Bulk fill Sheridan F model

Author Topic: Bulk fill Sheridan F model  (Read 2750 times)

Offline SnoValley

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Bulk fill Sheridan F model
« on: November 20, 2011, 12:47:07 PM »
I have a Sheridan F Silver Streak rocker, that is missing the fill cap and associated parts.
One option is to convert this to bulk fill. this a early version with the tube threads on the outside.
Can anyone give me some guidance on parts sourcing?
I could machine a fitting with a oring to fit inside the tube with a foster and anchor it thru the existing vent hole..Would this one screw be strong enough?
How would I determine the correct weight of co2 to fill the tube so as to not overfill?
Any other ideas?
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Offline TimmyMac1

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Early F
« Reply #1 on: November 20, 2011, 08:46:50 PM »
I make a bulk adapter for late F Sheridans and that can be fitted to the early gun if you can come up with a Cap. A spacer needs to be fabed so the cap takes the load of the pressure in the vessel while lining up the anchor screw with the factory tubes vent hole. The grub screw in a vent hole isn't going to be trusted to hold 1000 psi. The full thread engagement is the only sane way to contain the forces.
I use the vent hole as an achor point for the adapter to keep it from turning so the Charging tanks from old Crosman guns or the Painball Tanks with a Tank top adapter can be utilized to fill the gun easily. An alternate cap holds the adapter in the Late F gun (internal tube threads)and a hole in it lets the charging section stick out the front of the cap. It basically looks like a 114 Crosman on the front of the tube. You can always add a Foster male to that as the threads on my CO2 systems are the same 1/8" NPT.
Adapter is $50
Using hoses with CO2 transfer will always diminish the amout of liquid that will enter gun as they act as a vaporization chamber because of the warm surface area of the hose.
The best fills are done with gravity and temperature working for you and the gun real low on pressure and cool. Tanks should be warmer than the gun so the presure differential is greatest.
The F uses the hammer from the C and that is too heavy causing excessively long valve duration. If you grind the nose of the hammer down so it is considerably lighter it will create a much more efficient arrangement and the guns shot count will improve without losing power.
Early F guns have a nice finish and wood as well. Good Luck finding an early F cap. John Groenwold (JG Airguns)will be the guy who probably has it.
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Offline Ribbonstone

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Re: Bulk fill Sheridan F model
« Reply #2 on: November 20, 2011, 10:11:34 PM »
Am pretty sure there must be some fault with this inelegant solution, but it did work.  Did own an “F” and did something very much like this with it (but it was a later “F” with the inside threads).

This is for a Challenger 2000 co2 rifle...pretty much the same tube, vent hole, but made to run real slow.

Cut off a chunk of some cheap Mag-Lite wanna-be flashlight (think it was a “gimmie” light with some company's logo stamped on it).  Decent fit to the inside of the tube.

Cut two o-ring seats and let it straddle the vent hole.  Didn't seem inclined to move, so was just a friction fit (pressure on both ends of it, a tight fit, so it just stayed where it was). Think of how the Discovery mounts the gauge in the tube.

Standard bulk fill end cap.

Didn't leak...and on a gun already designed to get 70-85 shots on a 12gr., seemed to shoot forever.  Couldn't think of a real good reason to keep it as bulk fill, so just considered it an experiment to see if it could be done.

So let me have it Tim....must be some problem, even though it did work...just seems too simple.  Had considered tapping that spacer for a 1.8K burst disk, both as a safety and as a way to keep the spacer from moving...but gave up on bulk fill before going that far.

As to how to know how much to fill....would need to estimate the volume of the gas tube in either cubic inches or cc's.  IF you use the normal ratio of gas to air that is used in paintball tanks, then soemthing like 1 ounce of co2 per 43cc's.

How to know how much is in the gun would require a scale.  Just get the weight of the gun empty...then weight filled.  Most digital food scales can handle the job, at least to the accuracy needed for this job.
« Last Edit: November 20, 2011, 10:34:58 PM by Ribbonstone »
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Offline TimmyMac1

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Re: Bulk fill Sheridan F model
« Reply #3 on: November 21, 2011, 10:08:35 AM »
A small percentage o0f guns will leak CO2 past the Valve chamber as the solder joint is not always a 100% sealer.
I always look at 7/8" ID tubing like it had cartidges in it. If you can lay down four cartridges in the volume to be filled via bulk you get an idea of how much it can hold. An F could propabl;y fit 4-5 CO2 cartridges and at 12 grams per that translates to about 50+ Grams of CO2 or about two ounces. If you weigh the gun before and after or even the tank you can get an idea of how much you have transferred.
Since the gun is warm it cannot help but cause the liquid CO2 to vaporize as it enters making a 2oz charge pretty hard to accomplish without a prtetty good temperature differential.
The only downside to the F being easy to bulk is it is also too easy to air up to High pressure and do stupid stuff.
I really like the idea of a pressure relief built into the Bulk adapter vent. One other feature that would be prudent is the location of the back oring should be such that is someone decided to take the adapter off under pressure the back oring would get to the hole before the adapter blew off the end.
I used to do a dual CO2 conversion to F's that if you used the adapter in the wrong gun it would charge the system but not release the gas from the tube into the valve group and the gun would not fire but it was charged. Take that cap off without a vent hole at the oring and you have a nice hole in the ceiling the silhouette of the Adapter.
1000 psi is nothjing to be playing around with.
The F's achilles heal is the cheap Face seal they use and fortunately the Bulk adapters don't care if that is functional or not and a Gun that will not take 1 grams can often be bulked to to the durability and quality of the original F exhaust valves. They are good 90% of the time and outlive the face seals 3-4 times over.
Bulk adaptation is pretty practical when you consider the cost of F rebuilds and the cost of operation with 12 grams.
20,000 rounds for $20 of CO2 is pretty low cost shooting if you can find some decent 5MM ammo cheap.
That is some heavy usage and not everyone will appreciate the savings before they die. They will appreciate the consistency and shot count which seems to go forever.
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