Reflex LDC combining 3d print and generic aluminum filter tube from banggood

[MrP]

I have a modified Air Force gun that shoots at around 110 to 120 FPE with a noble valve an .25 18 inch barrel. It's a talon P frame so the shroud is short. Silencing this so far has required a very long extension off the end of the muzzle.the size of the can I had to use to quiet this down was just kind of annoying - protruding way off the end of that barrel, heavy with metal internals... so I decided to make my own solution.

The 18 inch barrel protrudes a good 5 inches or so out the front. And the DonnyFL adapter on the end adds to that. I decided to try to make my own reflex shroud LDC type deal Making the best of what I had on hand.

I 3-D printed and epoxy coated a short baffle core with a small expansion chamber and airstripper plus BIG vents in the back - air is forced back hard. This screws (plastic threads) onto the DonnyFL adapter. I added a small sketch of what I did. In reality the baffles are very thick heavy duty and reinforced unlike in the drawing where I just represent them symbolically with some thin lines.


I then surround this with an aluminum tube (banggood fuel filter host) that was considerably longer than the baffle stack - but attaches so it extends back towards the TalonP shroud. Air is pushed back into this space So a small baffle in the front behaves like a much larger volume ldc.. I then 3-D printed an insert to fit into the open space behind the muzzle to keep tube centered on the barrel and to cap the back end (block air) and provide a second anchor point ... I don't trust plastic threads (past issues with flying ldc's!). I don't know if the diagram makes it clear but that LDC isn't going anywhere because that plastic brace in the back is actually pretty robust. Doesn't look like it in the drawing I didn't quite draw it right. Forgot to photograph before assembly 



Anyway this works really well. at highest power It's not as quiet as a 9 inch metal LDC coming off the end but it's very close.

I know 3-D printed plastic is not really an ideal material to be battered by 100 FPE blast of air but I have 100% infill on those prints and unlike in the drawing everything is thick and critical areas are covered with epoxy. Fingers crossed this will hold up. I haven't really checked but accuracy seems excellent possibly improved.

 

[Long_Gun_Dallas]

That's an excellent design. When possible it's always great to implement these methods. Divert as much pressure as you can immediately. Tight exit on the brake and big reliefs. Lots of tight cone baffles. I bet it works great

 

[MrP]

Here is more or less what the internals of the baffles is like. Imagine this but slightly fatter this particular print was for a narrower tube but it's the same design.

What would you change??

 

[Long_Gun_Dallas]

Hmmm.. honestly I think I would cut the number of baffles down to maybe 4 instead of 6. You can put them pretty close and have them be very effective, but I think too close, and it may start to have declining effectiveness. You want a little room for expansion. And less baffles would mean a bit more volume as well.... I count the end cap as a baffle as well. You can put a small cone there as well

Also putting a pinhole at the rear of the tube body can help vent some pressure. But may also be undesirable (can eject lead dust rearward)

I designed a tiny one last week, (75mm long, 26mm wide, 0.9 oz) and put a vent right on the primary baffle (thru side of tube) to allow a little pressure to be alleviated from the forward baffles

 

[MikeVV]

Hmmm.. honestly I think I would cut the number of down to maybe 4 instead of 6. You can put them pretty close and have them be very effective, but I think too close, and it may start to have a declining effectiveness. You want a little room for expansion. And less baffles would mean a bit more volume as well.... I count the end cap as a baffle as well. You can put a small cone there as well

Also putting a pinhole at the rear of the tube body can help vent some pressure. But may also be undesirable (can eject lead dust rearward)

I designed a tiny one last week, (75mm long, 26mm wide, 0.9 oz) and put a vent right on the primary baffle (thru side of tube) to allow a little pressure to be alleviated from the forward baffles

As noted in bold above...

I turned the tube around on a silencer that I recently bought, so that the vent holes were in the back, closer to the barrel. I also enlarged them to .13" dia. Originally they were very small.

The sound, while didn't seem like it got any quieter, doing this did seem to soften the "crack" of the sound to more of a thud.

Doing this also helps keep the air pressure that is built up within the silencer from traveling back up the barrel toward the breach before it can follow the pellet out of the silencer. That pressure, just like any pressure, will take the least resistant path, and that would be back toward the breach.

Mike

 

[MrP]

There are little vents in mine as well... front end right now but I had them in the back on previous tests. I didn't notice any large difference in sound when I had the vents at the back But it seems a little louder and it turns out there is a way for air to escape inherent in the way that I designed the rear part that goes in the reflexed portion so that's probably why I didn't notice a difference there's always a little air escape anyway.



clearly pressure relief is critical at 100+ fpe because I've had some of these launch off the end before I added the rear anchor point.


May reprint the baffle core with fewer baffles and more space per chamber and see how that works out. Maybe with fewer baffles it will not take quite so long to print because that one was a long print with 100% infill.

 

[Long_Gun_Dallas]

Yep, I'm usually shooting in the 15-30fpe ballpark. I print the baffles separately at %100 infill, they are thin, though (1.5mm). Caps I still do at %35... for now. I do like the idea of coating the baffles in epoxy. 



Far simpler than yours, as I was making it to go on the end of a gun that already has a full reflexed shroud on it. But that's the last one I printed. Only 3 baffles including the end cap. 6.3mm baffle bores on a .22 caliber gun. The tighter you can get clearances, the better it will work. I always try and shove a little felt in the tip of all my mods as well. Using hardware cloth to retain it. That almost always seem to really cut down on the sharpness of the report.

 

[MrP]

OK here's a model with more volume and fewer baffles what do you think? Tolerances can be very close because this is actually screwing onto the barrel and centering is very good with the 3d print inserts. Have been able to do 1/2 mm clearance but for now the bore is closer to .30 than .25

 

[Long_Gun_Dallas]

Yeah, I've found if you make clearance too tight, you will actually get pressure waves bouncing back onto the projectile.... Not so great for accuracy... Will not cause clipping, but not desired effects on target. Best I can get to work is a .7mm clearance (3.5mm on either side of projectile) if alignment is PERFECT

I might remove one more baffle (maybe?) and make the cone on the bore exit smaller. Free up a little more volume in there. if you look closely at the teal-ish end cap above it's not a full sized cone. And the exit bore is long. I believe that will add some resistance to air escaping as well? The longer passage I mean. I think the flared exit is a design that might actually magnify the report. Or is this just an insert, and there would be a flat end cap? I might try that out as is in that case.

 

[MrP]

Yeah that flared exit was something I was thinking about. This is inside of a metal tube so there is actually an end cap there. I've also been printing flat washer discs and putting a little felt in there like a sandwich. So there's a metal end cap being screwed against that flared exit but between the endcap and the exit there's a layer of felt between 3-D printed plastic washerS with a small hole in it. These are pressed up against the end of the core with as much force as I want depending on how hard I screw the end cap on. I found that sometimes when I 3-D print the endcap on to the baffle it gets popped off unless there's a really thick wall there which I opted not to do.

I plan to try with different thicknesses of felt and different apertures in the washer that's pressed on there when the cap screws on. 

 

[Long_Gun_Dallas]

That looks good as is. Looks very sturdy, too! I've been curious what filament I could get my hands on that would have high tensile strength. I'd expect at your power level to need a very sturdy end cap. Maybe you could print and pit it to the tube? But would require more holes... that may not end up ultimately being used.

 

[MrP]

I'm just using PLA! Obviously I have had many failed baffles and have settled on something thick enough to work in pla. Epoxy just in case. 


I have to move to some other filaments like ABS. There's this one flexible filament that is used a lot in making parts for drones and things like that. TPA maybe? It would be interesting to produce a core Or some baffles that were flexible / rubbery maybe act like a spring dampener. I wonder how that might affect its function. 


this silencer is short in front and long in back so as you might predict, while it is quite effective at lower power levels like 30-50 fpe, moving up to 110 fpe, it gets noisier of course. I would not say it is "backyard friendly" at moderate to high power but it is "garage friendly". I'm sure someone walking by outside might hear a loud sound but it really sounds kind of like a sledgehammer hitting a spike or something. The tank makes a bit of a "pang!" and the muzzle sound is not a crack or bang it's like a bright "CHIFF" sound. I feel like this is a function of the plastic material and something to do with its resonant frequency or something like that. At the highest power level it does have a bit of a bang albeit a MUUUUUUCH quieter one than the deafening one it makes without the ldc. 


it is definitely "garage friendly" but I'm not sure it's "paranoid nosy neighbor garage friendly" at 110 fpe. We shall see...

Finally I hope this thing stands up for a little while since it is made out of PLA it's not the strongest materials to be working with.



looking at that model I posted earlier (Modified a bit and printing now) I fear the walls are a little thin. I will have to wrap this in one or two carefully cut layers of painter's tape to have it be completely snug in the aluminum outer tube anyway, so it will be reinforced on the outside. Still I wish I'd made it a tad thicker. 

 

[Long_Gun_Dallas]

That does sound interesting. I think ABS may end up being the most effective for overall cost and ease of use. Plus strength.

 

[MrP]

Well you were 100% correct the lower baffle count plus higher volume is much quieter. I reprinted last night, glad I decided to try it out. I added also a solid end cap with a small hole. The tolerances are a little close - I haven't tested with a projectile yet - hoping for no clipping.


It's funny because the tolerances in this design of my own are much better than when I used the threading on the tube itself and screwed it on the end of the barrel - guess it was not particularly well machined. 

 

[Long_Gun_Dallas]

Hey, that's awesome I think part of the issue with having baffles close is that the air doesnt have room to spread out.... it's coming thru the previous baffle in a column. Without room to disperse, it will mostly stay in that column, and pass on thru the next baffle. Reduced volume meaning less expansion, still. I think it's a lose-lose. I think about the closest you'd want to stack them might be 1" or so?

Do you think the end cap will stay put?

The poor machining isnt so much of a surprise. I had one of those and was going to get a $200 tax stamp for it.... But everything was out of alignment. I was going to use it on a .45 ACP, but was afraid to use it lol. Plus it weighed a ton.

I got my tiny mod all levelled out, aligned, and tested Zero moved up 1 click on my scope. Probably the smallest adjustment I've seen going from one mod to the next. I set this up with the idea of saving weight and length. As well as freeing up my huma moderator for use on a different gun. I tried to make it to match the gun, but have not been able to find this tube size with a matching pattern.... not a big deal I guess. Only saved 1.9oz, lol. But on the nose of the gun. .9oz vs 2.8oz. Saved maybe 1/2" Just as quiet with maybe half the actual volume. 

 

[JohnnyPDX]

Awesome discussion and very cool work. Congratulations Mr.P on a well thought out design and execution!

 

[MrP]

I was doodling. Here is a schematic in case it helps any of you. I will share some pics of the part models. 
effective! All plastic guts and it couldn't fit a different gun so hopefully it's all good with the powers that be. 

 

[MartinT]

This is great! I came up with the same idea for my Leshiy2 as there is a lot of wasted space in the handguard behind the (aftermarket) silencer.

I have not had the time to work it all out yet, but you have, and confims that it works as intended!
How many holes do you have towards the back? My idea is to drill holes into the flat back of the silencer (incidentally a Huma too) and use a 3d printed adapter as connector between the silencer and a pvc tube running aft to the action.

 

[MrP]

Just a couple of holes towards the back.


Here is a new one I made. Same internals, rescaled for a narrower aluminum tube. Could only find blue spray paint in the garage... will be black eventually.