Leshiy2 power jets configuration Q?

[bigHUN]

I don't want to post this Q in the original L2 thread, it will be burried soon, so here me go.
What I am trying to do is minimize the airblast coming out of the muzzle after the "projectile"
My current setup:
L2 with FX conversion kit for .22 FX 600mm liner;
Pellets testing in increasin increment 15gr->18gr->21gr->24gr (this is my target for cutting the elements);
Reg is irelevant because I am watching my grouping @ 50 meters, the target speed is 880-900 fps;
Last known Jets configuration was 2x0.8 mm that resulted a decent group size with 15gr and 18 gr, but wanted still to minimize the muzzle blast @ 900-920.
I swapped the jets to 2x0.9 for 18gr, and imediately noticed a timing issue between the Dwell and Mag indexing. The projectile didn't entirely left the Mag but the indexing wheel already started turning - resulting a "shave" of the pellet.
Last night I toke all apart (the R2D2 head), inspected an no signs of any wear or parts interference.
This brings me a headache and would like to ask a

Question:
Where it says in the Q&A Tips and Tricks

Is this directly means 2x0.9=1.8 mm (adding two jets ID to a Sum)?
or
Area (A = π r2) of 0.9=0.636*2=1.272 mm sq?

Sum of ID's or Sum of hole(circle) Area?

Edit: I am targetting Sub Moa at 50 meters with this L2 setup

 

[delooper]

That document is a little weird. The sum of the jet cross-sectional hole diameters isn't really relevant to the physics of the Leshiy 2. For the functioning of the jets, its (the square root of) the sum of the squares of the cross-sectional hole diameters that matters. This isn't unrelated to the sum of the two diameters, but it's not quite the same thing. The two are the closest when one of the two diameters is zero, and they're furthest apart when the two diameters are close to equal -- off by a factor of the square root of 2, i.e. about 40% off, which is significant.

My .22 with 35cm barrel has two 1.2mm jets, which is maybe on the extreme end. So perhaps the rule of thumb should be for .22 cal, you want 1.4 < sqrt(d1^2 + d2^2) < 2.4. That makes more sense to me.

 

[ctshooter]

So I am going to tell you to try going in a completely different direction with a 600mm barrel. Your dwell is way too short and you probably have to set your reg way too high to fill the barrel with air.

Try this setup and I think you will be very pleased with the results. Go 0.3/0.4 on the nozzles and you should see 880 fps with the 18.1gr pellets around 70-80bar on the reg.

 

[bigHUN]

Yes, I could not copy the (square root of) formulas for Area, so pasting the screenshot. First is using radius or the second is using a diameter:

This is my calculating each jet size - hole area:

According to this chart, 2x0.8 jets =1.6 mm (1.006 sq mm) is smaller then a 0.7+0.9 jets = 1.6 mm combination (1.021 sq mm).

2x0.7 the indexing worked well, but 125 bars won't be enough to propell the MRD's,
2x0.8 the indexing works well up to 125 bars and above no bueno,
2x0.9 the indexing not working well at 115 bars as well.

 

[bigHUN]

So I am going to tell you to try going in a completely different direction with a 600mm barrel....

Up to last week I shoot with 16gr AAFT 2x0.8 at 91 bar 850 ish and I had about 120 shots between refill.
But ran out with that weight and I switched to 18 gr but raised the Reg for speed, and after some 250 shots the mag indexing started failing.
{as a side note, this is not a mag indexing wheel (6.3mm OD), I have there steel bearings (6.0mm OD) instead and worked well for over 3K shots}
{also not a barrel length rubbing against the mag}
{not a pin length that leads the indexing jaw, I made sure to be shorter not to rub against the mag}
So, when I exclude all the above, the next suspect is the jets size.....

 

[bigHUN]

I fixed the Mag indexing/stuck issue. This was kind of stupid from my side not to start troubleshooting from there....
The Mag rotating shaft hole...it wasn't dry but the grease inside picked up some fine powder and maybe the extra resistance created the indexing lagg. Cleaned the hole + new grease = the Mag indexing working now fine regardless of Reg up or down.
2x0.6 jets 18gr AAFHeavy at 91 bar 895 ish, StDev 6.1. Need to work on the shot counts...
Going back to play with jets again.
Tomorrow I will be back to 0.7 and maybe 0.8 jets and targeting minimum Reg.

 

[sb327]

I can’t offer advice as far as jet (dwell) setting but I will offer this. For a given fpe, it takes a certain average pressure at the base of pellet through its travel down the barrel. This ends up that a higher reg pressure should yield a lower muzzle pressure (muzzle blast) for a given fpe (pellet/velocity combo).

Dave