Why are factory regulator pressures so high?

[Mink]

Recently, I have spent a lot of time tuning my Taipan Veteran Long in .22. The goal of my tune is to shoot JSB 18.1s at ~885 fps with consistency of every shot including the cold bore shot(s). To do this, I have (painstakingly) tuned the Huma regulator to the point where the “knee” is 880-890, with the max being 905-910. 


An interesting finding that I have made is how low I had to adjust the reg pressure to get to this point. My gun hits this tune with the regulator at ~80 bar!

To a novice like me, this was surprising, as I frequently read about .22 regs in the 120 bar range that shoot 900 fps or less. When I tried 100 bar pressure, my max velocity was still 970 fps (knee at ~950 fps). 

Also, I find it strange that the Huma’s adjustment tape ranges from 85-170 bar, considering many people seem to want to shoot 860-900, which in .22 can seemingly can be achieved with MUCH lower reg pressure than the median of this range (not to mention non-FACs). 


Also, in Ted’s new video “Discussion: Ultimate .25 cal FX Test...”, he explains how he tunes his .30 cal Impact (non-power plenum) to shoot 44 gr pellets at 850 fps with 95 bar reg pressure! 


So my question is, doesn’t it seem that the “standard” factory reg pressures are too high for the “standard” speeds that we want to shoot?

 

[biohazardman]

First off you can't trust the gauges to read the pressure accurately. They are only good for estimating the pressures. Most are within 20bar or 300psi but one of my FX gauges was off twice that. So I bought new gauges they were better but one was still off 20bar. So I took the best of the old gauges and added the best of the new ones so they would be close at least.

The newest thing is the power plenums they will let one lower the reg pressure quite a bit and still not loose power. If you don't have the newer larger plenum you will have to turn up the reg to make the same amount of power.

Let us not forget that feet per second sells the guns so I would expect that some manufacturers pump the pressure up to meet or exceed their specs as well.

 

[Dairyboy]

Also depends on what you want to shoot out of the gun. Lots of people nowadays want to shoot the heavy pellets out of all there guns. Manufacturers are going that way of having the capability to send those pellets fast enough. 

 

[elh0102]

My guess, that reg is actually over 100 bar. I have a Huma reg in my Royale, works fine, but the pressure scale is way off.

 

[Motorhead]

While many regulated guns can make the wanted power at lower pressure, it seldom is the most efficient.

Longer sips of lower pressure will generally use more air than Small sips of high pressure.

When you understand that PRESSURE is ENERGY you will start to understand the relationship and "why for" many guns come factory adjusted at higher regulator set pressure.





Scott S

 

[Mink]

While many regulated guns can make the wanted power at lower pressure, it seldom is the most efficient.

Longer sips of lower pressure will generally use more air that Small sips of high pressure.

When you understand that PRESSURE is ENERGY you will start to understand the relationship and "why for" many guns come factory adjusted at higher regulator set pressure.





Scott S

Thanks Scott, but I am trying to figure out why I am seeing conflicting viewpoints on this topic. 

From what I have read, the way to reach the most efficient and consistent tune for a given speed is to adjust reg pressure such that the MAX velocity is 10-20 fps higher than the desired velocity. From there, back off the hammer spring until you are at the desired velocity. In my case, to shoot 18.1s @ 885 I needed to lower reg to ~80 bar (according to the Huma scale). Note that when I was struggling with consistency a couple weeks ago you told me that my reg/HST settings were not at the knee like they are supposed to be.

Now you are suggesting that low reg pressures are not as efficient, which I would agree with if I was operating on the "plateau". However since I am on the "knee", isn't this the MOST efficient?

 

[Motorhead]

Most CONSISTENT ...



When operating on the knee, slight changes in pressure shift speed very little, changes in strike energy from hammer have a similar effect in only making slight speed changes.

This miens said PCP will shoot very very stable shot to shot and when coming off regulation staying nearly flat for some shots even tho your losing pressure. WHILE at the same time if you get regulator creep and pressure rises within plenum the speed is not effected much and speed remains quite stable.





Efficiency and Consistency are different things.





Scott S

 

[Motorhead]

Wanted to continue on this conversation ...



When you have a high set point it buys you much more power flexibility. Changes in HST yield Large shifts in output power.

The Issues we read about where folks say the first shot is faster or slower than normal is because gun is NOT tuned on the knee and for a gun to have a broad power range changeable on the fly with HST changes .. IT CAN'T BE !!! Factories have no idea what power you will shoot at, weight of pellet shot etc .... Then folks want high shot count too & the way this is achieved is HIGH SET POINT PRESSURE. 

Tuning for High Consistency really limits the range of power one can get with simple HST changes. This is not to say you CAN NOT tune on the knee at high pressure, you can indeed. Issue being when at higher pressure the "Knee" is much steeper and falling off either end happens much quicker. Consistency suffers far quicker when off the knee at HP than it does at lower pressures has been my findings.



There is never any free lunch, with causes and effects that shift with differing set ups. There is no right or wrong way being all will shoot well ... Some tunes will be consistent, some efficient and generally ONLY BOTH when set as described above. Even then pending just how hard you leaning on the tune a compromise between both.





JMO,

Scott S





PS.

There is much more to this base story ... Hammer Weight, Stroke, Springs within Valve & Hammer, Porting specs etc ... ALL HAVE EFFECT as to the degree of how the tune profile will be +/- of optimum.

 

[Mink]

Wanted to continue on this conversation ...



When you have a high set point it buys you much more power flexibility. Changes in HST yield Large shifts in output power.

The Issues we read about where folks say the first shot is faster or slower than normal is because gun is NOT tuned on the knee and for a gun to have a broad power range changeable on the fly with HST changes .. IT CAN'T BE !!! Factories have no idea what power you will shoot at, weight of pellet shot etc .... Then folks want high shot count too & the way this is achieved is HIGH SET POINT PRESSURE. 

Tuning for High Consistency really limits the range of power one can get with simple HST changes. This is not to say you CAN NOT tune on the knee at high pressure, you can indeed. Issue being when at higher pressure the "Knee" is much steeper and falling off either end happens much quicker. Consistency suffers far quicker when off the knee at HP than it does at lower pressures has been my findings.



There is never any free lunch, with causes and effects that shift with differing set ups. There is no right or wrong way being all will shoot well ... Some tunes will be consistent, some efficient and generally ONLY BOTH when set as described above. Even then pending just how hard you leaning on the tune a compromise between both.





JMO,

Scott S

Got it, thanks for the clarification Scott. I agree that there is no free lunch, however there seems to be 2 different efficiency goals to choose between: (1) MAX SHOT COUNT with low ES, and (2) MAX FPE / AIR USED.

• MAX SHOT COUNT: In this case, the goal is to maximize total shot count using modest velocity. To achieve, set low reg pressure, and being on the knee with the HST will allow for max consistency across a HUGE range of fill pressure (e.g., 250 bar --> 90 bar). Even though the per-shot efficiency may not be optimal, the sheer range of usable fill pressure balances it out, allowing for a ton of consistent shots.
• MAX FPE / AIR USED: In this case, the goal is to maximize the energy per CC of air used of all shots from a fill with reasonable consistency. To achieve, set high reg pressure, and carefully tune to the knee with the HST. This gives fast velocities and very high per-shot consistency, but leaves a tighter consistency window due to steeper "knee curve" and a smaller usable fill pressure range.

I opted for MAX SHOT COUNT because my goal is long range accuracy with ~light pellets (I am hand pumping), and I have discovered that the gun likes to shoot JSB 18.1s at 880-890 fps, and it does considerably worse in 920-950 fps range. So to me, the extra energy is not valuable if I can't hold a group at 100 yards. 



Would you agree with my synopsis?

 

[Bigragu]

Great topic, guys, and great input, Scott

 

[MacGyver]

Let us not forget that feet per second sells the guns so I would expect that some manufacturers pump the pressure up to meet or exceed their specs as well.

That's where my mind went right away. The marketing department wants the highest number they can get in that ft/sec or fpe field. Always follow the money.

 

[tor47]

My taipan veteran standard in .177 maxed out at 1040-1050 fps with JSB 10 grain heavies, when I chronied the gun after I got it. The jumbo heavies 13 grain maxed out at around 950 fps. I did lowered the speed on the hammer, when I started to use it.