Author Topic: The effect of a powder chamber on VELOCITY (Read 2722 times)

Cat Whisperer · « **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!

Will Bison · « **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.

jeeper1 · « **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.

Cat Whisperer · « **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.

jeeper1 · « **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.

Cat Whisperer · « **Reply #5 on:** May 22, 2005, 03:08:44 PM »

jeeper1 -

Thanks, that adds a another bit to our storehouse of knowledge.

jeeper1 · « **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.

Cat Whisperer · « **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.