Tuning ES, tell me if I'm wrong ... did I miss something?

[bchannell]

I'm always doing some reading online and found several "experts" crowing about how airgunners are too focused on extreme spread in pcp airguns. One advocated a 25fps es, as excellent, another 40fps es as being the holy grail. The gist was that it makes absolutely no difference.

Got me to thinking and I did some quick math and ballistic calcs and came up with some numbers that I'm wondering about. Let's take a common round and velocity, a 25 cal 25gr pellet at 850fps. Doesn't really matter as you can check 22 cal and get similar numbers. at a 25fps spread, you're looking at an almost exactly 1moa drop from high to low. So you've used your 1moa of accuracy right there. If we consider 40fps, then we move to a ~1.8" drop from high to low, so you're using up roughly 1.8moa spread in group size. Am I missing something here? Those numbers represent a 2.9% and 4.7% es, which to me is too high. I have no trouble getting a good shooting (accuracy wise) tune that produces less than 1.5% es, and a lot of times, less than 1%. That to me is where you should be for long range pellet accuracy. I had a Katran 177, that almost NEVER had a %es of over .8% and most tunes were .6%, yes, zero point 6. Those numbers, of course, don't take into effect wind, shooter, angle, so add some of that in and you have NO chance of shooting 1 moa at 100 yards.

I know this is getting in the weeds with stats and tunes, but if you want to shoot moa groups at 100 yards with pellets, then this is exactly the field you need to be in.

Tell me where I messed up?

 

[Trucker3573]

All sounds solid to me. I absolutely agree that especially at 100 you need a tight ES if you plan to shoot really well. Pellets have low speed and bad BC to begin with. We need all the help we can get at long range.

 

[Scotay42]

40ES is high..short range it doesnt matter, alot of airgunners never go past 40yds. Those of us that shoot further all the time or aim for varmint eyeballs at 60yds, the smaller ES the better.

 

[Vetmx]

I also concur that there is too much focus on ES. But don’t confuse that with having a horrible ES. Even 25fps is too much. The best way to explain it is I have an unregulated gun with a big ES that will outshoot any of my regulated guns with a tiny ES but on a bad tune. Focus on groups first, then look at the numbers. Just like velocity numbers, we can’t make a gun shoot to its potential if we are stuck on numbers. It’s all about groups. The biggest thing I use numbers for is detecting a problem. Generally if you’re cutting holes at your max distance, when you look at the numbers, they will be good. You do this enough times, you’ll understand when it’s time to worry.

 

[Gerry52]

I agree with Vetmx above. Consistent accuracy is what I'm looking for (& mostly getting) from my guns. If something gets squirrely my chrony is used as a diagnostic tool to help find what might be causing inconsistencies. All my guns shoot in the 860‐910fps range & ES doesn't concern me, major DROPS in fps do. With guns, like my drumming, FEEL is all important. I can tell if something is "off". The chrony just helps tell me where to start looking, not to start sweating the numbers. I'm much more of an intuitive shooter than a technical one I guess.

 

[Franklink]

Wait til you have a gun that has a 30-35fps ES at the muzzle, but only has a 10-15fps spread at 100 yards. I have one of those, and used it to win one of the 2024 Extreme Field Target Grand Prix.

The flip gets a guy thinking too: when you've got a gun with an 8-12fps spread at the muzzle, but it produces a 40-50fps spread at 100 yards.

The barrel/pellet/speed that produces the tightest downrange extreme spread will be the more accurate/precise one. Every time. And downrange extreme spread isn't as simple as a tight ES at the muzzle.

There's something about certain barrel/pellet/speed combinations that make them settle into a consistent speed downrange. Ie the external ballistics takes over and settles them into a consistent speed at x yards, once they've flown through some wind. Probably land and groove symmetry, but perhaps more than that too.

I don't worry myself into the ground with ES at the muzzle. I've just won far too many field target matches with 25-35fps (at the muzzle) extreme spreads to care.

Might matter more for the hair splitting benchrest crowd. But for field target and long range pest bombing, spend your time practicing and you'll achieve more than you will by spending your time "tuning" for a single digit ES at the muzzle.

 

[Vetmx]

Wait til you have a gun that has a 30-35fps ES at the muzzle, but only has a 10-15fps spread at 100 yards. I have one of those, and used it to win one of the 2024 Extreme Field Target Grand Prix.

The flip gets a guy thinking too: when you've got a gun with an 8-12fps spread at the muzzle, but it produces a 40-50fps spread at 100 yards.

The barrel/pellet/speed that produces the tightest downrange extreme spread will be the more accurate/precise one. Every time. And downrange extreme spread isn't as simple as a tight ES at the muzzle.

There's something about certain barrel/pellet/speed combinations that make them settle into a consistent speed downrange. Ie the external ballistics takes over and settles them into a consistent speed at x yards, once they've flown through some wind. Probably land and groove symmetry, but perhaps more than that too.

I don't worry myself into the ground with ES at the muzzle. I've just won far too many field target matches with 25-35fps (at the muzzle) extreme spreads to care.

Might matter more for the hair splitting benchrest crowd. But for field target and long range pest bombing, spend your time practicing and you'll achieve more than you will by spending your time "tuning" for a single digit ES at the muzzle.

Your first two sentences would throw just about anyone into a tailspin. Hopefully not to many read that because you may be responsible for numbers guys loosing their minds moving forward.

 

[elh0102]

Don't get caught up in analysis paralysis.
Test your rifle and pellets at the distance at which you compete. Some will shoot much better than the ES suggests, others may be lousy, but with exemplary numbers. ES becomes important at the extreme distance of a rifle/pellet combination. That is usually not the distance at which you compete.

 

[manabeknives]

This is something i have been working on for the past few months that may be of a little help. It goes with what @Franklink is saying

As others have said, The E.S and the S.D at muzzle might be consistent and very tight, but it doesn't tell you the stability of the flight of the projectile

On the Fx Ballistic chronograph app, you can set 2 distances for the chrono to target ..I.E. the muzzle and target distance.
If you have a pellet shooting a low S.D./E.S. at the muzzle, but the results at 100 have the E.S./S.D. a significantcantly higher or erratic ...then the pellet flight is not stable. It might be spiraling or overstabilized.
If you have a low muzzle and low target E.S/S.D. .. then you are on the right track

can be done with 2 separate chronographs ..1 at target and 1 at the muzzle

Though it is a simple process ..it is very time consuming and dependant on your conditions being fairly stable

Comparison of the 2 distances stat's is what i found to be a better indicator than just relying on the 1 at the muzzle for getting accurate shooting

 

[bchannell]

I approach it a bit differently.
First, I get decide on a velocity, ie 890 for a 18gr 22 pellet. I tune my gun to shoot as low an es as I can, then I test at the distance I'm looking at shooting, ie 100 yards. If groups are good, I'm done. If not, then i start moving the velocity around, retune and try again. 9 times out of 10, I find the correct velocity (range) needed for that pellet in less than 4 tries.

Yes, Yes, Yes, there are DEFINITELY tunes that are good and groups that are horrible. You can clearly see that in some of the online reviews. Pellets have a "correct" velocity that they will shoot long range and outside of that they go crazy. For instance, a pellet will lose velocity faster than it loses spin, which can cause it to veer off course and will fly off concentric, meaning head up and out of line of arc of the track of the drop. This is one of the reasons that FX has been more successful with slow twist barrels for pellets.

 

[Dairyboy]

As others stated I don't stress about that one bit. If it's around 15-20fps spread I'm good with that. Am I a BR shooter? Absolutely not. As a pester I've had no problems shooting out 100yds+. Wind has a larger affect than the ES does so that's what I focus on.