RT shoot up. Whats to be expected?

[Smokee_2_7]

well, tonight is my night for random questions. With Properly cleaned and functioning retrovalves and x-valves, what kind of velocity shoot up can I expect? What causes shoot up to become worse? I have seen my gun on many occasions only have shoot up in the range of 5-7 fps by the RT chrono procedure. Then at a later date, I have seen it jump 30 fps. . . That just dosent work if your first shot is 270, and in a string you are hitting 302. That is a pretty noticable difference.

Is shoot up related to the reg. seat in any way? What part of the system do I need to pay special attention to to keep this from being a problem?


Thanks for the help,

Carl

[athomas]

A higher input pressure into your mag will cause a larger shootup problem. Environmental conditions will have an effect.

A higher input pressure causes a larger pressure differential and causes the air to rush into the front valve chamber more quickly. This surge and rapid repressuring of air in the front chamber creates more heat. This hot air causes the shootup associated with retro mags. The environmental conditions may exagerate the effect by further creating a larger temperature differential from normal to heated air temps.

When chronoing your gun this should be recognized and you should chrono using the accepted method of chronoing a retro mag. Hold the trigger, release and then fire in one quick motion. The air that is use to propel the ball will be heated air. This chrono speed will reflect the effect that the balls will have placed on them due to higher air temp because the trigger is pulled immediately following a rapid air charge.

Under continuous shooting conditions, the retro mag will be very consistent in the velocity due to the heated air. Its only the cooled air that will be different. A single shot will yield a slightly lower velocity due to cooled air in the chamber. The air is regulated while hot and then cooled. The cooled air is at a lower pressure due to reduced energy.

So, theres two ways to look at it depending how you use your gun. If you are always rapid firing, then a single shot will be low (first shot low problem). If you are always firing single shots, then a string of shots will appear to increase in velocity (shoot up).

The only know way to reduce it is to lower the input pressure of the gun to reduce pressure differential.

[Smokee_2_7]

Gotcha. Thank you.

The main downside to this is that you loose reactivity in the trigger with a lower input pressure. I need to find the happy medium- - - The main factor would be that I would like shoot-up to be in the neighborhood of 5-7fps. Basicly I want my first shot to be around 290, with shoot=up keepinig me under 300. Any suggestions on what Input pressure would yeild these results?

Additonally, are enviromental conditions the only other factor that could potentially increase shoot-up? The main reason I ask is that I've seen major differences in shoot-up on the gun when the input pressure has remained the same, and the enviromental condtions were very similar.

Thank you for the help,

Carl