I currently own some suppressors, sbrs, SBS and a MG. Looking to get something different possibly a AOW or DD.

Most of the AOW stuff doesn’t interest me.

So I’m currently looking at getting some sort of DD. Would love to have some sort of RPG but haven’t seen any for sale at a reasonable price. Which leads me to my next question.

What type of DD do you guys have and what do y’all think is the funest / most economical to fire?

remember, each projectile will require a $200 stamp

Well, you just missed DS Arms selling M203 contract overruns

Word in the thread is that they might produce more.  Check with them to see when that might happen

It would be great to get more people into 40mm

That's not true

There was an experimental 40mm round that fired a dart and there were holding lips that would keep the gas in the cartridge so there was no real noise.  It was an experimental round for tunnel rats in Vietnam.  Something like that would require tax stamp for each one because each one was a suppressor.

Topic Moved

Moved to the DD section never to be heard from again.

O well maybe some folks will see it.

The RPG-2 seems to be the best canidate for a F1 but the only place I have found them in stock has them listed for $550.

Also any suggestions on a gunsmiths that can reweld the tube to withstand the blast of the launch charge?

And is anyone aware of new production cannons or imported deactivated cannons and mortars?

I have an lmt rail mount m203 and love it. So much fun. The previous poster talking about $200/projectile tax stamps is incorrect, it's only $200 if the projectile contains more explosive material than allowed by the BATFE. You can fire all kinds of projectiles that have no, or less, explosives with no extra tax stamps at all.

I shoot my cannons with non explosive cannon projectiles and I don't have to buy stamps at all, hell we have a blast with bowling balls, it is amazing how far those suckers will fly!

No joke. Was hoping your post would stir up some interest.

@prebans

Let's see if I can get the man to show up....

Doing a google search some members here years ago reactivated a B40 / RPG-2. Would like to see what they came up with on the projection charge and dummy warheads.

Attached File

What type of cannons do you have?

Are they Front stuffers or DDs?

for a DD... what about a Cobray Streetsweeper?  

for reals, how about a 60mm mortar or some sort?

It would match my Cobray M11.

The StreetSweepers seem kinda boring to me. Think I would rather have some sort of launcher, mortar or cannon. The 203 40mm doesn't really interest me either.

Japanese knee mortars or a 50mm french or german mortar might appeal to you. RIA is auctioning a couple:
French 50mm
German 50mm
Jap Knee Mortar

I have a Striker-12 DD.  

While “impractical” on the overall firearm use/utility spectrum….. in comparison to most destructive devices they are not that bad as at least you can fire them at most ranges and ammunition is easy to come by.

I always wanted one of the Striker/Streetsweeper rotary drum shotguns due to their pop culture popularity when I was a kid (Miami Vice, etc.)  and they still remain pretty iconic in modern culture today.    

They are pretty unique from a mechanical/operating perspective if you like to take stuff apart and learn how it works and of course they make liberals hands shake with fear.  They are also capable of  “semi-auto” fire with ammunition that would not normally cycle a semi-auto shotgun (flares, flechettes, shell crackers, less-lethals) and/or fire ammo from an extremely short barrel configuration that most semi shotguns would not function with.

It took me a year or two of searching to find one of the late model Sentinel Arms manufactured Strikers with the top folding stock and the self-eject feature, which none of the SWD Streetsweepers had and most of the original Sentinel Strikers did not have either.

Cost isn’t too bad on them as they are between $1000 and $2000 depending upon manufacturer, features, and condition and they seem to have held their value or even slightly increase over time.   There are no more Strikers being made as Combined Systems (who owned Penn Arms) discontinued them a couple years back so there may be some additional room for value appreciation over time as there is no new supply available.

If you want a DD for your  “stamp collection” the Striker/SS guns are a somewhat practical option as they not gigantic in size/weight and can also be easily shot with commonly available ammunition.  

If I was to do another DD, I would probably get an M203 just to scratch "grenade launcher" off the ownership list while probably acknowledging up front that  it would probably just become a wall hanger given the ammunition and range availability restrictions.

Good luck in your decision.

I have seen the videos put out by Forgotten weapons on the mortars you have listed. They are very cool but out of my range on what I am willing to spend on a DD that I can not fire.

I did not realize the Striker/ SS brought so much. Out of all of the DD that I am aware of they are probably the most economical to fire.

@Tim_McBride - you can!  This may not be the Rusty Spur, but I'll still drop in if you call.  

@swampfoxoutdoors - I used to be a DD FFL/SOT (Type 09 / Class III) and am still friends with a lot (well, there aren't many of us) of active DD FFL/SOTs.  DDs are my favorite NFA category, probably followed by AOWs.  We'll talk about your weird views on AOWs later.  But for now, let's talk DDs.

DDs are a world unto themselves.  There's a lot to know, but let's start with the three biggest things to know; size, powder, and ammo.

Size:  I nearly bought the same US M1 57mm cannon Henderson Defense purchased.  It wasn't an issue of money; the seller and the seller's rep are all friends and I had the cash.  Plus I had shot it some years prior.  (Wished we could have met at SAR last year- will you be there this year, @HendersonDefense ?)  The issue is size.  Cannon and howitzers are really big and really heavy.  You need a place to park them.  You need a trailer to pull them around.  You need a vehicle to pull that trailer and gun.  You need a bunch of friends to help you unload the gun and get it back on the trailer.  You need to handle shells that can be as big around and as tall as your leg.  If you want to work on it, you need a jack and a hoist.

Okay, so you're not talking cannon or howitzer.  A 20mm rifle can be 9' long and not break down for transport.  (Lahti!)  Will that fit in your vehicle?  How will you protect it from the elements and from observation by thieves?  It also weighs 109 lbs.  Can you move it around by yourself or will you need a friend?  I used to own an 82mm Soviet mortar (model of 1937).  Sure it broke down into three pieces (tube and cup, bipod, and base plate), but that took up a LOT of room.  Each 81mm or 82mm shell wasn't light either.  Moving all of that to/from the firing line to/from your vehicle WASN'T fun.  Hint- a strong but collapsible rolling cart or wagon is your friend!  Now let's say you have a dud round.  Do you want to be detaching the mortar from the base plate and trying to muscle the tube upside down to drop out that shell?  Or do you want a friend to help?

Powder:  The next problem is powder.  ATF doesn't like slow burning powder.  Although it's safer than common commercially available powder, it's still restricted as a low explosive.  That means you need a FEL, or Federal Explosives License, for the right powder.  Not only is that licensing, but it means getting cozy with your fire marshal, having a magazine that meets federal specs, and having that magazine x number of feed away from any inhabited dwelling (including your own), railroad tracks, roads, highways, blah blah blah.  You must also inspect that magazine weekly and keep records of your inspections.  Plus have a bound book denoting deliveries and use of the powder.  This can be a major problem depending upon where you live and what your local, county, and state laws have to say, including additional permits and licenses.  (This killed me because Wisconsin SUCKS for explosives licensing.)

Ammo:  Some seemingly cool DDs are dirt cheap because ammo isn't available.  I own a Soviet 50mm mortar model of 1939r.  They're cheap; C&R originals are $1,500 or less.  I built mine from parts I scrounged over many years for $700 counting the tax.  Practice shells are as rare as hen's teeth.  I've got two (one true original and one that some moron chromed out at some time in the past), and I'm grateful for them.  I had to build my own dummy practice shells through trial and lots of error.  Jap Knee Mortars (more correctly projectors) are also still cheap around $2,500-3,500.  Why?  Few original dummy shells are available.  You have to DIY your own dummies to shoot.  If you don't want to DIY, find a US 60mm, 81mm, or a Soviet 82mm.  (You can use a US 81mm in a Soviet 82mm, but you can't use Soviet 82mm shells in a US 81mm. This was done purposefully by the Soviets.)  20mm stuff can be found, although original brass is getting scarce.  That's why the Lahti, Solothurn, and Anzio are so popular and are generally $10k+ (Lahti being cheap around $10k, Anzio around $15k, and Solothurn normally being $25k+).  Odd chamberings like the Jap Type 97 20mm keep its prices down, even though it's select-fire.  (Great, you found a shell!  How helpful is it to have one shell for a MG?)  40mm stuff is everywhere, but the M203 still being commonly available and in production keeps them around $1,500.  The M79 is more like $7,500 since it's out of production with shells being commonly available.

$200 tax on ammo:  Only for HE ammo.  All other types of DD ammo are untaxed.

Shipping DD ammo:  Major problem if it's loaded.  The regs allow for "small arms" ammo, which is .50 or less.  DD is larger than .50.  Thus, you're either buying it and taking it home in person or it's getting shipped to you as components and you hand-load.

Bonus question for you to consider: Do you have a safe range that will contain the shell being fired?

So let's start with those three considerations.  Think carefully about size, powder, and ammo.  If you can't handle any one of those three, you just bought a wall hangar or a lawn ornament.

Now let's talk about you.  Honest question- just how handy are you?  How creative are you?  There's no wrong answer and I'm not trying to be insulting by asking.  But if you're not handy and not creative, stick to stuff with commonly available ammo and components.  Let's say you find a Jap Type 97 20mm.  You scrounge and scrounge and scrounge and eventually find ONE piece of original 20mm brass.  Can you spec it out and start making your own shells using a mill and lathe?  If your brass is lucky enough to have one original projo, can you spec it out, weigh it, find another more common projo, and use the lathe to fit it as close as possible to original Jap specs?  If not, what will you use to make your new projos?  Even rarer than original brass are original Japanese WW2 era 20mm primers.  What primer will you substitute?  Original Japanese powder doesn't exist.  How will you create your own load using currently available powder?*  These questions all have answers.  Maybe you are creative, but this project is only way over your head for now.  Cool!  But if these questions just made you squirm and you're not into this type of work, stick with more common stuff.  If you've got a T-H-I-C-K wallet, I can also introduce you to people who you can hire to do these things.

*If you are a reloader, I used a 1.1 pound mixture of IMR5010 plus Fg and Fffg black powders in my US M18A1 57mm recoilless rifle.  Yes, I mixed .50 BMG powder with two types of black powder to replicate recoilless rifle powder because original recoilless rifle powder is unobtainable.  Also, if you aren't a reloader, stay out of the DD world entirely.

Tip:  When reloading for cannon and howitzers, convert an old log splitter to be your reloading press.  Smaller stuff like 20mm, 25mm, etc., can be done with specialty presses and dies.

Want to start experimenting with a forgiving but inexpensive gun?  Find a QUALITY AND OVERBUILT 37mm or 26.5mm flare gun.  I recommend finding a RV-85 on the 26.5mm side or a Spike's Havoc on the 37mm side.  The RV-85 has gotten expensive (that Bud's price is LONG gone) but is still very cheap as DDs go, and its quality and strength are amazing.  It will be very forgiving of mistakes, although it's certainly not bomb-proof.  The Spikes is dirt cheap and still strong, but not as strong as the RV-85. Plus they can come straight to you with no FFL needed as flare funs.  Or just buy a M203 40mm to begin with.

File and have an approved Form 1 in hand for the 26.5mm or 37mm before even thinking about developing an anti-personnel round.  But don't let the lack of a F1 stop you from mixing up your own flares and non-anti-personnel rounds.  Start learning with basic safety and signaling flares.

Okay, I typed a book.  But if you're looking to get into DDs, this is how I would begin.

OP read the above!

Thanks Mike, I owe ya lunch at SAR this year.

@swampfoxoutdoors

You can fire them.  But it means DIYing and creating your own rounds.

If that thought gives you pause or makes you shudder, DO NOT GET INTO DDs.  Not saying this to be an ass or rude, but DIYing is a MAJOR part of the DD world.  Even the 40mm guys reload.  If this is something you don't want to do or fear doing, cool.  Frankly, you're smart- you may be making your own shell, modifying an existing projo to fit, and tossing in untested powder to see what happens.  It doesn't go according to plan.  (I've had the privilege of firing many guns at the end of a loooooooong string.)

There's no disrespect from me if this isn't your cup of tea.  None whatsoever!  But if I just made you shudder, this probably isn't your world.  That's not good or bad.  YOU need to be comfortable with experimentation, WECSOGing, and a lot of "well, this should work..."

It'll be good to see you again- missed you passing through Murdo this year from the WY shoot.

No offense take. Thanks for stopping in with all of the info.

I am a reloader have been reloading for 13 years. I enjoy tinkering but do have limited tools, very minor metal working experience. As far as land goes I have 2 tracks of 100 & 200 acres at my disposal with large hills. As far as storage I have very little at the house but do have access to larger storage at family's property.

When I spoke of cannons I guess I should have prefaced that with small cannons. lol Not wanting anything huge but something that could be transported in a pickup, panel van or car. I have seen a video on IV8888 YT channel of a parrot rifle which was about the size I would consider.

But I would rather have some sort of launcher. The B40/RPG-2 seems to fit my needs/wants the best. Looks neat, could fit in a safe and in theory fire it with a inert round with a home made launch charge.  The only issue with it is welding up the whole cut in the tube and it being strong enough to handle the blast. And of course making the launch charge.

I have looked into the 37mm and 40mm launcher and they are kinda neat. Dont really care for a weapon mounted launcher. I would rather it be a stand alone unit.

Also since you were in the business.

Why dont we see any factory new / imported DDs? With the NFA world getting more main stream I would think there would be a market there.

Also open to AOW suggestions. When I think of AOW I think of Serbu Shortys, pistols with vertical grips and knife guns. Am I missing something much cooler?

ok.

 

 

I've also mounted it on a CETME, but don't have any pics of it in that configuration.

You're welcome!  I want others to get into DDs, but only if they're truly ready to do so.  Hence all of the warnings.

Barring local/county/state issues, you've got enough land for a low explosives powder magazine.  The big question is your ability to access the land; you have to inspect the magazine weekly.  If you're in some city and the land is 100+ miles away each way, you're still heading out there once weekly.  Your reloading experience and experience with tools should be enough to get you started.

A pickup or panel van will pull a trailer.  That'll get you into a smaller cannon like a Hotchkiss or Puteaux. That'll also handle a Lahti, Anzio, Solothurn, etc.  I can tell you that a M18A1 57mm recoilless rifle will fit in a Camry with its seats folded down.  

If you want a Parrot Rifle, I have good news!  That's a black power muzzle loader.  Barring state or local laws to the contrary, you have no need for a tax stamp or a FEL.  It's not even a Title I gun since it's a black powder muzzle loader.  Here's a discussion from nearly a full decade ago.....

Welding a doughnut hole back in place is easy with the right people doing it.  But the RPG-2 and RPG-7 still aren't that popular because of the requirements to avoid a DD classification of the round itself.  Check out the definition of a DD:

26 U.S.C. § 5845(f):

(1) any explosive, incendiary, or poison gas, (A) bomb, (B) grenade, (C) rocket having a propellant charge of more than 4 ounces, (D) missile having an explosive charge of more than 1/4 ounce, (E) mine or (F) similar device.
(2) Any weapon by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, the barrel or barrels of which have a bore of more than one-half inch in diameter (.50 inches or 12.7 mm), except a shotgun or shotgun shell which the Secretary finds is generally recognized as particularly suitable for sporting purposes; and
(3) Any combination of parts either designed or intended for use in converting any device into a destructive device as defined in subparagraphs (1) and (2) and from which a destructive device may be readily assembled.

Just how much propulsion and fun will you get as per 1(C) with only 4 oz of propellent?

Now, here's a cool exemption to consider from 26 U.S.C. § 5845(f).

The term destructive device shall not include any device which is neither designed nor redesigned for use as a weapon; any device, although originally designed for use as a weapon, which is redesigned for use as a signaling, pyrotechnic, line throwing, safety or similar device; surplus ordnance sold, loaned or given by the Secretary of the Army, pursuant to the provisions of section 4684(2), 4685, or 4686 of Title 10 of the United States Code; or any other device the Secretary finds is not likely to be used as a weapon, or is an antique or is a rifle which the owner intends to use solely for sporting purposes.

Imagine papering a Schermuly line throwing pistol.  Or load for a Sculler line throwing cannon, but no paperwork needed since it's a black powder muzzle loading cannon!

As to your question about new and imported DDs, new imported NFA of ANY flavor has been illegal since passage of the GCA '68.  Post-68 imported NFA is SOT/govt only by law.  Think of it like a pre-sample MG.  I've got a Benelli M1 14" SBS that was imported by HK before Benelli even opened a PO Box in the USA.  It cost me $250 from another SOT without a stamp on a F3.  It's worth about that because it can never be sold to anybody but a dealer or government.  Occasionally you'll find a post-68 HK M320 or AG36 40mm launcher.  I also found half a dozen Milkor 40mm rotary launchers THE WEEK AFTER I surrendered my FFL/SOT.  (That's still a sore spot.)

New DDs, excepting the M203 family, don't come on market due to the huge liability.  Imagine being a company producing some DD, you sell one, and someone buys it.  Either they do wrong or it gets stolen and the thief does something wrong.  Or the buyer blows themselves up with it.  What gets in the media? "A shadowy company called Swampfoxoutdoors Inc. sold the 500 mm GRENADE LAUNCHER to UNTRAINED MEMBERS OF THE PUBLIC..."  I've also been told that the Lawful Commerce in Arms Act (the no-sue law) only protects SMALL ARMS (.50 or smaller), which means it doesn't cover DD manufacturers.  But don't quote me on that; I've never looked into it to verify what I was told.

Turning to AOWs, I am a fan of the Super-Shorty as a hotel room defense gun.  It's not for use at range, but it'll do the job inside of a hotel room.  Combo guns are cool.  If you're a backpacker or a hiker, a breech loading single shot rifled barrel over shotgun barrel is an AOW if the barrels are between 12-18".  Combo guns are also the only AOW that can have a buttstock.  I like smooth bore handguns.  Used to have a S&W 1917 that was converted to smooth bore in the 1950s with a choke tube welded in place.  It was fine snake medicine.  The H&R Handy Gun, Type 1 with the spurred grip, is probably the best pointing handgun.  If you can find one, an Auto Burglar is fun.

Not enough demand, prices are low for the M203 only due to military mass production. With smaller niche items, less would be made, and the prices would be much higher... and production would be much less frequent.

Thank the 1968 GCA. Much like post-1986 MGs aren't transferable, neither are post-1968 imported DDs (or imported NFA items of any type).

click view quote, my response are in red.

The 4oz limit on propellant is by weight.

The 1968 ban is on importation of any NFA items, the 1986 ban is on MGs (imported or not)... helpful to anyone even mildly dyslexic!

Serbu shotguns are fun, but they are a bit spendier than most people want to put into a basic 12ga. The main demand seems to be from states such as CA, where AOWs are allowed but SBSs aren't, which along with the amount of work going into them, drives the price.

The Chiappa (or the Savage, or the M6 Springfield) could absolutely be registered on a F1 as an AOW. It fits the definition of having a stock, one rifled barrel, one smoothbore barrel, manual action... depending on barrel length, of course.

I haven't seen anyone producing new AOW pen guns lately, but every now and then it happens.

No. Not true at all. I really wish people would stop spreading this rumor.

Mortars are easy. What caliber you want?

550 is way too high for an RPG2. @Wingnut116ACW can hook you up with someone to reweld. I could too, but I think the guy here will only deal with locals.

What part of Montana are you in sir? We may need to get together next time Jenzilla and I are back on the ranch.

Explosives for the win... I realize this is not practical for most people but I am a fan and very fortunate to do work (Our other company is a Type 10 FFL / 20 FEL) that involves explosive weapons systems... See video below:

Line Charge Development

It's been over 10 years since I was into high power rocketry so my memory of the rules are fuzzy.

I was a level II and could buy and launch motors up to an L.  The largest commercially available L motor uses more than 6 pounds of propellant.

Most of the legal stuff we dealt with was fire code/storage requirements.  I can't remember any sort of exemption from DD regulations.

Seems to me the only real difference is that we launched rockets vertically and they were made of plastics, fiberglass/carbon, and cardboard.  DDs launch things horizontally/mostly horizontally and are made of harder materials.

I know I found were RPG2s had sold in the past for $200. But if they are the only ones with them I guess they can charge what they want.

If the the charge weight is 4oz weight I wonder how much Cannon grade or Fg black powder or Trail Boss could be stuffed into a launch charge. I’m sure their is some sort of formula to figure this out.

And another question.

If the charge weight is separate from the fake warhead wouldn’t that be the same setup as a black powder cannon. With the RPG2 it’s not even a sealed tube so half of the blasted is shot out the back. I guess it’s more of a recoiless rifle.

WOW!  lots of great info.... especially with the DD's and reloading.  check out Grog's forum too.

i used to have a Spikes Havok.  one of the original 12" ones with Chaos stock.  i was going to make it a DD, but i ended up selling it towards NV, etc.  was cool to own, but couldn't really shoot it anywhere and the Czech flares were going up in price... so I profited.

i've been looking at gunbroker for Streetsweeper stuff for a very long time.  the current DD's there have been posted regularly.  the only one i have seen sold was $800-ish, the other ones just sit.  parts kits sell pretty good there.  last one was like $570-ish.  i have a parts kit, but would like a complete one and keep my parts kit for spares.

i own a Super Shorty.  fun toys.  pattern is crazy wide.  very loud, especially indoors.

If you hunt down parts and give it time. You can build a 60mm M2 for 2500. And shoot it for 2.00 a shot.

I registered one of my RV-85s as a DD,  its fun and relatively inexpensive to load rounds to shoot out of it.    I'd like to pick up a 60mm mortar at some point.

@swampfoxoutdoors - Had to go offline to handle some work BS and some flooding at my building.  Other people answered things though.  I'm not trying to rain on our parade with a RPG, but just be aware that non-DD rockets won't be too exciting.

Pen guns seem cool but be sure to test fire them first.  I used to own a Quicksilver .22 pen gun.  High quality but painful to shoot.  Even a tiny .22 can leave some nasty blood blisters with high velocity rounds and little mass behind the firearm.

One thing to remember- a Form 1 is always $200, even for an AOW.

@eyesofdeath13 - That sems really cheap, even for a parts build 60mm.  Did you fab any of your own parts or was it a lot of scrounging?  Same story with your $2 shells; what's the story?  I'd love to know more, especially if it translates over to my Soviet 50mm mortar.  My shells darn well aren't anywhere near two bucks each!  

@shooterpatriot - What are you doing with your RV-85?  I just got lucky and found one at an estate sale for $250 last month.  Another friend papered his long ago and is still developing loads.  I look forward to having mine papered to work with him on load development.

-----

I bought my 870-based Serbu AOW back when they were only around $500-something each dealer wholesale.  But that was over a decade ago.  Host gun prices have risen since.  Mark has plenty of call for his BMG rifles, so some of that is making it worth it to change tooling to do runs of the SSS.  And he told me he earned very little per gun back then.  I assume some of the price increase is related to earning a fair profit for all of the work he puts into those (and there IS a LOT of work in modifying a basic 870 to SSS spec).  I don't begrudge him profit (stupidly high profit) at all- he's an innovator and deserves it.

I was burglarized back in 2007.  No guns lost (all in the safe), but my laptop was stolen.  I had a photo of about a dozen NIB SSS in their boxes all lined up on a table from a non-Arfcom group buy I ran.  Wish I still had that photo- it always got people talking.  

For the RV 85 I mostly shoot rounds made out of PVC pipe.

I use a small lathe to do it but you could probably do it with just a drill press.
I telescope a 1/2 piece inside a 3/4 inch piece.  The half inch piece is a little too big to fit inside the 3/4.   I turn a short section of the OD down  until it fits inside the larger piece and glue them together.   The 3/4 pipe is just a hair too big for the barrel,  you need to remove a few thousandths from the entire OD of that piece. I then plug the ends with PVC rod.  These are fired out of cases I turned specifically for these projos.  The small diameter fits inside the case and the larger diameter matches the barrel and sits on the case mouth.

As long as you keep the CG forward they fly nice and stable.  I've filled them with sand, and also made fused smoke rounds by drilling the rear plug.  I haven't tried it yet, but I want to try scoring the front of the tube so it breaks easy and fill it with chaulk dust.

I'll try to remember to take some pictures tonight.

I found an eBay seller in Europe (I forgot exactly where) that had the tripod and baseplate. He had it listed for $1700. I privately offered $1400 for it witch he took. The cup was new made $600. And tube I made from seamless 4140. Cost me 125.00 to have it honed to ID size and I think $220 for the tubing.

The rounds Yes are expensive at $300-$350 each. But are completely reloadable and about $2 to do that.

What's the OD of the rounds you use on your 50MM mortar? Witch mortar is it?

O!  ebay sight for M2 $56

Has anybody here bought one of the 60mm mortars from Vega Ballistics with their 60mm "trump" rounds that take shotgun blanks and detonate on impact?

Those Vega units are not cheap but you can actually fire them and get reusable "spotter" type rounds.  It all fits into a reasonable sized case and the main tube would fit in a normal gun safe.  For someone who wants a DD and doesn't have the tools, time, storage space, skillset, etc. many of the other DDs require,  it seems like it may be nice turnkey, albeit expensive kit.

My impression is that it would more fun than an M203 with chalk rounds or an RPG with some sort of training rocket.....granted its also like 10x the pricetag of an M203.  That said I am not sure how quick the fun-factor would wear off either.

For making the PVC rounds with a drill press I would open up the ID of the 3/4 pipe with a drill or reamer, to fit the 1/2 inch.  Then glue the pieces together. Chuck up the half inch piece and sand the OD of the 3/4 as it spins until it fits smoothly in the barrel.

I purchased some of the reloadableshells.com cartridges so I could shoot without dealing with Black powder fouling but haven't tried them yet.  The wall thickness of the case is less than mine so the pvc sits too loose.  If I want to shoot my PVC rounds I would need to wrap the "tail" in something.
I've never reloaded the Czech flare cases, but have saved them all in case I get the itch.

My round


ETA: I made this specifically for the RV85 so the rim is the proper thickness.  The thick Rim will not fit in a flare pistal

Case and projo separate


Case head



Reloadableshells.com and my case showing wall thickness difference.

For a moment I thought you'd turned the case out of solid bar stock... then I saw what looks like silver braze. I have to ask, to see for sure: are those tubing and a brazed on rim/base, or are those from bar stock? If that's from bar stock... you're dedicated, but went overboard for the pressures of even the RV85.

Almost all of the cases I make for my flare guns/DDs (up  to and including 34mm, at least) are 260 "cartridge brass" in the usual 70Cu/30Zn, and the usual 26.5mm case head thickness I go with is 0.102", also of 260. I went with H58 for the temper, and it has yet to be any issue thanks to the low pressures involved. Small square of the 0.102" sheet, brazed onto a faced section of tube, faced to length, flipped around and turned to the right diameter on the rim. Spot, drill, bore for the 209 primer, chamfer... easy enough. The largest I've made multiples of with that method are for a 34mm 5" case used in a Swiss flare pistol, and even that ended up being under $15 in materials, and the 26.5mm cases were a bit cheaper. Plus, they look like gigantic brass shotshells, which is a plus for the RV85!

When you're doing a batch, it can be nice and quick to cut the rim material to size, face off a bunch of tubes close to finish length, set them all up and braze the base on, and go from there. I was surprised how little time it took to finish a batch, but brass can be like that... much easier to cut than the usual materials I deal with.

It's a two piece case epoxyied together.   I can't remember if the base plug on these is 3/4" or 1" tall.  I get barstock close to the rim diameter.  Turn down the rest to match the ID of the tube, and do three drilling operations.  A powder chamber on the inside, the primer pocket on the outside, and a though hole for the flash hole.  Then epoxy them on the tube.   The tube is a standard size and requires no turning.   Both pieces are 6061.

Making them out of brazed brass sounds interesting, I'll have to try that out sometime.

That's a bit concerning! Epoxied aluminum might not hold up too well, even with a smaller diameter powder chamber. Keep an eye on that, and since it's 6061, it's cheap enough to ditch if any problems crop up. Have you taken a peek to see what the corrosive salts are doing to the resin? It can break down rapidly.

In my opinion, the brass cases do look very sharp and are worth the few bucks in materials. Here's one I made as a test for my 34mm... inert, no primer pocket, but great for laughs and display:

80gr starting of Trailboss... should give (with a 2000gr bullet, substantially more than the 1300gr of 3oz, but I don't have any 3oz 4ga bullets modeled) around 900FPS out of the 19.75" barrel, and generate in the ballpark of 11kpsi chamber. 130gr Trailboss, 2000gr bullet, 1200FPS but 19kpsi.

Of course, you'd want to play with those a bit and model the exact case you make, but it's a ballpark for your velocity range.

ETA: Rough and dirty, to give you an idea. 1300gr generic 1"/4ga bullet, approximately 900FPS from 55gr Trailboss 5,200psi chamber. 90gr Trailboss with the same generic 1300gr 4ga projectile gives approximately 1200FPS and 10.5kpsi chamber.

I also have a registered RV85 and dream of shooting 4 bore slugs.