SpudFiles

While such a research organization probably has access to better resources than most punkin chunkin teams, I'll take your word that it can be done.

So assuming you've got a captive piston, couldn't you make something like a springloaded "pumpkin cushion" to act as a shock absorber and allow greater acceleration of the sabot at launch? The spring would probably also extend when the sabot is caught, returning a good portion of its energy to the pumpkin...

saefroch wrote:So assuming you've got a captive piston, couldn't you make something like a springloaded "pumpkin cushion" to act as a shock absorber and allow greater acceleration of the sabot at launch? The spring would probably also extend when the sabot is caught, returning a good portion of its energy to the pumpkin...

That would definitely make sense, here's how I would make it...

So you're increasing the area of the barrel (and thus force on the sabot) by a factor of what now?

Dang, with a design like that, spudfiles should enter a build next year.

saefroch wrote:Dang, with a design like that, spudfiles should enter a build next year.

We would totally win

My piston (sabot) was not captive, but the results are impressive. AA batteries launched from a 1/2 inch barrel on a 1 inch valve vs a sabot and 2.5 inch barrel on a two inch valve show the potential.

This thread has info and more photos of my sabot AA battery shot on page 2.
http://www.spudfiles.com/forums/flat-aa ... rt,15.html

1/2 inch barrel at 100 PSI

vs about 65 PSI and the 2.5 inch barrel.

Gun Freak wrote:We would totally win

Totally

Tech wrote:My piston (sabot) was not captive, but the results are impressive. AA batteries launched from a 1/2 inch barrel on a 1 inch valve vs a sabot and 2.5 inch barrel on a two inch valve show the potential.

While it can be a pain to put together, the advantages of using a sabot can be condensed into the following:

- low sectional density in the barrel, meaning that much higher acceleration is possible than a full bore projectile

- high sectional density outside the barrel (for the projectile), meaning lower deceleration in flight and higher penetration

To give an illustration of the extent of the difference, here's some data for the British 17 pounder gun (with penetration in millimetres at various ranges):

Ammunition Weight Muzzle Velocity 500 yards 1000 yards 2000 yards

APCBC 17lb 2900fps 140 131 111

APDS 7.625lb 3950fps 209 192 161

As you can see, the discarding sabot projectile weight is significantly lower, however the velocity at the muzzle is over 1000 fps higher and there is a corresponding increase in penetration, to the extent that at 2000 yards it penetrates better than the full bore at 500 yards. The rounds being compared are the bottom two in this diagram: