New 1377 Power output?

[Hung2]

Thanks WyoM,

I am not an air-flow engineer and my curiosity has triggered all kind of logical questions.

[K.O.]

Hi Hung2

I chose to keep the pump cup for WyoMan's reasons  Durability and reliability.

Now about the more pumps thing  yes you can pump more to make up for headspace but past a certain point the results can be erratic  one shot will be 20-50 or so fps different at the same number of pumps than the next. That means one shot  low the next high etc...

With my setup that is happening at about 20 pumps.

So I stop where my carbine is predictable... 17-18 pumps.

here is where headspace  shows it self   the valve holds  .1 cubic inches of air = about 1.63 cc if I have .053 of headspace(=about .26cc) that makes it  16% bigger

or

If I take away the headspace then each pump will develop 16 % more pressure. ( http://en.wikipedia.org/wiki/Boyle%27s_law )

Boyles Law is basically       "At a fixed temperature, the volume of a gas is inversely proportional to the pressure exerted by the gas."

which translates to  double the volume  half the pressure or  increase volume by 16% decrease pressure by 16%...



Ok so I am pretty sure these things develop about 1000-1200 psi  and that translates to having about 160 more psi if I am stopping  at that level  of predictable results...

17 pumps with headspace = 840 psi
17 pumps  no  headspace  = 1000 psi

I do not think it is that simple in reality but is close enough to show the logic

I am one of those that believe the .177 pellet likes to be hit with as high velocity charge as possible so seat the pellet just past the port not way past.

You are going from a .140 port to a .177 barrel so the further from the port the slower the charge.

If you are curious about charge velocity look up choked flow.

[Hung2]

K.O,

I appreciate you and WyoM taking the time and effort to explain the logic beyond a layman's perception of pumping vs desired result. That's what I came here for. Maybe one day I will be MIA as well once I had learned all the related knowledge - I hope not, I do enjoy looking at the pic of all the dressed up 13xx.

What I have in mind now is to find a bar stock, get a machinist friend to cut a groove in it to make it a barrel shroud and put it on top of the barrel between the steel breech and the pump/front sight linkage. The naked barrel with the space in between the tube is not eye appealing to me.