Pushing non-regulated PCP's too far

[Ribbonstone]

Every so often, I tend to work in reverse.  Not using the chrongraph, just letting the "clusters" of pellets tell their own tale.

Working in REVERSE...which might bge a help to some new shooters without a chronograph.

Pushing a non-regulated PCP too far in shot count.

Set up targert at only 70 feet by steeol tape (23.3 yards if you like).

Filled the rifle (a small volume 3K non regulated PCP) and shot 25 shots on to that single target.


But I kind of kept track of the shots in order.

DSCN1615 by Robert Dean, on Flickr


OK...shots #1-#4 were low.

Shots #23-25 were low.

Shots # 5-23 were pretty much clustered together nicely (although a bit high).


So what does that suggest to you?  Tuned non-regulated PCP running over a pretty normal bell curve? Somthing really excessive in velocity varation?  Just bad luck?  The high shooting group being faster than the low shooting impacts?
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OK...lucky for you guys, I do have a chronograph (and even a chap one will take a lot of "mystery"out of testingso buy one).

This is the 25 shot string for that little rifle:

DSCN1614 by Robert Dean, on Flickr

Which if I think about the groups AND the chronograph, even at short range (23.3 yards) the best shooting in in the 3-4% velcoity varaion range.

DSCN1613 by Robert Dean, on Flickr

Which cuts off the 4-5 bad shots at the start and the 5 bad shots at the end of that bell curve.


So while I can tell 7% from 4% at 23.3 yards, haven'tbeen able to tease the difference betweern 1%,2%,or 3% vfelocity varaition at 40-50 yards.  Just too mcuh other "stuff" going on (hold/stablitty'trigger control/ WIND/ etc.) to make a firm difference between the 10-11 shots at 1% and the 18 shots at 3%.


So I'd better get use to 19 shots with this rifle (which is 2  9 shot mnags)....fill it (at this tune) to 2800psi...refill it to 2800psi after 2 mags,,,and go on with my happy-whappy way.


Logic tells me that if the difference between 7% and 3% is evident at 23.3 yards, then percentage-wise that the difference between 3% and 1.5% velocity varation should be evident at 46.6 yards.   

But all the other biologic and enviromental "snit" seems to cover up that difference.

[HunterWhite]

Excellent post  Ribbonstone !
I usually find it easier to understand the practical side than theory.
Your marksmanship is very good to be able to display the velocity as point of impact.

[CraigH]

Excellent!   Let's call the string 15 shots at high side of 1% and use the associated start and stop pressures.   That's how I look at my strings, and refill as needed to be in the pressure zone.

Of course the jest of it is to help new shooters without chrony; still, it's excellent for all.

[Motorhead]

23 yards is SOOOOO Close and for most actually under what one would have as a PBR ( Point Blank range or ZERO range )  It really is not telling you much shooting at such distances IMO.

[Gertrude]

23 yards is SOOOOO Close and for most actually under what one would have as a PBR ( Point Blank range or ZERO range )  It really is not telling you much shooting at such distances IMO.

yup, agreed.

[Ribbonstone]

Same rifle.
Same pellets.
Same sixe yellow bullseye
Same distance (23.3 yards)...although I had to rely on flood lights this time of night.

Only differences are:

1. Dialed in 3 chicks of "down".
2. Filled to 190BAR.
3.Limited to two mags (18 shots)....which should havew been somethingt oike 2.5-3% velocity varation


DSCN1616 by Robert Dean, on Flickr


The "COULD BE's":


Could be that I had more confidence.

Could be that the tube expansion for a smaller pressure change was more kind than a large pressure range.

Could be "luck"....for 18 shots in a row.

Could be I got better with some prcatice shooting the rifle'

But I don't think so...but you are fee to think whatever you like (as some airgun folks get offended by "cheap" airguns shooting as well as they can).


Think I learned a couple of things (or at least re-learned/taken them to heart).


1. Over s short range of pressure,shot whot count, unregulated seems to shoot just as well as regulated PCP' for a short run of shots.
2. Pushing non-regulated PCP's past their sweetest-0f-the-sweet spot is a losers game.]
3. Using such a small range of pressure for the best-of-the-best shots makes the rifle efficinent and easy to fill every 2 mags.

----ok...by my measure by the little gauges, it's like 2800-2750 psi to 2250-2200psi of air use,which ain't too bad for 18 shots at 19.4 footpounds.


Very little pump-effort to refill..fill to 2800psi,,,shoottwo mags...refill... it's like "warm-up pumping".



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That's enough for hunting.

Hunting Season limit on Squirrles is 8  a day.  So basicaly that gives you 2.2 shots per squirrel....and I've never gotten 8 fair shots at squirrels in a single afternoon's hunt.

[oldpro]

At that distance I suspect it’s harmonics I doubt velocity or ES has much of and effect unless we’re talking near sonic speeds. Good write up and documentation

[Ribbonstone]

Typical long range metality

(good God...not every "green weenie" wanted to be a sniper...some were "tunnel rats"...which do you think had the most "guts"?)

OK..the "FullMonty":

Not being a convicted felon and not living in a restictive state and not living  in a restrictive area of that state...can use firearms during hunting season.


I choose to use airguns becasue I get CLOSE.  If there is something wrong with sneaking up/planning to be closer, I'd like to hear about it (should I walk backwards for 20 yards if I am presented with a 15 yard shot?).


 Airguns are hard pressed to manage what a .22LR can do(100footpopunds at 100 yards)....and lets comapre $$$to $$$ here...put your $1000 airrifle against a $1000 rim fire using the best ammo for either).

Not wanting to kill  critters out of serason, no matter the legality, airguns are relagated to the "outlaw"(no season) critters.  During the hunting season, if I use airguns (which I have done for the last 10 years),how am I "ahead"?

(f you believe your PCPcan manage better long term accuracvy (in MOA) at 100 myards for 15-20 consecuitive shots,are free to try and post results.  While you are at it, may as well get them to shoot to the center of the target rather than off to some odd corner of the paper (can't be that hard...I've managed it).

So no....not going to back down..REGUARDLESS OF THE DISTANCE:

1. Shooting in a smaller velocity varatuion area does make a difference.  I just canbt tell the difference bgewtween 1% varaition and 3% varaition because so many otrher variables.

2. If the target suits the scope (basically being able to evenly "quartered"), can shoot well with a lower power scope. 

3. Self regulating PCPs (AKA "non regulated') do have a short range of pressure where they actually do act as if they were regulated.  It's just up to the shooter to find it and live within it.

basiucally it is this:

Non-airguns are a better/simpler solution to long range.
With airguns,it'snot about long range...it's about 50 yrds or under.
Bigger bores/more powerful airguns are for biggercritters (which is why the ones that are powerul wear 6x,4X, or night vision 2X scopes).


I do understand the "drive of the hobby"...it; what keeps cast bullet shooters in the hunt for match bullet accuracy...what keeps black powder cartridge shooters in the searh for match accuracy....what keeps  airgun shooters in the searcdh for long range acuracy.

It's all just dust on the looking glass.

[CraigH]

Not much to disagree with.   I don't mind short, low ES shot strings with a non-regulated air gun.

As for the .22 caliber rimfire, with CB longs at 30 fpe and .22 Long Rifle at 140 fpe, it is quite efficient and versatile.

[squirrel_hunter]

 i think ribbonstone is correct...his data supports what we all know.his method of getting the data is different or backwards as he describes but very effective.its right there in black and white,shoot best on the curve with lowest ES...

[anti-squirrel]

Robert- thank you for the write-up and validation.  A common-sense approach like this really comes down to learning your equipment and taking advantage of what it offers.  Since consistency is the absolute most important thing in ANY shooting endeavor (from atlatl to palma-shooting), knowing where you can be most consistent points you in the right direction, always.

Not gonna knock anybody on this thread, but for folks like me who focus on short-range pest-killing, working with the ideal chunk of the ES/efficiency is preferred. Now that I have a Maximus, my intention is down-tuning the power level to make wadcutters shine.  I know the barrel is accurate, and likely accurate-enough for my needs...  so using basic chronograph data and some common knowledge with non-regulated PCP operation (shooting for the knee, not the cliff) means a focus on working with the ES gives me the best "kill-accuracy-per-fill".  In simplest terms, shooting for (pun intended) that tightest ES, which in turn means breaking out the chrono and documenting.  Lucky for me, I already have some expectations for the Max since so many of you have blazed that trail well in advance.

As an aside, PBR range for me is 6 feet, and I've taken 30 squirrels in the last 6 years at such a range, and knowing aim points at short ranges is as important for me as knowing ballistic trajectory for reaching out with big lumbering pellets like Polymags in my .25 95QE.  So the knowledge gleaned from Robert's shooting experience here need not be scoffed at.  It refutes what we already know: work with the ES on non-regulated guns, whether inside so-called PBR or when reaching out and touching pests at 100+.  Heck, I've taken squirrel at 9 feet using my horsebow.  Trust me when I say a shot like that is a dozen times harder than using the same bow at 15 yards since harmonics including the paradoxing of the arrow shaft around the stave of the bow is in full effect to about 10 yards out.  This in turn leads me to believe that ES is not the only factor.  As Travis added, harmonics are playing a role- especially in a rifle.  A short-barrel gun such as my PP700 doesn't have much in the way of harmonics affecting the shot, since the barrel is not only short and tensioned, the gun itself is regulated...  Which is why it is my preferred short-range-squirrel-extinction-device.

Phew, sorry for being so long-winded.  This is a worthy discussion and everybody's posts have real merit based on viewpoint, experience, and application.

Side note: this is the type of thread that really exposes the vast amount of options available to us airgunners nowadays.  Great time to be into airgunning!

[grand-galop]

With the same point in mind, the UNREGULATED airgun would benefit greatly of big reservoir to get a narrow es..
The cheap air rifle are a treasor trove for the thinkers and can scratch the SNOB elitist in the accuracy dept..

[triggertreat]

I do like tuning my unregulated guns below a 2% ES.  It's just one factor in the accuracy equation I can eliminate right off the top.  Up at close ranges this doesn't matter so much, and could probably have an ES of 10% or more within ~20 yards and still punch a ragged hole,  but at the longer ranges that I prefer to take shots, it does create an accuracy issue having a larger ES %.  Too bad that's not the only factor to contend with for long range shooting, lol.  There are many others that get in the way as well besides extreme spreads.

I also like to run my guns at higher velocities if the barrel and pellet cooperates.  If not, they get backed down until they do.  The higher velocities have a much less loopier trajectory.
 

[Ribbonstone]

Also going to be a bit long winded.

Grand-galop: Yep...MAc1 did take that idea, and produce (maybe still does) large air volume/low pressure/bench rifles that are unregulated.  Kind of pricy last I checked ($2500-$2700)…. he is often not-welcome on many airgun boards (being rather vocal and opinionated....heay...why does that sound familiar?) it evidently works (and I do admire the simplicity of the idea).

So far, have not found a non-regulated PCP that doesn't have a nice little run of near regulated  performance....or at least has the potiental for it if the adjustments were corrected.

Guess the point of all this is that if you want to shoot the best that a non-regulated PCP can offer, you have to find where the "balance" of the system is.  Might be a short area/few shots.....might be a lot more shots than you expect.

Was trying to adjust a .177 Pneuma (the old single shot version of the HAtsan) to 12 foot pounds.

I failed at that.  Stumbled upon a spot where it seemed to live very happy at 14.6 foot pounds.   




(there is a niced run of about 37 shots at 2% in there as well.)

Pretty well stubbed my mental toe on that.....and looked for soemthing like that area on all the non-regulated  PCP's (high power or low).

Regulation certainly helped make for LONGER shot counts (nothing is truely "free"...you use as much or more air per shot) but didn't really change the accuracy results.

Logically, it should make a difference...1% has got to be better than 3%....but all the other stuff (esp. the variablity of wind and the varaiblity of the biologic mass doing the shooting) just hid any advanatge.  All it takes is one cock-eyed pellet,one stray gust of wind, one mental "oops", and the mathamatic advanatage is just scrambled.



OOOh...maybe old-time "string measure"...I gotta think about that.

[rsterne]

First of all, let me state that I agree with Ribbon's belief that unregulated (ie self-regulated) PCPs, if kept within the proper pressure range, can rival regulated PCPs in terms of ES.... Whether or not his target, which does reflect what happens when the ES is allowed to stray too far below the maximum reflects JUST the vertical stringing from the velocity effect.... or if there is something else, such as barrel harmonics, coming into play.... is probably the one part left open to debate....

I used his velocity numbers and pellet in ChairGun and looked at the total Vertical Stringing for 3%, 5%, 7% and even a 10% ES at his 23 yard range.... Here is what ChairGun came up with for the total POI change from fastest to slowest shot....

3% ES (904-932 fps) = 0.07"
5% ES (885-932 fps) = 0.11"
7% ES (869-932 fps) = 0.16"
10% ES (839-932 fps) = 0.24"

While there is no disputing what allowing the ES to exceed 3% did to the POI in Ribbon's testing.... and I don't have the precise information about how much lower the first and last shots were at a 7% ES.... just judging by the group size compared to the size of the .177 pellet holes.... it would appear to me that there is more going on than JUST the ES variation....

The fact remains, for that rifle, at that range, staying within a 3% ES certainly seems the way to go....

Bob

[K.O.]

I do not run a lot of strings... But it pretty easy to find the sweet spot just by sending lead down range...and there are for sure factors beyond just extreme spread...

with 10.3g CPUM groups open up just a bit above about 2400 psi with my Buccaneer the AA 10.3 are the same but at about 2300 psi...

the 7.9 Benji only do great to 30 yards below 1800 psi...


My little Stormrider has problems with every pellet above about 2600 psi at this point...probably harmonics...

As far as long range well that is when hunting as far as I can pull off 10 out of 10 in about .75"...  in the old days many times did I wish for a rifle that could go 50 yards... 

I do feel that if you have a rifle that can keep a 1% es at that distance it is better than the same rifle at a 4% es...it is a fractal thing to me and small input differences can make bigger differences down range than you would think just using the stringing effect of the velocity difference...

[Marc In Iowa]

... the UNREGULATED airgun would benefit greatly of big reservoir to get a narrow es...

I've just completed an experiment like this. Using a Brocock Bantam Hi Lite (unregulated, 480cc carbon fiber bottle), I'm getting 60 shots @880 fps with ES 2.5%.

Shoots from 160 ->135 bar.

Gets 60 shots from 60 hand pumps.

[Ribbonstone]

No doubt there is some human error....and I'm particually looking at the lowest hit (dangling like a comma) as it wasn't the very last shot.  But you gotta count what you shot.

Realy, other than 3 low shots, the two groups are pretty darned close in size.    Not a match accurate rifle, but I don't regret the $.

[rjp]

I used his velocity numbers and pellet in ChairGun and looked at the total Vertical Stringing for 3%, 5%, 7% and even a 10% ES at his 23 yard range.... Here is what ChairGun came up with for the total POI change from fastest to slowest shot....

3% ES (904-932 fps) = 0.07"
5% ES (885-932 fps) = 0.11"
7% ES (869-932 fps) = 0.16"
10% ES (839-932 fps) = 0.24"

While there is no disputing what allowing the ES to exceed 3% did to the POI in Ribbon's testing.... and I don't have the precise information about how much lower the first and last shots were at a 7% ES.... just judging by the group size compared to the size of the .177 pellet holes.... it would appear to me that there is more going on than JUST the ES variation....

Old topic, but I have been calculating this myself recently and found this thread. According to my calculations, these numbers above for pellet drop seem to be assuming constant velocity. At 23 yards it is very unlikely the pellet is still going at 932 fps. The actual final velocity depends on air resistance, and I don't know the formula. But if we assume the pellet hits the target at half its original velocity these numbers would approximately double. So 10%ES would give about 0.5" drop.

So basically, ES is a bit more relevant to accuracy than the original numbers suggest.

[rsterne]

No, the numbers were calculated using Chairgun, for the 23 yard range stated.... I had to take a guess at the BC, because the pellet wasn't stated (that I saw)…. but with a BC of 0.025, the velocity at 23 yards would still be 800 fps (starting at 932)…. Slower shots would loose even less at 23 yards.... None would even approach the "half" you suggest, and even it that applied, the vertical drop would not double, because it is the average velocity that affects the time to target (and hence the drop), not the final velocity.... 

Bob