Tuning Bulldog.357 repair issues

[mac_was_here]

I loaned my bulldog to a buddy that has one on order (my mistake) My bulldog is modified with an n.302 port size modification, a huma regulated extended air reservoir with a quick connect fill nozzle on the end. The problem came when whistle britches decided to fill the air reservoir from the old, rear fill nozzle (that I hadn't removed) he says that at some point in the fill process, there was a loud sudden release of air, and that it then took an additional several minutes for the tank to completely drain.

I now have a bulldog that will not hold air. On disassembly of the receiver, a small green (composite maybe?) micro tube was found in the area of the trigger sear assembly area, loose and able to be picked out with tweezers (attached pic) not sure what this is, but my thinking is that it is toast. I can find no such part, or anything that looks like it on available schematics, so I am guessing it is an inclusive internal piece of another part, perhaps the valve body? I've ordered a kit from Captain O ring, and will be replacing all o rings, but that's not going to explain my little green friend and where he came from. Any help appreciated

Mac

 

[Ezana4CE]

@mac_was_here After the modifications, is the factory manometer now used to read the regulator pressure?

 

[mac_was_here]

Yes, it is registering the psi (2700) for each shot, released by the huma regulator installed in the extended reservoir. 

 

[mac_was_here]

So basically, using the old fill nozzle you’d be pressuring the wrong side (post regulator) of the extended reservoir. But I fail to see why this would cause a pressure failure, as all areas of the receiver and reservoir that would be affected by a backward fill situation are all rated for the same psi. But the facts show my thinking is wrong. Pretty sure replacing all the o rings, including the two on the valve body, may not solve the problem. I’ll know more when I get the valve body out, I’ve yet to pull it

 

[mackeral5]

Pressurizing the plenum to a pressure greater than the reservoir resulted in the regulator moving up the tube, exposing the vent, and nicking the lower regulator oring when it slid across the tube vent while under pressure.. the first loud hiss was the vent being exposed. The more quiet, slower leak was the oring leaking once plenum pressure dropped lower than reservoir and the regulator moved back against the plenum spacer.

The only purpose leaving the OEM foster in place on a regulated Bulldog is to cause the exact condition you just experienced, which is something you obviously wouldn't want to do intentionally. Thus one should not leave the OEM foster in place when converting to regulated.



Unless there is more to this story, there is no reason to fully disassemble. Pull the tube, disassemble to the reg, replace the reg orings, and reassemble....

 

[mac_was_here]

Thanks, that makes perfect sense. Pre-reg is designed for 4500psi, post is designed for 2700. Ive no idea how long it took for him to pump to a damaging pressure, but given the limited volume restrictions post regulated reservoir and receiver, probably under a minute. I’ve disassembled everything with the exception of the huma regulator inside the reservoir. I’ll pull it and take a look

 

[mac_was_here]

More to the story. None on the o rings on the huma regulator are bad, turns out the plenum being over pressurized did move it back up, away from the aluminum spacer sleeve and in so doing, lost seal. I’ve pulled it, and reinstalled, and it holds a seal, the reservoir will hold air fine, but I stopped filling at 3000psi, because I could tell from the ome gauge it was not regulated to 2700, but getting the full psi. I shot the rifle at 3000, and it shot fine. However, after the first shot, I could move the rifle around and could hear something loose in the reservoir. Upon disassembly, the c-clip was off of the regulator, free to move around within the aluminum spacing sleeve. I have cleaned, and put it back together, having really no idea if the above pictured tiny composite straw is or where it came from, or how it ended up in the trigger assembly area under the hammer. Also, I have to cock the rifle to fill. That may just be a 0 psi start fill level problem, and not a part of the issues the regulator is giving me (no regulated pressure at all)
I am not sure the new huma regulators offered by Pitbull air guns has an atmosphere vent hole. Thus, the undamaged o rings on the regulator. I can’t find a schematic of this particular regulator from huma air, as it is built specifically for the guys at Pitbull to offer with their extended reservoir, but I have reached out to them to inquire of rebuild kits, as well as a schematic showing the regulator parts. I still need to find out where my little tiny composite, broken tube came from. But the website at Pitbull says these new huma regulators do not require, or have a vent hole to slide past. Any help is greatly appreciated 

 

[mackeral5]

That is a new regulator setup from Pitbull, I had not seen that one yet. Its vent goes past the tube threads, outside of the plenum. Those details in my description of what likely happened obviously do not apply, but it is still a directionally accurate description....

Having to cock when filling from 0psi is normal.

You will likely need to replace some parts in the Huma, hopefully the circlip just popped out and didn't do damage to anything else. I believe Huma has several videos, the internals of all Humas are the same for the most part. What is custom/proprietary to Pitbull is the plenum configuration, venting, etc. Internal orings and seal should be issue Huma. If you do disassemble the reg just pay close attention to the bellville stack, it must be reassembled in the same manner as original.

----The random piece of composite material----it looks unlike any Bulldog or Huma part I have ever seen. I would give it a UFO status and not worry about it.

Thanks for sharing the pic and rest of the story.. Good luck 

 

[Ezana4CE]

@mac_was_here Saw this and thought it may be of some use to you. https://www.airgunsofarizona.com/regulators/huma-universal-diy-regulator-kit/