Strange Velocity problems- - - lvl 10?

[Smokee_2_7]

Weird things happening here:

here's the setup.

Retrovalve, level 10 (2 shims, 1.5 carier, middle spring)
AGD 3k flatline, input pressure at 850 psi.

First off, on a couple occasions over the past week, when I gas the gun up it get a HUGE rush of air- - - out of the back of the reg. De-gassing, unscrewing velocity, re-gassing and then turning up velocity seems to solve the problem.


More importantly, the velocity jumps. let me explain.
Last week for team practice, I chrono'd on first thing in the morning at about 275. this was strange, because I couldnt get the velocity to go any higher without leaking out the back. (brand new reg. piston). Well, i left it set where it was, and started to practice.

after 2 or 3 scimages, things changed. in the 3rd scrimage (about 30 minutes from the initial chrono setting) I stitched up a guy. Put about 6-8 balls on him. It hurt- - (he made a rather big deal out of it.) and left some really nasty welts. So, I go and put the gun back on the chrono - - - 330!!!. I turned the gun back down, and this time was able to get it to shoot consistently in the 285-290 area, with no leaking out the back. Earlier that morning i had oiled the marker (3 drops in the air line, gas up and fire 30-40 times.)


Jump to this week (yesterday). Same thing, different day. I chronod the gun at about 285, and shot a few balls through it. Let it sit a while, and shot some more through it. dry fired several times. Went to the chrono about 20 minutes later, and velocity was now in the 310 range. Had to adjust it back down.




The lock ring on the flatline is in place, and the input from the tank is not changing.

As i said, the reg. piston is brand new- - and the gun went in to AGD for an overhaul about 4 months ago.



Any ideas?


Carl


Edit- - I did twiddle around with the lvl 10 settings. I tried to go with a larger carrier- - - and was reminded that I was laready using the largest one that dose not leak. Could the presence of shims be causing this?

[battlegroup]

Before you gas up and chrono for the first time each day take off your valve and lube your bolt and powertube. It seems your bolt might be rubbing on the carrier o-ring and until you get it lubed up completely each day, you have to turn up the velocity to overcome the rubbing against a dry o-ring. That's why it starts to vent at 275 and once it gets lubed and worked in the velocity jumps. If you lube it before you gas up it should be consistent all day.

[Smokee_2_7]

ok, ill give that a shot.

I was just thinking that putting oil into the asa would work- - - i figured that within 30 or so shots the oil would work its way to the bolt and carrier o-ring.


thanks,

Carl

[BlackVCG]

I don't use shims. To me, shims are completely pointless. I've yet to come across a gun that actually needs them and unless it needs them, there's no reason to have them in there.

What kind of oil are you using?

Can you hold the bolt at the top of the PT and drop it and does the bolt fall all the way down and hit the bumper? If not, there's too much o-ring friction and you need a different o-ring/carrier setup.

[Smokee_2_7]

How do you know if a gun needs shims?

As far as oil goes, I honestly dont know for sure. It's the stuff that KAPP sells. (thats what we've been carrying in the shop.) The oil seems to work fine for everything else that we use it on- - - so, im not sure.

I haven't tried the bolt drop. Will do in the next day or so.

THanks for the tips.


Carl

[BlackVCG]

If it pinches a ball and doesn't retract, add a shim.

[rikkter]

black..
i dont have a level 10, but i'm interested on your take on why the shims are pointless?

[TheJester]

i would leave the shims, even if the bolt does stop on a ball and recocks, you can get it to recock earlier(less pressure on the ball) by adding more shims, that's what i did w/ mine, it would sometimes chop, sometimes not, i just added a 2nd shim and it never choped again, i think it's because the air is venting that much sooner, and pushing that much less on the ball

try a different spring though...in the instructions the spring selection well depend on velocity, paint/barrel match, you may be just using the wrong spring for your paint and barrel.....this is copied right from the instructions....

"The last thing to do is find the right main spring that pushes back hard enough on the bolt but not so hard that the marker does not fire. The right main spring will depend on many things such as what velocity you are shooting, what barrel you are using, the size of your paint etc."

other than that...i'm clueless

[BlackVCG]

Originally posted by TheJester
i would leave the shims, even if the bolt does stop on a ball and recocks, you can get it to recock earlier(less pressure on the ball) by adding more shims, that's what i did w/ mine, it would sometimes chop, sometimes not, i just added a 2nd shim and it never choped again, i think it's because the air is venting that much sooner, and pushing that much less on the ball


It doesn't work that way.