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Some info on velocities required for certain fpe

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Gippeto » Tue Jul 10, 2012 4:23 pm

79...sort of. :lol:

Not much "QB" left in my QB. :wink:

Old pic before that last round of changes...

Image
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Unread postAuthor: beastmode986 » Tue Jul 10, 2012 6:00 pm

THAT IS FREAKING AWSOME!!!
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 11, 2012 8:24 am

beastmode986 wrote:THAT IS FREAKING CHINESE!!!


Yep. Still looks good though, eh ;)
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Unread postAuthor: Gippeto » Wed Jul 11, 2012 9:30 am

jackssmirkingrevenge wrote:
beastmode986 wrote:THAT IS FREAKING CHINESE!!!


Yep. Still looks good though, eh ;)


:lol:
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Unread postAuthor: POLAND_SPUD » Wed Jul 11, 2012 3:25 pm

they are quite cheap too...
which model do you recoment gippeto ? I checked pricing of co2 cartridges and surprisingly it's cheaper to use 12g than 88g cartridges
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Unread postAuthor: Gippeto » Wed Jul 11, 2012 4:14 pm

Basically the same rifle....whichever floats yer boat. 78 and 78D have slightly greater potential for "max" power due to tube/valve volume. :wink:

Like the 78 deluxe the most...have one of those as well as a 78 and the 79. Nicer overall, heavier barrel and no plastic parts. Plenty of info on the net for tuning/tweaking. Will suggest a complete tear down, clean, polish/lube and build up as your first act of ownership.

It's not a Daystate...you really do get what you pay for, and in this case it's a turd that needs polishing. :lol:
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Unread postAuthor: D_Hall » Wed Jul 11, 2012 11:12 pm

jackssmirkingrevenge wrote:Also note that for a given energy, a smaller faster projectile will generally penetrate deeper than a larger slower one, even though it will make a smaller hole.

don't want to get into a big debate so I'll just say this: Not necessarily. There are many, many variables at play. Sometimes heavy, slower projectiles will penetrate deeper. It all depends....
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 11, 2012 11:58 pm

D_Hall wrote:don't want to get into a big debate so I'll just say this: Not necessarily. There are many, many variables at play. Sometimes heavy, slower projectiles will penetrate deeper. It all depends....


Hence the "generally" ;)

There are a host of other variables of course.

Some comments I had made on here a few years ago:

JSR in a debate about energy and momentum wrote:Penetration is a function of many things. If there's one area of research where the search for better penetration is most intense, it's in the field of anti-tank weapons, namely those that function mechanically as opposed to relying on explosives.

Let's take an advanced projectile as an example, here's a Soviet 125mm APFSDS round:

Image

In order to achieve optimal penetration, the following parameters are important:

1) high velocity - if a projectile travels slowly, the target will have time to deform and absorb the blow without penetration, and therefore in order to penetrate well you need as high a velocity as possible. A typical anti-tank round is travelling at around 5,000 fps.

2) high sectional density - in order to maintain its momentum, and transfer the energy in a concentrated manner, you need a projectile that is as heavy and narrow as possible - this is why APFSDS rounds are made of very dense materials such as tungsten or depleted uranium, which being long and thin to give the distinctive arrow shape.

3) high projectile hardness - nature will always choose the path of least resistance, so if the target material is tougher than the projectile, the impact energy will go towards shattering or deforming the projectile as opposed to the target.

A simple comparison is to look at typical airguns in the UK, which are legally limited to the same kintetic energy of 12 ft/lbs.

A typical 0.22 pellet weighing 16 grains travels at 581 fps for 12 ft/lbs.

A typical 0.177 pellet weighing 8 grains travels at 822 fps for 12 ft/lbs.

The 0.177 pellet only has 70% of the momentum of the 0.22 pellet, but will penetrate further by virtue of its higher velocity and smaller diameter.
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Unread postAuthor: jackssmirkingrevenge » Thu Jul 12, 2012 12:00 am

Gippeto wrote:It's not a Daystate...


Out of the box, certainly. But it turns out that you actually *can* polish a turd!

For some reason I'm reminded of the words of the great Charlie Brooker, "I generally look at meals as a shìt I haven't had yet."

:roll:
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