Sporadic FPS

[Madcat_MK2]

Hello all. I've have my ULE Custom for a little while now and have shot a couple of cases through it with the same o-rings. I've gone down a few carrier sizes since too since I started breaking it in. My problem now is my mags speed fluctuates pretty badly. I'll get two rounds to shoot at 280, then one goes 302 then 290 then 315, back to 280 again and it kind of continues. I usually just leave it so it maxes out at 285 fps, but it averages more at 260's.

The valves seems to be in perfect shape as I pulled out the velocity pin once to check it, and checked the little oring to see if its sitting right on the stem in the middle. The only thing I have noticed that is peculiar is sometimes it will leak air down the barrell noticably, but then if I fire a few rounds it usually stops. I'm using no shims, red spring and I believe .5 carrier. It fires great despite the sporadic FPS and occassional leaking.

Do you think the bolt o-ring is grabbing inconsistently enough to just work, but is causing my FPS to jump around and the occassional leaking I get? Would trying next size down be next thing to try or switch to another oring and start sizing all over again? Thanks for any help.

[lidocaine]

My tac one is the same way, just as you described. Looking for a solution as well.

[lidocaine]

Bump for justice.

[secretweaponevan]

You definitely want the largest carrier that doesn't leak.
Bump up .5 a carrier size (use the same carrier o-ring in it) and see if it still doesn't leak. If it doesn't, repeat.

Other than that it is probably a paint to barrel match. If you don't have a barrel kit there is not much you can do. If the paint isn't round, fuggedaboudit. I was shooting footballs this weekend and my velocity was +/-10fps.

[lidocaine]

wow plus minus 10 is on a good day for me..
Im going to test my JJ barrel kit this Sat. hopefully that clears it up.

[secretweaponevan]

wow plus minus 10 is on a good day for me..
Im going to test my JJ barrel kit this Sat. hopefully that clears it up.

It should if the paint is round and you chrono properly (if using an RT valve).

[athomas]

Take the shims out to make sure you aren't getting leaking due to the bolt stem vent hole being too close to the oring. Then go to the largest carrier that doesn't leak.

Check the roundness of the balls you are using. Use a larger barrel to compensate for odd shaped balls.

[Madcat_MK2]

I'm not using any shims as it vents just fine without them. If I go one carrier size up it leaks horrendously so this one should be right, but it still does that sporratic leaking. I was under the impression that if the oring is sized right that it never leaks down the barrel unless it comes time for a new one?

I dont have a barrel kit as Im just using a j&j ceramic, but the balls we've been using are pretty good and fit fine in my barrel. Another guy on my team, I forget his name that he uses on here, doesnt seem to have any troubles using the same paint and I dont recall him using a barrel kit either.

[TheRock]

is your hpa system in good shape?
If i chrono not using the rt way its low fps and big variations, but if i chrono it like you should its only a few fps difference sometimes only 1-2 fps with a paint/barrel fit that paint barely touch insides of barrel.
im down to smallest carrier and same oring about 30 cases through it now, i feel the autolube is not the best for long term lubing because i get bolt stick after 2 cases after a fresh lubing.
and one dot carrier is to large its not leaking when first gassed up but after first shot it leaks badly.

Nothing but pleased :clap: :dance: never had to stop playing because of equipment since i went tac one.

[athomas]

... i feel the autolube is not the best for long term lubing because i get bolt stick after 2 cases after a fresh lubing.
and one dot carrier is to large its not leaking when first gassed up but after first shot it leaks badly..That's bolt stick caused by a carrier that is too tight. Go to the next larger carrier size. Don't forget to remove all the shims so you don't get shim induced leaking that seems like a carrier leak.


Madcat_MK2: Take the regulator piston assembly out of the back and clean the back of the valve. Grit in there could cause fluctuations in velocity.

[Madcat_MK2]

Nah, I got a brand new Crossfire 900psi output tank, so that is good.


Athomas, you do mean to take out the velocity pin again and clean inside there along with that spring pack, correct? If it is, what should I use to regrease them again when Im done cleaning them? Does any paintball gun grease suffice?

[lidocaine]

Im running a 850psi output tank.
I cant seem to get it to bounce the "rt" way.
Does it really matter, if its good consistency when bouncing wouldnt it be good when its not?
All your supposed to do it pull the trigger once, hold it, release, quickly pull trigger again and hold it on the sweetspot?

edit: if thats not true, what is the proper way?

Thanks

[lidocaine]

I just searched for proper chrono procedure.
Fire, hold trigger, fire quickly again and hold trigger again, fire again. repeat, correct?
Why wont the gun shoot consistently when shooting normally, because thats not how I would shoot in a game..

[secretweaponevan]

I just searched for proper chrono procedure.
Fire, hold trigger, fire quickly again and hold trigger again, fire again. repeat, correct?
Why wont the gun shoot consistently when shooting normally, because thats not how I would shoot in a game..

The above procedure mimics rapid fire. The air recharges in an RT valve so fast that it heats up , increasing pressure and therefor velocity. To chrono an RT valve slowly would allow you to shoot hot during rapid fire.

[lidocaine]

Alright I understand that I would be shooting hot if I didnt mimic rapid fire like the above procedure, but shouldnt the consistency be as good when your slow firing as you are when rapid firing because I cant even rapid fire more than 2-3 shots no matter how hard I try, thats crap if I have to live with 25fps jumps because I cant rapid fire 10 balls a string.
Dont most people shoot x vavlves semi auto one shot per pull when in rec games and such where 15 bps isnt necessary? Is their consistency horrible too?

Thanks!

[secretweaponevan]

Alright I understand that I would be shooting hot if I didnt mimic rapid fire like the above procedure, but shouldnt the consistency be as good when your slow firing as you are when rapid firing because I cant even rapid fire more than 2-3 shots no matter how hard I try, thats crap if I have to live with 25fps jumps because I cant rapid fire 10 balls a string.
Dont most people shoot x vavlves semi auto one shot per pull when in rec games and such where 15 bps isnt necessary? Is their consistency horrible too?

Thanks!

Be sure to clean your piston area as athomas pointed out. That and ball to bore matching (as long as the paint is round) and you should have good consistency.

[lidocaine]

So it should be as consistent when slow shooting as when you do the proper chrono procedue, right?

[secretweaponevan]

So it should be as consistent when slow shooting as when you do the proper chrono procedue, right?

Nope. You should see greater fluctuations due to the gas cooling down. The proper procedure is the rapid fire simulation as you previously described.

Also, if you have an almost inaudible leak in your powertube, the quick method will definitely be the most consistent.

Be sure to clean your reg piston area.

[athomas]

Athomas, you do mean to take out the velocity pin again and clean inside there along with that spring pack, correct? If it is, what should I use to regrease them again when Im done cleaning them? Does any paintball gun grease suffice?Take the velocity adjuster out of the back. This will allow you to remove the spring pack and the regulator piston assembly. Dirt in this cavity can cause fluctuations by impeding the movement of the piston. Only use light synthetic lubricant on the orings in the mag. Grease will gum up with dirt and cause issues.

[lidocaine]

Then why bother shooting a mag if you have to rapid fire 15 shots for it to be accurate?
Because I for one shoot quick bursts of like 3 at max and run, usually even one ball so if its not going to be accurate as when im rapid firing.. :confused:

[athomas]

Shot to shot any mag should be consistent. If you shoot a single shot, it should be the same as any other single shot. If you shoot several shots in succession, after the first couple of shots, each shot should be consistent with the previous shot. Its the 2nd, 3rd and following shots in a rapid succession that change when compared to the first shot. Due to heating in the valve due to the fast recharge, the next shots immediately after a trigger release contain hot air which is a higher pressure than the cooled air, so the shots will be at a higher velocity. Each shot with the hot air should be the same as the previous shot with the hot air. As the air cools when you are not shooting, the pressure falls back to normal and the velocity also falls back to single shot values.

If you are only ever shooting single shots, each shot will be the same as any other. If you need a bit of extra range, hold the trigger after a shot. Then after you line up your next shot, release and pull the trigger immediately. The hot recharge air will give a few extra fps.

The amount of increase is dependent on the tank input pressure. The higher the value, the hotter the air gets and thus the higher the velocity increase.

[lidocaine]

athomas thanks for the excellent explanation.

[Madcat_MK2]

Alright, well after doing what athomas suggested it seems my mag is now firing with 1-3 fps differences pretty consistently. Only thing I noticed was at first my mag would not fire at all. So i took the bolt out, oiled the stem some and switched to the next size bigger carrier which leaked horrendously. I then returned to the original carrier with no extra oil added and it began to shoot as consistent as it does now.

Other then that I had no real problems except for some occassional leaking that goes away after I fire a few rounds and a few times when firing some pretty long strings, the bolt would not reset all the way and I had to stop firing and sometimes bang down on it and heard the click of it resetting. This normal sounding or something else going on?

[lidocaine]

thats good to hear, thanks for the update madcat.
If mine doesnt clear up next weekend ill have to try it too. 1-3fps diff. that is sick!

[athomas]

Other then that I had no real problems except for some occassional leaking that goes away after I fire a few rounds and a few times when firing some pretty long strings, the bolt would not reset all the way and I had to stop firing and sometimes bang down on it and heard the click of it resetting. This normal sounding or something else going on?That is bolt stick which usually indicates that the carrier is too tight. You may have a faulty oring. Try a different carrier oring and retune the bolt setup.