Benelli .22 Magazine Maintenance

[Gwhite]

Between the college team I help coach and my own two MP90S's, I have roughly 50 Benelli magazines to take care of. After solving some of the mysterious jam problems being caused by overly long firing pins, the team still has some pistols that are less reliable than others. I think a lot of that is due to feeding issues where the rounds don't chamber smoothly. The rounds load OK, but varying amounts of lube and lead gets scraped off, and if that gets into the chamber, you can get malfunctions where the round doesn't chamber fully (misfire), or it causes extraction problems. Five of our fussiest pistols came with no bevel on the chamber edges, which makes the lead-shaving problem much worse. I'm slowly stoning more & more of a radius on the chambers, but I've also found that some pistols work much better with certain magazines. Up until now, we've just swap in spare magazines and hope we find a good combination.

The shape of the bullets in different ammo is also an issue. The fussy pistols work much better with RWS Target Rifle ammo than either Aguila or CCI. I used to think it was something about the recoil characteristics, but I'm pretty sure it is actually the bullet shape. RWS Target Rifle is no longer being imported, and it was MUCH more expensive than the other two brands we shoot. However, Norma Tac-22 is made by RWS, uses the same bullet shape, and costs only slightly more than CCI. We've done some testing, and it also appears to work just fine in the fussier pistols.

I decided it was time to take a closer look at the magazines. I know from experience that they can get pretty badly gunked up, especially with ammo that has a lot of bullet lube. CCI is the worst, especially if you get a batch that has tons of extra wax on the bullets. I wanted to quantify how high the bullets sit in the magazines, and see what effect fouling had on that. My theory was that if I can identify magazines that feed a little higher or lower, I could match them up with pistols so they would feed cleanly.

Step 1 was figuring out how to measure the bullet heights. I wanted to reference the height to the top of the magazine catch slot, and then use my digital microscope to measure the bullet height. Ideally, I wanted to measure the height of the tip at the centerline of the bullet, but I couldn't figure out an easy way to do that, so I just used the top of the bullet nose. I used dummy rounds for the testing, and I used the same rounds, loaded in the same order, for all of the tests. I 3D printed a fixture, and machined a steel lever that would fit into the magazine catch slot.

The end of the scale is at the same height as the top of the magazine slot, and I located the fixture at the 40 mm mark in the microscope for consistency:

I went through all of the various magazines. The fixture only works for 6-round magazines, but that covers the majority of the ones we have. I figure the lessons learned would also apply to the 5-round versions. I may redesign the fixture to work with both if I think it's important. I measured a bunch of dirty magazines, and then re-measured them after cleaning. Ideally, you would want the bullet height to be consistent from the 1st round fired to the last. There is always some variation, but cleaning reduced that in all of the magazines I tested. Some of the magazines were really grubby, and showed the biggest improvement.

After cleaning, the average height was 39.8 mm, and the average peak-to-peak variation was 0.8 mm. What I discovered is that most of the pistols with sharp chamber edges had managed to get paired with magazines that had a LOT of variation in bullet height (as much as 1.6 mm). My hope is that the average height isn’t too critical, and that pairing low variation magazines with the sharp chamber edge pistols (which I’m still working on) will minimize the problems.

The key takeaway for most Benelli owners is that the feeding can deteriorate over time as fouling accumulates. You can clean some of the crud off the inside front of the body by depressing the follower, but a proper cleaning requires disassembling the magazines. I’ve made a video on how to do that, with some tips on how to make it all go smoothly.

https://www.youtube.com/watch?v=Cjul3QA ... gWQ63KB80h

[ghostrip]

nice presentation. i wonder if you have data on .32 magazines

[Gwhite]

Collegiate pistol is all .22, and I've never seen the need for another caliber in my own shooting to want to mess with the .32. I suspect the .32 will behave a bit more consistently because the rim is much smaller compared to the cartridge diameter, and the dimensions are better controlled. The wadcutter bullet should also keep things a lot cleaner in general.

[-TT-]

Nice videos, very comprehensive! And the thingiverse jig is going to come in handy.

One comment on the spring orientation. I agree that the free end at the top is oriented to the front from the factory, but I've discovered the magazine actually feeds a little better when it's placed to the rear. I suspect this is because the spring ends up applying a tiny bit more force on the stacked rims, and they "pop up" more positively, for the bolt to catch them as it goes forward. I doubt it makes any difference at first, but as the mag gets a little dirty/sticky, it seems to help, at least a little. I haven't seen any downside anyway.

Thanks for this!

[Gwhite]

Interesting idea. Thanks!

I collected data on a lot of the various springs I encountered. There a huge range of lengths, number of turns and wire size. Most of them are 9 1/2 turns:

That means the ends are parallel. I also found quite a few where they had an even number of turns, so the ends are not parallel. I have several relatively new magazines that have never been cleaned, and the springs were all oriented with the top end loop forward.

Most of them averaged about 107 mm in length, but I found some as short as 85 mm. What's weird is that I found long springs in a few 5-round magazines, and short springs in some 6-round magazines. I cleaned all of the Team magazines about 4 or five years ago, always one-at-a-time so I wouldn't mix up any of the parts. Many of the magazines showed no sign that they had ever been disassembled in the past, so I'm guessing the various springs came that way from the factory.

Other than when they've gotten pretty dirty, I've never had any issues with the 8 or so magazines I have for my two personal pistols. Based on all of the springs I've seen, I don't think the details are all that critical IF you don't have other issues (like the sharp chamber edges).

The same goes for recoil springs. I've got a spreadsheet with dozens of springs I've measured, and they are all over the map. If it was super critical, half the pistols would never have functioned well as they were shipped from the factory. Over time, the factory has been making them stiffer & stiffer, but we have very old pistols with softer (worn) springs that all work just fine.

[-TT-]

...Other than when they've gotten pretty dirty, I've never had any issues with the 8 or so magazines I have for my two personal pistols. Based on all of the springs I've seen, I don't think the details are all that critical IF you don't have other issues (like the sharp chamber edges).

Yup, totally agreed. But I found the nose of the rounds tipped up just a little higher, and they definitely entered the chamber more reliably, with that flip. OTOH, as you say things can vary a lot, without any obvious down- or up-side. So, it's a possibly tiny tweak.

All my springs have that half-turn, so the final leg hits "angled" when the follower reaches the top and the spring unwinds. In my view, that angle is best applied to the rear (rim) end, where the follower actually touches the round. The front (bullet) end of the follower doesn't touch anything at all.

[Gwhite]

The one thing that more upward force near the back will do is wear out your followers faster. The follower wants to hold the back of the rounds offset to the right, but the top of the magazines wants to hold them centered. When the last round is being fed, those two argue, and the left side of the offset groove in the follower will lose. I've replaced quite a few followers. Here's a comparison of a new one and a very worn one:

When they get that worn, the back end of the last round is lower, so the bullet ends up higher. I took data on a magazine before and after I replaced the follower with a new one:

5-16-24 Mag 't' Old Follower.jpg (30.28 KiB) Viewed 514 times

5-16-24 Mag 't' New Follower.jpg (29.72 KiB) Viewed 514 times

As you can see, the worn follower affects the height of the last 2 rounds quite a bit. The second to last is actually affected more than the last one.

[-TT-]

Good data. I'll check the follower condition on the two mags that responded to the flip.

[Gwhite]

Spare followers are hard to come by, so you want to be nice to them. I've considered trying to 3D print them, but I'd have to change the design in places and probably cut the offset groove on my mill as a post-processing step.

[rmca]

Good info.

Here are my two cents:

From my experience, it's the dirt in the magazines that make them fail.
My explanation is that they can't keep up with the bolt velocity.
Once clean, most problems tend to go away.

Feed angle is only a problem if the round is presented way up/down, but also left/right. Usually magazine lips are too far apart, from people letting the follower escape and bash against them..

A .22LR round is heavier in the front (lead bullet), hence the magazine spring pushing the follower in the front vs rear. Swapping may work in some cases, but I think it makes things worse in the long run (parts wear faster).

Hope this helps

[Gwhite]

One thing I discovered the hard way is that you should NOT attempt to adjust the shape of the metal magazine lips. I have been thinking about trying that, but was concerned that the metal might be brittle from work hardening during the forming process.

I accidentally knocked one of mine off my work bench. Of course, it landed on the ejector tab. I figured it might be bent a bit, but when I retrieved the magazine the tab and a good chunk of the top side was broken off:

If you decide you absolutely MUST bend them, you'll want to try to anneal them a bit first.

[-TT-]

If you decide you absolutely MUST bend them, you'll want to try to anneal them a bit first.

They're definitely hardened, you can tell by the DING! they make when you remove the parts.

The most I'd do, personally, is squeeze the sides of the body gently to square them up, using a good vise or parallel pliers.

[-TT-]

Question (which is by no means criticism!)

My printer-equipped friend printed the Thingiverse bench block and I discover it is oriented such that the follower button is beneath the magazine, so it can't be reached when the mag is in it. It's flipped relative to the red height gauge version in your photo. Was that intentional?

It's a super-handy tool, and super-interesting printing layers too btw. Thanks!

[Gwhite]

It never occurred to me that anyone would need to access the follower button when the magazine is in the fixture. I don't think you can get the follower button down far enough to remove it while the magazine is in the fixture, and if you could, it would likely damage the follower when it shot up to the top after you pulled out the the button.

It was probably 50/50 as to which way I designed it. If it is really an issue most 3D printing software can mirror-image designs, but I still can't see why this is needed...

[-TT-]

I was thinking to use it for your tip-up nose height measurement, and being able to exercise the follower in-place to restack rounds seemed logical. Definitely not wanting to make a follower zip-gun! :)

It's all good, thanks.

[Gwhite]

The bullet height fixture is a lot more complicated. You need to machine a metal bar that fits into the magazine catch slot, or you won't have a consistent reference point for the height measurements. That fixture does have the button accessible for the reason you stated. I would tip the magazine with the bullets up after removing each round and relax the tension on the follower. That way all the remaining rounds were seated at the back of the magazine. I think I started out by mirroring the disassembly bench block design.

The shiny silver object in the bullet height test fixture is a rare earth magnet. It holds the magazine body down against the locking arm, and also helps secure the fixture on the steel base of my microscope so it doesn't slip around too easily.

One thing that may be important is that once you start firing, it's not clear that the remaining rounds in the magazine stay all the way back. For example, depending on how well the buffer works, if the slides stops very abruptly at the rear, it could jolt the pistol hard enough that the rounds in the magazine will shift forward from inertia. That will tend to make them tip up more. I've never had a Benelli misbehave in a way that I could trace to the buffer, but it's possible.

I have definitely encountered Pardini SP's that will jam more if the buffer is not in good shape. It mostly occurs after the 4th round fires. The 5th round isn't held as tightly by the follower, and I think it actually shifts forward after the 3rd round fires. If the 5th round is forward, the tip may come up enough after the 4th shot to knock the 4th case case off the extractor.

[-TT-]

I was wondering what that silver piece was! Clever.

I'm with you on the buffer condition not making a huge difference, but only the solid Larry's ones. The OEM rubber bumper type is another story entirely.

[Gwhite]

I like the OEM ones because they are WAY easier to install, but they are very expensive (if you can get them). I've never noticed any difference in how the pistols shot between the two buffer types.

I just sold my old car, and the keys came with the rubber fob material that is supposed to work well for home made ones. I kept the fobs & may experiment with them at some point. I also have some sheet polyurethane that I think would work well. It should be pretty indestructible, but that means it's also nearly impossible to cut...

[-TT-]

In my experience, the OEM buffer material deteriorates over time. This leads to cracking, and that means the recoil tube penetrates it and bottoms out on the retaining block. The longer distance then causes the recoil tube retainer to contact the end of the slot, and it bangs them both up. Net result is damaged hardware. A used pistol I bought had this happen to it - never my MP90S!

When I bought mine, I asked Larry what parts I might need, he immediately said use his buffer. And at least a firing pin. I ended up getting a few other bits and pieces! :) I think I've replaced the buffer maybe once since then, and only because it looked bad.

Tom.

[Gwhite]

In my experience, both buffer designs tend to deteriorate in a way where chunks break off before the tube ever gets that far back. I've been using the LGI buffers for a long time without any particular issues. I've only recently obtained some new factory ones, and I'm curious to see how they hold up. Benelli has had about 30 years to optimize the material, so I'm hoping they last longer than the ones that came with my new MP90S back around 2000.