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11B30B4's RO T-21 Version 2 Build


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I built a RO T-21 last year and documented it on FISD here:



This is how it turned out



However, I used plywood as the base material, and it is a bit heavy after trooping with it for any period of time. I also used Spool86's cast kit (heavily modified) for a lot of the parts. So, I wanted a more arcuate and lighter weight T-21.

To this end, I have modeled a lot of the parts and 3D printed them. I will make these parts available for free download from my Thingiverse page here:  https://www.thingiverse.com/11b30b4/designs


So, a few notes before we begin. The overall demission’s are very close to Pandatrooper’s diagram. I will be reusing the already made stock from my original RO T-21 and some of the other parts. I hope to re-use the barrel, but I will need to determine if it will mate with the new printed parts.


Yoshix created a thread in this forum to discuss the RO T-21 differences but I had not seen it unitl now since most of my previous stuff was on FISD. A good catch was the space on the barrel before the rubber tubing. I did not build my previous T-21 with this gap in mind but I will endeavor to include it for this build.


Although there are five different variants of the Lewis gun and there are a ton of different manufacturers of each variant I will be primarily using the MK1 variant. There are not a lot of pictures of the RO T-21 and the ones that I have found are lacking in detail. I have collected a large number of detail pictures of actual Lewis guns from across the internet to develop the 3D models. Although I could make a completely accurate model, there are a few areas I will need to divert from to make this something more buildable. One specific thing I have omitted is the underside of the cooling vent area mid-section of the gun. Seen here (yellow outline) is what was omitted for anyone wanting to go overboard in their build.



There are a few other very minor details that I did not include in the 3D models but for the most part, they should be correct. I have embedded many of the roll marks seen on various pictures I have found. Most notably will be roll marks on the feed tray.


For the base material of this build I will be using ½” (12.7mm) thick Sentra. I purchased a 4’x’8 sheet of Veranda HP brand PVC board from Home Depot for $69.00. Obviously, you will not need a whole sheet of this stuff but its hard to find in smaller quantities. Sentra is PVC board and Veranda is just a different brand.


Keep in mind that I am working within the limitations of Tinkercad as I am not a CAD engineer. That being said, here are the models I have built so far.


This is the main feed tray cover, mid-section cooling vents and vent housing.





This is the center feed tray, ejector, feed operating arm, rear sight mount, forward feed tray, and assembly pegs.






Receiver left side






Receiver right side






Rear receiver and stock mounting plate






I have already started printing these parts and here are some of the raw prints before finishing.












I have a Prusa I3 Mk3 and I use MatterHackers MH Build series 1.75mm ABS filament. Some tips on printing:

Any of the parts with horizontal holes or overhangs should be supported. I printed everything in ABS and to prevent any elephant foot (warping near the build plate) I printed everything with a brim. As for detail I used 0.07mm ultradetail with a fill of 15% for anything that had any detail. I printed the receiver rear and stock mounting plate at 0.10 detail with all the same settings for fill, brim, and support.


That is it for now, thanks for the interest.

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Update 12/2/19

I have added a few additional 3D models to my Thingiverse for this build.

First, I redesigned the rear sight mount. I added the rear sight with roll marks and adjustment knob and combined them with the receiver rear and stock mount plate.





I modified my T-21 transition to fit a Shop Vac Extension Wand (read further to understand why) and included the front radiator and flash hider, a backing for the radiator, the front end cap ring, and two barrel ends for the sides of the receiver.





Lastly, I finished the models off with the two end caps for the oil brush that are mounted in the stock, the front sight, the trigger, and the gas key adjustment lever.





Once I finished the models, I printed them, and they came out great. I should note that each file is printed in 0.07 Ultradetail which takes about 30 hours.






After printing, everything got sanded and cleaned.



After cleaning, everything got primer and then paint.



Next, using Pandatrooper’s pattern and making some minor alterations, I cut the rifle out of Sentra. Once I had the shape, I started to dry fit parts and figure out where things would sit. Initially I was using a larger PVC pipe for the sides of the receiver and in these pictures, the lines you see where for the larger pipe. Here I was working out the trigger and test fitting the trigger guard. I reused the trigger from my previous T-21 but I have made a 3D model for anyone wanting to print one.





Around this time, I realized the pipe I was using was a bit larger than I wanted so I found some ¾” SDR 21 PVC pipe which is irrigation thin wall PVC. I used this pipe along with a section of ½” Schedule 40 PVC pipe to make the side barrels on the receiver.



I cut each pipe lengthwise in half then sanded them. Next, I drilled the ejection port and finished it with the dremmel. Next, I painted the ¾” pipes black and the ½” pipe silver. I glued the ½” pipe inside the ¾” pipe and then test fit them on the gun. Notice the remainder of the glue line under the new pipe, from the larger pipe I removed. This size pipe better aligns with the barrel part of the radiator.



Next, I needed to replace the top aerial gun sight that is seen on the Rogue One version of the T-21. On my previous build I used an iron pipe I-bolt. Since reducing weight was one of my primary goals, I needed to find a new solution. I eventually decided to make the sight out of aluminum. I took some aluminum stock and worked it on my metal lathe. Next, I threaded the parts then cleaned the parts for painting.









I also needed to remake the aluminum legs that protrude from the stock mounting plate and into the stock. Once everything was cleaned, I painted all the parts with a black bake on metal paint I use for gunsmithing. While the parts were baking, I took a hard look at my previous T-21 to determine what were the heavy parts. As I stated previously, the base of the T-21 was plywood and the switch to Sentra seamed to reduce the weight buy more than half. All the resin parts on the previous T-21 were heavy as well and switching them with 3D parts further reduced the weight. Switching from the Iron sight to an aluminum one reduced the weight; however, I soon realized that one of the heaviest parts on the previous T-21 was at the extreme front end of the gun, the 2.5” electrical conduit I used for the tapered bore of the barrel shroud was very heavy. I originally used this part because the outside diameter was 2.75”. I looked for a good replacement, but I had very little luck. I could special order a pipe with the outside diameter of 2.75” but most of the options were either too expensive, the wrong material like acrylic, had too thick a wall, or weighed too much. I was forced to consider a pipe with an outside diameter of 2.5” and again I was hard pressed to find a light weight option. Eventually, I found a shop vac extension wand a Lowes that had an outside diameter of 2.5” at one end and tapered to 2.25” at the other end of its 20” length. I only needed about 7” in length and if I measured the seven inches from the larger end the outside diameter of the smaller end would be just shy of 2.5”. The wand was fairly thin walled (about 1/8”) and very light. So about $8.00 this should work.




I reworked the T-21 transition 3D model and included it on my Thingiverse page. So with all the parts gathered I continued to assemble the T-21.




Next, I looked over the reference pictures and discovered that there are only two rings visible on the large part of the barrel shroud. One about 2” from the rear of the shroud and one with the front sight attached to it. There is also only one on the smaller part of the shroud at the extreme front of the barrel. So since I was reusing the barrel from my previous build I needed to remove some of the rings, fill some holes, re-score the exposed parts of the shroud and re-apply the rubber tubing. I used ¼” windshield washer tube for this. I added 4 mounting screw holes near the rear of the shroud that will be covered by the rear most ring and will make the barrel removable for easy transport. I still need to apply the feed tray parts and grips and finish painting then do a black/ brown wash over the whole thing to weather it but it is coming along nicely and the weight is amazingly very very light. I wish I had though to weigh the previous gun for a comparison, but I would say this thing will end up being 1/4 -1/3 the weight of the previous version.




That is it for the update so far. Thanks for the interest.

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Update 12/5/2019

I assembled the radiator, flash hider, back plate, and end cap ring on the tapered part of the barrel shroud. Next, I installed the tapered barrel shroud to the transition then I dry-brushed silver on all the parts and attached the Feed operating arm, ejector, and the barrel ends on the sides of the receiver. I used E6000 to adhere the grip scales then masked off the radiator and bolt and applied a weathering wash comprised of black acrylic and light brown. Once this dried, I applied a flat clear coat over the whole rifle.








Tonight, I will complete assembly and this T-21 will be complete. I will weight the completed rifle and report back.


Thanks for the interest.

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You are doing some amazing work here mate!:duim: I really like your attention to detail. 

That T-21 looks great. 

Some points to think about though:

Your silver dry-brushing looks a little unnatural, maybe just slightl too much. Have you tried Rub'n Buff? That stuff is really cool but you will also have to seal it with some clear coat. 

I couldn't really see this specific detail in your reference pic but I would suggest using some putty to smoothen the transition of the tapered barrel shroud. That what I did when I did my first T-21 scratchbuild. 

Keep up the great work and keep those pictures coming, looking forward to seeing your progress! 

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Hausi, thank you for the comments and suggestions. German Garrison, man I really miss Germany. I lived in Illesheim for three years (1988-1991). I loved living in Germany, got to do cool stuff, make a lot of amazing friends, Watched the Wall fall, Watched Germany win the 1990 World Cup. Some of the best years of my life.

I digress, I think the dry brush will look more natural in these pics. I did the black wash over the dry brush and it mutes the silver. I am inclined to agree with you about using bondo between the transition and the two parts of the shroud. The line between the transition should not be as defined; how that change will need to wait a bit before I can address it. For anyone interested the total estimated weight of the T-21 is 4.5 pounds.



















Thanks for the interest,

Now I need to get back to the armor build.

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Hey Jeff, good to hear that you enjoyed your time in Germany and still have some fond memories. :)

I've been to the states several times and it was always a blast. I'm still addicted to those Reese's peanut butter cups. :sweat:

The black wash has done the job to tone down the silver dry-brushing, looks much more natural now. 

So the stock is wood, man, that's a piece of art and really sells it,great work. How did you paint it? 

You even sourced the right sling, which looks very different to the Enfield sling on the ANH T-21. 

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Hausi, thanks again for the comments. REESE'S Peanut Butter Cups are actually my favorite candy; however, I do not snack very often. As for treats in Germany, The cookies from Nuremberg are delicious but The treat I miss most from Germany is Dampfnudels with chocolate from Cafe Dampfnudelbaeck in Nuremberg.


Back on topic, the stock is white pine, as are the grips. I made the stock for the previous version of the ROT-21 and re-purposed it here. The stock consists of two halves roughly ¾” thick and 8” x 18” once I have the outside rough shape, I hollowed out the interior with a router then glued the two halves together. The stain is Minwax Ebony with a satin clear coat on top.


As for the strap, from the best images I could find I determined the width of the sling webbing to be 1.25” and the webbing to be black nylon webbing (most likely Mil Spec: MIL-W-4088 Type 10, Class 1A). At one time I made tactical gear and I am familiar with webbings and types.

Some things to note from my research: In this screen grab you can see where and how the forward end of the sling is attached (Yellow Circle) and it looks to be an AK-47 sling mount screwed to the top of the barrel shroud just behind the front sight. Note the round (looks to be an areal gunner sight) sight just forward of the feed tray and is in the dead space of the barrel shroud between the two barrel shroud rings (Red Circle). Also note the rubber wrapped tubbing on the barrel shroud goes past and covers the middle barrel shroud ring (between the Red Circle and Yellow Circle). Lastly, note the rear sling mount appears to be on the side of the stock (Light Green Circle) and is most likely in the spot as the bras ID disk seen on some Lewis Guns. An assumption can be made that they are using an Uncle Mikes style sling mount and quick detach since this has been used on several weapons from Rogue One.





I hope this build helps others out in making RO T-21s and feel free to ask question and/or point out anything I missed.

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Yeah mate, Dampfnudeln are delicious.:)

However I also don't snack very often first of all because Reese's aren't as easily available here in Germany and secondly because I still want to look good in armor. :sweat:

I first thought that they just tried to match the look of that ANH thing visible in the middle of the gun which most people thought was some sort of sight (it was obviously some sort of twisted phone cable). 

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  • 2 months later...

So Sentra was not the best idea I have ever had. The T-21 snapped where the stock meets the receiver when I snagged it going through a door. Since plywood was too  heavy and the Sentra was too weak, I have rebuilt the rifle again using all the previous parts but this time I used a 3/4" white pine board that I planed down to 1/2" thick and seems to be holding up great and the weight is fine.

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Before long you're likely going to set some sort of record for number of times reconstructing the same blaster! Your two threads have been VERY insightful as I've been gathering materials and plans for my own T-21 build, currently part of my HWT thread on FISD. Right now my plan is to do a pine stock and receiver with waste pipe and your 3D deck and other greeblies. I'm still deciding on the narrow barrel tip.

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