Tuning Pitbull / huma regulator on modified benjamin bulldog update
- Thread starter bd2021
- Start date
Wanted to try it tonight, but not sure as we need to run around to a few stores. Just going to shoot into my trap in the garage a few times and see what I can see. I expect it is 100 to 200 psi too high for "max" power for my set up. Before putting this in/on I tested one last time, shot 1 was low, shot 2 was a little low, shot 3-5 were right where I wanted them. And that let the stock tube pressure down to about 2400-2500 psi from the stock 3000psi fill. So maybe it is close.
What really helps is I have a baseline on my rifle where you don't. So I can tell if it is doing something strange within a couple of shots and know what speed/power I'm hoping to hit. If it offers more, I'll take it, but I think I need to work on the hammer and hammer spring to get more. Or I need to reduce pressure on the valve return spring (might be eliminated on yours). Removing the valve return spring has generally been good for 20-30fpe, but will probably use a bit more air since the valve will fly open farther. Cutting it slightly shorter might be the way to go for me, I have a spare already (was like $2 and I was ordering other parts).
Also different is mine is only ported to .221-.225 ish, whatever a #1 drill bit got me and some smoothing with files. Yours is probably open up close to .300 ports, not sure how this will change the results if the regulator is set the same. Mine should flow less air which should allow more shots per fill and compromise 20 or so foot pounds of energy. It's never going to go 600fpe, so I'm just giving up trying. Eventually I'll get a higher power rifle, but the last attempt has left me $300 in the hole! Maybe I'll get a Pitbull 457, it should be able to get a 3 shot up to 500-600fpe which was where I wanted to go with the Umarex Hammer that just didn't work out.
What really helps is I have a baseline on my rifle where you don't. So I can tell if it is doing something strange within a couple of shots and know what speed/power I'm hoping to hit. If it offers more, I'll take it, but I think I need to work on the hammer and hammer spring to get more. Or I need to reduce pressure on the valve return spring (might be eliminated on yours). Removing the valve return spring has generally been good for 20-30fpe, but will probably use a bit more air since the valve will fly open farther. Cutting it slightly shorter might be the way to go for me, I have a spare already (was like $2 and I was ordering other parts).
Also different is mine is only ported to .221-.225 ish, whatever a #1 drill bit got me and some smoothing with files. Yours is probably open up close to .300 ports, not sure how this will change the results if the regulator is set the same. Mine should flow less air which should allow more shots per fill and compromise 20 or so foot pounds of energy. It's never going to go 600fpe, so I'm just giving up trying. Eventually I'll get a higher power rifle, but the last attempt has left me $300 in the hole! Maybe I'll get a Pitbull 457, it should be able to get a 3 shot up to 500-600fpe which was where I wanted to go with the Umarex Hammer that just didn't work out.
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Every bulldog shoots and likes different settings especially once modified. That's why in previous posts I stated that my gun settings can be a guide, but other guns will have to be tweaked. A chronograph is a must in this instance or you will be only guessing. I did this too before buying a chrono. Now I know when my gun is acting funny or something isn't right. One change at a time will tell you a lot about how the gun responds to what modifications were made. My gun has been ported to about .265 to .267ish, polished and smoothed out the transitions to the best of my abilities. PITBULL normally sets the regulators at 2700 psi, and I tried my shot strings there, my rifle prefers 2900psi and I adjusted my hammer spring around that. I reshaped my valve and removed my valve spring and I am happy with my results. I do have a balanced valve from JSAR that I have yet to try. That will be my next mod if/when I decide to do it. I find that tuning and modding is almost as fun as shooting. Veradium air is also another company that modifies bulldogs, his mods are super high power going to the 380ish fpe range, but not regulated. 10 to 12 shots, last ones not near the high power mark. Don't know what he does to the barrels, but also from what I have read, makes the bulldog super accurate.
-JP
-JP
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Tested mine tonight, 10 shots and a little air left so maybe 11-12 total. Messed with the spring a little, right up around 200fpe now and where I may leave it sitting. Might put the Pitbull spring in it and back the adjuster out a bunch.
Top 5 shots are stock airtube, but ported. Left most column is meters per second, second column fps, third fpe. The next 10 shots are meters per second after the mod with number of hammer spring turns out from binding (4 turns, 3.5, and 3 turns out). 3 turns out is right about where I think I want to be. Shooting 155 grain Lyman flat nose sized at 0.357 and powder coated.
Note on shot 1 of regulated that the speed is low, that's the regulator creep over night.
Pretty happy with the Pitbull tube and Huma reg. so far, will need to send a bunch more ammo through to really finish the settings.
Top 5 shots are stock airtube, but ported. Left most column is meters per second, second column fps, third fpe. The next 10 shots are meters per second after the mod with number of hammer spring turns out from binding (4 turns, 3.5, and 3 turns out). 3 turns out is right about where I think I want to be. Shooting 155 grain Lyman flat nose sized at 0.357 and powder coated.
Note on shot 1 of regulated that the speed is low, that's the regulator creep over night.
Pretty happy with the Pitbull tube and Huma reg. so far, will need to send a bunch more ammo through to really finish the settings.
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Greg E, your numbers are great. Looks like you are getting your Bulldog exactly where you want it. Great job.
-JP
-JP
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I think the valve return spring needs to be altered or changed, then I might be able to lighten up the hammer spring a little. The 3 turns out from bind kind of bugs me, I know it can allow some bounce like this. Alternate is the Pitbull hammer spring which is much stiffer and shorter. I may have to try it since I do already have it.
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Just leave the valve return spring out and give it a try. I did try the Pitbull hammer spring, I could only manage to have it flush with the receiver body. It made my gun shoot more violently and got closer to 300 fpe, but it was way too powerful for me and using more air on my gun. Your experience may differ, give it a go too. Never know unless you try.
-JP
-JP
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Again, thanks for the advice, gives me a starting point. The Pitbull spring has a spacer, maybe if I leave the spacer out I can get a very small free flight to stop any bounce.
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Checked today, still holding pressure at the 3100psi where I stopped after the test. Regulator at this pressure has not crept but it is so close to reg pressure I wouldn't expect it to creep. I'll put more air in it this weekend, need to test using batteries on my Traveler compressor and see how it does. Last time I aired this up I was surprised that it only took 5 minutes from 3000psi to 4500 psi on AC power, took way longer to get up to 3000 from empty. I'll need to look at the compressor one of these days and see what's what.
BD2021, any word on yours yet?
BD2021, any word on yours yet?
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Well, they did identify a problem with the regulator and gauge, and fixed them. The gun is on its way back via what looks like UPS ground.
When they first shipped it, they did USPS overnight, which was nice...but since it was in an airplane I wondered if the cold temperature caused the regulator to let more air into the firing chamber, then when it got back to a normal temperature there might have been back pressure on the regulator. Initially they shot that idea down. I have no clue if this hypothesis was ridiculous or not. But I do hope it is fixed, I'll test it out sometime next week. They warned me that the regulated pressure gauge may vary depending on whether +/- 100 psi.
When they first shipped it, they did USPS overnight, which was nice...but since it was in an airplane I wondered if the cold temperature caused the regulator to let more air into the firing chamber, then when it got back to a normal temperature there might have been back pressure on the regulator. Initially they shot that idea down. I have no clue if this hypothesis was ridiculous or not. But I do hope it is fixed, I'll test it out sometime next week. They warned me that the regulated pressure gauge may vary depending on whether +/- 100 psi.
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Maybe +/- 100 psi, but generally mine has been much closer than that. But your previous experience would suggest either the gauge was WAY off, or the regulator was set much higher than 2700/2800psi.
Hopefully they adjusted it down to this level for you so you can get a good solid 10 shots. If not you may need to turn it down yourself.
Hopefully they adjusted it down to this level for you so you can get a good solid 10 shots. If not you may need to turn it down yourself.
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