Boring out air adapter

[1996XJ]

Has anyone with a backbottle GF Phantom every tried to bore out the air adapter to help reduce the shootdown when autotriggering.  Im wondering if the velocity will stay up if there is more room for the gas to expand behind the valve.


The only problem i see is that the vavle spring isnt wide enough, but i figure a washer should be able to counter that.

[thkyle]

You can't pump fast enough to cause "shoot down" with a Phantom or any pump for that matter.

If you are experiencing a drop in velocity from heavy auto triggering, it's from the chilling of the CO2 tank. This drops the operating pressure and in turn will drop your velocity and range. You are not fast enough to starve it for gas, even with micro line.

The only way to prevent this is to.............

1. Slow down!
2. Keep your CO2 warm with a remote that lets it expand in the line.
3. Use HPA.

[1996XJ]

I already use a 13/3000 on it and still have a problem.  Im just thinking that the internal expansion chambers are small to increase the 12g efficiency.  If that expansion chamber is larger i figure more HPA would be able to expand and there would be less shootdown.

[Have Blue]

Are you sure that you're not just seeing a feeble recharge on your HPA reg?

[thkyle]

That would be my next thought also if you were already using HPA.

I have heard a lot of people that were disappointed by the performance with the regs that came on some of those small HPA tanks.

If you can't get a good flow out of your tank because of the reg not recharging fast enough, then increasing the volume it needs to fill will only make matters worse. A smaller volume behind the valve should be easier for a bad reg to fill up to pressure.

[Ed]

Plus HPA doesn't need to expand as does CO2.....

[1996XJ]

My field has a 20 person selfserve HPA station that is already regulated at 3000psi(first 10 spots), and the guage is reading exactly 3000psi after i fill.  So that isnt an issue.

I can see the paint drop drastically closer when i use the AT.  When i shoot it over the chrono it would shoot at 270, once i start to AT the velocity will be anywhere between 200-250 depending on how fast its pumped.  Im just tired of paint bouncing because of the AT.

HPA technically would have to expand since every time you shoot a lower pressure area will be created around the valve til gas from the tank EXPANDS into the expansion area.  But not nearly as much as co2.

[1996XJ]

That would be my next thought also if you were already using HPA.

I have heard a lot of people that were disappointed by the performance with the regs that came on some of those small HPA tanks.

If you can't get a good flow out of your tank because of the reg not recharging fast enough, then increasing the volume it needs to fill will only make matters worse. A smaller volume behind the valve should be easier for a bad reg to fill up to pressure.

Air should flow though the reg at the same rate regardless of the area.  If there is an abundance of air outside the valve should the velocity remain higher before the shootdown sets in?

[Rayodder]

Auto Trigger shoot down is due is flaw of the mechanics, During auto-trigger the sear trips the bolt before the breech is complete sealed right behind the ball, so that is always a minute amount of gas that gets diverted around the seals and out the back.

It's a problem all guns experiences even with Sheridan valve ones like Snipers and Palmer, it's a trade off with Auto Triggering.

[Punishers Customs]

There isn't a 'flaw' in the mechanism, just a fact of the layout. However, your forward stroke should be quick enough to seal the breach as the sear is releasing. Generally speaking, you should see something more like 10fps drop off at most while autotriggering.

As has been brought up, it's far more likely a supply issue and even MORE likely (also as stated) the reg on your tank. Chances are better than 50-50 that the recharge rate isn't up to the flow requirements and that is the cause of your drop off. Try swapping to a CO2 tank and see what that does. Try an HPA tank with a better reg like a Centerflag etc.

[1996XJ]

I dont really think reg flow is a problem since i was able to fullauto dryfire my old 98 with rt.  Ill have to try it over a chrono though.

Ill try going back to a 9oz and see what happens.

[Unimoose]

My field has a 20 person selfserve HPA station that is already regulated at 3000psi(first 10 spots), and the guage is reading exactly 3000psi after i fill.  So that isnt an issue.

All that pressure reading means is the tank is full.  It in no way measures how the air moves out of the regulator and into the marker.

[1996XJ]

If the autotrigger releases the hammer before it reachs the full stroke then then the hammer wont have as much force when it hits the valve which means lower velocity.

Would this be correct?

[thkyle]

Don't think that's true. The main spring has the same potential energy stored in the compressed main spring as soon as the sear locks onto the bolt. The main spring has the space to completely expand before it reaches the forward position where the sear can be tripped by the hammer (frequent complaints by new owners of a rattle inside their gun)

Over the last year I think that there has been at least three people that have posted here wanting to know why their gun didn't fire.

The reason in every case has been because the bolt wasn't all the way forward, so the sear wouldn't engage the trigger. To be exact, the very small space of the bolt o-ring seating was all the it took to prevent the Phantom from being able to shoot.

So in summary, I don't think you can shoot the Phantom until the bolt is almost completely forward, and even if it was possible, the spring would still have the same energy to propel the hammer into the power tube.

This is a problem with other pumps, and is true with a Nelspot, but the timing of the bolt being forward and contact with the trigger and sear on Phantoms is nearly perfect.

[splattttttt]

If the autotrigger releases the hammer before it reaches the full stroke then then the hammer wont have as much force when it hits the valve which means lower velocity.

Would this be correct?

I think you're getting warmer now.
I'd look at the valve spring next. Increasing the dwell on the valve pin by using a softer spring will allow more output, and help maintain higher velocities.
I could be wrong though, since I never used the AT function of a Phantom and have never experienced this problem.
I have on the other hand experienced co2 pressure drops especially from a twelvee. But never in warm weather.