Fx impact M3 second reg slow recovery.

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Redwolfpaul25

Member
Apr 5, 2020
199
15
Devon, United Kingdom
Hey everyone, i use a M3 in .25cal first reg at 175bar , second at 155 bar and use 41g slugs at 960-965fps on power setting 16 and for 33.95g king heavy mk2s at about 960fps i use power setting 10. Last night i was doing some chrono testing and i noticed the velocity would jump 10-15 fps higher when the second reg hadnt recovered properly ( it would stick at about 145bar) but after another shot was fired the plenum would refill properly and the second reg would then settle back to where it should be, thus giving me my normal expected velocity for the 33.95g pellets.
Is there anything i can do to remedy this slow reg recovery/sticking ? Would changing the second reg washer stack do anything? Or maybe install a huma reg??
 
No, and there have been several posts with members trying to address this issue. Bear in mind temp alone can have a slight effect. Other issues involving valve stiction are more of an issue than a bar or 2 difference. I run a high pressure huma 2nd reg and my setting stay within a bar or 2 all the time.

Also, How old is you m3? The old ones had a delrin piston if I recall and the newer ones are brass. Some people polish these parts to try and alleviate it slightly. I believe that valve stiction gets worse after the gun sits for a while causing the initial velocity differences.
 
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Redwolfpaul25 said:
So i upped the front reg pressure to 190 bar and the second reg to 160 and now its working wonderfully! Quick plenum refills and the consistancy is straight away better, i took it out at 100 yards and it was grouping well under a inch so all good.
Click to expand...

Nice it was an easy fix. The sky is falling theme catches on pretty quick around here.
 
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7Green said:
No, and there have been several posts with members trying to address this issue. Bear in mind temp alone can have a slight effect. Other issues involving valve stiction are more of an issue than a bar or 2 difference. I run a high pressure huma 2nd reg and my setting stay within a bar or 2 all the time.

Also, How old is you m3? The old ones had a delrin piston if I recall and the newer ones are brass. Some people polish these parts to try and alleviate it slightly. I believe that valve stiction gets worse after the gun sits for a while causing the initial velocity differences.
Click to expand...
Since upping the first reg pressure so far so good the second reg refilling quicker now ,i have thought of fitting a gen 3 huma reg to replace the M3 s second reg but i want to see how things fair with this increased pressure .
 
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aklonewolf said:
I wish this issue had a fix.
Click to expand...
Step 1 is make sure the hammer spring tension is set to about 97% of the maximum achievable velocity. That will make gun least sensitive to minor variations in pressure and/or hammer strike. This state of tune is equivalent to an unregulated PCP operating in the sweet spot of its pressure range, where it holds a tight velocity over a wide range of pressure.

If that simple step doesn't fix it (or doesn't remedy it completely), move on to the two items described by 7Green....regulator creep and valve stiction.

Regarding regulator creep, start by assessing how much creep is present. If it's less than 5%, creep is not the root cause. How do you do that? Fire a couple of shots in fairly quick succession and check the gauge to see where the pressure settles to after 5 - 10sec. Then again in 5 minutes, then again at an hour. If you can wait, check again after 24 hours but it would be highly unusual for creep to continue after an hour. Let's say the gauge settled to 105 bar after a few seconds, and proceeded to climb up to 115 bar after an hour. That represents a percent change of (115-105)/105 = 9.5%. Which is greater than 5%, therefore sufficiently high to warrant correcting it. Inspect the end of the regulator piston with magnification to get a sense of how badly it is indented and worn. Wet sand it against a piece of glass or granite until it is flat and smooth. Recommended final grit of 2000 or so.

Or if the wet sanding is too daunting, replace the piston. The newer brass version should exhibit a more consistent setpoint over a wider range of temperature. The Delrin piston is more sensitive because of its differential coefficient of linear thermal expansion, which is about 5x higher than that of the regulator body.

Regarding valve stiction, refer to the following thread. A lengthy one so you might want to read it from the end if you are short for time.

Tuning - FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis

Hi guys, Welcome everybody. This is my first post here. I have a problem with my Impact Mk2 PP .30. The reg pressure is 145 bars. When I shoot shot after shot then my v0 is 260m/s. However, when the gun sits for a couple of hours then the first shot is 250m/s despite the exact same reg...
www.airgunnation.com www.airgunnation.com
 
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