Author Topic: The effect of a powder chamber on VELOCITY  (Read 2727 times)

0 Members and 1 Guest are viewing this topic.

Offline Cat Whisperer

  • Trade Count: (2)
  • Senior Member
  • *****
  • Posts: 7493
  • Gender: Male
  • Pulaski Coehorn Works
The effect of a powder chamber on VELOCITY
« on: May 22, 2005, 03:27:53 AM »
If you read through the article on handgonne's:

http://www.musketeer.ch/blackpowder/handgonne.html

you will find, right after the use of the ballistic pendulum, a few paragraphs on the effect of increasing velocity that the addition of a powder chamber makes.

I'd always figured that it was only to increase the strength around the powder - added benefits of greater velocity!
Tim K                 www.GBOCANNONS.COM
Cat Whisperer
Chief of Smoke, Pulaski Coehorn Works & Winery
U.S.Army Retired
N 37.05224  W 80.78133 (front door +/- 15 feet)

Offline Will Bison

  • Trade Count: (0)
  • A Real Regular
  • ****
  • Posts: 591
The effect of a powder chamber on VELOCITY
« Reply #1 on: May 22, 2005, 06:57:06 AM »
That was interesting reading. It's hard to argue with empirical testing. If I were to hazard a casual guess, I would have gone with the full bore tube as producing a higher velocity. My rationale would have been that the expanding gas has a greater distance to act upon the projectile. Live and learn.

Also of interest that someone actually still uses a ballistic pendulum. The last one I saw was the one I built in 1964.

Thanks for the interesting link Tim.

Offline jeeper1

  • Trade Count: (0)
  • A Real Regular
  • ****
  • Posts: 662
  • Gender: Male
The effect of a powder chamber on VELOCITY
« Reply #2 on: May 22, 2005, 11:11:53 AM »
I have been aware of how much a powder chamber helps for quite some time. Look at the distance differences between a 37mm launcher and a 40mm launcher. The powder chamber is worth 4 times the distance.
I may not be completely sane, but at least I don't think I have the power to influence the weather.

Offline Cat Whisperer

  • Trade Count: (2)
  • Senior Member
  • *****
  • Posts: 7493
  • Gender: Male
  • Pulaski Coehorn Works
The effect of a powder chamber on VELOCITY
« Reply #3 on: May 22, 2005, 12:01:31 PM »
Quote from: jeeper1
I have been aware of how much a powder chamber helps for quite some time. Look at the distance differences between a 37mm launcher and a 40mm launcher. The powder chamber is worth 4 times the distance.


Interesting!  (and here I'll show my ignorance, which is which?)  I assume you're talking M79/M203 vs civilian version & the powder chamber would be in the shell casing.
Tim K                 www.GBOCANNONS.COM
Cat Whisperer
Chief of Smoke, Pulaski Coehorn Works & Winery
U.S.Army Retired
N 37.05224  W 80.78133 (front door +/- 15 feet)

Offline jeeper1

  • Trade Count: (0)
  • A Real Regular
  • ****
  • Posts: 662
  • Gender: Male
The effect of a powder chamber on VELOCITY
« Reply #4 on: May 22, 2005, 02:48:48 PM »
Yep.
 The 40mm is mostly military usage and the 37mm is mostly civilian usage.
The 37mm cases have 3 basic designs for the inside of the bases from flat to concave.
The 40mm's have two common designs.
One is a spherical hollow  with several vent holes at an angle.
The other uses a 38 blank cartridge with several variations of vent hole layouts. Both are high pressure chambers which vent the burning gasses to a low pressure chamber to push the projectile out the barrel.
The 37mm will launch a projectile little more than 100 yds. The 40mm will easily go more than 400 yds with the same weight projectile.
I may not be completely sane, but at least I don't think I have the power to influence the weather.

Offline Cat Whisperer

  • Trade Count: (2)
  • Senior Member
  • *****
  • Posts: 7493
  • Gender: Male
  • Pulaski Coehorn Works
The effect of a powder chamber on VELOCITY
« Reply #5 on: May 22, 2005, 03:08:44 PM »
jeeper1 -

Thanks, that adds a another bit to our storehouse of knowledge.
Tim K                 www.GBOCANNONS.COM
Cat Whisperer
Chief of Smoke, Pulaski Coehorn Works & Winery
U.S.Army Retired
N 37.05224  W 80.78133 (front door +/- 15 feet)

Offline jeeper1

  • Trade Count: (0)
  • A Real Regular
  • ****
  • Posts: 662
  • Gender: Male
The effect of a powder chamber on VELOCITY
« Reply #6 on: May 23, 2005, 02:46:18 AM »
If you want pictures that show the differences then email me at  rlachance@earthlink.net  since some of the pictures are copyrighted.
I may not be completely sane, but at least I don't think I have the power to influence the weather.

Offline Cat Whisperer

  • Trade Count: (2)
  • Senior Member
  • *****
  • Posts: 7493
  • Gender: Male
  • Pulaski Coehorn Works
The effect of a powder chamber on VELOCITY
« Reply #7 on: May 23, 2005, 02:21:58 PM »
Quote from: jeeper1
If you want pictures that show the differences then email me at  rlachance@earthlink.net  since some of the pictures are copyrighted.


Thanks for the offer!  I do recall looking into a few of the empties (back in 1972 or so) and seeing the raised area in the middle of the case - didn't attach it to the idea of a powder chamber until now.
Tim K                 www.GBOCANNONS.COM
Cat Whisperer
Chief of Smoke, Pulaski Coehorn Works & Winery
U.S.Army Retired
N 37.05224  W 80.78133 (front door +/- 15 feet)