How to machine the end of a 1.5" dia rod perfectly round?

[toysareforboys]

This looks pretty cool. Can you tell me more about the projectiles and intended use? Do you recover the blue projectile? Why round instead of stock? Do you launch other objects in front of it? What other kinds of load does this use. (aside from grenades!)
Robert

The only range close to me is an indoor range (50 yards) and that's the only place I can use my new 40mm launcher (unless I find a friend that lives on a farm out of town). They for sure don't allow explosive or incendiary ammo and don't allow use of projectiles that bounce off the backstop. I tried some real commercial police rubber rounds (called strikers iirc) but they bounced off the backstop all the way back to our feet so those aren't allowed. I would like to test a solid Delrin round and see how much it bounces back. These rounds will be just for range use.

All of my home made rounds I used with my 37mm launcher (which you can launch "anywhere") were using Goex Fg black powder which has way too much smoke and fire to use indoors, so I was going to try Triple Seven or smokeless Trail Boss for the indoor rounds with Delrin projectiles.

At the end of the day when they sweep out the range they put all my projectiles in my locker for me so I can reuse them.

I wanted to try round so it looked more like commercially available rounds, and that it'd probably slide into the launcher slightly easier and possibly have better aerodynamics.

In Canada, having your firearm license allows you to manufacture some explosives (binary like Tannerite), and you can also get your pyrotechnics license and display fireworks class 2 license if you want to cook up even more special rounds. When I asked the local authorities if I could launch such items out of my launcher they said "don't do it" but couldn't give any reasons or laws against it. I looked through all the regulations and the only thing I can see is that the round can't detonate on impact, but time delay (fuse) is fine. I'm sure it'd be super unwise to launch a Tannerite round out of your launcher (even if it didn't blow up in the chamber it'd probably blow up on impact if it hit something before the fuse lit it off, which would make it illegal, even if unintentional). Flash powder would be way more stable and wouldn't detonate on impact, but if it ever lit off in the barrel you could kiss your launcher goodbye (at the minimum).

Other rounds you can shoot are smoke "grenades":

And there are chalk marker rounds, parachute flares (you shoot them straight up), some people shoot golf balls but the ones I tried were a VERY tight fit in the barrel (pretty much had to use a press to force it in), or D batteries

-Jamie M.

 

[rwm]

Very interesting. I would think the Parachute flares could be a lot of fun. Delrin projectiles could get expensive if not reusable.
Robert

 

[toysareforboys]

Very interesting. I would think the Parachute flares could be a lot of fun. Delrin projectiles could get expensive if not reusable.
Robert

I bought the Delrin super cheap from China, it's probably not real Delrin but feels like real Delrin when machining. I looked on alibaba and found a supplier, any colour, any diameter, any length, and the prices were half the price per foot of the local shop. And get this... I thought the crazy price was per foot (which was half of the per foot cost of the local shop), but it was PER METER!!! That makes it one sixth the cost of the local shop Takes a month to arrive but as long as I plan ahead it's not an issue. I ordered way way too much because I thought it was per foot, so I got triple what I thought I was getting, so I'm well stocked up for now lol.

The machining and mess could get real annoying, so hopefully they will be reusable at least a few times! I'd imagine the tail will get worn out and not seal tight anymore, then I could make a cup with a slightly smaller chamber and re-machine the tail a bit smaller might work to extend their use.

The project for today is done! Portable 50 ton hydraulic press with adjustable height:

It should save me a ton of time and effort instead of doing it on my arbor press as I use it to press in primers and the projectile.

If I exceed the strength of the 1/2" threaded bars I can upgrade them to 1" but I only have good drills up to 1/2" and home depot only had two 1" threaded rods in stock and I didn't feel like driving around to a bunch more then buying a nice $$ 1" drill bit (or trying with my china 1" bit).

-Jamie M.

 

[toysareforboys]

OMG! Yes yes YES! The press works sooooo good! Pretty quick to change the height as well! Can't believe I was putting all my weight on my arbor press all this time, and having it give up with the projectile tail half way in usually, then have to resort to the sledge hammer

It pressed my projectile tail into the case/hull without breaking a sweat, didn't even notice any difference in pumping handle pressure! It was 0.014in oversized (hole was 0.884, tail was 0.898).

After pressing it together I filled it up with Trail Boss smokeless powder (through the primer hole) and it held exactly 7 grains! Nice. I'll start with that as my first load, and if everything goes smooth and I think I need more power I'll either trim the tail a hair shorter to fit more powder or drill out a bit of the center of the tail.

Going to be super sketchy pressing the primer in as the last step!! I'll have to figure out a way to rig up a rope to the pump handle so I can pump it from outside my shed incase it goes boom

-Jamie M.

 

[Tozguy]

Why not load the conventional way ie. press in primer, add a measure of powder then press in projectile?
It is not usually a problem if the powder gets slightly compressed when seating the bullet.

Whichever method you use to press in primers and bullets, there MUST be a provision for venting pressure away from the operator if there is a BOOM.

Pressing a primer into an empty case allows venting through the case but there must be a vented bushing between the press and the top of the case that directs flow away from the operator. I would continue to use the arbor press for installing primers.

Likewise when pressing in the bullet, there must be a vented bushing between the bottom of the case and the press. The vent must be large enough to pass the primer and direct flow away from the operator.

 

[toysareforboys]

Why not load the conventional way ie. press in primer, add a measure of powder then press in projectile?

If I put the primer (and powder) in then try and press the projectile in the air pressure builds up huge in the chamber and either pops the primer out or prevents me from fully seating the projectile I'm pressing the projectile in 1 inch, that's compressing the chamber from 0.666cu in to only 0.05cu in! I'm not sure how to calculate what the air pressure inside would be at the end but I assume it must be pretty high. I also know when you're compressing air that much it gets very hot, if I compress it too quickly it might get hot enough to ignite the powder = boom.

If I'm pressing the primer in as the last step I can't figure out a way to use a pressure release bushing. With the press holding both the projectile in as well as the primer, wouldn't the actual case/hull explode?

-Jamie M.

 

[RobertB]

With the press holding both the projectile in as well as the primer, wouldn't the actual case/hull explode?

-Jamie M.

Make a jig to hold the case by the rim when pressing in the primer.

 

[Tozguy]

As Robert just mentioned or maybe shorten the stem on the bullet? The compression ratio of .666 to .05 c.i. seems extreme to me.

 

[Eddyde]

The project for today is done! Portable 50 ton hydraulic press with adjustable height:

It should save me a ton of time and effort instead of doing it on my arbor press as I use it to press in primers and the projectile.

If I exceed the strength of the 1/2" threaded bars I can upgrade them to 1" but I only have good drills up to 1/2" and home depot only had two 1" threaded rods in stock and I didn't feel like driving around to a bunch more then buying a nice $$ 1" drill bit (or trying with my china 1" bit).

-Jamie M.

Um, be careful, that ½" rod isn't nearly strong enough to handle 50 tons. The grade 2 hardware/big box store rod is only rated at around 1,100 pounds. Even if you calculate the tensile strength of mild steel at around 50,000 psi, the root diameter of the rod is only about .405 so about 6,400 pounds, still far short short of 100,000 pounds.

 

[toysareforboys]

Make a jig to hold the case by the rim when pressing in the primer.

The rim is pretty weak (2mm thick aluminum) but it should be strong enough to just press in the primer. I don't have a milling machine but I think I can build a thick tube that the case will slide into with enough room for the projectile to come out and the back cut out to allow the flame/pressure to go away from me. Thanks for the ideas

As Robert just mentioned or maybe shorten the stem on the bullet? The compression ratio of .666 to .05 c.i. seems extreme to me.

I'm used to having to keep black powder compressed, with smokeless I guess I can shorten the stem some then use some wadding to keep the powder in front of the primer.

Um, be careful, that ½" rod isn't nearly strong enough to handle 50 tons. The grade 2 hardware/big box store rod is only rated at around 1,100 pounds. Even if you calculate the tensile strength of mild steel at around 50,000 psi, the root diameter of the rod is only about .405 so about 6,400 pounds, still far short short of 100,000 pounds.

Thanks for the great info. Princess Auto (local shop) sells grade 5 and grade 8 threaded rod and nuts but they are renovating or something and had zero in stock If I used four 1" threaded bars of grade 8 what could that take approximately?

Thanks again everyone, tons of great info

-Jamie M.