Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 82 users online :: 7 registered, 0 hidden and 75 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

A Marble and a Cork

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
Sponsored 
  • Author
    Message

A Marble and a Cork

Unread postAuthor: boyntonstu » Tue Apr 20, 2010 7:50 am

Image

I countersunk a dimple on the face of the cork and hot glued the marble into it.

These are rough prototypes before cleanup.

This design may offer 'cartridge' loading.

The natural cork round weighs 112 grains.

The artificial (rubber) cork round weighs 148 grains.

What do you think about its ballistic coefficient compared to a sphere?
  • 0

User avatar
boyntonstu
Brigadier General
Brigadier General
 
Posts: 1039
Joined: Sun Jun 28, 2009 8:59 am
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Tue Apr 20, 2010 8:15 am

Poor man's Brenneke slug:D
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Re: A Marble and a Cork

Unread postAuthor: dewey-1 » Tue Apr 20, 2010 2:20 pm

boyntonstu wrote:What do you think about its ballistic coefficient compared to a sphere?


It would be much better if the marble was recessed to it's half diameter point. Eliminate the flat surface of cork which defeats the purpose somewhat.
  • 0

User avatar
dewey-1
Major General
Major General
 
Posts: 1298
Joined: Wed Mar 28, 2007 10:24 am
Location: NE Wisconsin USA
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Tue Apr 20, 2010 2:25 pm

Even better, why not drive a short fat bolt into the cork?
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: Brian the brain » Tue Apr 20, 2010 2:36 pm

Replace the cork by a small section of pipe and be done ..
  • 0

Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
User avatar
Brian the brain
Moderator
Moderator
 
Posts: 3494
Joined: Mon Dec 05, 2005 2:06 am
Location: Holland
Country: Netherlands (nl)
Reputation: 29

Unread postAuthor: skyjive » Tue Apr 20, 2010 4:58 pm

I agree that putting the marble farther in so that the center of the marble is level with the front of the cork would reduce turbulence and thus drag in front. Also, the flat back of the cork will give you additional drag, you could file it down to a tapering curve for better performance.

On the other hand, being really careful kinda defeats the purpose of easy cheap ammo. Your choice.
  • 0

User avatar
skyjive
Master Sergeant
Master Sergeant
 
Posts: 163
Joined: Mon May 26, 2008 3:52 pm
Reputation: 0

Unread postAuthor: Marffy » Tue Apr 20, 2010 5:38 pm

I would put the marbles farther in if you wanna use corks. if it were me i would use pvc instead of corks because then you could sink the marble in to your desired spot and have a hollow back end for stabilization. For both ammos i would only expect exceptional accuracy to about 30 feet with a proper metal barrel.
  • 0

"Hard work has a future pay-off. Laziness pays off now."
User avatar
Marffy
1st Lieutenant
1st Lieutenant
 
Posts: 258
Joined: Mon Jul 27, 2009 2:03 pm
Location: earth
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: boyntonstu » Tue Apr 20, 2010 6:34 pm

Brian the brain wrote:Replace the cork by a small section of pipe and be done ..


Like this? Or, should I shorten it?

Image

Note that the metal primer holder ring has been removed.

The plastic "pipe" that remains is a perfect fit for copper type L 3/4"!

I couldn't get the marble to where I wanted it, but you should get the idea.

BTW have you seen these shots with a flat front and rear projectiles?

Pretty darn good. 905 grains!

http://www.glbarnes.com/field_justice.html
  • 0

User avatar
boyntonstu
Brigadier General
Brigadier General
 
Posts: 1039
Joined: Sun Jun 28, 2009 8:59 am
Reputation: 0

Unread postAuthor: Marffy » Tue Apr 20, 2010 9:26 pm

Thats a good idea, to bad i don't have a shotgun. :evil:
  • 0

"Hard work has a future pay-off. Laziness pays off now."
User avatar
Marffy
1st Lieutenant
1st Lieutenant
 
Posts: 258
Joined: Mon Jul 27, 2009 2:03 pm
Location: earth
Reputation: 0

Unread postAuthor: Hawkeye » Tue Apr 20, 2010 9:28 pm

Do these all weigh exactly the same...in grains?
  • 0


Hawkeye
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 462
Joined: Sun Jan 21, 2007 7:12 pm
Reputation: 0

Unread postAuthor: ONEWING » Tue Apr 20, 2010 9:41 pm

I really dont see the appeal of using marbles inconsistant, light and expensive, as Jack suggested previously in this thread a bolt and nut would be a far better option. I posted chronograph results for shotshells at low pressure here http://www.spudfiles.com/forums/brass-h ... 20581.html , if you want a blunt projectile use a bolt in place of the nail. You already have a perfectly centred hole to use in the primer socket, so make use of it!
  • 0


ONEWING
Specialist
Specialist
 
Posts: 47
Joined: Sun Mar 07, 2010 2:11 pm
Reputation: 0

Unread postAuthor: boyntonstu » Tue Apr 20, 2010 9:46 pm

Using the primer hole up front, you add dead space inside the empty hull.

You push a marble into the hull and place hot glue on the crimp.

When you turn it over, the marble falls and it centers itself in the crimp and is glued in place.

Prochrono results today:

10d nail 184 gr 879 fps 600 psi
192 701
180 658
166 664
182 714

Marble 156 854
162 614
160 766

I believe that my manual operation of the 1/2' BV pilot is causing the inconsistencies.

The potential is there as seen in the higher numbers.

I need a spring and a trigger.
  • 0

User avatar
boyntonstu
Brigadier General
Brigadier General
 
Posts: 1039
Joined: Sun Jun 28, 2009 8:59 am
Reputation: 0

Return to Construction Materials/Ammo Discussion

Who is online

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'