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PostPosted: Tue Aug 19, 2014 9:30 am 
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Posts: 6845
Location: Rocky Mtn Hse Alberta
Please do a shot string again from a full fill and record gauge pressure after each shot.
That will determine if the trouble is the regulator or the gun.

Do that and report back asap.

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PostPosted: Tue Aug 19, 2014 7:40 pm 
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I too would have bought a regu;ator from Walter instead of anybody else.

Walter you let me know when you decide to make one for me.

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PostPosted: Wed Aug 20, 2014 3:34 pm 
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I took the gun completely apart. Lubed hammer. Inspected orings on reg and carefully reinstalled.
Filled to 2900 psi. Reg is set at approximately 120 bar. Took pictures of the pressure gauge on my gun between each shot. The needle was in the exact same place on every shot for the first 20 (about 1/3 the way between 100bar and 150 bar).
Here is my string with 18.13 grain.
879.3
875.7
869
866.6
876.2
871.5
878.4
865.8
868.5
869.1
867.9
869.7
869.9
869.8
872.8
867.9
875.4
864.7
867.7
869.1
854.9
853.8

Is this acceptable?

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PostPosted: Wed Aug 20, 2014 4:07 pm 
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Posts: 8977
Location: Coalmont BC
That string looks perfectly normal.... It's not unusual to see a slightly higher (a few fps) first shot after a fill, while the O-rings on the reg settle in.... and after shot 20 the velocity is dropping below the setpoint.... I'm curious about the efficiency, however.... Taking an average of 870 fps, that is 19.8 FPE times 20 shots = 396 FPE from 2900 psi (200 bar) down to 120 bar, a drop of 80 bar.... I'm not sure of the capacity of your reservoir, but I seem to recall that the AA uses about a 180cc tube, less your regulator and spacer of course.... If the remaining reservoir is 150 cc, that is about 9 CI, so the total amount of air you are using is 80 x 9 = 720 CI.... That would indicate an efficiency of 396 / 720 = 0.55 FPE / CI, which means you are using about twice the air you should be, and therefore getting only about half the shot count....

This is fairly typical of a gun converted to using a regulator if you don't reduce the hammer strike to compensate for the lower pressure the gun is running at.... If you gradually reduce the hammer spring preload, while recording the velocity, I think you will find that you can drastically decrease your air consumption and increase your shot count, without losing any velocity....

Bob

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PostPosted: Wed Aug 20, 2014 4:14 pm 
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Thanks for the insight bob. I have a 231cc tank. I don't want to mess with the gun past this. I'm currently looking for someone in Canada to do a full once over and optimization.
My valve spring requires 2.5kg to open 2mm. According to the manual for the reg I should be increasing that by a factor of 2.5. So around 6kg. There is no adjustment built into the gun so I would have to do a spring swap.
As far as reducing hammer strike I would assume a lighter spring?

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PostPosted: Wed Aug 20, 2014 4:58 pm 
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Adding valve spring or reducing hammer spring do basically the same thing.... so if there is no provision for adjusting the hammer spring preload, then yes you could have to substitute a smaller spring, or cut a bit at a time off the one you have.... If you can get a replacement hammer spring in case you go too far, that would be the method I would use.... I would expect you to be able to cut off a fair amount (by 1/4 - 1/2 coil at a time) before the velocity even drops.... Once it begins to fall, I'm betting at that point your shot count would be nearly double what you have now, at say 850 fps.... maybe even more considering your tank size....

Bob

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Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Aug 20, 2014 5:26 pm 
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Location: Central West River Nova Scotia
After installing my Lane reg., I tried to see how much speed I could possibly get. On the Hatsan It's just a matter of hammer spring adjuster screw. What I found out is the more preload or stronger hammer strike, the LESS speed I got. And much less shots per fill. I also increased the valve spring by I'm guessing about a third. Chances are your valve spring is too weak and your hammer spring is too strong. The mistake a lot of PCP owners make is thinking the more air they can get behind the pellet, the faster it'll push it out of the barrel. While it is true up to a point,, its the un necessary air after the pellet has left the gun that is wasted. The extra air might also account for more than optimal extreme spread .

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PostPosted: Wed Aug 20, 2014 7:29 pm 
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I read somewhere on the forum that reducing the mass of the hammer also lightens up the strike without changing or cutting the spring. So do they just drill holes in the hammer or machine it shorter? Just curious.

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PostPosted: Wed Aug 20, 2014 7:58 pm 
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Lightening the hammer doesn't reduce the energy (which lifts the valve off the seat, and needs to be reduced for lower pressures).... but it does reduce the momentum (which reduces the dwell, which saves air).... It will have an effect, but even getting rid of half the weight would probably not be enough in your situation.... Also, hammers are usually hardened, and must be ground, not drilled to lighten them....If you had the ability to lighten the hammer, and then also reduced the hammer spring preload, you might get the very best results for consistency and efficiency....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Aug 20, 2014 11:08 pm 
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I have been farting around for the last 4 hours with this thing. lol

Cut a couple coils off the hammer spring.

This is what I just got with crossman premier hp with a 2500 psi fill. (getting low on air)

There are a couple groups of great consistency then a couple of anomalies. Any thoughts would be appreciated.



930.4
898
900
899.2
895
899.1
897.1
898.7
900.7
893.8
898.9
900.5
909.2
907.2
903.8
908.7
935.6
907.1
909.6
904.7
917.3
909
913.9
909.1
915.5
911.4
911.0
908.3
919.9
899.7
904.6
895.4
897.7
894.2
891.3
885.6
881.7
871.9
870.7

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PostPosted: Thu Aug 21, 2014 12:54 am 
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Location: Coalmont BC
Well, lookie there!.... velocity up and shot count up as well, with less hammer spring.... *grin*....

You're now at about 30 good shots, from just 2500 psi, at about 32.6 FPE, so that's 978 FPE.... Starting at 2500 psi (172 bar) down to 120 is 52 bar, and your reservoir is 231 cc which is 14 CI x 52 = 728 CI.... That means the efficiency is up to about 1.34 FPE/CI.... That's a LOT better, in fact you probably won't improve it much from there.... Once you fill to 2900 psi you should be well over 40 good shots.... Not sure about the velocity swings, but I'm sure you'll get it sorted out....

How far away is your Chrony from the muzzle, and how are the lights placed (or are you outdoors?)....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Aug 21, 2014 7:58 am 
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Muzzle to chrony is 4'. I'm using a 50 watt halogen hung 4' over the chrony. My shop is all fluorescence lights so I use the halogen for the chrony to work.

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PostPosted: Thu Aug 21, 2014 9:36 am 
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You're getting close to what mine does, at those energy levels,the airtube should be closer to 300 cc unless Air Arms really shortened them fyi..kelly


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PostPosted: Thu Aug 21, 2014 10:26 am 
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Quote:
I'm using a 50 watt halogen hung 4' over the chrony

A single light source can give errors and varying velocity readings, depending on how far above the sensors you shoot.... The higher you shoot, the faster the velocity will be, and the closer to the sensors the lower.... That could easily be your wide ES.... You need two lights, one above each sensor, if you aren't shooting outside....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Aug 21, 2014 11:29 am 
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Posts: 3099
Location: Alberta Canada
rsterne wrote:
Quote:
I'm using a 50 watt halogen hung 4' over the chrony

A single light source can give errors and varying velocity readings, depending on how far above the sensors you shoot.... The higher you shoot, the faster the velocity will be, and the closer to the sensors the lower.... That could easily be your wide ES.... You need two lights, one above each sensor, if you aren't shooting outside....

Bob


Totally agree with Bob here.
The consistency of the height of the projectile crossing the sensors especially with artificial light will play a big part for setting up a good regulated shot string. You could try having the gun fully supported upon shooting bags or what ever, to keep a consistent line of fire over the sensors. One can also mark the rods as to the horizontal line of the scope's cross hairs to assist with the consistency as well. JMO

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