Leaking Reg 2 on used M3: Upgrade Delrin piston to Brass or go Huma?

Worzel_

Worzel_

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Hey everyone,

I could use some advice from the tuning experts on here. I recently picked up a used FX Impact M3 and have been digging into it. I found out the previous owner fitted it with a Reg 1 bypass, so it's currently running on a single reg setup.

The issue I'm dealing with is that the rifle is leaking heavily from the Reg 2 vent hole. I went ahead and pulled Reg 2 out to investigate, and I found that it’s still running the old-style Delrin piston.

Now I'm at a crossroads and trying to figure out the best path forward to get this thing holding air and shooting consistently.

What would you guys recommend?

  • Option 1: Should I just replace the old Delrin piston with the newer upgraded brass version, give it a complete reseal, and call it a day?
  • Option 2: Should I scrap the factory reg entirely and drop in a Huma regulator? I've seen some mixed reviews on how well the Huma regs actually perform in the M3.
Any insights, experiences, or recommendations would be hugely appreciated!

Thanks in advance.

photo_2026-04-05 16.13.15.webp
 
Not an impact but I had creep that worsened on a stored Dreamline. Hadn’t ever touched it from new so not adjusted to explain the wear. Figured just worn from use. Rebuilt with the “new” brass piston and it has been spot on. Cheaper than a whole new one.
 
If the reg was performing ok then I'd go with option 1,also make sure to change the o ring in the block behind the trigger.
 
Full kit will be an easier fix using all new parts though you’ll have to sort the belleville stack to suit…some of the internal o-rings are a bit of a pig to change!
 
You could just clean it all up and replace the 'O' rings. Some polish the piston sealing face to try and reduce creep. The reg is about the only thing I haven't had to mess with on my MK3, but if I did need to I would likely change the lot out and be done with it.

John.
 
The newer reg body also has 4 holes instead of 2 to replenish the plenum.By the time you've bought a new piston,o rings and cleaned it all up then you may as well swap it all for new.Don't forget the o ring in the block.
 
Bigtone said:
The newer reg body also has 4 holes instead of 2 to replenish the plenum.By the time you've bought a new piston,o rings and cleaned it all up then you may as well swap it all for new.Don't forget the o ring in the block.
Click to expand...
Thanks, didn't know that.
 
Old style reg body on the left,you can just make out 2/4 holes,the pick is the one l use for the o ring in the block.
 

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Bigtone said:
Old style reg body on the left,you can just make out 2/4 holes,the pick is the one l use for the o ring in the block.
Click to expand...
Great thanks, I'll pickup the new reg from SGC. My current reg with delrin piston only has 1 hole.
 
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