I bought a Nate Chronograph to check my tune on my .25 DRS Tactical. The chronograph had sensor issues so I messed up my tune. I received the replacement chronograph and tried to tune my ar but t couldn’t get above 630fps with regulator screw screwed out as far out as possible and hammer spring to max. I degassed and bottomed out regulator screw plus one full turn. The fps increased when the regulator screw was turned in and reached 925fps bottomed out with max hammer spring. The regulator adjustment is opposite of what I would expect, am I looking at a bad oring on the regulator valve?
FX DRS Tactical Tuning Issue
- Thread starter Bigbaby
- Start date
No. Max pressure and max spring doesn’t equal max fps. You’re overpowering your hammer spring. That’s why your velocity went up when the pressure went down. But at very low pressure you’re just wasting a ton of air by smacking the ever living piss out of your valve pin. Do not think of the tuning system and reg as volume knobs. They absolutely are not. You must balance them. Picture this as a balance scale, you know the old scales of justice type. Every time you raise pressure. The scale tips you’ve placed another coin on the pressure side. So the scale tips on the empty hammer side. You must place an equal coin on the hammer spring side. There’s a learning period and you’re going to have to get familiar with your fx. What are you trying to shoot. A velocity means nothing without a projectile and weight. What barrel length.
Back your hammer to minimum. Drop your reg to 100-110-120 wherever you want. Leave it set. Then load your mag. Take a few shots through the Chronograph. Then start taking up the hammer spring a click on the big wheel at a time. Your velocity will rise and rise. Until you reach a point where it stops and likely starts falling. At that point you’ve reached the max velocity potential for that pressure. You either dial back the big wheel one or two positions and then start moving the micro wheel
Up a click at a time. Until you find a velocity you like and minimize the spread. Or you raise the pressure. Which will again drop your velocity if you’ve done this correctly. Because your reg pressure is overpowering the hammer strike. And you must start working up again.
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common mistake
your hammer+spring can not generate enough power to open or keep the valve open long enough with that high plenum pressure.....less air will get behind the pellet....lower speed
your hammer+spring can not generate enough power to open or keep the valve open long enough with that high plenum pressure.....less air will get behind the pellet....lower speed
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The DRS Tactical only has one wheel with 100 clicks for hammer adjustment. I installed a meter on the plenum yesterday only got good fps with the regulator bottomed out (evidently had residual air) and max hammer spring. I took a look at the plenum pressure today and it read “0”. I adjusted to plenum to 100 bar and backed the hammer spring down 40 clicks, then adjusted the hammer spring up until I got 900fps on the chrony. I went up on the pressure and fps went down, so I backed pressure back down to 100 bar and readjusted the hammer spring to give me 900-913 fps. 900fps is what the DRS was shooting when it arrived and has been very accurate so I think I’m good again. I appreciate the advice.
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what projectile are you trying to shoot? which barrel length, what are you trying to do.
100 on a .25 can obtain 900, but pretty low. Might have better luck at 120-130
bump that reg up to 125-130, try starting at the middle of the wheels adjustment range. MAX is not exactly meant for lower pressures.
100 on a .25 can obtain 900, but pretty low. Might have better luck at 120-130
bump that reg up to 125-130, try starting at the middle of the wheels adjustment range. MAX is not exactly meant for lower pressures.
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It’s a .25 with a 600mm barrel shooting JSB 25.39gr. My velocity dropped when I increased pressure above 100bar with same hammer setting. I may try again with higher pressure if my accuracy is off, right now I’m just happy to get my velocity back to where it was before I started messing with it.
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Correct, when you increase pressure, you increase hammer SLOWLY. go up 10 bar, click up 1 or 2, shoot 3 shots... see where velocity goes, then click up 1-2 more, see where its at. until it stops rising, or it drops. wherever the velocity stops rising or drops, is your absolute peak velocity for that regulator pressure. Then roll back a click or 2. that'll be your sweet spot.
The air presses against the valve, Every 10Bar higher, thats 150lbs more force pushing on the valve stem. so your hammer has to strike harder to get a full open. More air pressure also pushing on the pellet.
So, when you raise your pressure 10-20bar and leave the same hammer set.. you're going to lose a lot of speed. You have to work up the wheel. but do it in controlled small increments. 1 hammer wheel position can be the difference between a good spread and a perfect spread.
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but also, if you increase your hammer strike power above the peak for a given set pressure, you're now wasting air
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I’m probably about 85 clicks in on the hammer spring at 100bar. If going up on plenum pressure would require a heavier hammer spring adjustment wouldn’t it defeat the purpose. I’m thinking that the lowest pressure to get the desired velocity would be the best option, am I wrong?
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Thats extremely high for 100bar your gun is capable of well over 70ft lbs of energy.
I would actually go to 10 and work up notch by notch, your gun is capable of breaking the sound barrier with 25.39
I would actually go to 10 and work up notch by notch, your gun is capable of breaking the sound barrier with 25.39
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Mine actually has an exposed wheel on the left side that adjusts the hex head that you’re showing.
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Awesome.
yes, try using much less spring. Theoretically if you go by fx's claim of 78ft lbs max for the 600/25 you should be topping out at 1176 with 25.39 pellets.
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I guess I need to back off the hammer, set regulator to 110 or 120bar then adjust the the hammer to get 900fps, hopefully not having a heavier hammer than I do now. There’s only about 15 clicks left before I reach max. I wish I knew the stock plenum pressure on the DRS Tactical, it’s probably lower than the Classic DRS because of the larger plenum volume.
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The regulator pressure is the plenum pressure
900 with 25.39 is the STARTING point for that gun. You should be way lower in the hammer spring range
I’m trying to tell you you work up to find what you’re looking for. Tuning to 900fps at 100b is going to use a ton of air. 900at 130 will use very little.
Your gun can do 900 with 40gr
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