Tuning FX Impact M3 modified plenum front part remedy for slow initial shots

In fact with low reg pressure while using 18.13 grain pellets at around 870 fps, M3 is not consistent for around 4 shots taken first time in the morning. 

Means it settles gradually after a few shots.

Seeker found a solution for it that worked for him perfectly but it worked for me partially. He used peek disc to avoid the O ring from protruding. 

Hence I went back to MK1 system of O ring sealing the valve rod in the plenum.

MK1 didn't have the problem that MK2 PP and M3 have.

Very few people notice it.

But for those who notice it, it's very irritating. 

Hence for more for consistency and for using various weight of pellets at various fps without much adjustment of reg pressure I understand that the new setup will work. Just like mk1 worked for all this.

I didn't do it for fitment. This is M3 hence no issues of fitment.

As discussed above, I did it to improve the potential of Impact M3. 

Too notch work, and a sensible fix. Hope it works well.

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Yes it's a very tricky part to make on laith.

Nice hopefully it fixes the problem for you

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I hope so.

Thanks

Just checked the pressure gauge. It's holding pressure perfectly whatsoever. 

The machinist has done his job perfectly as per my instructions. 

Bhaur

Hello Friends, 

The modified front part of M3 plenum is working fine.

In fact I understand that there are two factors.

One is better arrangement of O ring placement. This matter has been solved with the new plenum part even with PU90 O ring.

Although the O ring doesn't protude or extrude now but the stickines of O ring is still there.

Hence if I do not tune the way I have found best the first shot may be 20fps low. But the 2nd shot is always perfect. 

In order to overcome the first shot issue due to the stickiness of O ring , I tune it in the following way;

In case I need to achieve 900fps with a certain projectile, I take the power up to around 980fps by tightening the hammer spring.

Now I start closing the valve to the extent that I get the required 900fps. 

In this kind of tuning, since the hammer spring has enough power to produce 980fps the powerful hit of hammer nicely overpowers the stickiness issue of O ring and I get the desired 900fps in the very first short. For the 2nd shot although the hammer hit is high but as I have already adjusted the valve to such limit that it cannot produce more than 900fps the 2nd shot is also consistent. 

So with the mod in combination of this kind of tuning, the 1st shot and all the next shots remain in single digit spread.

Hope it helps.

Bhaur

@mubhaur, was your part CNC made?

Thanks for the tuning tips. Sounds smart.

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The front modified new part that I am using is made on a laith.

So 3 days labour involved for precision work. 

Bhaur

Mubhaur I like your idea making a new end-cap, way better then dropping the 2 orings (in sandwich) against the peek puck inside cavity.

I would do pretty much the same for my MK2, but I shoot BR so the first 4-5 shots I can just dispose.

>>> But this is not a lathe work - this is a CNC mill work (including cutting the thread) and the machine must have a good spindle break.

Second, the threaded end cap I would do deeper pocket so the metal doesn't even touch the NBR90.

Could even happen that the new=separate oring pocket not compressing the PUR90 and can work now stand alone....worth to test it.

Edit:

To make this same piece on CNC Mill, 3 side setup, total cutting time less then 6 minutes.

or the option #2

On a traditional=manual lathe a "offset diameter" separate into two pieces, and the smaller OD seal + lock in the same way as the Valve House titanium body. Only need an extra oring...

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People using Impact in competition in my country also complain.

The reason being that after the sighter shots there is 10 minutes gap in actual starting of competition and even in so short tome the 1st shot goes South sometimes. 

Bhaur