with 4 rounds in the magazine, just to be sure. There are often machining marks on the rib the hammer rubs on, and the rim of the next round also slides there. A little smoothing there can help:

Attachment:
Benelli Bolt Rib.gif
Benelli Bolt Rib.gif [ 180.38 KiB | Viewed 248 times ]

When all else fails, try a drop of thin oil on the top round of every magazine. I've never found this necessary, but the folks at Pardini USA swear by it.


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PostPosted: Sat Jan 06, 2018 12:36 pm 
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Gwhite wrote:
Back to the topic at hand: I really don't think your "gap" is the issue. It sounds like a little careful tuning of the extractor nose will solve the problem.


So here's where I'm at, which is retaining the brass pretty tightly right now. Headed to the range to try things out.

I used your "Bad/So-So/Good" lineup from the pdf as a guide, and moved the "point" as far to the lower edge as possible without removing too awfully much material. It's at least around to 9:15 on the brass, and the sharper edge holds pretty well. A good rap on the bench still holds tight in the bolt. It never did that before.

I didn't have a small enough stone, but realized I had a diamond "Crystal Crafter" in the kitchen knife block. It's a half-round diamond file, maybe 1/4" diameter and perfect for lightly and precisely filing the compound angle, which I make out to be about 30 degrees from vertical and 95-100 degrees from horizontal. Tricky!

Thanks again for the encouragement (and extra mag info too).

Attachment:
ExtractorHoned.jpg
ExtractorHoned.jpg [ 89.42 KiB | Viewed 242 times ]


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PostPosted: Sat Jan 06, 2018 1:54 pm 
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Looks good! I think that will make a huge difference in how it behaves. Let me know what you find out.


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PostPosted: Sat Jan 06, 2018 3:32 pm 
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120 for 120. Yay.

I discovered it can even hold an unfired round in place after thumping the whole gun on the bench. Very happy with it now.

BTW I did the honing with the extractor out of the bolt. I found I could get the most accurate angle on it by placing the extractor on its "back", with the angled edge down and the point sticking more or less straight up. That let me use the table as a guide for the honing strokes, with some good control using needle nose pliers to hold the part. The half-round tool really came in handy since it allows rocking it backwards to get the flat side lined up. A flat file or stone would mean doing this freehand, off the table.

Next time, I may sketch out the angles on a sheet of paper and use that as a template. It's tricky to have to peer over both sides to see if the angles are right before doing the deed. Doesn't look like that'll be needed for quite a while.


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PostPosted: Sat Jan 06, 2018 3:38 pm 
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Hooray! As a friend of mine used to say "Once again, Science triumphs over Technology!"

If you have a small stone that has sharp square corners, you can fine tune things with the extractor still in the bolt. I make a small protective piece of thin plastic with a slot that fits under the extractor hook, so you can slide the stone back & forth against the plastic, which covers the bolt face. It's easy to see the angle you need when the extractor is installed.


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PostPosted: Sat Jan 06, 2018 4:41 pm 
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One suggestion for an update to your extractor info pdf: add a brief discussion of the "radius" at the underside of the nose. It seems so superfluous, but as you observed it's pretty important to the rising round. If the tiny rounded edge is rough, or small, the round catches on it. This in turn leads to jammed feeds since the round basically gets squished when it can't find its way onto the seat against the bolt. It squirts out the side, or forward, at the absolute worst moment.

I corrected the curve slightly on mine, and also polished it with some 1000- or 2000-grit paper, with good results.

The other observation is to be sure there is no flaking of the nickel plating at the sides of the extractor, which can interfere with it moving aside as the round starts to engage from below. In my case as I mentioned, I simply honed the failing plating off by sliding it flat across a stone.


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PostPosted: Sat Jan 06, 2018 5:33 pm 
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Duly noted. Thanks! I've never had a case where the extractor interfered with feeding, but it's easy to see how it could happen if that radius is too small or rough.

I documented the Benelli bolt I'm working on that appears to have a weak extractor spring. I'm ready to open it up, and I just received some new parts form Larry's Guns. It includes his re-designed extractor spring & push rods. I'm going to label them carefully, and compare them with a spare factory spring & pin I have from long ago when I bought my first Benelli. I'm hoping I can measure or see a difference so I can make sure we use the new ones in the future.


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PostPosted: Sat Jan 06, 2018 9:07 pm 
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Gwhite wrote:
I just received some new parts form Larry's Guns. It includes his re-designed extractor spring & push rods. I'm going to label them carefully, and compare them with a spare factory spring & pin I have from long ago when I bought my first Benelli. I'm hoping I can measure or see a difference so I can make sure we use the new ones in the future.


Big differences, I mentioned these earlier and they work very well.

The plunger has a radiused front edge that has much less friction on the extractor. The spring, while a little shorter once it takes a set as shown here, has thicker coils and is noticeably firmer.

Snapshot:
Attachment:
ExtractorPlungers.JPG
ExtractorPlungers.JPG [ 73.33 KiB | Viewed 205 times ]


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PostPosted: Sat Jan 06, 2018 10:21 pm 
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I just finished checking my extractor pin & spring collection. All of my factory pins are plated, where Larry's are black. I measured the springs and the wire in the factory ones is ~ 0.041 mm thick with 18 turns, where LGI's springs use 0.043 mm wire, with 15 turns. Both are about 14.5 mm long. I didn't see much difference in the radius on the ends of the two flavors of pins, but I can check them under a microscope later.

In any event, I took apart the misbehaving bolt. It had a factory spring in it, but (I think) more important was a flake of plating about 1/2 a millimeter square that could easily account for the sudden drop in functioning. I cleaned and lubed everything and reinstalled the extractor with an LGI spring. You can definitely feel that it takes a bit more force to get a round up into the extractor. I just hope that doesn't cause other issues.

Using the Lyman digital trigger gauge with a monofilament loop, the extractor force went from about 1 lb 12 ounces to 2 pounds 3 ounces. That's right up with the tension I measured on my two good Benelli bolts.

I also came up with a new dodge to make sure I'm pulling the extractor to the same point. I put a fired case under the extractor, and I read the force just when the case falls out.

With luck, the student who shoots this Benelli will be back this coming week and she can give it a thorough testing. In the meantime, I have a Pardini extractor to work on...


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