What is the best way to make air cannon/bazooka ammo out of spray foam?

I’m sure yo havea reason to use the spray foam. I use potatoes. the front edge of the tube is tapered so it cut the potato as i push it in.

Since you want to use foam, try lubing the inside of another tube with Vaseline. Then squirt a setting foam like Great Stuff inside. When it dries, you should be able to push out the cylinder of foam and cut it to the lengths you want.

Or yo can spray GreatStuff into cardboard tubes and cut those.

By the way one winter I filled juice cans with water, let them freeze and used the ice as ammo. It is spectacular when it hits a rock.

@worriedguy has the right idea. I’m not sure if vaseline would work (it reacts badly with some things, latex especially, but it might react weird with the urethane that’s spray foam).

Check out a good art store and see if they have mold release spray, coat the inside of your molds with that before putting the spray foam into it, and it’ll be sure to slip right out.

@grumpyfish Mold release, huh.. Never tried it. I’m kind of lazy (and cheap) and would not bother to go to a store to buy something like that. I wonder if WD-40 would work.

Salt potatoes and/or tomatoes work great.

I hope @XOIIO isn’t planning to shot it at people.

@worriedguy LOL I am using great stuff! I spray out a bunch on something flat and then rip chunks off, like I said. I stuff it into the ¾ inch tube and fire it. I wasn’t Wink Wink planing to fire it at people. I just need a way to keep the back end of the “pellets” to stay together and not open during flight, because then they go only a few feet.

@worriedguy Meh, if you’re buying great stuff to make foamie pellets…

I prefer potatoes, they work really well.

The other option would be to get some actual AB Urethane foams, make a mold, and actually cast the projectiles. Something like the soft polyurethane foam here: http://www.fxsupply.com/poly/poly.html

¾” tube?!? I use 2” ID with a 4” inch combustion chamber. Gas grill sparker is the igniter.
With carb cleaner as fuel I’m pretty sure it sends the potato into orbit.

I use a bike pump to pressurize this.

I think pre-making ammo is going to be your best bet, if you want to keep doing it the way you’ve been doing it (which it sounds like you do), get some 3M Foam Fast 74 (NOT Super77—that’ll eat the foam) and rip off two pieces, then glue them together back to back. You’ll want to wear gloves, as you’ll rapidly be covered in the stuff (and it doesn’t wash off easily).

Oh, one more thing… PVC isn’t rated for pressure. If you’re pressurizing it above… maybe 30psi I’d be really worried that it might explode.

ABS pipe is a much better choice for this.

@grumpyfish I am only taking it to 100 PSI, and the PVC/ ABS pipe I have can easily handle that.

The ABS pipe is the chamber, and the PVC is the barrel.

@XOIIO Good that the chamber is ABS. Your PVC pipe says that it’s rated to more than 100psi?

Apparently the ABS pipe is rated to 300PSI and the PVC 500PSI.