I have made 40mm buckshot, but not have specifically tested his. He's on Grog's forum if you want to ask directly.

Mine were loaded to the same specs as M781, so around ~250fps, give or take. It penetrated 1/4" OSB, but not something I'd want to rely on for self defense. Certainly could work...but it's a far cry from 12ga loads.

250fps is the velocity of M781, so I was kind of guessing (same charge, same load weight). I'll have to crack out tge chrono one of these days. Been planning on ordering a sample kit from azao one of these days...

I have some on my desk... haven't had the opportunity to test them yet.

Was going to test them at my dad's place after a successful hunt. Alas, by brother got drunk, caused a ruckus and hurt his face several times in an unfortunate incident.

Yeah. I should be able to swing it before new years.

According to TM 43-0001-28, M576 buckshot is 855 ft/sec.

Doesn't say, but I would assume 12" because this ammo was developed long before 9" became a thing, although it could be 14" (M79).

I took a round apart for inspection, very cool round
It fires ~1.6oz of buckshot+wad using a standard 38s&w lift charge
Considering a 6oz chalk round is going at ~250fps with same lift charge, some napkin math says that the buckshot will go ~3.75x faster or roughly ~930fps out of the muzzle
Of course this doesnt count for loss in peak pressure due to geometry differences, different drag profiles,  etc etc

But it should give you a number to work with.

I know these are fairly low pressure but I would have expected a bigger payload. What's a 3.5" 12ga buck load weigh?

38 #3 buck, well technically they are steel ball bearings not buck. Id rather see lead buck in there at the velocities these are going, I dont think shot deformation is a concern at these speeds and as far as I know nobody is taking water foul with these.
My shell arrived last week for age reference.




20 pellets of steel #3 in a 20ga 2 3/4 shell

I think your math may be incorrect. Heavier loads use less powder, lighter loads usually use a higher charge. Ergo, all things being the same, a lighter payload will be slower. I could be wrong though.

Side note, I've kind of put my personal buckshot load on the wayside (though I do need to order a sample pack from Azao one of these days). Pace has a wait list for a 40mm to 10ga adapter, so I'm going to go that route instead.

Im assuming a similar lift charge between a chalk and the buckshot as the buckshot included what appears to be a fairly typical 38S&W lifter.

Yeah, I was missing a few steps in my line of thinking, and was running low on caffeine at the time of that post.

Ordered some AZAO buckshot rounds before the new year. When they arrive, I'll try to chrono them.

I ordered some with some chalk to try out.

Did that buckshot round come with the rings scratched/printed in, or was that from chambering/shipping/other?

Those are the print layers

Looks like the printer was out of alignment/calibration...purely cosmetic, but almost looked like scrape marks vs normal layer lines.

With the 576, your barrel length is irrelevant. GROG

Fired 3 rounds today. One errored out the chrono, one was 269fps, and one was 470fps. Recoil was very light on all 3.

Yes… my crossbow fires bolts at 250fps. You want at least 800+ for buck. With the 576, there are a lot of things going on with that round when fired. First, it uses the M199 cartridge, which is nothing like the M212 or even the M118. It is actually closer to the M169 (MK-19 HV case) than the low velocity M118. More powder, in line vent holes… lots more power on firing.

The carrier in the 576 has air scoops to slow it after firing. Under the carrier is an orbituator (sp?) plastic ring that engages the rifling, spinning on the base of the carrier to actually prevent the carrier from spinning itself.


When fired, the hard plastic cup that holds the 21 #4 lead pellets moves slightly rearward due to the lead shot weight. This slight rearward movement pops the plastic top cap off the shot cup. Everything starts moving down the barrel. Most, if not all, of the power imparted on that carrier is when the case is fired. It does not build pressure in the barrel, as most, if not all, of the powder in the high pressure chamber is burnt before the carrier even starts moving. (That’s why barrel length doesn’t matter with this round. It imparts neither additional room for the powder to burn, or additional accuracy from additional rifling).


Once the carrier leaves the barrel, the air scoops start slowing it. In the base of the shot cup is a small rubber disc. The inertia from the lift charge, and weight of the shot, starts moving the shot forward, out of the cup.


Scot Pace and I worked a number of months on recreating a Reloadable M199 case, and tried several renditions of carriers and cups to replicate the performance of that round.


After months and perhaps even a year or so of experiments, case modifications, and do on, we developed the Cannon round that is on his website. Ended up making basically a large shotgun shell with plastic pedal wads that open and dispersed buck or even flechette darts at very good velocities. (See my ammo reviews page on my website for more details).


It was easier, and provided a better platform to abandon trying to redo the 576, and use a better casing and materials to get better results. Hope this helps, GROG

Chrono-ing shots helps is always a crap shoot. Never know if you're getting shot, wad, or what. That said, it does seem to be lower velocity.

I've had a DD M203 for years that I've never even fired.  I need to look into where to buy rounds I guess.  I have new Garmin chrono too.

Wonder how that new Garmin chrono does with shot.

If it's anything like the LabRadar....it doesn't.

I should mention....Chrony Beta through an M79. Chrony was tested with a few rounds of .22 mag to ensure readings were somewhat consistent.

So... Basically just too much pressure for a 3D printed hull?

Because that Cannon Round isn't what I'm looking for in terms of cost effectiveness.