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Tool Making (picture heavy)*


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*Note: These forums don't allow me to post more than 2 images, and the ones I posted seemed not to work,

so I have to link the images as URL's. Apologies! The flickr set is available here:




I've read on several threads here about the importance of keeping the recoil tube clean on the m4,

and I decided it would be a good idea to clean mine. After removing the stock and the circlip, I soon realized that I would not be able to remove the recoil spring retaining nut without a specialized flathead screwdriver (16mm wide by 2mm thick blade!). I posted a thread awhile ago

asking if anyone knew where to get such a specialized tool, but to no avail:




Try as I might, I was unable to locate a screwdriver of the necessary dimensions (though maybe Benelli makes a special tool for the purpose?) So, I decided to make one, and chronicled the process in case it might be of use to others.


1) Draw out the plans for your tool. I used digital calipers to take exact measurements (all in mm)




2) Obtain a length of O-1 oil-hardening tool steel (ebay), 1 inch wide by 5/16 inch thick



3) You will need some basic tools: dremel with grinding/ cutting wheels, metal files, fint-tipped sharpie, etc



4) Carefully mark out your tool as per your design. Measure twice with calipers.



5) Begin making cuts with the dremel. Obviously you should wear eye protection. A respirator is a good idea too.



6) Finish cutting:



7) File down the driver blades and slightly bevel all edges. Keep tabs on exact dimensions with calipers.



8) Drill a hole (you'll see why...) and sand with 200, 400, 800 grit metal sandpaper to finish the operating surfaces of the tool.



9) Make sure the tool fits and operates exactly how it should at this point. We are going to

heat treat it, after which it will become un-machineable.




Notice the wire that has been installed so our tool can be plunged into the depths of a charcoal furnace.


10) Next we harden. You will need: charcoal barbecue igniter plus charcoal, tongs or pliers, a magnet, oil (I used motor oil).



11) Heat the tool to 1450 plus degrees F. This means cherry red to orange.



At the critical temperature threshold where the carbon and iron shifts phases, the steel will become non-magnetic. Confirm this with the magnet and tongs.


12) Once the correct temperature has been reached, plunge the tool into the oil bath:




The tool should now be about 62-64 RC hardness. Confirm this by running a metal file over its surface; the file should not bite.


Hardened tool:




13) Finally, we temper the tool to make it tough and resilient (and not just hard). I tempered in the oven at 450 degrees F for one hour, to get a final Rc hardness of 58-60.




You may also use this opportunity to bake some cornbread, should you see fit.


Here is the finished tool:




It may not be so pretty (the blue indicates that it will be very tough), but it is extremely functional (fits *perfectly* on the recoil spring retaining nut), hard, and strong. Also very small, so I can carry it on my keychain. Total cost was $10 for the O-1 steel stock. (granted, I already had the tools, charcoal, oil, etc.)


EDIT: In the design of the tool, the 6.5mm tab at the bottom (really 6.1mm after filing) is designed to center the recoil spring nut. I *should* have beveled and filed the tip of this tab so it could be used as a rear sight adjustment screwdriver. The 5/16 in stock is just a tiny bit too large to fit in the slot of the adjustment screw without filing. I'd also consider machining a flathead blade on the side of the tool for the picatinny rail screws, so as to have a "Benelli multitool" on a keychain.

Edited by etale
Improvement of original design
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Guest cleefurd



With your permission of course, I would like to make some of these and put them in our store.

What you've done here is above and beyond the call of duty, especially given the void where your initial inquiry was concerned. Even after our collective inability to render (in open forum at least) a solution to your inquiry, you brought us your solution in hi-res detail. Thank you. Bravo!!!


If allowed, I'd dub it the "e-tool" (e for etale). You dug yourself out of your own hole with it, so I believe the name fits.

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Excellent job. I completely missed your original post asking for assistance with the tooling.


Your solution was much more involved than mine. Albeit a better product in the end.


Part of the solution is to take the sprung weight off of the plug. The tension adds to the resistance in unscrewing the plug. This is accomplished by inserting a punch through the bottom hole and compressing the spring upwards towards the receiver. Then inserting another punch through one of the drainage holes in the side of the recoil tube.


On my older 11703 tube, I was able to disassemble the unit with the use of some snap ring pliers.


On my newer 11707 production tube, this plug was seated more firmly. I got a cheap tool for prying off paint can lids that spread out in a Y shape. This Y shaped end was wider than the plug, so I filed it down to fit inside.

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Kip-I am flattered that you are interested in producing some of these, and would be truly honored if you saw fit to do so. Given the outstanding quality of your workmanship (already have the extended Ti tube and picatinny rail!), I am certain that your e-tool will be far superior, and I know I'd buy one.


Stranger-I of course feel quite sheepish now that you tell me your solution: unloading the spring is certainly more elegant! The paint-pry tool sounds effective too... I was surprised that screwdrivers aren't commercially available with blades wider than 10mm or so.


All- Thanks for your accolades and interest. I have really enjoyed visiting this forum for a while now, and have learned from you, so it's a pleasure to give back in some small way.

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