I'm working on designing a cheap, easy to manufacture, readily available dummy/inert projectile to be used in place of surplus practice rifle grenades. Anyone that's looked for them knows they aren't cheap, and that they only get harder and harder to find, not to mention projectile-less cartridges to fire them.
I'm hoping there are a couple people here with some knowledge on these. Unfortunately, I don't have one in my hands to get any data off of. Although I may have to buy one if necessary.

On videos of these, it seems that the grenade's inner tube is simply closed off at the opposing end. It also would appear that this end is able to sit flat on the muzzle of the M7 when fully seated. Is this true? Or is there some kind of porting/pressure relief that isn't obvious? I don't believe any kind of porting would exist, as that would open the potential to spraying the operator with hot gases.

Also, I need an approximate weight. What little info I can find seems to mean that the M11 grenade weighs approximately 1.3 pounds.


If you're interested in possibly making one yourself (or if you're just curious), keep reading. Part numbers will be listed.

The goal is for something that's inexpensive and fun to send downrange, not necessarily visually or historically correct. Although there would be nothing stopping a person from welding on a dummy grenade to the end of this to make it look more legitimate, along with a coat of OD green.

Originally I was hoping that a simple piece of black or galvanized pipe with an end cap would do the job. Unfortunately, it would appear that common available pipe sizes possess an inner diameter that is far too large.

My M7 launcher has a.... barrel? Spigot? Whatever it's called, with a diameter of .862". The closer the better of course. On McMaster Carr, I was able to find some round tube stock with an inner diameter of .870". Close enough. Now, this round stock has no threads or otherwise, and the open end still needs to be closed off. The easiest, and cheapest, solution seems to be a "Compact Extreme-Pressure Steel Pipe Fitting", which seems to be a glorified bolt with an o-ring on the other end. This plug has threads which are 7/8-14. 7/8 converted to decimal is .875. That means I should be able to tap threads into the opposite end of the pipe without any extra machining. The threads may be a tad tighter than normal, but I don't see this as an issue. A smear of red loctite should also keep it from coming loose, although I'm not sure that it's entirely necessary.

I do intend to make one, completely reversible, modification to the launcher itself. Near the end of the launcher exists a spring, intended to increase friction and hold the grenade on the launcher in a given position. There are position grooves cut into it that are intended to allow the user to set the ordnance's range, when the weapon is held at a particular angle, either 30 or 45 degrees. Since the tube stock will not be as close a fit as the originals, I intend to replace this with a rubber o ring, which has a larger diameter. This should also make for a better seal.

One thing that is tripping me up, is the unknown internal volume of the originals. If it's intended to sit flat, then a 4" section is all that is required, as the launcher barrel itself is only 4". A one foot section then yields three bodies. Any longer than that, and you only get two bodies per 1 foot length, however. The internal volume isn't exactly a trivial dimension, either. It directly determines the peak system pressure, as well as the maximum range of the projectile.

Now is a good time to mention my choice of using that plug vs a standard 7/8 bolt. The plug has a space on the inside of it milled out, which will increase the inside volume, especially if the projectile is sat flush against the launcher's muzzle. I'm not sure how much of an effect this extra volume would have, but I figure it couldn't hurt. And for the price, it seems worth it to me. Plus, it's also better suited to high pressure vs a standard fastener, given that it will be the part being smacked the hardest by hot gases.


One other thing. The ammunition. There are two different kinds of cartridges that could be used to fire these, or dummy rifle grenades. Blanks, and rifle grenade cartridges. In the case of the M1 Garand, I think these are designated "M3" but I don't know for sure. These two cartridges are very different, and will severely change the performance. A typical blank is really only intended to make noise, not much else. Although totally usable, you won't get much distance. The real cartridges made for this task, however, have a ton more powder inside them and will lob these much further with much more recoil. Both of these seem to be even more difficult to source than the rifle grenades themselves. So, I intend to make my own as I'm already equipped to reload anyway. That's about all I have to say about that.

I'd love to hear some thoughts and opinions.


Everything from McMaster.

Tap: 26035A241
Pipe: 89955K639
End fitting: 50925K419
O Rings: 9452K187

I actually made a grenade launcher for my M1 back in the 80's.  The grenades however were 35mm film cans filled with black powder. Basically a golf ball launcher.  No need to overthink it.

The first one was made from basic PVC parts and used blanks.  It quickly failed because to fill the gap between the smaller and larger PVC pipes I used the rubber gasket made for that purpose. The PVC just slipped over the blank adapter and was made to look like the rifle grenade itself.

The second version used a piece of leather to seal between the two sized pipes.

The first version got about 60m-70m of range till the rubber bit failed and the range dropped with each subsequent shot.

The second version got about 300m of range and worked very well.

Most folks I know who have done this currently used 3D printed rifle grenades and blanks.

Here is the only image I have of it. You can see it on the end of my M1 Garand.  I do still have the actual item around here somewhere.

 

I'm inching closer to do doing the same thing. My plan was to buy an m7 launcher and one m11a3 grenade then make some of my own grenades out of tubing the same shape and weight as the practice grenades.


I really want to find somewhere selling cheap m1 projector adapters. I asked on here once and someone posted a budk link where they were selling them for $19.99 I think. Guess who didn't buy any.


If a guy could find some projector adapters I think you could tie the adapter to the ground with 30' or so of string and when it's launched the grenade would come loose and continue on but your projector would be on a string 30' foot out in front of you.

Inert little pineapple grenades aren't expensive. $10-15. I also have wondered if you could get away with not crimping the blank ends but sealing them with wax or paper. This would mean you could reuse your blank brass.


If you can reuse the brass and can get some "practice" grenades of realistic weight and size you could launch your grenades pretty cheaply. I think it'd be a ton of fun.


But paying $100 for a launcher and $100 a piece for grenades that can break and paying $2.50 a a shot for blanks is more hassle than it's worth to me. Loading my own blanks, reusing brass, and being able to make several 'nades myself would make all the difference.

30.06 blanks are typically $0.50.  The older M1909 blanks are not crimped and might be reusable.

If you look around, you can probably find the M9 3d printed for launcher use. Ebay had a few for $20 but not able to be put on a launcher.  Some company in the UK makes them out of wood and rubber for launcher use.

Would using a wax bullet let you get away with not crimping home loaded blanks? Similarly, a card stock/wooden plug might also work.

M1909 blanks use a lacquered paper seal on top of the blank to seal it.  You could go that route.  If you are doing this for your own fun, then wax could be used as well.

A wooden plug would likely damage whatever item you are using as the rifle grenade or the launcher itself.

M1909 blank Sorry about the size.  I stole the image from the web.

I’d be hesitant to use the wooden plug, my fear is you’d get a chunk bounced back at you. After all you’re jetting the cartridge contents into a long cupped bore obstruction with the only opening pointing back at you.  

Interesting, google shows a guys selling rubber dummies to be used WITH BLANK CARTRIDGES NOT RIFLE GRENADE CARTRIDGES.

I think they’d be easy to make out of Delrin on a lathe with a tube shaft.

Hmm I may have fun project and may have to pick up a launcher for the garand.

Oh an as far as I could tell the M3 cartridges had a 5 grain black powder ignition charge and a un named IMR progressive burn powder iirc hat half a standard ball cartridge pressure.   Around 25,000 cup.iirc. Source: Bill Ricca (RIP)

Post war the use black powder was phased out.  

The M6 cartridge for the carbines used a 60mm mortar ignition powder as its powder.

So, slight update. The round tube and orings I bought are an absolutely perfect fit. Like, you could not get any better of a fit. However, that's about where the good news ends. The threaded fittings I bought, despite being labeled 7/8ths, are absolutely not 7/8ths. I browsed two hardware stores, in both general bolts/nuts, and in plumbing, and dammit if nothing there is truly what it claims to be. Pipe sizes, thread sizes, pipe thread sizes, etc absolutely do not agree with each other. A very frustrating affair. However, armed with calibers, I did find a possible solution.

It turns out that a certain size of copper pipe has an internal diameter which is only very slightly bigger than the pipe I bought. And, of course, copper pipes have copper end caps that can be soldered on quickly and easily. All for cheap. I think it was 3/4 pipe, but I'm not for certain.

However, copper is pretty soft. I'm unsure if the copper would withstand the pressures involved over time, much less the fall back to earth and not get bent up.

I've decided just to have the plugs I bought welded into the pipe sections and use those that way.

Perhaps I'll get the copper pipe too and try it anyway, but I'm not decided.

The copper does have some advantages, however. Being a slightly larger inner diameter, although it will still seal, it will require less pressure build up to move off the muzzle. It's also much lighter weight, again requiring less pressure, as well as perhaps being able to send it farther. I'd need to have both products finished and weighed to see for sure.

Hi guys I've been looking around for some practice grenades for sale. I want to get a real m11a3 (which is the inert practice version of the m9 heat) and attempt to build my look/launch alikes. This will require launching a real m11 ( I'm going to call the m11a3 practice grenade the m11 for brevity, there is another separate m11 grenade) several times at various distances and then creating something of equivalent length diameter and weight to the m11 and getting it to launch like a "real" m11.


I've found some m11 grenades for sale here for $80
https://www.libertytreecollectors.com/productcart/pc/viewPrd.asp?idproduct=903


There is a guy on ebay selling 3d printed m9 heat replicas for $20 here
https://www.ebay.com/itm/314267409111
The eBay guy says his 3d printed parts will interchange with practice grenades. That might be a easy way to get the tail fins. He says he sells just parts also. ETA: I'm wrong on this I don't know what I'm talking about. I THOUGHT I found a resource like I'm describing but now I can't find it. doesn't seem like eBay guy is any use to us.

Id like to be able to fire the m11's and the m1/m1a1/m1a2 grenade projector adapters. The adapter is the piece that allows you to fire pineapple hand grenades from a rifle.


In an ideal world I'd like to have one adapter and several hand grenades BUT the launcher seems to toss the adapter a pretty good ways with the grenade. Videos online show them separating midway through flight. Maybe if the adapter was tied to a stake in the ground with 30-40' of rope it could be reeled in and retrieved/found easily.

Ive found some adapters for sale here for $65
https://www.indianaarmysurplusstore.com/product/m1a2-grenade-launcher-adapter/

and here for $20
https://www.herooutdoors.com/rifle-grenade-adapter-m1a2-model-369/

I'm not sure if the $20 ones are real surplus adapters or not. Does anyone have any experience buying from hero outdoors?

The way my range is at the base of a large steep hill, I think I could set up grenades targets out there. The hill would make impacts easy to see and grenades easy to find.


Im going to purchase one of the m11's from the above linked site. I'll get to mocking up some easily fabbed m11 look alikes once is comes in.



This site has info on blanks
http://www.uscarbinecal30.com/Ricca_M3_Cartridge_page.html