Joy of tuning

[MEC17670]

Hey Folks,
I was out the other day, with my Crown mk2 600mm. 22 barrel on it trying to find that "magic spot" for shooting the nsa 26.8 slugs. I played around a small bit with my reg pressure , staying withing +- 2.5 bar. Everything was going so so until I moved my power wheel down and ended up shooting this shot string. With each shot, I was waiting for a weird spike or drop but much to my surprise after 10 shots , this is the result. One dip but returned to the line. Loving it.

 

[Kgphotos]

Sweet shot string. I would be super happy with a tune like that. Do you find that the tightest shot strings also deliver the best groups on paper?

 

[bigHUN]

I like to tune, I have a small little booklet and writing down my steps, and this is a great learning curve

 

[Chuck-in-Ohio]

That looks like success!

Good going on getting it there!

 

[MEC17670]

Sweet shot string. I would be super happy with a tune like that. Do you find that the tightest shot strings also deliver the best groups on paper?

Combined with continued barrel harmonic tuning , yes.

 

[MEC17670]

That looks like success!

Good going on getting it there!

Thanks, now to keep it .

 

[Bigragu]

In the past, my experiences with low ES has been 75/25. 75 % looks great on paper but not accurate, and every once in awhile both low ES along with accuracy mend and that’s the 25%.

The majority of the time I get the best accuracy I’m typically anywhere from a 7 FPS spread all the way to around 14 or 16 FPS, in a regulated gun. Once in awhile I see the best accuracy in the mid 20’s for spread but not too often.

I was just telling QBall today that once I shot a string of like 94 shots straight, with an ES of 14 FPS. On the way there at shot 32 or 36 my ES was 2. My accuracy was not where I wanted it, though. Not tight enough.

 

[athlon_oved]

Sweet shot string. I would be super happy with a tune like that. Do you find that the tightest shot strings also deliver the best groups on paper?

Oh yea. That with pellet weight

 

[MEC17670]

I like to tune, I have a small little booklet and writing down my steps, and this is a great learning curve

Lots of notes, all ammo specs, I found cup base worked better in my gun, all ammo sorted to weight, weather conditions, and sorts of fun info. Do I look at it while I'm messing around, only as a reference to history, good and bad.
When I shot that last shot string, I was shooting working on barrel harmonics shooting 5 shot groups at 57 yards. While adjusting the Swan gen 6 tuner . I watched the groups move around open and close while having the Crown on a good ballistic tune, vary similiar to my .25 600mm hunting tune. Fair groups considering a 3 to 5 mph right to left, some just under 1/2 some 1" 1/4. Funny how that node works. Anyway got to 1L got a flat line group with 1 jumper, I the std 3.5 reg 160, pw 23, tf H. , decided to try pw 22. The group this time remained flat, no jumpers to speak of but to my pleasure with a std .9 over 10 shots.
I'll be shooting for groups as soon as the glorious rain stops.
To be continued.

 

[bigHUN]

...Do you find that the tightest shot strings also deliver the best groups on paper?

No. Not me.
I tune always at longest distance I will be shooting at, but let say 100 meters. That distance will show the artifacts on paper.
Also, when I am tuning, my mind is ready to accept at least a hundred shots string to get to the point what I want, sometimes takes me a full tin.
I have found that the tightest ES of 2-3-4 ish will give me flyers. Loosen ti to 7-10 maybe and that is my tightest group.

 

[Nomadic Pirate 66]

No. Not me.
I tune always at longest distance I will be shooting at, but let say 100 meters. That distance will show the artifacts on paper.
Also, when I am tuning, my mind is ready to accept at least a hundred shots string to get to the point what I want, sometimes takes me a full tin.
I have found that the tightest ES of 2-3-4 ish will give me flyers. Loosen ti to 7-10 maybe and that is my tightest group.

Interesting.

 

[bigHUN]

Interesting.

Simple, you have to try it yourself what works for you the best.

 

[Nomadic Pirate 66]

Simple, you have to try it yourself what works for you the best.

Ho I believe you, I have no interest in regulated guns I just find your findings interesting after I read mainly people seeking the very minimum in fps variation.

 

[nervoustrig]

A very consistent regulator will give a super low ES when the hammer spring tension is set high such that the gun is operating up on the velocity plateau. This state of tune produces an excess muzzle blast and may also aggravate harmonic vibration, neither of which is good for accuracy.

 

[Stone02]

A very consistent regulator will give a super low ES when the hammer spring tension is set high such that the gun is operating up on the velocity plateau. This state of tune produces an excess muzzle blast and may also aggravate harmonic vibration, neither of which is good for accuracy.

Would this also apply to a Daystate solenoid hammer system which has a very short lock-time compared to traditional knock-open valve firing systems ?

Lock Time – The Key to an Airgun's Firing Cycle - Daystate

The brief moment that elapses between the trigger’s sear being slipped and the pellet exiting the barrel, is more commonly called its lock time.

daystate.com

 

[nervoustrig]

Yes, we’re talking about a scenario where the valve is simply being overdriven…smacked too hard so to speak. Excessive dwell. That condition can be produced with a solenoid just as it can be with a conventional hammer.

The concept of lock time is something different altogether.

 

[Stone02]

Thank you.
I had assumed that a shorter lock time would result in less muzzle blast.

Muzzle Blast, Lock Time and Accuracy Revisited. - Page 2

Before I start, please note that the following is based on my observations since the introduction of MCT and MVT guns, they are not necessarily Daystate views. A pattern has been emerging for the last few months since the launch of the Daystate Mk4 and has caused me to revisit my thoughts and...

www.airgunbbs.com

 

[nervoustrig]

I had assumed that a shorter lock time would result in less muzzle blast.

For what it’s worth, short lock time might help with the muzzle blast or it might not. Just depends on how it is achieved. To reiterate what lock time is, it is the time between the sear releasing and the pellet leaving the muzzle. That time includes two principle actions:

1. The hammer accelerating and hitting the valve stem.
2. The pellet accelerating up to its final velocity as it reaches the muzzle.

So for example, if we take a gun and simply increase its hammer spring tension, we will improve (reduce) lock time. Why? Because more HST accelerates the hammer more quickly so it reaches the valve stem sooner. And the hammer arrives at the stem at a faster velocity, knocking the valve open more fully and quickly, producing a sharper pressure pulse at the pellet, accelerating it and getting it to the muzzle more quickly. All of which contributes to faster lock time...but simultaneously more muzzle blast.

However rather than adding hammer spring tension, if we instead switch to a lightweight hammer and make the valve easier to knock open (e.g. by using a harder poppet material or some other approach), this lighter hammer will accelerate more quickly and produce a similar fast opening of the valve to accelerate the pellet. But because the hammer weighs less, it has less momentum. Less momentum means shorter dwell. Shorter dwell means less muzzle blast.

Anyway that’s just an example but it’s one of those “it depends” things.