So I got my first dozen successfully printed in white PLA.  Has anyone else tried them?  They seem to be plenty strong,  maybe stronger than the originals. It took me 4 versions to get them to fit just right on the zinc.  They fit on them without any hassle,  but don't fall off when you turn then upside down.  So should be very easy to glue/silicone them on.

Admittedly I don't have a 40mm launcher yet so I can't test them myself.  Though I will test my 37mm versions soon.  So I'll need some help if there are any volunteers to test them out.  It'd be great if someone was local to central Ohio.  Though I am willing to mail some to someone (grog?) or email them the stl file and my print settings.  If it's someone local,  I can bring complete ammo and have a fun day of testing.

With my settings now,  I can print at least a dozen a day if I'm not making anything else (but I am). So it's not a super high production rate but a couple weeks of hitting "print" before bed will yield a good supply for a person or two. With blanks being available and reloadable, cases and zinc (mostly) reuseable,  this seems the be the choke point on these components (except when chikkengumby posts them on gunbroker).

If anyone wants my file to print them for themselves and not for resale, I'd be willing to share.

I'm also gonna work on some cooler stuff.  Maybe some smoke or flare projos, longer m781 nosecones for extra chalk? Who knows.  I'm printing my 37mm versions with a 37mm m781 base that thickened up and print as well.  I scaled them to press fit into those cheap plastic 2" shells. So I'm gonna try those out in my registered 37mm launcher and maybe make versions for other common shells

Thoughts?  Volunteers?

I have plenty of new zincs, and 781 blanks, so I can thump a few downrange for you if you want. GROG

I have an M203 ,and would love to try your file out.I just need the STL and will print myself.
I’ll pm you

Man I live north of you near Findlay and have a 79 would loved to have had you come up and try them out but just left for Florida for at least a month just yesterday! If when I get back works get in touch with me...Damn!

Sounds like a good time.  And that'll give me time to print a bunch more and order some more of the blank charges. PM me in a few weeks and we will set something up.  I have a few other 40mm rounds I've been collecting as well.

In the mean time,  I'll try to get some in the mail to Grog for him to test as well.

PM replied with link to file

Can do, thanks. GROG

To the OP,

Thanks for the idea.  I have a registered RV-85 26.5mm DD.  I've just been shooting solid projectiles, but will ask my son in law to 3D print a "pusher" with a reduced front ledge diameter and a nose cone to attach to the pusher's front ledge that I can fill with color chalk dust and do some test firing.

How thick have you made the walls of the nose cone?  Thin enough to break on impact, yet thick enough to withstand the firing stresses.

Box of nosecones on their way to Grog!

The top 8mm or so of the cones are very thick,  so much so that they have empty space and an "infill" pattern in them.  Not sure how necessary it is, but I think it helps them print in the orientation that I print them (nose down). The side walls come out about 1.2-1.3mm thick. And the part that interfaces with the pusher is about 0.8+-.1mm thick.  I'm not sure how they will perform on impact.  I think they'll survive the launch and may actually be too strong for soggy/muddy ground.  I know I've been to some military ranges where I've picked up quite a few unbroken projectiles and even skipped them off of puddles pretty easily.  But I've also dropped one in my garage and had it shatter.  So it's just gonna have to take some testing.  If Grog has a majority that don't burst,  I can thin out the walls a bit or add grooves to make weak spots.  Heck I could even make thicker ones to make your own smoke shells if they are that tough.

I sent Grog mostly PLA cones,  but there are also half a dozen or so PETG cones that won't Warp in the heat and will survive storage better.  PETG is an interesting material.  Almost non-newtonian as it will bend and stretch when a force is applied slowly,  yet it shatters without any sign of stretching with higher speed impacts.  PETG also retains more strength with higher temps where PLA will Warp in a hot car.  So if I do produce any for sale,  it will likely be PETG to prevent people from having trouble,  especially in the southwest

The only problem I see doing the pushers is the weight. If you have something you can print with a similar weight to zinc, they would work, but if they are light plastic, the projectile will tumble. BTDT with resin poured pushers. GROG

There are two routes I'm debating exploring for making pushers.  First is to print them with a bronze powder infused PLA.  It is heavy in weight,  actually feels like metal,  but is brittle like PLA is. Also the filament is more expensive and can be difficult to get setup.  So I'd have to do some cost calculations to see if it'd be worth it.

Second option is simply the "lost PLA" method.  Which isn't so simple,  but is proven to work well for casting aluminum and other objects.  It's also the method that ARDEC used to make pushers when they 3d printed a whole 40mm launcher and m781 ammo for it.

When I was trying to print a complete projectile I had the problem with the projectile breaking up in the barrel.

What I want to try next is printing a hollow projectile and filling it with wax to get more weight.

How about printing a pusher with a cavity on top where you could glue in a 12 slug or some similar?

I thought about that last night.  Print up some pushers that have basically a cup that you epoxy in a bunch of 1.5" washers or similar.  It's have to be wide to keep from just blowing gas around it.  But nylon filament would probably make a good driving band/cup material.

It's all stuff I can play with down the road.  Especially once I get these nosecones figured out then I can move on to pushers.

In the end though,  3d printing may not be the best method for making pushers.  I have come to that realize a lot of people who get into 3d printing tend to see it as the solution to every problem.  I've been trying to come up with a term for it.  Maybe "3d printer tunnel vision?"

Maybe it comes from many people that never made anything any other way.  But I'm not gonna design and print plastic bracket that is inferior to one I can cut out of scrap metal with my bandsaw in the garage in 10 minutes.

It may be possible though.  And I've even thought about trying to print 40mm cases out of nylon or abs just for fun.  Instead of the burst disks in the 38 blank,  maybe I could leave out the vent hole,  and just design the whole top of the chamber to burst out for a one time use.  But the best answer is to buy some of Scot pace's cases that will last forever

SUCCESS!  Grog generously tested a variety of my printed nosecones with factory milspec components he provided. The only issues he had were with some older versions that had design flaws.  Trajectory was similar to factory m781 nosecones and they all broke on impact.

The latest successful version was printed in both PLA and PETG plastic in a variety of colors (anything I had on hand).  The PLA is actually starch based so it's technically biodegradable, but not easily.  PLA also warps from the heat of a hot car in the summer,  so that makes it less desirable for me to make.  .

PETG doesn't cost much more per roll,  and doesn't deform when left in a hot car.  So it will probably be all that I print them in from now on unless I find a reason to use PLA (I have some rainbow filament left over... Lol).  As I said before,  if anyone wants the file for their own personal use,  hit me up for a link to download it. Other wise I may print some to sell as I don't have my launcher done yet.  So if you think it'd be something you'd buy,  leave a comment or send a message. Colors will vary as I print them with whatever leftovers I have (currently OD green and purple, tan on the way). Though I could do a custom color if someone wanted a large quantity.

Otherwise I'll just make myself a stash whenever the printer is free.  And I'm still working on other exciting fun projects and open to ideas.  I think it'd be cool to apply this concept to ammo for other DD's like the RPGs that are being made and maybe mortars (if I ever get that project done!)

Testing went very well, thanks! The design was easy to put together, fit perfectly onto the zincs, and had no pumpkins. Loaded and fired the same as the factory 781s.

All the components I used to test these were from AMTEC, including the casings, blanks, and zincs. The only part not was the chalk, and that was a mix of mil spec orange dye powder and chalk from Lowes. The powder was tamped slightly into the nosecones to fill them.

For loading, I recommend placing a thin ring of RTV around the inside lip of the casing first, and seating your zinc. Allow that to set for a day or two. Then add your blank. If you are storing the round for any length of time, I recommend applying a very thin bit of RTV around the blank itself. Next, fill your nosecone with chalk, then tamp it, then fill it again to 1/4" below the rim. Apply a bead of super glue gel around the zinc, 95% of the way, seat your nosecone then twist it 1/4 turn. This will allow the air to escape the cone, then seal it 100% when you twist. Allow that to set nose down for a day or so for the glue to dry. After that, you are ready to fire.
GROG

IM sent

Joat

For those that are wanting the 37mm files. I will get them to you in the near future. I haven't printed enough of them or enough versions to test them out. And I don't want to post them until they are ready.

in the mean time, ive been printing nine 40mm cones a night though I have squeezed 20 onto the build plate and will try that out tonight. I will be posting some in the EE for those who don't have a printer. I also have a couple other cool ideas for these that I'm working on and one of them may need tested before I post it.

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Now how about some flare/parachute ones!

I definitely would like to.  Before I sent the test samples to Grog,  I quickly printed a 100mm tall version of the cones in petg and threw it in the box.  Grog did test it with chalk powder and it came apart as it came out of the barrel.  I debated printing some more with thicker sidewalls,  but we both agreed that it's kinda pointless for chalk.  So I'm going to work on designing smoke and flare components more before I print anything.

I can pretty easily print canisters for the top of m781 zinc pushers,  though you'd have to drill a hole and epoxy in a fuse,  and then get it to light on firing.  But what I'd really like to do is make my own bases that are printed as a cup sized for a few 1.5" or so fender washers to add weight,  and then epoxy/resin/hot glue can be poured in. That will take a little more time but is sustainable for the future if I can get them to work.  Parachute flares could be salvaged from the rocket style ones that they sell at gun shows.  But would cost a couple bucks a piece.  Maybe there is a commercial firework that could be used to the same effect.

I have a feeling that either me or my new llc will have an FEL before too long

Awesome. Would be cool to have a longer cup and fitted ogive

Email sent about print file. Thanks!

Some of those are pretty tough.  The other option would be to make it rocket propelled so that it has less of an impulse on launch.  But I'd be willing to try it.  I'm printing some projos right now that kinda mimic the sponge rounds and their extra large low pressure chamber.  Hopefully that can be a good base for many other projos