air gun (PCP pistol) baffle design idea (to 3D print)

[wasatch]

The small shelf inside Gunny's cone seems a good idea, but perhaps difficult to clean regularly. Perhaps a specially shaped brass brush?

Air guns aren't all that dirty. On some of the AG forums they're called LDCs (lead dust collectors) to avoid 'silencer'. But looking around silencer talk the powder burners have much more of a mess collecting in their units.

[quietoldfart]

My mistake, apologies for that silly interruption. I'd forgotten which thread this was on replying, thought for some reason it was to be used with .22lr. Of course there's no need to clean any airgun suppressor! In that case should it prove possible to draft it into the printing drawing, by all means insert that shelf in the cone as it can't hurt and looks very well placed to help with further disruption of air flow, without sacrificing a significant volume of air.

[gunny50]

[quote="wasatch"]Thanks for the suggestion. I can do the raised portion in the face in Solidworks but the small flat area in the skirt looks tricky to me. I've been off on a tangent figuring out how to fasten the different cores into the shroud and I think I've come up with the design i'll use. /quote]

The flat part is not all flat, I did this as A contoured disc with a rib unadorned for support. ( circular extrusion) protruding thru the side of the skirt and than a circular cutout on the skirt'a outer contour, Hole thru all part for projectile and DONE.
After making each part in SW make an asm. that asm can be saved as solid model (parasoled) and your done.

PRINT that Solid model and no need to attach each (baffle) part by itself.

Simple. Good Luck, and post picture of core when done.

Gunny

[gunny50]

My mistake, apologies for that silly interruption. I'd forgotten which thread this was on replying, thought for some reason it was to be used with .22lr. Of course there's no need to clean any airgun suppressor! In that case should it prove possible to draft it into the printing drawing, by all means insert that shelf in the cone as it can't hurt and looks very well placed to help with further disruption of air flow, without sacrificing a significant volume of air.

When printed in the right materials even possible for 22 as one can use an solvent to clean baffles.

Gunny

[wasatch]

Over this while I've been experimenting with how to fasten the core into the shroud body so i can try different cores. I'm pretty curious how much apparent sound difference there will be between the three core designs at 5.5 fpe (Otherwise I could draw one of the cores integrated with the body and print it as one piece). Gotta be able to shoot in the garage late without disturbing anyone, yeah!

The threaded design wasn't to secure, probably because of the 0.2mm clearance between the parts. So here's another experiment with a different fastener design and tighter clearances. The threads didn't stay snugly together very well probably in part because the 0.2mm clearance everywhere was to loose.

Instead of threads this assembly uses a twist lock action. There are three 3mm dia cylindrical tabs that rotate into slots over 0.1mm bumps at the entrance. Going over the bumps is -0.1mm clearance. Then at rest, locked into the slot there is 0mm clearance. It snapped into place but if i pushed the two parts together i could rotate the tabs without feeling any bump.

So to lock the red core part into the grey tube in my OP there will be 4 larger 3x6mm tabs that will similarly twist lock into the grey tube. Kind of like what is drawn onto the parts in the 2nd pic.

Here are pics of the drawn assembly and the printed result. Can't use 0 thickness edges like were printed on the end of the outer cylinder
The twist lock action at the other end of the outer cylinder are drawn with a 0.2mm space between the tab and the cylinder and i can flex them with a pencil point, but they're likely to fragile.

[wasatch]

Along with the fastening design I printed the shroud mount ($12) as part of risk reduction before i'll order the shroud body which'll cost around $49 to print and have dyed black. The mount has a hole printed at the tapping diameter (4.2mm) of an M5 grub screw to secure the breech end of the assembly. Inside is a cylinder that slides onto the barrel and solidifies the mount. The barrel OD is 11.97mm and the bore of the mount was drawn at 12.1mm ID but printed 11.98-11.99mm so it was very tight. The holes seem to print smaller than drawn. The hole for the grub screw was also a bit smaller than drawn. I revised the print so the shroud body and mount have 12.2mm ID bores for the barrel to slide through. But I'll probably keep this shroud mount and file the inside of its bore a little to get it to slide on more easily.

Here's a cutaway drawing of the mount and the print installed on my LP50.

[wasatch]

Then here's the K core (red) installed in the shroud body (transparent grey).

[wasatch]

And the three cores. 4 K baffles and a cap. The mesh core which will be wrapped with scotch brite or felt. And my swirl vane core design. They've all got the twist lock tabs drawn into the caps.

[Bendersquint]

When all is said and done I am looking forward to seeing how you make it permanent to the air gun, from the airguns I have played with there isn't much metal to weld a can onto.

[wasatch]

Weld? It is printed in nylon The overbarrel shroud and mount assembly will be secured with grub screws.

[Bendersquint]

Weld? It is printed in nylon The overbarrel shroud and mount assembly will be secured with grub screws.

For ATF to consider it a non-silencer it has to be permanent to the airgun.

If it is not permanent to the airgun to ATF specs (core non-removable as well) then it is an unregistered silencer.

Did you ever notice that none of the factory moderated airguns have removable cores or assemblies?

Its because they could be used on a firearm....yes, even printed Nylon works on firearms and on some surprisingly well. Glock even makes a disposable one made from nylon.

[a_canadian]

Gosh, I suppose these guys are in trouble then, as they've sold thousands of their surprisingly effective tiny suppressors.
http://tko22.com/
I've heard with/without comparisons on several PCP rifles (a lot of Canadians order them as well) and can say they're extremely good at reducing noise. I say surprisingly as they're very small, yet work as well as some 'LDC' devices twice their size.

[Bendersquint]

Gosh, I suppose these guys are in trouble then, as they've sold thousands of their surprisingly effective tiny suppressors.

No, TKO isn't in trouble, its the user that could be in hot water if they don't attach them properly, then again most people are naive to the laws, yet its not a valid defense.

[wasatch]

Crosman Marauder shroud tubes thread on to the mount. At the muzzle end of the tube is a threaded cap that can be removed and the baffles fall out. Nothing permanent about the assembly at all.

If what you are suggesting were true Crosman would've had to change things a long time ago.

Many other shrouded PCP air rifles are assembled in a similar manner without use of locktite (which would only be semi permanent) or welding (haven't seen one instance of such).

[quietoldfart]

While I can not find this on the Crosman USA website today, I did save this image from their site last year. The image displays their airgun monocore 'K' baffle suppressor, which seems to be intended as an after-market accessory, not bonded to an airgun barrel.

Of course as it seems they are no longer promoting the product (or perhaps my site search skills are lacking) it could be that the BATF has contacted Crosman's attorneys and suggested that the product be removed from their line. Only guessing, as I can find nothing else online regarding the product.

[Bendersquint]

Crosman Marauder shroud tubes thread on to the mount. At the muzzle end of the tube is a threaded cap that can be removed and the baffles fall out. Nothing permanent about the assembly at all.

If what you are suggesting were true Crosman would've had to change things a long time ago.

Many other shrouded PCP air rifles are assembled in a similar manner without use of locktite (which would only be semi permanent) or welding (haven't seen one instance of such).

ATF Ruling 2005-4 is pretty clear.

"Noteworthy, the definition of “firearm silencer” and “firearm muffler” requires that the device be one for diminishing the report of a portable firearm. The device
under consideration is permanently attached to and an integral part of a paintball gun, which is not a firearm as defined in the GCA or NFA. The device cannot be
removed from the paintball gun without destroying the barrel and rendering the paintball gun unusable. Under these circumstances, the integral device is not a
firearm muffler or firearm silencer.

However, once the device is cut from the paintball gun, it can be used to diminish the report of a firearm. As stated previously, the design characteristics of the
device are consistent with those of commercial silencers, and testing indicates that the device functions to reduce the report of the firearm. Moreover, removal of the
device from the paintball gun indicates some intention to utilize the device for something other than reducing the report of the paintball gun. Because the device
will no longer be permanently attached to an unregulated item, and because of its silencer design characteristics, removal will result in the making of a silencer under
the NFA and GCA. This is consistent with the definition of “make” in the NFA, as removal of the device results in production of a silencer"

After reading that if you say "they are talking about paintball not PCP's" then you are only trying to fool yourself as it does apply.

Can't get much clearer than that.

[Bendersquint]

While I can not find this on the Crosman USA website today, I did save this image from their site last year. The image displays their airgun monocore 'K' baffle suppressor, which seems to be intended as an after-market accessory, not bonded to an airgun barrel.

Of course as it seems they are no longer promoting the product (or perhaps my site search skills are lacking) it could be that the BATF has contacted Crosman's attorneys and suggested that the product be removed from their line. Only guessing, as I can find nothing else online regarding the product.

ATF shut it down.

I had one on order and before it was even shipped ATF contacted me about surrendering it, explained I was a manufacturer and they went away and I cancelled the order.

[wasatch]

Did you ever notice that none of the factory moderated airguns have removable cores or assemblies?

I was responding to this statement. No i've never once noticed that, not once. Its simply not true.

[Bendersquint]

Did you ever notice that none of the factory moderated airguns have removable cores or assemblies?

I was responding to this statement. No i've never once noticed that, not once. Its simply not true.

I guess all the airguns I have looked at are the anomalies, learn something new every day.

[a_canadian]

Seems like the AirForce Talon SS is another example, with the simple plastic 'film can' type baffles removable via a set screw to remove the aluminum end cap, to be replaced by this optional 'kit':

These have been selling for a couple of years. Here's how they go into the tube which is integral to the AF line of rifles, though obviously they are silencer parts and could be put into any old tube:

An accessory being sold separately from their airguns, not to be glued in nor welded. Is the ATF going to act on this? Seems odd that they haven't if they are so bothered by such things, with the product being on the market for more than 2 years. Here's the product page:
http://www.airforceairguns.com/AirForce ... /kitsl.htm

[wasatch]

Did you ever notice that none of the factory moderated airguns have removable cores or assemblies?

I was responding to this statement. No i've never once noticed that, not once. Its simply not true.

I guess all the airguns I have looked at are the anomalies, learn something new every day.

The PCPs sold in the US have overbarrel shrouds and the large majority (can't say 'all' as i'm not absolutely certain) are easily removed, not just the shroud but the internals as well. Some have nicely machined aluminum baffles inside the overbarrel shroud (Colibri: http://postimg.org/image/o3cypf873/).

Screw in supplemental thread on LDCs are openly mfg'd and sold without there having been a crack down.

And maybe the picture isn't updated but one of the pics of this NP2 includes the core pictured above.
http://www.pyramydair.com/s/m/Benjamin_ ... Stock/3368

In any case, I'd appreciate any functional feedback on my design if you have any. Thanks!

[Bendersquint]

Is the ATF going to act on this? Seems odd that they haven't if they are so bothered by such things, with the product being on the market for more than 2 years.

They have acted on other companies.....2 years in circulation is nothing, ATF has gone 6 or 7 years after the product hit the market and put a nix on them. Sometimes it takes them awhile to discover products.

[whiterussian1974]

The small shelf inside Gunny's cone seems a good idea, but perhaps difficult to clean regularly. Perhaps a specially shaped brass brush?

Don't I get any credit for the concept?

Of course, Gunny's look like a church key can opener pushed the cone skirt inward toward ceterline. So perhaps a significant improvement to my concept. I really like how he uses the rain guard analogy, as opposed to the static shelf I suggested to increase local pressure across boreline.

[whiterussian1974]

And the three cores. 4 K baffles and a cap. The mesh core which will be wrapped with scotch brite or felt. And my swirl vane core design. They've all got the twist lock tabs drawn into the caps.

I'd recommend shifting your twirl vanes to begin on the cone mouth and stop short of the OD. This way the gas can continue spinning once it reaches the sidewall. Otherwise the gas will simply reverse direction up the vanes to reenter boreline. However, several points intersecting at boreline might act to disrupt airflow transiting into next chamber?

[wasatch]

After being temporarily lost in shipping the printed parts arrived today! Everything fit together perfectly. The zero clearance OD of the baffle fit smoothly into the shroud with just a bit of resistance. After I first put it together, I shot the pistol a few times then slid the shroud off the barrel. At the back of the shroud and in the shroud mount was blown some remaining printing material. When the laser sintered nylon parts are printed the unprinted (unsintered) powder remains inside the object and is blown out with compressed air after the print job is complete. Because of the restricted cavity details at the barrel muzzle inside the shroud there was powder trapped and was forced out when the gun was fired. Luckily it didn't cause any damaging fliers. I had the baffle cores printed white so any clipping would be more easily seen. It is really very quiet. My pellet trap is a frayed mat of ~80 layers of kevlar from body armor test panels. It is soft and stops the pellets very well. The pellet hitting the trap at 7m inside my garage is now much louder than the pistol being shot Below are a number of pictures of the parts and results.

The shroud assembly installed:


The various parts. The white mesh core is as long as the full depth between the fixed blast baffle/stripper and the shroud muzzle.


A closeup of the three baffle cores and the shroud mount. Note the tabs on the baffle core caps. The printed wires of the mesh core are square, 1mm on a side and flexible. We'll see how it holds up....

Whiterussian, the swirl vanes do end before the OD so the air can circulate.


The tabs slide into the slots then twist lock. There are 0.1mm negative clearance bumps just inside the channels that the tabs in on the core caps click over and are then locked in place.


The shroud mount on the right and the breech end of the shroud with the barrel bushings visible.


The mesh core wrapped with felt before installation.


POI shift from core to core. Each hole is two shots at 7m. V is vane core, K is K baffle core and F is the mesh core.


5 shots with the vane core at 7m rested on the edge of a board.


The unsintered nylon printing powder that blew out from the muzzle barrel mount area. Its really fine soft powder that clumps a bit. The larger bits are not at all firm.