Air Venturi Avenge X: inconsistent FPS

[phoenix_cow]

Having a bit of an issue with my Avenge-x (.22 with carbon fiber bottle) I'm hoping that maybe someone here knows what is going on.

I was shooting some a few days ago and I was getting a little below 890fps. I tried shooting again today (without touching any settings and with the same ammo) and I'm getting 860fps. Normally I would chalk this up to differences in weather, but that seems like quite a drastic change in fps.
The gauges seem to be reading all correctly, so I'm thinking it might be the hammer spring is starting to wear. I wanted you guy's opinion before getting a replacement, although I might get one anyways they don't seem that expensive.

My settings are:
2500psi on reg
+7.5 turns on the HS
TP set to High
Shooting JTS Domed (25.39gr)

 

[phoenix_cow]

Just shot it again (half hour later) and it is back up to 890fps. I don't get it.

 

[JaceSpace1369]

Just shot it again (half hour later) and it is back up to 890fps. I don't get it.

Just how drastic has your weather been? Here in South Florida, going from hi 50's to high 80's.We'll give you a pretty good change in fps. Is is the gun new? Have you noticed any regulator creep?

 

[nervoustrig]

Many possible causes, including but not limited to:

1. Regulator break-in (setpoint shifts up, needs more hammer strike to compensate)
2. Other break-in (e.g. hammer spring settling, poppet taking on a bit of compression set, etc.)
3. Hammer spring tension self-adjusting due to vibration
4. Wear of breech / bolt O-ring
5. New tin of pellets (potentially more bore friction due to tolerances)
6. Adjustable transfer port not returning to the same precise location (I’m not familiar with the adjustable TP on the Avenge-X, but many wheels have a spongy detent)
7. Temperature effects (e.g. lubricant viscosity changes, air density changes, etc.)

Not sure where you fit but most people don’t have the time and inclination to investigate every possibility. However maybe you see and item or two in the list that you want to look into.

If the gun is fairly new, it’s tempting to chalk it up to break-in, in which case you may want to just readjust the HST and run it for a while to see if it continues to drift.

 

[nervoustrig]

I was typing when the update came in so the last post probably isn’t relevant to your particular scenario but I’m leaving it up since it applies to any generic “why is my gun’s velocity different today” scenario.

 

[phoenix_cow]

I do notice some creep for my first shot, after that it stays stable (unless I let it sit for a while). My fps is consistent after the first shot taken. The weather has been a bit crazy here, maybe about +-10 degrees (between 50 and 60) between shooting. I'm a bit new to PCP air guns, does that normally effect fps that much?

It is a new gun, been shooting for the last two months. I shot about 300 pellets threw it, not sure how long a break in period is for it.

Ammo I am shooting is from the same tin as my first session. So, that seems to be ruled out.

Transfer port in avenge-x is only two settings, high or low. It is not extremely easy to move once in place. I don't think that is the problem.

I'm going to have to say it is ether the weather or maybe it just needs broken in more. Or, strange as it might be, my chrono was just reading incorrectly. I know that some chronos are finicky about light and it was cloudy this morning when I went shooting.

 

[Chukar60]

I have never owned an AvengeX, but I doubt 300 pellets would be fully broken in. When I get a new gun I will run around 1000 rounds down the tube before I attempt any serious tuning.