Tuning FX Boss .30, weird shot string - FPS goes up.

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strangeluck65

Member
Jul 10, 2020
238
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Florida, United States
First a little back ground on the rifle. It's a Boss .30 I bought last year and have been tinkering with. It has a 28" Lothar Walther barrel fitted to it, a Huma regulator and a 6.3mm valve seat. I'm somewhat new to the hobby but I've been asking a lot of questions of the long time members here, who have been an invaluable source of information. With that being said, I've got a head scratcher going on.

I started out with a 250bar charge. The first mag started with 811fps and went up to 853fps by the end of the mag. the second mag times were 867/start, 898/end. 3rd mag 907/start, 944/end. 4th mag 938/start, 959/end - with a high in this mag of 960fps. 5th mag 957/start, 924fps when I stopped at 150bar.

I know you guys will ask "what was the reg set at?". I tinkered with it until my speeds went up and stopped when it quit overpowering the valve/hammer. So the reg set answer is "hellifiknow". So is the FPS going up a problem or should I not worry about it and STFU?

I was using JSB Diablo 44.75gr pellets.
 
I had this problem on 2 different guns - as I would shoot each shot would be faster and next faster until I reached a platue then would go back down acting like an unregulated gun. 
Gun 1 turned out to be the regulator locked up and allowing tank pressure through needed rebuilt reg. 
2nd gun was low reg pressure. The hammer spring and reg were way not working together. Increased the reg pressure not the es is 3fps. I’ve noticed humans like higher pressure than low. Others have mentioned this on here before. 
 
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So the general opinion is that the reg took a dump. Well that sucks - it was a new reg. I guess I'll put the factory one back in, any tips on how to adjust it up? The reason I need more FPE/breach pressure is that with a fully rifled barrel requires a larger amount of air to force the projectile out of the barrel. When I first changed out my barrel my FPS dropped to 635 from 850(ish), and I would like to get it up to about 900-925fps.
 
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To adjust the factory reg, just hold the center stem stationary whole turning the adjusting nut. Turn it in for a higher setting, but go slow, no more than a quarter turn, and test. Given your mods, I have no idea of an appropriate reg set point, or whether the FX reg will accomplish it. 

If you haven't tested the Huma reg, your set point may be a full revolution off. And a tip on removing the Huma, don't drain the plenum by loosening the bottle adapter. The pressure will push the reg forward where it can lodge in the adapter, and when you unscrew it you will also turn the Huma adjusting screw and you will have no idea where your set point is. Drain the plenum by loosening the stock screw attachment base. Always measure the OAL of the Huma when installing, as a reference point.
 
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Best I can figure is that your reg is either not working.... or is set so hight that your hammer weight is not enough to properly overcome the pressure behind the valve (valve opens more as pressure behind it decreases, resulting in more power)
Click to expand...

That's my guess also. I would find out the OAL with the reg at its default setting, and start from there. A reg tester would make it a much faster process.
 
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Best I can figure is that your reg is either not working.... or is set so hight that your hammer weight is not enough to properly overcome the pressure behind the valve (valve opens more as pressure behind it decreases, resulting in more power)
Click to expand...

Well it is a new Huma reg, so maybe I'll tinker with the settings. Adjusting it is a real pain, you have to pull the bottle and the fill port housing.

Also, my factory reg is just fine. I kinda remember someone on the forum saying that it can be tweeked to get higher pressures from it. I've checked the youtube videos for information, but my reg looks a little different and I dont' know if that is a concern
IMG_20210730_011916588.1627623169.jpg

 
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FX has either changed its reg design, or the Boss uses a different one than the Royale, because that one is definitely not like the one that came in my Royale. Looks like it may be designed to hold the stem by the knurled wheel while turning the adjustment end, or vice versa, can't tell from the photo.
Click to expand...

That's what I'm trying to figure out. If you need better photos, I finally figured out how to upload pictures to the forum. All of the videos that I have found concerning the FX Boss factory reg have one with a lock nut - mine doesn't. I don't know how much of a difference that makes.
 
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To adjust the factory reg, just hold the center stem stationary whole turning the adjusting nut. Turn it in for a higher setting, but go slow, no more than a quarter turn, and test. Given your mods, I have no idea of an appropriate reg set point, or whether the FX reg will accomplish it. 

If you haven't tested the Huma reg, your set point may be a full revolution off. And a tip on removing the Huma, don't drain the plenum by loosening the bottle adapter. The pressure will push the reg forward where it can lodge in the adapter, and when you unscrew it you will also turn the Huma adjusting screw and you will have no idea where your set point is. Drain the plenum by loosening the stock screw attachment base. Always measure the OAL of the Huma when installing, as a reference point.
Click to expand...

At the risk of sounding dumb (again), what is OAL?
 
Upvote 0
To adjust the factory reg, just hold the center stem stationary whole turning the adjusting nut. Turn it in for a higher setting, but go slow, no more than a quarter turn, and test. Given your mods, I have no idea of an appropriate reg set point, or whether the FX reg will accomplish it. 

If you haven't tested the Huma reg, your set point may be a full revolution off. And a tip on removing the Huma, don't drain the plenum by loosening the bottle adapter. The pressure will push the reg forward where it can lodge in the adapter, and when you unscrew it you will also turn the Huma adjusting screw and you will have no idea where your set point is. Drain the plenum by loosening the stock screw attachment base. Always measure the OAL of the Huma when installing, as a reference point.
Click to expand...

At the risk of sounding dumb (again), what is OAL?
Click to expand...

OAL is overall length. If you take that measurement you can always get back to the same set point. It's important on a Huma because the adjustment is way to easy to turn, and it can move during the disassembly/removal process. 
 
Upvote 0
To adjust the factory reg, just hold the center stem stationary whole turning the adjusting nut. Turn it in for a higher setting, but go slow, no more than a quarter turn, and test. Given your mods, I have no idea of an appropriate reg set point, or whether the FX reg will accomplish it. 

If you haven't tested the Huma reg, your set point may be a full revolution off. And a tip on removing the Huma, don't drain the plenum by loosening the bottle adapter. The pressure will push the reg forward where it can lodge in the adapter, and when you unscrew it you will also turn the Huma adjusting screw and you will have no idea where your set point is. Drain the plenum by loosening the stock screw attachment base. Always measure the OAL of the Huma when installing, as a reference point.
Click to expand...

At the risk of sounding dumb (again), what is OAL?
Click to expand...

OAL is overall length. If you take that measurement you can always get back to the same set point. It's important on a Huma because the adjustment is way to easy to turn, and it can move during the disassembly/removal process.
Click to expand...

thanks for the clarification.
 
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