Goofing off


I was going to write up something of value. . . but nah.

I am seeing if I can 3d print a 40mm projectile I could use. Right now it takes me an hour to print 1 projectile. This first one (v1) looks like the bands will engage the rifling ok, but the base is to narrow to stay in the casing.

Version 2 just finished printing as I typed the last sentence.

That looks like it might work.

I’m fairly sure there is nothing else of interest in that photo.

The major, and I mean major, downside to these 3d printed projectiles is that they are super light. About 20 grams. The chalk training round is somewhere over 100 grams. My reloading scale only goes up to 100 grams and I won’t have access to a precision scale that could tell me the real weight until next week.

At best, these projectiles would be 1/5 the weight of the real deal. Most likely, much much less than that. Thus the sights wont work and who knows where these rounds will go. The weight distribution will also not be centered due to the random infill pattern. But they should go “thump” and go down range, so I have 4 printing right now.

I was thinking about throwing some 20 gauge lead round balls in there to get the weight up, but I realized the way I wanted to do it would still leave it too light. I might design v3 to be two parts that screw together, and the fill it with lead shot. Making it smaller & simpler parts I could give it solid infill to perhaps make the weight distribution more consistent.

I dunno. I want to try shooting some of these really light one first and see what they do.

I was looking at an argument about how to zero the M16/M16A1. One group said you set up a target at 25m and adjust your impact to be 2.4 cm below your point of aim. The other group says that you are suppose to set up your target at 25m and set your impact to be your point of aim.

Much disagreement and people quoting manuals.

Well. . . . I might not be a “printer repairman”, but I can read. The M16/M16A1 has TWO apertures. Not one, but TWO. And guess what? You can zero it two different ways. You can use the unmarked aperture at 25m impacting 2.4 cm low, or you can use the L marked aperture and zero at 25m and shoot point of aim point of impact.

That doesn’t sound any fun. Perhaps we should just shoot at 42m using the unmarked aperture. Wouldn’t that be easier?

The left wants a boogaloo more than you do.

The left hates gun owners, the left hates cops. They dream of the day when they could stay at home and watch CNN to see gun owners and cops killing each other in the streets.

Shawn has written up a fair bit of instructional stuff for this site. I’ve also written a few things where I act like I know what I am talking about. Unfortunately I worry that too much good content we have created has been sorta lost to the public in our archives. Hopefully they would show up in a google search. But who knows for each individual article.

When I get around to it, I want to make a “tutorial” or “training” page on There would be a curated list of the instructional stuff we have written up. That way, say if I wrote a post about how to zero a M16A1 sight, it would be listed in some appropriate category on the tutorial page.

Some other time though, I am just goofing off right now.

Oh, and since I prefer freedom units. 25m is sometimes rounded to 1000 inches. 42m would be about 46 yards, or .21 furlongs.


  1. Somewhere I saw that a 36 yard zero is optimum for getting hits out to 500 yards with a dead hold. They even had a target to simulate that 36 yard zero at 25 by zeroing a little low at 25. Any truth to that?

    • Yes, but no. . . . You gotta consider the details.
      The M16A1 was zeroed for M193 55grain ammo. We used a 42m/250m zero on the unmarked aperture, and about a 375m zero on the long range aperture.
      When we switched to the M16A2, we changed ammo to the 62 grain M855.
      The USMC, to get a 300m zero sighted in at 36 yards. The Army to get a 300m zero sighted in at 25m using the sight setting 8/3+1 (or 6/3+2, the Z mark on the detachable carry handle.
      Given a 300m zero, you are going to be about 40-45 inches low at 500m using a dead center hold. (For the M16A2/A4)
      The 300m zero using the M16A2/M16A4/M4 allows a person to shoot center of mass at a wide variety of distances and hit a torso. But at 500m, you really should be holding over or making a sight adjustment.

  2. “They dream of the day when they could stay at home and watch CNN to see gun owners and cops killing each other in the streets.”

    This is an interesting observation.

  3. I’d think think it’d be fairly easy work to bore out the base and hot glue some cheap .45 or 9mm slugs in there for some mass. Future iterations you could print the slots so you’d get better concentricity.

    Are you putting any kind of payload inside; chalk, flour or whatever?

  4. I was wanting to see if I could just print a ‘solid’ (actually 15% infill) lightweight projectile for direct firing. I thought about putting in a hole to press in a couple of 20 gauge lead rounds balls, but I realized that would not be enough to make it comparable weight to the chalk rounds.
    I went to fire the v1 prototype today, and it turned to confetti in the firing process. The v2 did the same. I think the cup shaped bottom is splitting. I wonder if a flat bottom would survive better. But it might just be that the pressure is too much for what the 3d printed layer lines can handle.
    Doesn’t help that I am using old PLA that is going bad.

    • Do you think something almost like a gas check on a lead bullet would help? The hollow base is probably what is doing it I think as well.

      Here’s where a bench top CNC lathe would be good. I bet turned out of delrin they’d be plenty strong and dense.

      • Funny, I was showing photos of it to someone about 5 minutes before your post and they suggested what would be a gas check. The guy isn’t a gun guy so I explained to him about gas checks.
        I wanted to try 3d printing because it is just so simple and cheap. Ordering plastic like nylon or delrin would cost me something like $3 each before we factors in shipping costs, time, and labor.

        • Oh yeah 3D is definitely easier.

          How’s about coating it in an epoxy like truck bed liner. It might give it enough integrity to hold it together. I mean it’s gonna cost extra and I’ve never priced TP rounds to know what the point of diminishing returns is but it’s a thought.


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