Tuning Regulator pressure VS Hammer Spring tension

[Cajun1024]

Would some of you guys in the know,please take a minute to explain how regulator pressure and hammer spring tension relate to each other. In other words, if you increase or decrease regulator pressure how does it affect velocity, shot count and accuracy etc? your thoughts would be greatly appreciated.

Thanks

 

[nervoustrig]

With regulated airguns, the relationship between the regulator's setpoint and the hammer spring tension is really quite simple. There is only one hammer spring setting for a given regulator setpoint that will yield the best consistency (extreme spread or standard deviation).

To find the optimal hammer spring setting, keep increasing the tension until the velocity no longer increases. Then back it off until the velocity is somewhere around 95% - 97% of that maximum. So for example, if your max velocity was 900fps, dial the hammer spring back until the velocity drops to about 855 - 873fps.

When adjusted in this manner, your airgun will be somewhat insensitive to the little inevitable variations in pressure or hammer strike. It is akin to how an unregulated PCP operates in and around the top of its bell curve (the sweet spot). It will also be reasonably efficient. Better efficiency would be possible by backing off the hammer spring tension further, but that puts the airgun operating at a state of partial valve lock. It will take little sips of air on each shot but the extreme spread suffers. For short range shooting (e.g. 10m practice in the basement), that may be fine....preferable, even. But it's no good for 50+ yards unless your accuracy standard is a soup can. 

Accuracy on the other hand can't be so easily correlated to something as simple as the balance between regulator and hammer spring. Many, many things play into it. Having a stable velocity certainly helps but it's just one piece of the jigsaw puzzle.

 

[Bigragu]

@ NT- great post and advice, as always

 

[Cajun1024]

Thanks for the info.!!

 

[JayJay]

Very good info from nervoustrig. I also learned a lot from Bob Sterne's PCP tuning articles at Hard Air Magazine.

Index -- https://hardairmagazine.com/ham-columns/the-definitive-index-to-bob-sternes-ham-technical-articles/

Regulator tuning -- https://hardairmagazine.com/ham-columns/tuning-regulated-pcp-airguns/

I'm no expert, but following Sterne's regulator article, here's how I recently set my .22 FAC HW100K. I wanted to increase the number of shots from 40 and was willing to give up 100 fps. (from 900 to 800).

1. Pick an initial regulator pressure. Ideally, by the end of a full shot string, cylinder pressure should drop to about the same as the regulator pressure. That's to make sure all shots are regulated. I initially set regulator pressure to 100 bar. This is down from 120 which is the beginning of the 'yellow' zone on the Weihrauch cylinder. To get more shots, I figured I had to go to a lower final pressure.
2. Pick an initial pellet velocity. I picked 800 fps. Increase hammer spring tension until velocity levels off. That's what Bob Sterne calls the 'knee' or sweet spot. It's the max your rifle will produce with that regulator setting.
3. Back off the velocity about 3% to 5%.
4. If this doesn't meet your target velocity, bump the regulator pressure a little, then re tune the velocity.
   [/LIST=1]
   
   I found the knee was around 830 fps and set velocity to 800 fps. It now gets 60+ regulated shots @ 800 fps before cylinder pressure hits 100 bar. I didn't map the shot string after that (garage was too cold and I was tired of pumping the Hill Mk 4).
   
   Bob Sterne discusses tuning on the downslope of the curve, i.e., backing off even more on the hammer, then increasing regulator pressure to achieve your target velocity. He says it can improve efficiency but may result in erratic velocity jumps, unless the gun is exceptional. This is probably what nervoustrig is referring to when he mentions partial valve lock. The theory seems to be that a light hammer doesn't open the valve as much, thereby conserving air. Also a lighter spring may reduce hammer bounce. 
   
   My HW100's original regulator setting was 145 bar (way above the yellow zone) so I suspect the factory tuned it on the downslope. The gun originally shot a beautifully even string, maybe it's an exceptional gun. Now that I have a new EC3000 and a warm garage, I may go back and tune the HW100 on the downslope. 
   
   HW100 owners may be interested to know that I got the regulator gauge and two full o-ring sets from the UK site HW100tuning.com. Just to be safe, I took the o-ring specs and ordered 100 of each from oringsandmore.com. A lifetime supply for about $25.
   
   I was concerned that my HW100 might have an 'anti-tamper' setup, where the hammer adjustment screw is bonded into the aft hammer block to prevent people from raising power above 12 fpe. There are several youtube videos about this. I even ordered a replacement spring, screw and block from the UK (ebay). However, it was not necessary. The hammer screw came out easily after removing the little locking grub screw. I was able to re-use the original parts.
   
   
   
   

 

[tommyb]

With regulated airguns, the relationship between the regulator's setpoint and the hammer spring tension is really quite simple. There is only one hammer spring setting for a given regulator setpoint that will yield the best consistency (extreme spread or standard deviation).

To find the optimal hammer spring setting, keep increasing the tension until the velocity no longer increases. Then back it off until the velocity is somewhere around 95% - 97% of that maximum. So for example, if your max velocity was 900fps, dial the hammer spring back until the velocity drops to about 855 - 873fps.

When adjusted in this manner, your airgun will be somewhat insensitive to the little inevitable variations in pressure or hammer strike. It is akin to how an unregulated PCP operates in and around the top of its bell curve (the sweet spot). It will also be reasonably efficient. Better efficiency would be possible by backing off the hammer spring tension further, but that puts the airgun operating at a state of partial valve lock. It will take little sips of air on each shot but the extreme spread suffers. For short range shooting (e.g. 10m practice in the basement), that may be fine....preferable, even. But it's no good for 50+ yards unless your accuracy standard is a soup can. 

Accuracy on the other hand can't be so easily correlated to something as simple as the balance between regulator and hammer spring. Many, many things play into it. Having a stable velocity certainly helps but it's just one piece of the jigsaw puzzle.

NT: Very good explanation.

As an experiment, I tried this with my .25 caliber Veteran Long a while back. Naively, I was hoping to achieve optimum accuracy at 50 yards with the JSB .25 25 g pellets. My calculation ( ie., 95-97% of max HST ) was around the 940 FPS range. Interestingly, my ES values and groups were not nearly as good as to when I backed off the HST to 890-920 ranges. 

Your last paragraph says it all. Lots of variables to achieving desired accuracy.

Tom 

 

[GerrywithaG]

Apologies for bringing up an oldie, but a great ttuning thread imo.

I have a thought for conversation...,My .22 zelos likes 870 fps for the 18.13 pellets. I have gotten there bumping up the reg, and backing off he h.s., and vice versa with the same group sizes. What are your thoughts.

My set up with...
1. Higher reg psi, and less hammer spring feels ,and sounds sluggish compared to...

2. Lower reg. and up the hammer spring? Seems snappiier, and quiet.

let's leave shot count, sd and es at the proverbial door for now. I am more interested in finding if your rig groups better with a higher reg.?, or more H.S. Tension to get to the same fps?

Thanks for your ideas....
Gerry

 

[Trucker3573]

Apologies for bringing up an oldie, but a great ttuning thread imo.

I have a thought for conversation...,My .22 zelos likes 870 fps for the 18.13 pellets. I have gotten there bumping up the reg, and backing off he h.s., and vice versa with the same group sizes. What are your thoughts.

My set up with...
1. Higher reg psi, and less hammer spring feels ,and sounds sluggish compared to...

2. Lower reg. and up the hammer spring? Seems snappiier, and quiet.

let's leave shot count, sd and es at the proverbial door for now. I am more interested in finding if your rig groups better with a higher reg.?, or more H.S. Tension to get to the same fps?

Thanks for your ideas....
Gerry

I always set up my guns more along the line of #2. Just like the second post in this thread states. Set just a tad below the max velocity the gun will produce with a given reg pressure.

 

[tommyb]

Apologies for bringing up an oldie, but a great ttuning thread imo.

I have a thought for conversation...,My .22 zelos likes 870 fps for the 18.13 pellets. I have gotten there bumping up the reg, and backing off he h.s., and vice versa with the same group sizes. What are your thoughts.

My set up with...
1. Higher reg psi, and less hammer spring feels ,and sounds sluggish compared to...

2. Lower reg. and up the hammer spring? Seems snappiier, and quiet.

let's leave shot count, sd and es at the proverbial door for now. I am more interested in finding if your rig groups better with a higher reg.?, or more H.S. Tension to get to the same fps?

Thanks for your ideas....
Gerry

“ I am more interested in finding if your rig groups better with a higher reg.?, or more H.S. Tension to get to the same fps?”

Following here……

I’m equally interested in others answering this question. Essentially, your question is getting at achieving better accuracy with adjusting for higher reg pressure and increasing HS.

FWIW - I participate in a regular 30-40y informal AGN target challenge. Although I have shot some really good scores with rifles (outdoors with wind at an open range) at lower velocities in the 800-830 fps range; I find that turning my HS up and increasing velocity has been yielding excellent accuracy and scores, especially at 30 and 40 yards.

Three examples: Taipan vet2 shooting AEA 21.9 at 910-930 fps range with tweaking Speed Dialer only at 135 BAR set point. RAW HM1000x shooting JTS 22.07g at 990 fps range with reg at 150 BAR. FX Royale .22 with JSB 20.83g lights at 880 fps and 150 BAR set point.

These three rifles consistently out shoot my other lower velocity, efficiently tuned rifles for both accuracy and scoring purposes.

 

[HogKiller]

When you hit nirvana you get this....

 

[kwaping]

I was testing out different pellets yesterday, using my Blackwolf and Athlon chronometer. The heaviest pellets with Max power wheel were much more consistent with speeds versus the lighter ones with Min power wheel. I didn't touch the regulator because I didn't feel like degassing the gun.

That convinced me that more hammer is better for consistency. BUT...

As my main ammo is the heavy pellets, I'll just deal with some variation with the lighter pellets. It's great being able to shoot both 25.39 and 18.80 without having to change the regulator!

 

[Trucker3573]

Harmonious balance between the two is the best way in my opinion. You don’t want low reg high hammer or high reg light hammer. Balance balance…

 

[kwaping]

Harmonious balance between the two is the best way in my opinion. You don’t want low reg high hammer or high reg light hammer. Balance balance…

As in all things in life

 

[JungleShooter]

Balance balance….

As in all things in life.

My friends,

may I remind you that many here on the forum would respectfully disagree with you on this particular point....

𖠢 They would argue that: "ꓢcrew balance! — having too many guns is better than having less guns!"

𖠢 They might argue that: "having more scopes than guns to mount them on is a good thing — I don't need balance (I need more scopes)!"

𖠢 And: "Overkill is underrated — balance is for sissies!"


Respectfully/ submitted,

Matthias

 

[elh0102]

NT: Very good explanation.

As an experiment, I tried this with my .25 caliber Veteran Long a while back. Naively, I was hoping to achieve optimum accuracy at 50 yards with the JSB .25 25 g pellets. My calculation ( ie., 95-97% of max HST ) was around the 940 FPS range. Interestingly, my ES values and groups were not nearly as good as to when I backed off the HST to 890-920 ranges.

Your last paragraph says it all. Lots of variables to achieving desired accuracy.

Tom

If your most accurate velocity is 890, then you can adjust your reg down to the point at which you achieve a MAX velocity of around 940, then back down the HST to get your 890. That should yield more efficient air consumption, noise, etc. Find your best velocity first, then tune for efficiency at that speed.

 

[rong1966]

I have always seen that hammer spring and regulator setting have to be balanced, but what if your gun doesn't have an adjustable hammer spring but has an adjustable hammer throw like my Daystate Revere?

 

[tommyb]

My friends,

may I remind you that many here on the forum would respectfully disagree with you on this particular point....

𖠢 They would argue that: "ꓢcrew balance! — having too many guns is better than having less guns!"

𖠢 They might argue that: "having more scopes than guns to mount them on is a good thing — I don't need balance (I need more scopes)!"

𖠢 And: "Overkill is underrated — balance is for sissies!"

Respectfully/ submitted,

Matthias

I like your approach Matthias!

 

[tommyb]

If your most accurate velocity is 890, then you can adjust your reg down to the point at which you achieve a MAX velocity of around 940, then back down the HST to get your 890. That should yield more efficient air consumption, noise, etc. Find your best velocity first, then tune for efficiency at that speed.

Yeah, this was back in 2021 time frame when I had the Taipan Long .25 caliber and I saw NLT’s post. But, your suggestion is extremely valid nevertheless.

I’m good at tweaking HS’s to try and identify optimum accuracy at a specified distance and velocity. But I avoid messing with regulators ( like the plague) mostly because I don’t trust my skills and knowledge, and it’s cumbersome doing this on my rifles. I’m totally bought in on achieving the balanced tune for best efficiency at a certain reg setting, I’m just not comfortable taking the gun apart and adjusting the reg myself. In fact, you did this for me with my HW100 .22 Carbine at your house a few years ago, to illustrate the concept.

Regardless, I also don’t mind higher reg settings and lower shot counts at the expense of using more air. But, only if I am getting the accuracy I want at my normal 30 and 40Y target challenge distances. Some folks go nuts trying to chase efficiency, and I just don’t see as much value as they do. They’re also a lot smarter than me.

Maybe I will someday end up buying an externally adjustable rifle for both HS and Regulator adjustments on the fly, and at the bench.

 

[Trucker3573]

I have always seen that hammer spring and regulator setting have to be balanced, but what if your gun doesn't have an adjustable hammer spring but has an adjustable hammer throw like my Daystate Revere?

I’m not really familiar with that system never having owned one but I believe with hammer throw you would be essentially achieving the exact same “balance” as with adjusting hammer spring pre load. I believe more hammer throw will open the valve more. As you work reg pressure up hammer throw would go with it.

 

[bchannell]

Plateau is the max velocity
Knee is the 95-97% velocity