When to refill

[just.neil]

I have a hatsan at44 .22cal. I usually fill it to 200bar the max fill pressure then shoot down to100bar. Is that about right or can i shoot to lower? Also what can over filling do? Also the air tube gets warm while filling, now i know this is normal but should i let it cool down before shooting? Lol i bet y'all get the same ole questions asked all the time. 

[kbstingwing]

if you are using a scuba or SCBA tank to fill the gun I would fill at 100 bar, you might go lower the best way to check is with a Chrony, measure the fps curve with the pressure curve, when the fps drops drastically take note of the pressure and that will be your fill point, and if your fill hose is getting hot, that means you are filling too fast, this is not good, the heat is produced from friction created by fast moving air, heat will destroy the valve seals, fill as slowly as possible, don't rush it, you don't want to have to tear it apart to replace the seals prematurely, if you are using a pump then don't worry about the heat it is normal, Compressed air releases heat, you could fill at 100 bar but you might want to refill sooner, unless you really like the work out, depends on if you are hunting or target shooting, hunting fill sooner target fill later.

Never over fill, it can be dangerous, even though the tank is tested at higher pressures, over filling can damage seals and other parts, tank could possibly explode too.
Read the owners manual for proper filling instruction, operation and safety measures...

[GD Giles]

If your Hatsan isn't regulated you're probably losing quite a bit of performance per shot once you hit around 130 bar. Filling to 200 also makes your first 3 shots or so a bit slower as well as cylinder pressure is high and shuts the valve quicker. A lot of Hatsan shooters fill to about 190 bar. Do you have a chrony? Do you know what your shot curve is? I'm not sure what the factory performance of an AT44 is and I know it varies from the long to the short. On this forum, Rallyshark has tuned and modded his AT44 .22 a bit and is getting 50 shots at 30 FPE. I'm not sure where he's filling to and how far down he's shooting to. I know his ports are modded and he uses a regulator.

[Ribbonstone]

Only real way to tell where you are is by chronograph.  If you don't have one, won't ever really know how fast or how the velocity changes with pressure changes.
But you can get an idea of where to stop without a chronograph.  Not that I'm anit-chronographing, it's great for getting all the velocity/energy figures and figuring out where the best-of-the-best shots live.  Think many of us air-heads get some kind of fun out of manipulating the numbers into graphs, charts, etc.....kind of extending our gun-time.

 Non-regulated rifles do shoot differently than regulated ones.  But inside of each non-regulated rifle there is at least a short span of shots were they shoot every bit as consistently as a regulated rifle.  There is a point, although short lived, where a non-regulated rifle manages to self regulate quite nicely.
All you want to know right now is basically where do I really start to "lose it" and need to refill.  Won't know the vlelocity of the shots, but you can figure out a refill point without a chronograph. Actually, without a need to know how fast per shot, just how many shots that stay pretty close to on-target, doesn't require anything but paper/time/ and shooting.

You could just shoot idential paper targets at one set range and pay attention to the pellet's change in impact. Longer range would be better as the longer the range, the more change in the point of impact as velocity changes.  But you can get a basic idea at shorter ranges (like anything near 25 yards).

Try for identical targets.  Could shoot 5 shot groups or could just a sheet of "dots" and shoot each dot once. About every 5 shots, take a reading from the rifle's gauge.  (while the rifle's gauge may be hard to read, it is the only gauge you have with you).

Two examples:
A. Rifle with a pretty long shot count shooting home-made squares (you can download/print graph paper for free at several sites). Used 3 shots per square (45 shots total):


Which really makes more sense if you cut the targets out and past them in a row:


Can conclude a few things from this:
1. Rifle starts out slow and climbs in speed as pressure drops.  Basic reason for this is that the striker hit to the valve is a bit too weak for the fill pressure.
2. Rifle starts it's peak at about shot #12 and starts to fall off by shot #39.  So unless something gets readjusted, the best shots for this rifle are actually the 24 shots in the middle.
3. Can't get a clue about velocity from this, but at least we know where the rifle is shooting it's longest length of most uniform shots.
4. Whatever the speed is, the graph shows me that I may as well either (1) only fill to the pressure  of shot #12 or (2) increase striker spring tension a little and try again.



Example B: Small volume rifle, fewer shots.
Here is an eample shot on "dots" (one shot per dot).


Trends here are:
1. Whatever the velocity, it's pretty uniform from the first shot.  If we were to decrease striker spring tension, might see a shot or two more, but likely they would be low shots like the example above.
2. By about shot #15, it's starting to slow down.
3. By shot #19, it's really slow.

From  playing with Hatsans, expect that shooting from 200bar to 100bar is likely too wide a range of pressure for anything besides short range shooting. 

[just.neil]

Not regulated and filling with a hand pump.  I don't have a chrony... I have over filled a couple times but it wasn't much, I don't think it was enough to hurt nothing.  That's a really good idea ribbonstone.  I will try lining up some paper targets side by side and see when to refill that way.  for the most part its very consistent and I'm stoked with it!  It isn't factory, I bought it off of bwalton and he tuned it to shoot the jsb 18gr.  He didn't regulate it cause he said for what I'm using it for I didn't need a regulator. Thank yall for your input.

[kbstingwing]

just slightly over filled is not a problem you could shoot it till it gets to proper pressure.

[Ribbonstone]

Can get a whole lot of shots from a fill when plinking bottle caps (or paintballs) or busting back yard pests at 20-30 yards without velocity changes really making a bit of difference.  It's really only when you are shooting small stuff far away or trying to make small groups on paper that living in the sweet spot really makes a rat'srump.

Another way to look at is is that it takes about the same number of refill pump-strokes for each shot fired.  Lets say it takes 3 pump strokes per shot. So if you live in the 20 best shots, would refill with 60 strokes....if you take 40 shots, would take 120 strokes.  Same effort either way, so why not only live in the best area the rifle has to give?

[GD Giles]

If Baxter tuned it then he could probably give you the curve and optimal pressure range data.

[just.neil]

The farthest i shoot is around 50 yards. Usually20 or 30 ish. I do have a spot where i can make a nice range right out back. Might get75 yards or so out of it.   I have noticed that the poi will go up and down around 50 yards but i didn't take note of the air pressure. 

Gd giles....now i feel like a dummy cause i never even thought to ask him. Lol. Thank you
 

[Ribbonstone]

You'd be able to learn enough at 20-30 yards to figure out when it starts to drop enough to matter...and from that when to refill.