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and to clarify, RPG means "handheld antitank grenade launcher' when referring to the RPG-2 and RPG-7.
the article says the Yugo M57 PG-2 variant used sand in the projection charge to increase its weight. Reminds me of the newer "LAW" that uses salt water to decrease the back blast |
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here is a great article detailing the projection charge in the PG-2 and why it was done that way. Sounds like a lot of trial and error is in order to get it right.
Short answer here is that if you just wrap a bunch of very fine black powder in cardboard and light it off, you will end up bursting your tube and losing your head, or best case scenario is the projectile lands within 30 meters of you, effectively replicating a Panzerfaust. I'm still reading, and will continue to post my research findings. I'm glad I finally made an account to I could jump in on this before anyone blows a tube, though I 100% support this project, as I did the Form 1 hand grenade (still trying to decide if I want to fill one out for one of my M69 practice grenades) http://www.sadefensejournal.com/wp/?p=349 |
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Quoted:
here is a great article detailing the projection charge in the PG-2 and why it was done that way. Sounds like a lot of trial and error is in order to get it right. Short answer here is that if you just wrap a bunch of very fine black powder in cardboard and light it off, you will end up bursting your tube and losing your head, or best case scenario is the projectile lands within 30 meters of you, effectively replicating a Panzerfaust. I'm still reading, and will continue to post my research findings. I'm glad I finally made an account to I could jump in on this before anyone blows a tube, though I 100% support this project, as I did the Form 1 hand grenade (still trying to decide if I want to fill one out for one of my M69 practice grenades) http://www.sadefensejournal.com/wp/?p=349 View Quote |
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I don't see why. The PG-2 is not a rocket, and never was. The only people who say it is, still believe that RPG stands for "rocket propelled grenade." here is a very informative article by SADJ. Its just one a start of diving into the RPG family and their design. Wingnut, it also mentions why the projection charge is segmented into six pieces, the original 2-piece segmented charge would blow the tube. I assume you were joking about trial and error with body armor on, as a test fire stand would be easy to fabricate. http://www.sadefensejournal.com/wp/?p=1042 View Quote |
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Static testing and high speed cameras will be a given. But I'm still wearing body armor and will have a medic on staff. Once I duplicate projo performance and get 10 rounds reliably and safely fired, I'll start collecting data by tossing it on my shoulder and wearing blast sensors on my armor and helmet.
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Quoted:
here is a great article detailing the projection charge in the PG-2 and why it was done that way. Sounds like a lot of trial and error is in order to get it right. Short answer here is that if you just wrap a bunch of very fine black powder in cardboard and light it off, you will end up bursting your tube and losing your head, or best case scenario is the projectile lands within 30 meters of you, effectively replicating a Panzerfaust. I'm still reading, and will continue to post my research findings. I'm glad I finally made an account to I could jump in on this before anyone blows a tube, though I 100% support this project, as I did the Form 1 hand grenade (still trying to decide if I want to fill one out for one of my M69 practice grenades) http://www.sadefensejournal.com/wp/?p=349 View Quote |
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Static testing and high speed cameras will be a given. But I'm still wearing body armor and will have a medic on staff. Once I duplicate projo performance and get 10 rounds reliably and safely fired, I'll start collecting data by tossing it on my shoulder and wearing blast sensors on my armor and helmet. View Quote |
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Trying to condense some info into this thread.
Taken from this website mentioned earlier in the thread: http://www.sadefensejournal.com/wp/?p=330 (Worth reading all the info on that site, it is good stuff) Attached File "Dummy RPG-2 round with fins extended, and one type of dummy ejection charge underneath it. The ejection charge would be removed from packaging directly before firing and screwed onto the back of the round. The charges are very moisture and physical damage sensitive, but more so than RPG-7 charges." 7 info: Attached File "On the right of this close-up is the expansion chamber area. The expeller charge base slides in from the right and seats firmly into the narrowed section at the center. The foam plug at the base of the expeller charge actually seats there. This photo also shows the joint between the forward tube and the rear tube in manufacturing. Although this is threaded, this is not an armorer’s disassembly point as it is welded. Also, the narrowing at the joint is a venturi: a narrowing of the tube going to an increased diameter, which changes gas flow pressure direction and speed." "At the joint between the expeller charge and the rocket booster that is permanently part of the grenade, is the section that initiates the firing sequence. When the firing pin strikes the primer (located in the small threaded hole on the center side in this photo, but primer is missing) the primer ignites a train of events. Immediately the expeller charge to the left in this photo is ignited. The pyrotechnic pellet in the rocket booster is ignited when enough forward momentum has compressed the spring to the right in this photo, driving a second primer onto a fixed firing pin. This is a timed and blocked event – the rocket motor ignition delay is separated from the primer flash channel by solid aluminum. The pellet burns in a set time to ignite the rocket booster when it reaches 11 meters in front of the launcher. Some sources state that this event occurs between 5 and 20 meters. This is incorrect. The event must be a repeatable performance for accuracy, and the Russian, Chinese, Bulgarian, Romanian, etc., manufacturers are well aware of this and critical quality control is exercised in these fuzes. Manufacturers will target 10 to 15 meters for rocket assist ignition, attempting to keep their lots consistent. Initial design calls for 11 meters. If the ignition point is inconsistent from round to round, target acquisition will not be repeatable. Large deviations in that distance usually indicate improper storage and degradation of fuze train." "When the primer ignites, the expeller charge is fired off by the black powder in the center of the expeller tube. The expeller main charge propellant is double base NC/NG placed evenly around the central tube, in between the folded stabilizer fins. This is all wrapped with impregnated cardboard and a glued, waterproof tissue. This section is extremely vulnerable to moisture, so it is important to only remove from the carrying case just prior to firing. The expeller section placed in an RPG-7 is in an expansion chamber that is larger than the 40mm tube, so the expanding propellant gases rapidly build pressure and exert it onto the grenade" "At the rear of the expeller charge is a hard foam plug. As pressure builds in the expeller chamber, the grenade has forward pressure on it and eventually at a pre-determined pressure, this plug breaks up and the parts of the plug and any unburnt cardboard are expelled out through the venturi and the blast cone. Directly in front of the plug is an aluminum turbine that imparts rotation immediately as the grenade shaft leaves the expeller chamber and tube." "As the grenade leaves the RPG tube, it has been “boosted” out by the expeller charge. Forward motion allows the four stabilizer fins to extend out to the sides, and it is important to remember this when firing as there must be at least 8 inches of clearance above all obstacles in the flight trajectory. This is also a good time to point out another reason not to install the expeller cartridge onto the rocket and carry it around for a long period. If this is bent or damaged then the entire trajectory may be thrown off. The pyrotechnic pellet will burn through to ignite the rocket booster, as long as the spring held block is out of the way due to proper forward momentum. Propellant gases begin the booster action at 11 meters from leaving the tube of the launcher." "The rocket motor burns and the gases push forward into the nozzle block expansion chamber at the front joint just behind the grenade body. This chamber has six holes that point to the rear and outward, and the pressure from the gases blows out the seals and the six holes drive the grenade assembly forward during its assisted flight. This event leaves a puff of smoke – sometimes observed as a smoke “ring” – 10 to 15 meters in front of the operator. If the target has an oblique view of the RPG-7 operator, this will be visible as a separate event, making locating the RPG-7 position easy for return fire. It is important to note that the holes are canted in a direction opposite that of the rotation imparted by the fins. The spin rate imparted by the four fins is slowed after rocket ignition. This prevents over-spin and reduces spin degradation of the shaped charge on firing. Just behind the nozzle block is an elastic ring that holds the RPG-7 round in the launcher so slight downward firing is possible without the round coming forward and misaligning the primer and firing pin. When the rocket burns out, forward momentum keeps the grenade airborne until it reaches a target or approximately 900 meters where the safety fuze causes the nose cone area to explode. This does activate the shaped charge, although this author has observed many RPG-7 rounds that reached the five second mark, the safety detonated, and the shaped charge was still somewhat intact leaving energetic material on the ground." And this is another great read by Paul Newhouse from the website: http://www.sadefensejournal.com/wp/?p=349 "It is necessary to clearly differentiate between infantry antitank weapon systems that are rockets, and those that are recoilless guns. Most frequently the majority of such weapons are described as rocket launchers, but this is glaringly inaccurate. The well-known M136/AT4 single-shot weapon in wide- spread use by the U.S. Army is in fact a disposable recoilless launcher. The infamous RPG-7, despite firing rocket-assisted projectiles, is a reusable recoilless launcher. One supposes the key distinguishing feature is where the pressure, built up by propellant combustion, occurs, and where the pressure drop which produces the propulsive force occurs. In a rocket system, the propellant combusts entirely within the rocket itself and the pressure drop which produces the propulsive force occurs across the body of the munition. This may best be illustrated by considering the case of a rocket like that from an M72 LAW being ignited outside its launch tube. The rocket would travel just as far as if it were fired normally; the tube only provides for initial aiming, and does not contribute to the propulsive process. In a recoilless weapon, the launch tube is an integral part of the propulsive process, and incorporates a chamber for the propellant to burn at a relatively high pressure, and a nozzle to create a constriction that vents the high pressure gases rearwards, usually at an accelerated velocity, whose momentum is then used to balance exactly the momentum of the projectile leaving the muzzle. If one were to ignite the propelling charge of a recoilless round like a PG-2 or a PG-7 in the open, it would simply burn. The grenade would not go anywhere. Without a chamber to allow burning at a high pressure, no propulsive force is generated. It’s also worthwhile to take a brief look at the physics of recoilless weapons. Simply put, recoilless guns work by expelling a projectile from the front in the usual manner, and a countermass out the back of the gun. The earliest recoilless guns were the Davis Guns of WW1. These used a central propelling charge to fire a projectile out of a forward-pointing barrel, and a solid countermass of equal weight out a rearward pointing barrel of identical length. While solid countermass recoilless guns have been in use since then, and a few still are, in most applications a solid countermass is a nuisance at best and a danger to one’s own troops at worst. Between the World Wars it was found that it was only necessary to match the momentum (mass times velocity) of the countermass to that of the projectile. Thus, a very light countermass, such as propellant gas moving at a very high velocity, can have a momentum equal to a heavy projectile discharged at a lower velocity. Most recoilless guns using a propellant gas countermass feature a prominent nozzle or nozzles at the back of the weapon. These are sometimes called “venturis” (acceptable) or “blast cones” (incorrect); more on these below. But one can’t help but note that the Panzerfausts and the RPG-2 had simple straight-tube launchers with neither constricting orifices nor conical venturis. So how did these weapons function and qualify as “Recoilless,” without simply venting the propellant gases out the back at low pressure? The answer lies in the fluid mechanics of compressible fluids. Most of us are aware that passing a fluid through a constriction will raise the velocity of the fluid. (Simply take your garden hose and constrict the water stream with your thumb, and watch how the water speeds up.) The higher the upstream pressure the greater the downstream velocity. But in gas systems, this only happens until a condition called choked flow is reached. At that point further increases in upstream pressure do not cause further increases in downstream velocity. The result in a recoilless weapon is a rise in pressure sufficient to launch a projectile. While this principle is the basis for most recoilless weapons, in straight tube launchers it has substantial performance limitations. The outlet velocity of the propellant gases in a straight tube launcher remains subsonic. To achieve a choked flow situation quickly, very fast burning propellant is required; in the RPG-2 fine granular black powder is used. But this fast propellant in turn causes a rapid pressure rise in the area of the propelling charge. The maximum pressure must be limited to remain within the strength limits of the tube for function and safety. So there’s a limit to the weight of propellant that can be used, which in turn limits the mass of propellant gas available to form a countermass. As already mentioned, the gas velocity is limited in this system as well, the result is a relatively low available counterrecoil momentum. The final result of all these limiting factors is a very low muzzle velocity for a projectile of useful size. This was readily apparent in the early Panzerfausts, whose effective range was severely limited, at first to only 30 meters, by their low velocity and resultant highly curved trajectory Since gas velocity and tube strength impose limits on available counterrecoil momentum, the only way to really improve this system’s performance was to add additional propellant (and thus additional gas for the countermass), and since increasing the charge attached to the projectile would only increase the local pressure to unacceptable levels, the only solution available was to apply the maximum operating pressure over a greater length of the launch tube by distributing the propelling charge. In the later, longer-range Panzerfausts this was achieved by adding a secondary propelling charge approximately in the middle of the launch tube. The charge at the base of the projectile was initiated in the usual way, and this in turn ignited the secondary charge, boosting muzzle velocity and thus range, up to 100 meters and more. The RPG-2 uses a rather more ingenious solution, with the black powder propelling charge subdivided into 6 increments by means of cardboard tubes and discs, the latter with flash holes to foster ignition. The primer in the base of the PG-2 grenade ignited the first increment, which burns rapidly, creating pressure and pushing the remaining four increments back down the tube. After a few inches of travel, the second increment is fully ignited, then the third, fourth, fifth, and sixth. The result is high pressure over a greater length of the tube, rather than merely at the base of the projectile, and a greater volume of propellant gases for both propulsion and countermass. But even with this technique, there were limits to the performance of a simple straight tube launcher. One attempt at improvement was the Yugoslav M57 launcher, which incorporated a partial solid countermass in the form of a quantity of sand. However, this represented at best an incremental improvement over the simple straight tube launchers. While the PG-2 grenade performed well enough in terms of armor penetration (and remains a threat to all but the most modern armored fighting vehicles), the weapon’s fatal flaw was its very primitive recoilless launcher. While its simple cylindrical tube was easy and cheap to fabricate, its lack of a chamber and nozzle, and resultant low pressure combustion, as described above, severely limited the velocity of the PG-2. This made range estimation very important at all but the shortest ranges. Additionally, the low velocity meant a longer time of flight. Both factors limited hit probability against both stationary and moving targets. An interim solution was found in the RPG-4. While this fired purely ballistic grenades, which resembled PG-2s albeit with increased standoff for the shaped charge, the 45mm diameter launch tube incorporated a larger diameter chamber and a venturi, or nozzle, at its rear end, causing it to greatly resemble its successor the RPG-7. The RPG-4, developed in the late 1950s, was not produced in quantity. A brief description of the physics of the RPG-4 and RPG-7 is in order. These weapons incorporate the features seen in other, larger recoilless systems: a chamber of larger size than the propelling charge, and a convergent-divergent nozzle incorporating a constriction and a divergent (outlet diameter larger than inlet diameter) conical section. The constriction sets up the choked flow condition described above, albeit without the need to use a very fast propellant. The conical divergent nozzle in turn accelerates the propellant gases to supersonic speeds. Thus, in this type of system, there is much more counterrecoil momentum produced, both from burning more propellant over a longer time and from expelling the gas countermass at a much higher velocity. In the case of the RPG-7, this allowed the launching of projectiles heavier than PG-2s at velocities in some cases approaching double those of the older system. The RPG-7 recoilless launcher, introduced in 1961, reverted to the 40mm tube diameter of the RPG-2 while retaining the chamber and nozzle design of its precursor the RPG-4. A brief observation on the function of its ammunition will be made in the hope of finally putting to rest the absurd “rocket propelled grenade” name. The RPG-7’s principal munition is one of a series of PG-7 antitank grenades. All of these incorporate a rocket motor. As the RPG-7 is a recoilless launcher, the PG-7 may be considered a rocket-assisted projectile; calling it a rocket would be incorrect. The reason for adoption of a recoilless-launched, rocket-assisted antitank munition of greater-than-average complexity is simple: it increases the munition’s velocity and thus reduces its trajectory and time of flight, without imposing any additional penalties on either the launcher or its user. The result is greatly improved hit probability against both moving and stationary targets. In a 1970s study the US Army deemed the RPG-7 the best solution to hitting armored vehicles out to 300m. Better than pure rocket systems and better than pure recoilless systems." |
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For those with RPG-2s which ones are the more desirable to buy. I have seen 2 types of demilled RPG-2s. Those with the hole cut in the tube above the grip and those with the hole cut under the wood further back in the tube.
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For those with RPG-2s which ones are the more desirable to buy. I have seen 2 types of demilled RPG-2s. Those with the hole cut in the tube above the grip and those with the hole cut under the wood further back in the tube. View Quote |
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So buy whatever and scrap the tube and add on the demilled parts?
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Quoted: That was my plan at least after I get my stamp, but im just speaking for myself. View Quote I know you would be missing the sights and wood. |
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Quoted: You did a Form 1 for a grenade and it was approved? What year? View Quote |
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Quoted: I have also seen just the grip mechanism for sale on gun broker for much less. Could one just buy it and register it and then weld on a tube? I know you would be missing the sights and wood. View Quote |
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We should really have our own post to collect all this info and share it with each other. As a side not, I finally ordered one of the Chinese PG-7 projectiles as the price dropped a bit. Maybe it will give me some insight. On another note, I know the guy who gave airtronics the blueprints to make their RPG-7s. Haven't talked to him in a while but he is somewhat well known. I wonder if he happens to have a set for the "-2"
between this and my 40mm buildup, my 60mm Mortar plans are getting put aside, My 40mm is at the top of my list for priority, but ya gotta get when the gettins good |
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Can you get the -7 prints? Since Airtronix dont dare to consort with us lowly peasants.
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That would, indeed, be exceptionally helpful... if possible.
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i will reach out and see what i can do. Like i said, its been years since I've sat down with him. I also have a co-worker that translates Russian if need be.
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Ran across link while looking for a lock mechanism for a BP mortar.
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Quoted:
Ran across link while looking for a lock mechanism for a BP mortar. View Quote |
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Quoted: Video of it not blowing up when fired? View Quote The idea is kidna neat tho. One could take a RPG grip module and just make a BP shoulder fired cannon out of it. Not using the demilled tube of course. Not sure what bore dia you could use. Would have to be small enough not to knock you over when firing. |
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Quoted: Video of it not blowing up when fired? View Quote ETA: He's got a few. ETA2: And the last one... in boxers, apparently. |
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View Quote |
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Quoted: So...super no longer recoilless. Could be a cool trainer model though. View Quote |
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He has his glow belt on so hes super safe. No harm will come to him.
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I am also in the process of reactivating a pg-2. Big obstacle is how is the firing pin hole re created? Once the crossrod is removed, there is a 1/2" hole in the tube. I really hoped to not have to remove the firing pin block. But secure welding inside there while its in place is not going to happen.
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I am also in the process of reactivating a pg-2. Big obstacle is how is the firing pin hole re created? Once the crossrod is removed, there is a 1/2" hole in the tube. I really hoped to not have to remove the firing pin block. But secure welding inside there while its in place is not going to happen. View Quote |
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In another thread that I can no longer find, someone (possibly @RockHard13F ) mentioned that he wrote the tech branch to inquire as to whether an RPG2 requires a form 1 given that it does not use fixed ammo. Does anyone know if/how the ATF responded?
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In another thread that I can no longer find, someone (possibly @RockHard13F ) mentioned that he wrote the tech branch to inquire as to whether an RPG2 requires a form 1 given that it does not use fixed ammo. Does anyone know if/how the ATF responded? View Quote |
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That was the response I got to my inquiry regarding the PIAT and the NFA status thereof... since it doesn't have a barrel, and all. View Quote View All Quotes View All Quotes |
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They more or less told me to fuck off via phone, and never provided a written response. View Quote View All Quotes View All Quotes Quoted:
Quoted:
In another thread that I can no longer find, someone (possibly @RockHard13F ) mentioned that he wrote the tech branch to inquire as to whether an RPG2 requires a form 1 given that it does not use fixed ammo. Does anyone know if/how the ATF responded? |
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For those with RPG-2s which ones are the more desirable to buy. I have seen 2 types of demilled RPG-2s. Those with the hole cut in the tube above the grip and those with the hole cut under the wood further back in the tube. View Quote Most of the de-mil'd tubes have the rod blocking the bore welded through the firing pin hole. Robert Bowman has (or at least had, not sure if he still does), some that have the firing pin intact. They still have a hole in the side, and have an additional rod through the bore (one in front of, and one behind) the grip/firing pin assembly. Many people have opted to build a replacement tube, but you need to salvage the welded on bosses (and sights) from the old tube to weld on to the new tube. Not having the threads on the firing pin channel full of weld will make it a bit easer. Also, the firing pin on a PG2 has a vent going out the right side... when they weld the rods in, this area normally gets jacked up. So, IMO, the best one to get is one with an intact firing pin. |
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Helping with molding and filling some G class motors today, and that got me thinking... have you given any thought to KNSB single grain motors as a second stage? They're remarkably powerful, and easy to make.
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RPG2s don't have a second stage. It wouldn't be authentic, you may as well build a new design of your own making.
RPG7's have a second stage, but if you just put any old rocket it in it, it won't be an RPG7. It needs to be an RPG7 rocket. |
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RPG2s don't have a second stage. It wouldn't be authentic, you may as well build a new design of your own making. RPG7's have a second stage, but if you just put any old rocket it in it, it won't be an RPG7. It needs to be an RPG7 rocket. View Quote |
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Hopefully my RPG2 will be done soon if @Mad_Machinist can fit it into his schedule. Then I’ll work to get my FEL and magazine for black powder and rocket motor storage for my RPG2 and RPG7 projectiles.
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So, you're gonna try searching with Joogle? View Quote View All Quotes View All Quotes Quoted:
Quoted: I hadn't thought of this before, but there is a guy who is a member of my synagogue back in my hometown that used to design weapons for the Soviets (not by choice...it was comply or go to the gulag for being Jewish). I might try to reach out and see if he has any ideas. |
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I just got a de-milled RPG-2 myself, and would love to do something similar. This thread easily has the best RPG-2 information on the internet. Does anyone have dimensions of the PG-2 propellant tube to copy? I'm thinking a mock one could be 3D printed, or CnC'ed. I'm gonna pay the $200 for form-1 it, and I want to get as close to real as I can, without it also be a DD. (so I guess no real propellant or explosives)
To fix the tube, it looks like you can buy a ready-made one on GunBroker - https://www.gunbroker.com/item/840574787 But it seems like you'll need to do some machining to finish it off. There doesn't seem to be any rocket notch, or trigger holes in it. |
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I wouldn't 3D print a launch charge. The originals are paper, and pretty thin paper at that. You want something that won't melt, and stick to the tube when you fire it.
No machining to finish the tube on GB. You have to drill a hole, and you (may) have to make the notch to index the projectile. The inert/demil RPG2 you buy to get all of the other bits you need will be your template for size and placement of everything. You will have to weld some bits off of your old tube onto your new tube. |
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I just got a de-milled RPG-2 myself, and would love to do something similar. This thread easily has the best RPG-2 information on the internet. Does anyone have dimensions of the PG-2 propellant tube to copy? I'm thinking a mock one could be 3D printed, or CnC'ed. I'm gonna pay the $200 for form-1 it, and I want to get as close to real as I can, without it also be a DD. (so I guess no real propellant or explosives) To fix the tube, it looks like you can buy a ready-made one on GunBroker - https://www.gunbroker.com/item/840574787 But it seems like you'll need to do some machining to finish it off. There doesn't seem to be any rocket notch, or trigger holes in it. View Quote |
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There was a guy at knob creek in October who had the charges figured out, and had recreated the proper container for them. I’ll have to see if I can find his contact info. He had new tubes as well.
ETA: the guy on gunbroker you guys linked earlier is that guy I’m pretty sure. |
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Quoted: If you look at his description box, it says the tube is now indexed for the projectile notch. That said, he also sells the charge kits, I think he said all you need is 209 primers, powder and a drill bit. View Quote |
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Quoted:
I wouldn't 3D print a launch charge. The originals are paper, and pretty thin paper at that. You want something that won't melt, and stick to the tube when you fire it. No machining to finish the tube on GB. You have to drill a hole, and you (may) have to make the notch to index the projectile. The inert/demil RPG2 you buy to get all of the other bits you need will be your template for size and placement of everything. You will have to weld some bits off of your old tube onto your new tube. View Quote |
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