Umarex THE ZELOS IS AMAZING

[actionpistol]

Wow. That's interesting. I've had the hueban cricket regulator on my zelos for about 3 months. I haven't had any problems other than when I did a removal of the regulator and bottle to adjust my regulator on the zelos. The little o rings blew. Luckily I had already ordered several. Thanks to this forum. Yrmv

 

[LR_Plinker]

The through hole in the C88 to Zelos Plenum is @3.6mm . I'll get around to doing the math, but I think this is about as big a through hole is safe in the aluminum threaded post or the plenum.

 

[OldVet]

The through hole in the C88 to Zelos Plenum is @3.6mm . I'll get around to doing the math, but I think this is about as big a through hole is safe in the aluminum threaded post or the plenum.

If it was able to be drilled out more once inside the 8mm guage hole would it not be OK. I'm just wondering if that would help the air transfer to be stronger than a 25 fps increase.

 

[Ratzy]

All my experiments in Plenum i found 3x or 4x barrel volume was optimum. That allowed the pellet to accelerate the length of the barrel. That was on AirForce Condor and Talon.

Best is a port that is as large or larger than the barrel.

Where it falls apart is adding a plenum to a rifle with a poppet valve (or similar). The issue there is transfer port, hammer spring, poppet spring and dwell. I just dont know how to calculate the volume of air that passes through the poppet. Optimizing a plenum for that is a crap shoot.

All that said, if you can get any reasonable amount of air from the plenum to the pellet it will improve performance.

Gauge mounts usually have tiny holes, like 1mm or less, so they are far from useful with plenums.

 

[LR_Plinker]

If it was able to be drilled out more once inside the 8mm guage hole would it not be OK. I'm just wondering if that would help the air transfer to be stronger than a 25 fps increase.

the 8mm hole is threaded, thus reducing the ID of the threads to around 7mm. You need at least some wall thickness to maintain some strength in the 7mm tube with a 3.6mm bore through it... There is a formula that I will eventually run, but am busy with other stuff at the moment. I do not think there is going to be much there...

Opening the ID of the portion of the threaded post that sits inside the action will not gain you anything, as the 3.6 bore above it is still the choke point.

 

[LR_Plinker]

If it was able to be drilled out more once inside the 8mm guage hole would it not be OK. I'm just wondering if that would help the air transfer to be stronger than a 25 fps increase.

Your shooting the .22, right? I have it on my list of projects to convert one of my setups down to .22. When I get there, I will let you know if I find anything that would be easy for you to incorporate into your tune that will increase performance. I do have one of the C88 Plenums, but am waiting to mount it on one of my actions until I get some other stuff accomplished and tested. Does your pressure gauge read while you cycle and fire the action? You should see it drop of maybe 1000PSI when you pull the trigger. If the plenum is not feeding the action fast enough, there will be much less pressure drop reading on the gauge.

 

[KatoKevin454]

My Zelos came in today, intact and no damages, well packaged, checked and cleaned, cleaned the barrel, aired up and leak tested, no leaks, mounted a UTG 4-16x44 compact scope with medium rings, sighted it in at 36 yards, tested 2 types of pellets, Benjamin .25's and JSB MKll .25's, the Benjamins won, stacking on top of each other while the JSB's had a 1/4" group, almost one hole, I think the Benjamins are 27 grain or something like that, didn't chrony the shots, my chrony is buried in my truck and I'm to lazy to dig it out.... , I'll do it later.... it is shooting better than I expected, got 2 mags full before it dropped off the regulator at 2000 psi, suspect it's shooting around the low to mid 900's fps, it blew through 3/4" marine ply and a metal sign no problem so I think it will do fine on some medium size critters..... I really like it and the Magazines work great.
DonnyFL Sumo works good tooo

 

[OldVet]

All my experiments in Plenum i found 3x or 4x barrel volume was optimum. That allowed the pellet to accelerate the length of the barrel. That was on AirForce Condor and Talon.

Best is a port that is as large or larger than the barrel.

Where it falls apart is adding a plenum to a rifle with a poppet valve (or similar). The issue there is transfer port, hammer spring, poppet spring and dwell. I just dont know how to calculate the volume of air that passes through the poppet. Optimizing a plenum for that is a crap shoot.

All that said, if you can get any reasonable amount of air from the plenum to the pellet it will improve performance.

Gauge mounts usually have tiny holes, like 1mm or less, so they are far from useful with plenums.

In a Zelos the guage hole in the guage is 1 mm the hole in the plenum itself is a threaded M8 x 1. It goes all the way through.

 

[Ratzy]

In a Zelos the guage hole in the guage is 1 mm the hole in the plenum itself is a threaded M8 x 1. It goes all the way through.

I just can't see that as effective. My Gauntlet has about a 2mm hole access to the gun. I saw very little improvement putting a plenum on that rifle.

Plenum is about adding air flow after a regulator to keep the pellet under acceleration longer. If you restrict that air flow then you get no benefit.

 

[LR_Plinker]

I just can't see that as effective. My Gauntlet has about a 2mm hole access to the gun. I saw very little improvement putting a plenum on that rifle.

Plenum is about adding air flow after a regulator to keep the pellet under acceleration longer. If you restrict that air flow then you get no benefit.

actually, not air flow, but volume is the purpose of a plenum. By adding one, you are increasing the volume of regulated air. It is exactly the same as adding length or the air tube of an unregulated gun. On the Zelos, the hole between the external plenum and the onboard, regulated air supply held in the body post regulator is physically 3.6mm. Especially on the .22, this equates to @75% of the transfer port diameter. WIll it be 100% efficient at adding usable volume on demand for each shot cycle? Nope. Is it completely ineffective? Nope. It absolutely contributes to the shot cycle.

There are plenty of guys that have added one sort of another external plenum to the Zelos in a similar fashion that have all shown increased velocities throughout a given tune. On this particular action, there is not really many other available or possible solutions.

 

[Ratzy]

actually, not air flow, but volume is the purpose of a plenum. By adding one, you are increasing the volume of regulated air. It is exactly the same as adding length or the air tube of an unregulated gun. On the Zelos, the hole between the external plenum and the onboard, regulated air supply held in the body post regulator is physically 3.6mm. Especially on the .22, this equates to @75% of the transfer port diameter. WIll it be 100% efficient at adding usable volume on demand for each shot cycle? Nope. Is it completely ineffective? Nope. It absolutely contributes to the shot cycle.

There are plenty of guys that have added one sort of another external plenum to the Zelos in a similar fashion that have all shown increased velocities throughout a given tune. On this particular action, there is not really many other available or possible solutions.

I know exactly how a plenum works.
I just spent off and on over the last 8 months going through various configurations and sizes of plenums to work out what is the optimal size for a plenum.
A 1mm hole at pressure will supply some air. Just not very much.
An inline plenum would be much more efficient.
Optimal is a hole that is as large or larger than the barrel ID so that the *flow* is not restricted.
There is a school of thought that an oval transfer port is better just because you can make it as large or larger than barrel ID.
(I haven't tested this but it seems reasonable)
A fully optimized plenum will supply 3-4x the volume of the barrel.
That way the pellet is under pressure for the length of the barrel and maximizes energy imparted to the pellet.
A 1mm hole is (.03937/.22) 18% of the barrel ID of the Zelos
Zelos barrel volume is 16cc
Optimal would be 48cc or larger
But the variables associated with a poppet valve rifle become very complex.
Hammer Spring
Hammer weight
Transfer Port
Poppet Spring
Poppet Valve diameter
Poppet dwell
Air Pressure
Right Angles
Plenum port
Regulator port
...
So how much air will make it from the plenum to the barrel through the poppet is frankly far too complex for me to even think about modelling.
Each poppet valve rifle will have a different response to a plenum, especially one as restricted as through a 1mm hole.

 

[OldVet]

I just can't see that as effective. My Gauntlet has about a 2mm hole access to the gun. I saw very little improvement putting a plenum on that rifle.

Plenum is about adding air flow after a regulator to keep the pellet under acceleration longer. If you restrict that air flow then you get no benefit.

I don't understand what you don't understand.? The guage has a 1 mm hole .
The aftermarket plenum hole is 3.6 mm (which can be opened up to 4 mm I think) .
There is NO 1MM , OR 2MM restriction hole.
Threaded hole in rifle plenum = 8mm
Port hole in new aftermarket plenum = 3.6 mm.

 

[Ratzy]

I don't understand what you don't understand.? The guage has a 1 mm hole .
The aftermarket plenum hole is 3.6 mm (which can be opened up to 4 mm I think) .
There is NO 1MM , OR 2MM restriction hole.
Threaded hole in rifle plenum = 8mm
Port hole in new aftermarket plenum = 3.6 mm.

That makes more sense why people get improvement by adding a plenum there.
From the plenum into the gun is 3.6mm
That is .14" a little over 1/2 the barrel ID
Off the top of my head, and ignoring a lot of variables, are you seeing about 5% energy gain?

 

[OldVet]

I'm glad you understand I'm going to buy one , and drill it out to 4 mm install it , and I will measure the fps increase with my Chrony. My Zelos is .22 by the way.

 

[actionpistol]

Put the zulus on my zelos 25 today. Shooting 2.03 inch 7 shot group with H&N Baracuda 30.86 grain at 81 yards. Doing doing 876 fps .Got the bottle to for higher shot count. Very happy with both the 25 and 22 zelos.