Umarex Polishing ports

[88turbocoupe]

Decided to open all ports contour and polish to a mirror finish wasn't easy
Also got a peek valve
Ported polished the poppet seat all ports 4.2mm
Except the new gauge block that's at 6mm
My scope only goes to 5mm
Otherwise I could show all the polishing
Here is a pic inside the block
Also 2 new hammers being machined
One will be able to add weight to inside by 1 gr at a time
Using Mallory for those
Should be done by Wed morning

 

[Stubbers]

Looking clean, can't wait to read about the results.

-Matt

 

[88turbocoupe]

My new peek valve came is later in the day so I assembled last nite going to the range in a bit

 

[88turbocoupe]

Well very interesting results
Regulator set at 130 bar
Stiffer hs set flush
22gr jsb dead center
Next
150ish bar 1/2 turn in on hs
Shooting 25g jsb

What im scratching my head about is 5-7 more fps at 150 ish bar
but yet fpe went up to 51
Make sense
Doesn't to me

 

[Stubbers]

What I see is normal to me, left graph is 130 bar with 22 gr, right graph is 150 bar with 25 gr. Both are predicted outcomes using some maths.

Hope this helps. If you expand on what you're confused about I could try to shed more light on it. If your 955 with 22 grain and 960 with 25 gr was at the same pressure, I may be confused too!

-Matt

 

[88turbocoupe]

View attachment 497321View attachment 497323


What I see is normal to me, left graph is 130 bar with 22 gr, right graph is 150 bar with 25 gr. Both are predicted outcomes using some maths.

Hope this helps. If you expand on what you're confused about I could try to shed more light on it. If your 955 with 22 grain and 960 with 25 gr was at the same pressure, I may be confused too!

-Matt

so you pick up 1 fpe for every 1 fps
is that volume of air at the bottom of the screen?
im wondering i have 2 plenum extensions and a machined block that also adds some volume behind the regulator
i wonder if there is a formula to how much plenum volume i actually need
im still green in this sport 2 months in but not afraid to modify
that comes from racing drag cars in the modified division in the B+M racing series for 22 years
i still have my Flow bench for cyl heads

 

[Stubbers]

so you pick up 1 fpe for every 1 fps
is that volume of air at the bottom of the screen?
im wondering i have 2 plenum extensions and a machined block that also adds some volume behind the regulator
i wonder if there is a formula to how much plenum volume i actually need
im still green in this sport 2 months in but not afraid to modify
that comes from racing drag cars in the modified division in the B+M racing series for 22 years
i still have my Flow bench for cyl heads

No no, you swapped from 22 gr to 25 gr on the two correct? Sorry if I misunderstand. Once you push a certain limit, the only way to gain more FPE is with heavier ammo, as the lighter pellets out paces the expansion of gas behind it, where as the heavier ammo remains in the barrel longer picking up more steam. Although that only applies until it doesn't, which happens to be around 1.6~ grains of pellet per 1 grain of air...which takes a bunch of more math to figure out.

Curious what your total plenum volume is, definitely up there in CC's, you generally want around 1-1.5 CC to 1 FPE to achieve near maximum energy available for a given gun.

The bottom is the barrel length, although I am unsure if you have a 500mm barrel or the 380mm barrel in that bad boy.

-Matt

 

[88turbocoupe]

No no, you swapped from 22 gr to 25 gr on the two correct? Sorry if I misunderstand. Once you push a certain limit, the only way to gain more FPE is with heavier ammo, as the lighter pellets out paces the expansion of gas behind it, where as the heavier ammo remains in the barrel longer picking up more steam. Although that only applies until it doesn't, which happens to be around 1.6~ grains of air per 1 grain of pellet...which takes a bunch of more math to figure out.

Curious what your total plenum volume is, definitely up there in CC's, you generally want around 1-1.5 CC to 1 FPE to achieve near maximum energy available for a given gun.

The bottom is the barrel length, although I am unsure if you have a 500mm barrel or the 380mm barrel in that bad boy.

-Matt

380mm barrel 2 30cc plenum extensions i couldn't find my burette to measure the gauge block so I'm not sure

yes went from 22g at 130 bar to 25g at 150 Ish bar
thanks for taking the time to explain that makes sense I'm learning boss I'm learning

 

[Stubbers]

380mm barrel 2 30cc plenum extensions i couldn't find my burette to measure the gauge block so I'm not sure

yes went from 22g at 130 bar to 25g at 150 Ish bar
thanks for taking the time to explain that makes sense I'm learning boss I'm learning

You sure have a lot of plenum! 60cc extension + the 25cc on the block if I understand correctly, for a total of 85cc?

You gained FPE with minimal FPS change due to increasing your pellet weight, while also bumping the regulator. Hope that clears it up.

-Matt