Tuning Question: Why tune for speed first, why not accuracy?

[Revoman]

AGN'ers!
While my airgun is fairly well tuned now, I am wondering about why the "Tuning Magic" starts with "Pick a speed/FPS." That seems rather arbitrary to me.
Why does it not start with getting good accuracy first? How does one know that a particular pellet will perform it's best at say 930 FPS without shooting it at various speeds in order to find that desired accuracy?
1.) Most advice is "880-920ish FPS is a good range." Good advice, at least that narrows it somewhat.
2.) Some pellets, such as the RD's seem to need a faster speed, at least that has been my experience and much of the advice here.
Between the items above there could be a large disparity between the two.
So, why not shoot for accuracy by making the same adjustments as one would use for a "95% Tune/Knee" after shooting an ample amount to determine accuracy/or not. Then check that speed/FPS. Then adjust the regulator up slightly and adjust it back to the FPS that is the best performance for the pellet? Is it because of the economy of air is best doing it by guessing the FPS first? It just seems to me that finding accuracy then adjusting per the 95% rule might make more sense.
I'm not stating that any method is wrong, just questioning the reasoning for most tunes.
What am I missing?
mike

PS: I understand that there are many sweet spot nodes within about 10-15 FPS or so it seems. Depending upon the barrel whip action/pellet/speed combo. So, it's entirely possible to have accuracy nodes within say 882-897, 897-912, 912-927, etc. Right? I'm guessing that you would need to find each of those nodes and settle on which is best?

 

[jmohme]

good question.

For me, I started my first excursion into PCP tuning to find the best velocity to provide the best accuracy for my chosen pellet weight.

 

[MikeVV]

Yeah, most seem to feel like they need...the speed...for some reason.

Rick (Shooter1721 / Airguns on YouTube) has proven over and over, with several guns, you DON"T need 950fps+ to shoot accurately to 100 yards.
He's shot less than 1" groups with the little loved Ataman BP17 (.22 cal., bullpup), to 100 yards. He's done the same with other short barrel bullpups.
And for the record, I believe he's also done it with a pistol or two !

So...so much for "needing" a fast pellet speed.

While all of my shooting is at shorter ranges, all of my guns are turned down to around 800fps (+/- a few). Less stress on the gun, quieter .

Mike

 

[Removed]

Don't hear much about tuning a gun for efficiency anymore....I'm all about making the most power with least amount of air.

 

[Leon83]

@Crosman999 95% tuning is actually an efficiency tuning for specific reg pressure…

 

[SimpleGuy]

Yeah, most seem to feel like they need...the speed...for some reason.

Rick (Shooter1721 / Airguns on YouTube) has proven over and over, with several guns, you DON"T need 950fps+ to shoot accurately to 100 yards.
He's shot less than 1" groups with the little loved Ataman BP17 (.22 cal., bullpup), to 100 yards. He's done the same with other short barrel bullpups.
And for the record, I believe he's also done it with a pistol or two !

So...so much for "needing" a fast pellet speed.

While all of my shooting is at shorter ranges, all of my guns are turned down to around 800fps (+/- a few). Less stress on the gun, quieter .

Mike

Every video I've seen he shooter1721 has a hot gun!

 

[Nsboost]

Because you HAVE to start somewhere.

Am I the only one that things the OP makes ZERO sense? Lol

Like recently, I switched to a new projectile. I dialed the gun in at 940fps where my last projectile was a tack driver at. It was terrible. So I dialed it down… results were bad.. then dialed it up till I got sub MOA at 100y (100y is my base line. Any pcp worth owning will shoot hole in hole at 50y). I checked my fps (975fps).. then played with the reg/hammer till I got a good balance and efficiency at at that speed.


You can’t say “why don’t you tune for accuracy”. That’s silly. Obviously everyone is tuning for accuracy (unless they are new to the hobby and have tunnel vision on power. Nobody worth their salt gives a sh*t about what the actually fps is). BUT YOU HAVE TO START SOMEWHERE. So we pick a speed, dial the rifle to that speed, then adjust up or down till we find the groups tighten up. Be it 800 or 1100 fps, you have to pick a speed to start from to look for that harmonic happiness

Maybe I’m misunderstanding…. But I don’t think I’ve seen anyone obsess over the “perfect” tune at a speed that doesn’t provide the desired results. Pick a speed, get the rifle there, test test test, go up and down, find the right groups, then dial in the efficiency where the groups are good. That’s what tuning is

 

[Removed]

Honestly most of what I see is people maxing out pellet guns to be able to shoot slugs. Lol

 

[Steveoo]

This is just a personal experience.
There is a current trend in the UK to down tune guns to 10ftlbs. This is comes about as a consequence of chasing the softest possible firing cycle from the gun, by removing Top hat weights/piston weight in springers and more stable velocity curves in PCP but i remain unconvinced.
For me, a lot of the improvement in accuracy has come from much better pellet manufacturing, running along almost unnoticed while this tuning trend has had the greater focus, but If you try switching back to how the manufacturer intended the gun (ok with a bit of fettling and sharp edges removed accepted) I have found almost no difference, but find the extra velocity provides a flatter trajectory. Also the faster the pellet leaves the gun, the less time for recoil to affect the pellet. Indeed, maybe having a slight edge over longer shots.
I am not saying the down tuned gun does not feel nicer to shoot, but im a long way from being convinced its more accurate …..it just feels like it is..

 

[mubhaur]

To me the tuning for accuracy is the most important.

 

[Steveoo]

Yeah, but do we down tune for accuracy, or speed up?
Nobody has ever really got down and studied it. They just assume damping and slowing has to be better..because the gun feels nicer, but this damping/reduce piston diameter etc has been running along side of greatly improved pellet development, and their greater choice. That equals two changes at the same time.
A number of shooters now putting their guns back to spec (albeit with a bit fettling and correct lubing) and finding no difference in the accuracy but benefitting from longer range/flatter trajectory.
You can balance a gun up beautifully with correct pellet selection these days.

 

[elh0102]

So, why not shoot for accuracy by making the same adjustments as one would use for a "95% Tune/Knee" after shooting an ample amount to determine accuracy/or not. Then check that speed/FPS. Then adjust the regulator up slightly and adjust it back to the FPS that is the best performance for the pellet? Is it because of the economy of air is best doing it by guessing the FPS first? It just seems to me that finding accuracy then adjusting per the 95% rule might make more sense.
I'm not stating that any method is wrong, just questioning the reasoning for most tunes.
What am I missing?
mike

Mike, IMO you are exactly right. I think you should first find your desired velocity, based on accuracy, then balance the tune with additional adjustments to HST and reg set point.

 

[gendoc]

i tune my guns for hunting.
power, accuracy and efficiency in that order.

 

[douger]

I shoot for mid 800 and shoot groups. Raise speeds till my groups are best. Doing this while shooting over the chrony. Then I’ll make the gun most efficient.

 

[Gerry52]

ACCURACY is priority ONE! Especially for those of us who mainly & mostly hunt. Couldn't care less if my gun is shooting at 750fps or 1000fps if it can't hit what I aim for at 100+ yards. Gots to have that accuracy! Speed be damned.

 

[douger]

Every video I've seen he shooter1721 has a hot gun!

well if you watch few he shoots some mid 800

 

[douger]

Honestly most of what I see is people maxing out pellet guns to be able to shoot slugs. Lol

i here lotta people tune for slugs and still want to shoot pellets. got to have a gun that can adjust fast enough to retune rather than run a slug tune shooting pellets, i played with very few slugs at a mild pellet tune, and seems few slugs iv tried shoot pretty well at 860-940 pretty interesting that lotta people are 980 to 1000 fps

 

[gendoc]

i here lotta people tune for slugs and still want to shoot pellets. got to have a gun that can adjust fast enough to retune rather than run a slug tune shooting pellets, i played with very few slugs at a mild pellet tune, and seems few slugs iv tried shoot pretty well at 860-940 pretty interesting that lotta people are 980 to 1000 fps

thats why i have 2 mkII crowns, one compact for 18.1gr jsb @ 925
and the long range one for hybrids @ 1025fps
both are exceptionally accurate for hunting.

 

[Feinwerk]

For diablo pellets, the general consensus seems to have been that their accuracy tends to be better around 875ish FPS. This is not a hard and fast rule, though, and there are variations among pellets at the same speed in a particular gun. If the gun that I am tuning has enough power, I will start at a velocity below this and raise it, shooting groups as I go to try and identify a velocity sweet spot for that particular pellet.

I have noticed that, for me, once I get pellets going out upwards of 860 FPS or higher, the pellet leaves the barrel so quickly that my offhand and braced shooting accuracy improves because the gun is shifting less before the pellet exits the barrel while I'm trying to hold on target. So I have found some value in the physics of a faster velocity, up to a point. I say that, because I'm still hand pumping my rifles. Higher velocity means more air use and more pumping.

Most of my shooting is geared toward occasional pesting. I would guess that someone who prefers to shoot targets for best accuracy, would not follow this approach and would continue varying velocity and pellets to find the best single combination based on group size alone.

For my guns that have no transfer port quick adjustment, and only a hammer spring tension adjustment, once I identify a good pellet near the speed I would like to shoot, I look at the trajectory chart data from Strelok Pro ballistics app. Sometimes I favor a specific velocity because it gives me useful zero crossings at my favorite ranges, for the best overall Point blank range that has minimal holdover, depending on what the scope height is. In other words, I will take the ballistics trajectory curve into account when selecting a velocity, choosing the best compromise between trajectory, hold over / under, and accuracy.

If I'm setting up a gun for a high shot count and conserving air, then I will a choose a slower velocity range on purpose, and then shoot groups with different pellets to find the best pellet at a particular speed range. Once one pellet is identified, then I will dial the speed up and down a little bit to further refine the speed for that pellet. This may mean another compromise to give up some accuracy just to conserve air for a high shot count, compared to the speed that gives the best accuracy for that pellet.

If my gun has a transfer port power adjuster, such as my FX Independence that has a low medium and high transfer port adjustment knob, a pellet selection process must be repeated at all three speeds. The hammer spring tension is set for the best overall compromise, producing the most useful spread of speeds among the three transfer port settings. The Independence has the onboard pump and there is a particular advantage to shooting on low, which requires only one pump per shot to keep the air reservoir topped off for effortless plinking. On medium, it requires three pumps, and on high for hunting, five pumps per shot to maintain the same reservoir pressure. This gun in particular probably presents the most daunting challenge to select speeds and reservoir pressures and pellets for the best overall compromise. You become your own regulator and you simply pump as many pumps as needed and read the pressure gauge to arrive at whatever plenum pressure you deem is best for each speed and pellet.

Regards,
Feinwerk

 

[Revoman]

Since Nsboost isn't getting it, let me try this....
1.) Receive a rifle from the factory, shoot it, leaving the chronograph in the box.
2.) Shoot it to see if it's as accurate as anticipated at the range required and using the projectile of choice.
3.) If it is, then you're good. If not make an adjustment and shoot again. Repeat as necessary the entire time not using the chronograph.
4.) Once the accuracy is attained, then crack out the chronograph to see what speed has been settled upon by the rifle, projectile and range required.
5.) Then bump the regulator pressure slightly to elevate the speed and use the finer tuning adjustments to drop back to the accuracy velocity as established.
Make a little more sense?
mike