I already picked up a piece of pipe to make a 50mm mortar to 40mm adapter after seeing that video awhile ago. Haven't had time to mess with it though.

 

Launcher pope makes 40mm barrel blanks.

 

@joshs1ofakindxj
The rifling is important to projectile stability in flight ,saying that i ordered a 20 Ga. rifled barrel blank so i can do M183 PD`s loaded in 20 Ga. 3" shells . I load them for my H&R 1871 Ultra Slug hunter 20 Ga. 3" 24" barrel as a wild life scare AKA "The Poor Mans Nade Launcher " , i may have to down load them for mortar use from my current 13.7 gr. of Hi Skor 800X . With that load i have 0 failures out of 500 + launches but they reach a bit far well over the original 1000 yd range of the M31 . The A1 Load is supposed to be max 500 yd range out of the M31 14.5mm artillery trainer they were designed for . https://www.liberatedmanuals.com/TM-9-6920-361-13-and-P.pdf
Cool looking for the A1 load specs i found a new source for the PD`s don`t know if they are legit but 14.5mm M183A1 U.S. Lead Projectiles Point Detonating – 5 projectiles/pack
I have Plenty of them bought decades ago ....
And here is the A1 loading data http://pdf.textfiles.com/manuals/MILITARY/united_states_army_tm_43-0001-27 - 29_april_1994.pdf
It is for the 14" 14.5 mm rifled barrel direct engagement of rifling out of the original Alum 14.5 mm hulls it lists 3.5 gr. of HI SKOR 700X , the original loading was 10 gr. of 700X .
They are going to range differently in a poly wad out of a 20 Ga. 20" barrel with extension muzzle collar to exceed 28" and using 800X .......It may not even be a DD as long as length exceeds the 28" min for a shotgun ........
Oh this is going to be Fun !

 

@joshs1ofakindxj
The rifling is important to projectile stability in flight

No doubt, but for my shenanigans and just to "see how it works" my first sub cal adapter will just be smooth bore pipe. Not sure how far I will take this yet.

 

@-TX-
Can`t find him as a member but did find his site https://launcherpope.com/
His listed OD is 1.75 " or 44.45mm so it would work with an over sleeve for 50mm and 60mm tubes and his price is not bad $315 for 10" long and Chrome Moly steel no less !

 

Yeah he reached out to me when he was developing those blanks. Really cool process. All made using a homemade EDM setup. He made aluminum ones too but I advised him thay steel would be better to avoid the need for a hard coat anodizing. A few people have sleeved the Turkish 37mm m320 clones and he has done some other 37mm to 40mm conversions as well.

 

@joshs1ofakindxj
With your Brixa 45 being cartridge fired you i think can`t use M212 zinc`s/windscreen projectiles but printed no issue with smooth bore ! Now using a properly prepared (dill the blank pocket out way out )M212 hull & projectile and a launcher pope barrel the launch cartridge would fire it clear down range and a hell of a distance ! I see there is a little barrel sticking out closed so a securing of the 40mm barrel will be necessary not so much with a smooth bore but rifled yes most definitely . At 44.43mm a rifled barrel is a nice close fit it seems .......
Back in 23` you were looking for M183`s and M181`s did you catch the link 14.5mm
Like i said not sure if legit but it Seems so .......

 

I did buy some from Mutiny Machine. They're a legit seller.

I haven't done anything with them but I did intend to put them in 3D printed projectiles for the Brixia. Unfortunately everything I printed for the brixia failed to survive the blast pressure of firing. I had a friend molding me projectiles but he has been busy lately. Hopefully I'll get back to that this winter.

This reminds me that all of my 3D prints were in PLA+ and I never tried PETG, which might perform better. I might have to print a couple in PETG to see what happens.

 

@joshs1ofakindxj
I would . Rare little beast you have i think you already know the original rounds the tail was cast Alum . I was looking for the original launch cartridge info on it ,Na Da ! I can see why PLA+ is disintegrating in the barrel , 7.62 X 39 mm blanks have one heck of a high launch impulse . I am not an printer but PETG or Nylon Might work . Machining out of Alum is cost prohibitive but "Lost Wax " casting using PLA to make the casting investment mold you cast would work for Zamak alloy (melt 735* F 90-95% Alum) . Or to make reusable casting molds for the cavity/plug in pure Aluminum (melt 1227*F ) . I favor casting grade Plaster investment molding over sand casting for the fine finish and you can have a several mold cavity/plugs cast at once so you have several molds cast in Alum by a Pro . Your other choice is a multi piece steel/brass mold !
Zamak you can melt in a Lee melting 20 LB pot which goes as high as 900* F , so once you have mold/s you can do them your self ! Printing is "easy" but for the cost i would look at having mold/s made , they would be reusable and cast fins section would definitely take the launch impulse and be reusable ! The noses print them !
A $19 4 lb bar from RotoMetals would make i figure about 8 fin sets min ..... break a few and they can be recast into new ones ... Food for thought FWIW !
I did "Lost Wax" when i was much younger .

 

My friend who makes me projectiles 3D prints a mold then casts them in some fantastic plastic. It's flexible but strong. Plus glow in the dark properties are nice.

I agree the 7.62x39 blanks are pretty potent. Not much out there on the original 8mm Brixia blank other than some case dimensions. I managed to find two original blank cartridges but I don't have the heart to open them up or fire them because they cost $20 a piece.

 

@joshs1ofakindxj
Yea they makes some fantastic plastic`s that are not printable , i rather like the glow in the dark ! Maybe your friend will share the .STL file with you and the casting plastic source so you can print/cast your own .........

I would not open one either cause there is no way to tell what powder was used and getting a weight would not help either . Info i found says the rounds weigh about 16oz without explosive filler . What kind of range are you getting ? I know some blank makers will do custom loads with a Minimum purchase . Have you thought about making your own , how different are the 39`s from the live ones ? I figure you have already looked for near match brass , if only you could get away from star crimped blanks ! No amount of annealing will make them reloadable !! I noticed some M212 blanks are now using cast bullet gas checks and a simple mouth roll "crimp" to seal them and that is anneal able for reloading but the gas check goes flying into the projectile .... What a conundrum !

 

Took the mortar with me to my side gig so I could try it out on a longer range. I took 4 printed rounds and 6 m69s with bonetti motors loaded with 30gr of bullseye.

The m69s were fun. I wish I brought some powder and primers to reload them to shoot more. I had some stringing in distance, with 1/6 coming up noticeably shorter than the others when we shot 6rd groups. I suspect that the motor may need a cotton ball or something to keep the powder more condensed. We shot those about 150yds and windage was about 3ft in variation with some windy conditions.

The printed rounds were first shot with 30gr shotshell motors. The two from last time worked really well and got shot a couple times each. I loaded a new one and the fins came off right out of the tube. These fins were not epoxied or glued and can be pressed right back on(with glue this time). The round tumbled as expected and fell short. Easy fix.

While hammering out a spent blank from one of the older rounds, the fins became dislodged and slid up the stem slightly(maybe 3-4mm) and partially covered the vent holes. I launched it anyway with a 40gr shell and the fins blew into 2 pieces. As seen below

A new set of fins will be pressed on and more epoxy used next time. I'll also use more epoxy this time. Easy fix.

The other older round was then loaded with a 50gr charge as a stress test. It freaking flew! It felt like it was going to the moon. In reality it went 200-250m before darting into the ground. The blue fins sure made it easy to find. Only the fuze section broke as expected. Just screw a new one on.
I then loaded that same round with a 40gr charge. While pounding the shotshell out, the fins moved about 1mm up the stem, but most of the epoxy was still in place, and none of the holes were obstructed. I decided to shoot it anyway and it worked perfectly, landing similarly to the 50gr charge(we lowered the elevation).

Overall, another success. Still need to work on more nose fuze designs. The chalk tips just buried themselves and broke off. The walls of the cone are still too thick and the tip is too pointy. I may even make a fuze base that just holds a 40mm chalk cone since I already print tons of those.

I also will be making a press block/jig to press the shotshell blanks out. All of the trouble came from be holding onto the find and hitting a screwdriver with my mallet. So that should solve the reloading problem

 

@ SPC Fish ,
Fantastic slow mo ! It sounds like you need to rough the inside of the fins and exterior of the engine tube for best possible epoxy grip . The press block is for steel lower body rounds and shotgun hulls yes ? What about your full printed ones with the solid screw into the body ? You wrote shotshell ,how did Matt`s engine cases extract ?

 

@ SPC Fish ,
Fantastic slow mo ! It sounds like you need to rough the inside of the fins and exterior of the engine tube for best possible epoxy grip . The press block is for steel lower body rounds and shotgun hulls yes ? What about your full printed ones with the solid screw into the body ? You wrote shotshell ,how did Matt`s engine cases extract ?

The Bonetti launch motors are a real treat to use. They fit perfectly into the tailfins and all 12 of them just unscrewed and came out intact. I had a pair of needlenose pliers just incase but didn't end up needing them. I just wish I had more of them.

 

This particular round has been an absolute champion. Only because it was assembled properly and I haven't lost it haha. The other three just need some light fin repair and will be back firing.

This round has been launched half a dozen times. With 20gr to 50gr charges of bullseye.

@belt fed frog yes the press block will be used so that you can hammer the blank out without putting force on the fins. The fins were taking all the hammering force so thats why they dislodged on the round that failed.

I put the other style of launch charges on the backburner for now. While I still like the idea, I want to get these perfected first before I revisit that. But it shouldn't be a very difficult adaptation. But it can also add to the cost per round, though reloads would likely be cheaper. I also have more 20ga shotshells than I'll probably shoot in the next few years. So that doesn't hurt either.

 

I hear ya on lots of plastic hulls have about a K of 20 Ga. 3" for PD`s . I fondly remember paper hulls as a kid they would be perfect for engines and way easier to get out ! Still have the MEC 600 i used to load them ,ah the days of felt wads and shot cards ........
My $86 20 Ga. SS rifled 24" barrel arrives next Wed for the PD mortar project but i am going to have to sub out the machining since my lathe motor died in the flood from Ian and i am not able body enough to pull it and replace it .... Getting Old sucks !

 

Me, waiting for you to perfect this so I can modify it for 50mm

 

BARREL REPORT
I got this barrel Barrel Blank 24", SS, 20 GA, SAVAGE, HELICAL FLUTE, MUZZLE BREAK, RIFLED
It is well worth the $86 and change delivered ! It is chambered for 3" shells but the chamber is less than spectacular in the finish ,it has light circumferential score lines from lack of cleaning the reamer but nothing a little honing will not fix and maybe a little deep cut but not enough to be un workable since you can shoot 2 3/4" in a 3" chamber ...... It throated correctly . The chamber end taper has a small raised flat rim that blocks access to the rim of the case ,again no big deal hand filing or for those with a lathe just follow the taper to a sharpish edge to reveal the cartridge rim for ease of extraction . An unfired 2 3/4" and 3" shell pushed right in ! The muzzle is not crowned only saw cut square but since the porting has to go again no biggie . At the muzzle the barrel is .125" thick Very nice and thick ! 8 land and grove rifling i am not sure of the twist rate ......It has a nice beefy taper rate and is fluted (which are sand blast finished ) but you have a good deal of material to work with if you choose to shorten the barrel .
Overall i would say it is a good deal for the sub cal project with only a Very little work needed on the barrel when you compare to a Issued barrel at 2-3 X the price and the amount of work to make it in to an easy extraction Sub Cal mortar barrel in SS no less !

Summery of mods to finish barrel ,finish chamfer chamber end ,a little chamber honing (split stick and sand paper with a drill ! ) , cut to length and crown , run a die on/below the new muzzle for top bore slide/retention collar and you are done with the barrel !

Need To Make !
The bottom bore slide/slip in collar tapped to 1 1/8"- 20 tpi and screw on (can be as little as 1 1/2" long , longer will fit over current barrel Dia. ) , Top retention collar tapped to fit thread on/below muzzle and you are Done for a Brixia 50mm mortar !

 

Edited after reviewing ATF regs on legal shotgun overall length of 26" !!!!!!
Well here is where you start

Barrel Blank 24", SS, 20 GA, SAVAGE, HELICAL FLUTE, MUZZLE BREAK, RIFLED

www.sarcoinc.com

I chose this one because the cartridge rim is not counter sunk into the barrel , it is an old savage 220 bolt action barrel .
The bolt face was flat with 3 extractors which is why the taper on the breech face to accommodate them clipping over the cartridge rim . This will make extraction far easier . Being a blank it most likely require chamber reaming , if it is already chambered to 2 3/4" i may just cut the hulls since a PD sticks out anyway in 3" hulls by about 1/2" . 4D reamer rental has 3" 20 Ga. reamer a $49 base rental price .
Now the porting has got to go ! It is deceleration point enough to set one off in the barrel !! So it gets the "chop" !!
When i was first introduced to PD`s they were being fired out of a sub cal M79 same adapter offered by AUTOWEAPONS.COM bottom of the page , it is a cut H&R 1871/CVA single shot rifled barrel with the ejector assembly which are N/A as shotguns any longer .
While watching the firing they started to go off at the muzzle , the owner grabbed it from his son (running the rent a shot ) popped it open looked down the barrel and started to berate his son !! There was a little piece of wad plastic melted near the muzzle , I have said the bloody things armed are Extremely Sensitive and they Are !!! Cleaned with a brush cured the problem . I bought 2 rounds from the guy for $2.50 ea. to deconstruct . Just as the Old Ammunitionstore.com was going out of business i called and got 2400 M183`s for ( Muw HA HA hahaha Not telling but make you sick Cheap ) .

Now here is my approach i have a Spanish L model mortar with a seamed undersized tube and over size pod yoke so i am going to cut the cup down to a small size under 40mm and re tube it with a 26" tube , make a bushing for the yoke to fit the new tube .
The barrel is threaded 1 1/8" X 20 tpi so i got a tap for the bottom bushing to slide in the tube , the cut barrel is going to be less than 24" so i have to make a top bushing that installed will make the "barrel" length 28" and be Welded to the barrel ( got to be over min total shotgun length !! ) . I could do a striker fire or fixed cup firing pin but that may be over the ATF line !! (Laughing Maniacally ) I am going to go back to my child hood , duct tape and a BB !! We used to tape a shot shell to an arrow with the BB taped to the primer ,throw it in the air and Run like Hell !! Never had one fail to go off !!
So i will be making an unconventional Legal shotgun !! The top bushing will extend down the barrel well past the cut end as well as above it (for length ) with chamfers on the bottom of both bushings for ease of drop alignment !
No fixed firing pin /striker assembly , common caliber No ATF violation ..... Simple as i can make it (with a little Help hopefully !!) !!!

@joshs1ofakindxj
You will have to fix the short piece of barrel to the muzzle of your Brixia with a counter bored collar and brass/plastic tipped set screws . You will also have to make a rear collar that fits the bore of the barrel to support it in place with the chamfered end of the 20 Ga. barrel sticking out .
For Loads Drill out some of the base of the 20Ga. hulls . I use these and so did the deconstructed ones Fiocchi 20ga 3 hull new/primed (bag/100) and load the PD`s in
SG20L Sporting 20ga Long wads (250/bag)
You will not need powder with the 39 blanks but you need clear passage for the blank to pressurize the wad for launch ! Man will they Fly a long distance they weigh about 1200 gr. so you will have launches way over the Brixia`s 530m range at the correct angle !!

Thursday i will report on the barrel chamber if there is one ........
Even with my Hot load my H&R 1871 has Never had trouble ejecting fired rounds completely throwing them out with some real force !

P.S. To All Use only High Brass hulls !!!! I use these Fiocchi 20ga 3 hull new/primed (bag/100) and these SG20L Sporting 20ga Long wads (250/bag) Only !! Tested and proven with 13.7 gr. HI SKOR 800X Hot loads chrono at 900+fps !! Range almost `1/2 mile out of a 24" barrel !!!

 

@SPC Fish,
Dang i thought i found you some paper hulls Cheddite 20ga 2-3/4 Paper (100/bag) but they are out of stock RATS !!

 

PLAN REVISION M183 Sub Caliber Build
Well a PM prompted me to dig out the Spanish L model display tube and pod . What i discovered was a bit surprising , it went underwater during Ian and i have not it touched in 19 years . It was never oiled ! It turns out the cup and tube are SS with the tube having a wall thickness of .250" (way under 60mm) and No seam in fact the tube is quite smooth inside but dark . I rechecked the tube yoke fit and while a little lose it is not that bad ! This has me reassessing my plans for the PD sub caliber build instead of cutting the cup and downsizing the tube ,i am going to run with what i have . Oh i may lick the tube with a hone to make it shine ..... This makes the build Much easier i am still going to cut the porting off the barrel and do the extension top slide collar for a barrel length of 29" welded in place and the bottom slide collar tapped for the barrel shank threads . This reduces what i have to sub out on the build !! The barrel chamber is still a question but i can hand ream it if i need to . I am still going to use the BB ignition so any inspection of the tube/cup will reveal it is only a display tube assembly ! And it brought up a new idea 37mm !! As long as i stick to https://www.atf.gov/file/55446/download for 37mm launchers exemptions i am Legal so flare, pyro, smoke ,gas,line throwing and chalk anything not antipersonnel in nature and under 1/4 oz (104 gr. total launch and projectile load) of low energetic explosive (BP) i am good !! I already do 37mm using Pace Defense - Reloadable Launcher Casings Hi/Low cases and plastic projectiles . Fun and reusable !! In testing for him i took one finned projectile which screws together loaded it with 30gr. of BP and blew it apart 9 times and it still screwed back together !
Oh i destroyed one by not fusing it and failing to plug the fuse hole then shot it against a board fence at 30 yds , found the broken tail boom ,never found the rest of it .....

 

Got the 1 1/8" X 20 tpi tap Not a Chinese made one but US made and for Less than a Chinese one , NOS R&N manufactured . This will allow me the screw the lower slide collar on to the barrel shank . Should have barrel Thurs and report on chambered or Not !

 

BARREL REPORT
I got this barrel Barrel Blank 24", SS, 20 GA, SAVAGE, HELICAL FLUTE, MUZZLE BREAK, RIFLED
It is well worth the $86 and change delivered ! It is chambered for 3" shells but the chamber is less than spectacular in the finish ,it has light circumferential score lines from lack of cleaning the reamer but nothing a little honing will not fix and maybe a little deep cut but not enough to be un workable since you can shoot 2 3/4" in a 3" chamber ...... It throated correctly . The chamber end taper has a small raised flat rim that blocks access to the rim of the case ,again no big deal hand filing or for those with a lathe just follow the taper to a sharpish edge to reveal the cartridge rim for ease of extraction . An unfired 2 3/4" and 3" shell pushed right in ! The muzzle is not crowned only saw cut square but since the porting has to go again no biggie . At the muzzle the barrel is .125" thick Very nice and thick ! 8 land and grove rifling i am not sure of the twist rate ......It has a nice beefy taper rate and is fluted (which are sand blast finished ) but you have a good deal of material to work with if you choose to shorten the barrel .
Overall i would say it is a good deal for the sub cal project with only a Very little work needed on the barrel when you compare to a Issued barrel at 2-3 X the price and the amount of work to make it in to an easy extraction Sub Cal mortar barrel in SS no less !

Summery of mods to finish barrel ,finish chamfer chamber end ,a little chamber honing (split stick and sand paper with a drill ! ) , cut to length and crown , run a die on/below the new muzzle for top bore slide/retention collar and you are done with the barrel !



For 60mm DD`s or display tubes the bottom collar would be the same , the top slide collar will need to be longer for drop mass ignition and Safe drop delay time !
As i outlined in my Revised Plan i am going to use an undersized display tube with No firing pin to keep it legal and with the tube being 26" deep and the port less barrel 22 3/4" long i need to extend out of the tube enough to be able to pull for reloading so the Top slide collar will make the entire barrel 29" long (over legal shotgun overall length). The top slide collar will be 10" long and drilled out on the bottom 3" to fit the max barrel taper Dia. and tapped for a 1" length to fit threaded portion of the barrel muzzle , then counter bored from the top 6" way over 20 Ga. size ......I may go for a cone shape to minimize the chance the armed M138 PD will go off on exit ,Sensitive mothers !! They are Not really that dangerous as they do Not fragment at all !! But the Blast exiting the back of the projectile is rather impressive and i would rather not be close to it by at least 10-20 feet with eye/ear protection !!

Military EOD specs for handling undetonated M181/182/183`s are eye/ear protection and 2' tongs pick up nose down !! CAREFULLY place in burn pit/barrel and burn LOL standing at a safe distance !

 

For the bottom collar i found a 1 1/8" X 20 tpi tap here 1 1/8x20 Tap for sale | eBay which takes a 1 1/16" tap drill i also found used on ebay .
I forgot to post the barrel muzzle Dia. which is .866" after the porting is cut off so i found a 7/8 x 20 tpi tap and die set here 7/8"-20 UNEF Tap and Die Set Right Hand, 7/8 x 20 UNEF Thread Tap and Round Die | eBay

It requires a 27/32 tap drill for 50% thread here 1 Pc. 27/32" High Speed Drill Bit - #4UM80 - 6" Overall | eBay

Any one who wants to use the barrel i found from sarcoinc.com is going to need the the 1 1/8" x 20 tpi tap and 1 1/16" drill to fit the stock barrel threading for the bottom bore/slide collar . For the top barrel retainer/slide collar i would go with the same as i have 7/8" tap and die set and 27/32" tap drill .... This does not impact the barrel strength no matter how long or short ....YMMV but this is my suggestion !

 

I made a simple chalk marking adapter for the 60mm rounds and my new prototype 50mm rounds

 

That should make a nice chalk "splash" on the ground even if the body buries it`s self .

 

I also figured out a great way to weld the fin stems without all the misalignment I've been fighting all along. I welded up 2 stems this way tonight and it went extremely smooth. I should be able to crank them out a lot faster now. No more wasted material and crooked fins. Now I just need to perfect my vent hole drilling and it'll be smooth sailing.

 

Video of me welding a fin stem with the new jig. Yeah I know my tig technique stinks, especially at the end. Pretend I didn't do that.

 

Clever using wire wrap centering mandrel ! So you are using metal "flow" fusion , it works ! I see you have HF start and seem to have a foot peddle control but i am guessing it is only a start switch , not a Amp proportional control one or thumb wheel Amp control ...... You get into filler rod work upgrade if your welder will support one that way you can taper Amps down at the end of the weld . Working on small parts you have a heat flow problem so proportional Amp control would not help much ! In all my decades of TIG i had never seen a clear gas cup Very cool ! You do very well with what you have !

 

Thanks!

Yeah the foot pedal is just a on/off switch. The torch also has one but its only useful in weird situations like lying under a car, in which I'd probably be using a mig anyway. The welder is a cheap tooliom that I got off Amazon for well under $200. I figured it'd be good to learn on, and better for parts kits and other gunsmithing than my mig. Not much to adjust/control on this simple welder, a variable foot pedal would be sweet, as well as adjusting the post flow. Maybe I'll dig into the manual.

There is a lot of debate about the clear gas cups. I just think they look neat, but sizes are limited. But I figure they also let in more light when starting a weld, so that's gotta be worth something. I'm getting better every time I weld, and I'm mostly happy to just not stick my tungsten every time