My Field Target Project

[Motorhead]

Good deal .... Having a stable regulator is so important in a competition air rifle.
Could not be happier with the Huub in my .177 Custom M-rod ..... deadly stable and accurate for 80+ shots at 19+ # energy.

Hope you get your Huub soon and install it ASAP .... smile time 

Huub regulator for Mrod??

Indeed 

[michaelthomas]

Did a little more messing with the setup today......mostly just fine tuning the hammer (solenoid) for better efficiency.  I love this baby tank.

Lost a few FPS......about 4, but gained a lot in efficiency.

Reg is still at 1550psi......JSB Exact Heavies......10.4 average.

3000psi high
1450psi low
Hi 878
L0869
Ave 875
ES 9
SD 2
17.7 FPE average
Efficiency of 1.45 FPE/CI

23 shots on the 43cc (42.8 actual) tank

With the standard tank of 220cc.......maybe get 120 shots in 1 - 1.2% spread.

This scenario was an average of 3 sessions.......which were almost identical.

I may try enlarging the porting again and see if I can lower the reg even more and still maintain power.  I'm pretty sure I can.

If I shoot down to 1000psi......I'm still getting about 830 fps in the current form.

Mike

[rsterne]

As you enlarge the porting, you are creating wasted volume between the valve seat and the pellet.... That decreases the pressure available to drive the pellet down the barrel.... In addition, as you know, the bigger the ports the "peakier" the velocity curve.... It's just like using a hot cam in an engine, more peak power but over a narrower range.... If you go too big on the ports, you will start to get a drop in efficiency from the wasted volume.... You may start to get a larger ES because even slight pressure variations between shots will move you away from the "sweet spot".... Then, as you reduce the setpoint, you will lose efficiency just from the lower operating pressure.... What you will do is get a wider pressure range to use from the tank, which may increase your shot count....

Before you make ANY more changes, I strongly suggest you draw a curve of velocity vs. hammer strike.... If you are operating on the "knee" of the curve, and if you are happy with the FPE level you have.... DON'T change the operating pressure.... Finding that perfect balance between pressure and hammer strike is the most important thing once you get to the FPE level you want....

For reference, my .177 cal 2260 PCP setup for FT got the following results with the same pellets, over a total of 105 shots, 1500 psi setpoint, 13 CI Ninja tank: 

3000 psi high
1100 psi low
Hi 933
Lo 915
Ave 924
ES 18
19.5 FPE average
Efficiency of 1.20 FPE/CI

The maximum velocity occurred at 1300 psi, the ES and efficiency if I stayed above the 1500 psi setpoint was significantly better, but I did lose some shot count....

Bob

[michaelthomas]

OK.....I'll make a graph and see what I come up with. 

I'm happy with the power level......going much higher has proven to be slightly less accurate for me.  Going lower has been equally accurate, but I suppose it is more susceptible to the wind.  I have wondered if my 6000ft elevation has played into that since the speed of sound is slower here.

Mike

[Sfttailrdr46]

Good deal .... Having a stable regulator is so important in a competition air rifle.
Could not be happier with the Huub in my .177 Custom M-rod ..... deadly stable and accurate for 80+ shots at 19+ # energy.

Hope you get your Huub soon and install it ASAP .... smile time 

Huub regulator for Mrod??

Indeed 

Once I'm comfortable with the stock version and squeeze as much performance them I will begin the Modding process. Right now saving for the rest of my PCP support equipment . Going the Nitrogen route as it is readily available and I have a steel 80 cu ft tank already from doing HVAC repairs, Just need to upgrade the tank regulator to a a PCP rated rig and a Guppy tank for play dates 

PS: Once I am a little more familiar with the mechanicals of the rifle it will be easier to feel comfortable tearing into it

[rsterne]

Most of the FT guys I know find the JSB Heavies good to the high 800's (890ish) but usually don't push them over 900 for the best accuracy.... I guess it would depend on the barrel and twsit rate.... You're not far off that now anyway, and the efficiency will drop if you push the FPE higher....

Bob

[michaelthomas]

Bob, I figured out the chart......for the most part.  Copying and pasting was giving me trouble.

Anyway......I started each voltage change at 3000psi and shot til I exceeded 1-1.25% extreme spread.  The last column at 57 volts, however, would not hold 1% right from the start.  I'm not too worried about that since I won't be using that setting anyway.

The reg is still at 1550psi and everything else was untouched. 

If I stick with the 4th column (58.5volts).......I should net 145 shots on the full sized reservoir at 17.3FPE and 1% extreme spread.  This is about the point where the gun starts to quiet down a lot, too.

It's pretty interesting......I'm glad I made a chart, now.  Thanks, Bob.

There really does not seem to be too dramatic of a drop in velocity over the range of adjustments.

Mike

[michaelthomas]

I forgot it doesn't show pdf's without downloading.

Here is a scanned jpg.

[michaelthomas]

Most of the FT guys I know find the JSB Heavies good to the high 800's (890ish) but usually don't push them over 900 for the best accuracy.... I guess it would depend on the barrel and twsit rate.... You're not far off that now anyway, and the efficiency will drop if you push the FPE higher....

Bob

That is similar to something I read that quoted .8 mach.  I have shot a bunch of 250's on the international 25m benchrest target at anywhere from 830-885, but none over 900fps with those pellets.

Mike

[michaelthomas]

I put the standard size tube back on and tried a full string at 58.5 volts.

For grins I charged to 3200psi

I shot down to 1300psi.  The reg was at 1550psi.

I got 135 shots average fps 873.

Efficiency was 1.35 FPE/CI.

It seems to behave a bit differently with the bigger tube.  Looks like I can lower the voltage more.

The high was 878, and the low was 866.  Around 1.4% spread.

I had to put the data on two strings, so the first string had a standard deviation of 2......and so did the second one, but together they may have been different.  I don't know, and don't feel like calculating.

Mike

[rsterne]

Looks like you have a short plateau at 59.5 and 60 volts, I would expect that to continue.... Anywhere from 58-59 volts looks good, I'd use 59 if the spread is tight and the accuracy good....

Bob

[michaelthomas]

The 58.5 with the large tube seemed to act like the 60v with the small tube.  The gun was definitely loud compared to what I was getting with the same voltage and the small tube.

Is there any sense to be made from that?

I really don't need more shots than I'm getting right now......so I need to see if the accuracy is still there.

I'm expecting the Huub regulator to perform a little better than mine......although a few small changes on mine should improve it a fair amount.
He said I should be able to hold less than 1% over the entire string at this power level.  I need to get out and shoot once that is in. 

Sometimes the first shot on mine is weird after a fill......sometimes it's not.

I am experimenting with harmonic tuning.  A fellow named Tony Purdy has some calculations that have been performing very well for some bench rest (air rifle) guys.  I ordered a reamer that I need to finish the barrel tuner slide.......always waiting on something.

If anyone is interested in reading about it there is some stuff on benchrest central.

Mike

[lloyd-ss]

Michael,
The loudness almost always indicates higher residual pressure in the barrel as the pellet leaves the muzzle. But why? Maybe the larger tube flows the air a little more freely? If the tube is larger on the regulated side, I can see that happening. Louder also usually indicates lower efficiency because of the excess air.
I have to say that the consistency and shot count you are getting is pretty incredible!
Lloyd

[rsterne]

I can't understand why your reservoir size is making a difference unless it is the Plenum volume you are changing.... OR unless the larger tube flows the air better INTO the regulator, but even that would be a stretch to explain why.... Mystery, that!....

However, I do have a suggestion.... Redo your chart using the larger tube.... You only need to shoot a few shots at each voltage, not a complete string, to plot velocity vs. voltage, and that is all you care about.... finding the "knee" on the curve....

Bob

[michaelthomas]

Thank guys.

That's a good idea, Bob. 

Mike

[michaelthomas]

I got the regulator from Huub today.  He recommended that I set it no lower than 1600psi....I guess it doesn't work as well.  You can rearrange the springs to go lower....but there is a little gap in the pressures between the two settings.

Anyway..... I set it at 1600 and tried it with a 12cc plenum.  He recommended 8cc.....but I would need to make a spacer for 8cc.  Tried it out, and it was all over the place......something like 28fps spread on 25 shots or so.

I made an aluminum tube (spacer) to fit in my 12cc plenum......so I could make it 8cc.  Tried again, and this was way better.  It shot about 10fps slower....but held 6fps on 25 shots with my little tube on the gun.

I left it like that and put the normal tube back on and shot 60 shots from 3000 to 2150.  I got 1.33 FPE/CI with an average of 874 fps and  17.6FPE.  It held 10fps ES, and had a SD of 2.  Used 14psi of air per shot.  Should be able to get another 53 shots if I shoot down to 1400.

I may try a different spacer to choke the plenum down a little more tomorrow. 

This regulator likes a big change in pressure to reset, if you want a tight spread.......which is what Huub said.

I'm happy with it.  It settles to its peak faster than mine.

Mike

[rsterne]

Ahhhhhhhh.... so it requires a small plenum to get a large pressure change during the shot to reset consistently.... Got it!.... That would mean his design is better suited to low to medium power applications.... The only way to get high power with a small plenum is to greatly increase the setpoint so that the AVERAGE pressure during the shot is what is needed to provide the FPE you want.... unless the regulator design is so fast-operating that it can top up the pressure DURING the shot, which I have never seen....

Bob

[Motorhead]

Some fine tuning and you will get there I'm sure.
Just ordered another Huub for my AT44 this morning.  Really like his regulators 

[michaelthomas]

I have been doing 25m indoor benchrest shooting over here for winter, since FT practice outdoors is done.

I de-tuned my rifle to 12FPE, and am very happy with the way it shoots indoors.  I set the reg at 1150, and am shooting 8.44 JSB's at 788 or so.

I got about 280 shots today on one charge (3000-1050)......so that's pretty cool.

Late week I shot 2 25m targets with the gun at 18FPE, and got a 250 8x, and a 250 9x with JSB Exact Heavies.

Today, I shot 8 targets, and the best was a 250 12x, and the lowest was a 248 15x.......all on one charge. 

The gun seems to like a slightly larger head pellet in the 8.44's.......but not much.

It seems to be a little easier to shoot at 12FPE.  I like it.

If there is anybody close that wants to come shoot in a really nice, well lit, 70degree, 55 yard indoor building.......let me know.  I would enjoy the company.  Selittle came out last week for a few hours.

Mike

[Sfttailrdr46]

  Congratulations Michael it looks like you are getting your getting the new rifle dialed in