Wild velocity fluxuations

[DaFin]

Bought another classic mag here on AO some time back to use as a loaner and finally got a chance to air it up and *try* to chrono it. The gorey details, classic valve, level 7 bolt, no name expansion chamber NO modifications and running CO2. When shooting across an old fashioned Chrony I get strings like:

275, 282, 338, 280, 250, 352, 302, 277

There are no leaks on the gun and I've already thoroghly cleaned out the reg section and oiled it and replaced the O-rings. I did notice there are some wear marks on the 45 casing. Other things that *might* have bearing on this is that the trigger pull is really light, I can sweet spot it no problem but the on/off section looks totally stock and the CO2 bottle is mounted on a drop fwd and is not anti'siphon.

So, what do you think? Am I a) sucking liquid and that's what's causing this, b) The on/off is hinkey and not shutting off all the way or c) the slight wear marks on the 45 casing indicate that it's binding up and letting too much pressure past or not enough or d) ????

[egb groupie]

Bought another classic mag here on AO some time back to use as a loaner and finally got a chance to air it up and *try* to chrono it. The gorey details, classic valve, level 7 bolt, no name expansion chamber NO modifications and running CO2. When shooting across an old fashioned Chrony I get strings like:

275, 282, 338, 280, 250, 352, 302, 277

There are no leaks on the gun and I've already thoroghly cleaned out the reg section and oiled it and replaced the O-rings. I did notice there are some wear marks on the 45 casing. Other things that *might* have bearing on this is that the trigger pull is really light, I can sweet spot it no problem but the on/off section looks totally stock and the CO2 bottle is mounted on a drop fwd and is not anti'siphon.

So, what do you think? Am I a) sucking liquid and that's what's causing this, b) The on/off is hinkey and not shutting off all the way or c) the slight wear marks on the 45 casing indicate that it's binding up and letting too much pressure past or not enough or d) ????

It was probably a bad reg seat o-ring that was causing this. Whenever the two halves of the valve are cracked open, it is not required, but is recommended that you replace the reg seat o-ring, because the seal that is formed when the two halves are screwed together has been broken and really can't be exactly matched up again.

[SSD]

One other thing to be aware of,
The Reg, spring pack CAN get dirt, sand or whatever stuck in the grease. This debris can pump in and out of the spring pack causing velocity irregularities.

Clean the spring pack and repack with grease.

SSD