A little more chrono love.

I think I figured out, today, how I can rig up a chronography session so as to shoot off my front porch, mostly rested (right elbow unsupported), and shoot through the chrono at a measured distance (15') enroute to a target at a measured 10m (the de facto airgun standard).  This can be the basis of combined chronography and accuracy work for the relative quick-testing of new pellet/powerwheel combinations.  Notably, after setting chrono up at the further distance, I no longer had any errors from it.  Sure, it was a sunny day today, but I think I learned something and will go with it.

I continue, as well, to learn about the Caldwell Ballistic Precision app that I'm using on my smartphone.  It's got its quirks, but it's proving to be pretty handy.  Apparently it's set up so that you can designate (upfront, not after-the-fact) a "saved group" and capture a bit of metadata along with your shot string (e.g., temperature, humidity, distance to chrono, pellet used, etc.), including a photo of the target grouping.  I suppose I should start carrying in my pocket a dime and a quarter, which are often used in airgunners' pictures to give context to the group size.  (Airgun hunters speak of the one-inch "kill zone" for most quarry, which is just about the size of a quarter, and of the 3/4" zone for some critters, which is just about the size of a dime.)

I'll have to develop the practice a bit, to arrive at a consistency in picture framing, naming, and repeatability of setup, but I think this is going to be workable.  The distances are known, and at the 10m target distance one can probably successfully weed out which pellets just aren't shooting as well as others.  Check out these two strings, in the context of my first experiment with the powerwheel set as low as it could go.  This string was shot with the wheel set at "2.1":

#     FPS  FT-LBS

12    794      43.43
11    806      44.75
10    820      46.32
9    817      45.98
8    831      47.57
7    830      47.46
6    844      49.07
5    853      50.13
4    839      48.49
3    845      49.19
2    811      45.31
1    775      41.38
Average: 822.1 FPS
SD: 23.0 FPS
Min: 775 FPS
Max: 853 FPS
Spread: 78 FPS

Note how much more consistent this string is, than the other one.  The deviation and spread are much tighter, and the velocities begin to drop off steadily at the end of the string (once they do this, you can stop shooting, as you've got the answer you came for).  Based on what I've learned from Tom Gaylord, I believe I can "read" this data as suggesting that this configuration is good for about 10 shots (#2-#11) where the spread is even tighter, and since there is only one shot before the valve "wakes up" into that ideal series, that means that the starting pressure of 3000psi is pretty close to ideal.  (Sometimes, if the string starts to tighten up after several shots, it may suggest that the ideal fill pressure is not the 3000psi max, but maybe something lower, like maybe 2700psi.)

This string was then shot with the wheel set at "4.10":

#      FPS  FT-LBS
11    803      44.42
10    812      45.42 
9    832      47.69
8    847      49.42
7    859      50.83
6    870      52.14
5    881      53.47
4    884      53.83
3    886      54.08
2    880      53.35
1    885      53.96
Average: 858.1 FPS
SD: 30.5 FPS
Min: 803 FPS
Max: 886 FPS
Spread: 83 FPS

Now in terms of statistics, this one is starting to look interesting.  In particular look at how tight those first five shots are, with a pretty steady decline thereafter.  This one seems to suggest that the fill pressure is right on.

And at this point I had just figured out how to set the target in the right spot to get a group while chronographing.  This is what the final ten shots of the string did at 10m:

That's just about a quarter inch, center-to-center.  (The black dot is my crude aim point.)  Hey, I'll take that.  The rest was improvised, my right elbow was unsupported, and I wasn't exactly bearing down for these shots.  Looks like it may be worth trying at 25, and possibly even 50.  Especially since the power level seems more than acceptable.

At this point I decided to adjust the power wheel to 6.10 and shoot a few more shots, to set the valve for a full test at 6.10.  These were just fun shots, not chronographed;  they each clanked with a satisfying smack on the rimfire spinner at 25 yards.

When refilling after this series of about 20 shots (which took it down to about 1200psi), the behavior of the Hill pump seemed a little quirky.  I will have to pay attention to how it behaves going forward!

Chronography note.

Had a brief chance (everything's brief, with a seven-week-old in the house) to set up the new chrono and run a string over it with the TalonP set to absolute minimum power on the power wheel.

Some notes, mostly for myself, in no particular order:

• Used the chrono without skyscreens at all, based on a Tom Gaylord comment I saw recently.  This seemed to work well in the direct sunshine.
• I tried a very close distance-to-chrono this time;  about one foot.  Mostly this was in order to do it fast, rather than perfectly;  I will want to back off to about three feet as there is noticeable muzzle blast from the TalonP, and one foot seems kinda rude.
• The .25 pellets may be less susceptible than the .177s to get "missed" by one or both screens unless they are "close enough" down to the top of the chrono unit, but it can still happen.
• Power wheel was set to absolute minimum;  I wanted to see what the gun did here.  AirForce owners would refer to the setting as "1.1" on the wheel, and I understand that this is highly individualized to each gun;  that is, a setting of "8.11" on one gun is not going to translate to a second gun sitting right next to it.  It's a relative measure for that gun of how wide open the valve is.  The shooter uses it to make his own notes.
• Top hat was also set to the most polite setting, and over 20 shots later it is still tight.  We'll see how long that continues!
• Performance was interesting.  It was much more erratic than I was expecting, and it may be that this is my first taste of what Tom Gaylord calls "finding the right power curve" for a given gun and pellet.   Here's the string data--note some wide variations between successive shots:

#    FPS / FT-LBS

20    657 / 30

19    673 / 31

18    690 / 33

17    898 / 56

16    727 / 36

15    739 / 38

14    848 / 50

13    774 / 41

12    ERROR 3

11    ERROR 3

10    806 / 45

9    811 / 45

8    829 / 47

7    ERROR 3

6    847 / 49

5    850 / 50

4    791 / 43

3    846 / 49

2    791 / 43

1    793 / 43

Average: 786.5 FPS

SD: 68.6 FPS

Min: 657 FPS

Max: 898 FPS

Spread: 241 FPS

Starting fill was about 2900psi (two un-chronoed shots down from a 3000psi fill), and based on what the Hill pump told me when refilling afterwards, the end pressure was about 1200psi.  I was deliberately shooting until I could clearly see the gun dropping off, and after shot #17 threw me for a loop (how did that happen?), the next three pretty clearly showed the trend I was looking for.  These guns are known for maintaining a pretty tight spread over their ideal "shots per fill", and owners of TalonP and Escape models (which use the same 210cc air tank) seem to confirm a very reliable 10 full power shots per fill--sometimes more, but almost never less--once you've found the right setting(s).  (Interestingly, the ideal string of tight-spread, full-power shots doesn't necessarily begin with shot #1, but sometimes after a few "wake-up-the-valve" shots.  

It's quite possible that this "absolute minimum" setting is just not right for the gun, and next time I am going to try going up to "2.1".  (Of interest:  the test-fire data from Pyramyd Air, when I bought the gun, with a different pellet and power wheel setting at "4.6", showed a much tighter ES (118fps) and SD (42fps) for their 10 shots, with a clearly linear pattern of slightly-descending-velocity for each shot.)  

I'm interested to see what this gun's "miser mode" (whatever that turns out to be) can give me in terms of shots-per-fill;  also what "max power mode" (whatever that may be, and it may not be "full open", either) will yield, and finally I suspect I'm going to settle on whatever setting gives me the tightest spread for the 10-15 shots I think I can expect from the piece.  (For anyone reading this who is new to PCP guns:  there are many PCPs out there which can get many more shots-per-fill than this one;  AirForce's own "Talon" rifle, with a different valve and tank than the "TalonP", is one of them.)  The attraction of the TalonP, for me at least, was 1) short carbine length, 2) adjustable LOP, 3) more power for its size and ergonomics than anything I have yet found, and 4) "quickly" and easily topped off (refilled for a new string) with a hand pump.  The idea of having 10 shots at hand for hunting or pests, and then hand-pumping a refill in a matter of minutes, is just fine for what I wanted.  (Once I can afford a SCUBA tank and/or a 3000psi compressor, it could get just plain addicting.)

And jeez, look at the power at this minimum setting.  An It's actually so high that I again wonder if this is out of the valve's optimum range, and I might see some more sedate performance with the power wheel set a little higher.  At any rate, I was figuring that even at minimum wheel settings this gun (known for its gonzo valve) would have power to spare for whatever I'd want to do, and--yeah, you could say that.  That last shot, at 30 foot-pounds, is still pretty whopping for a smallbore airgun;  if my charts are correct, it will still retain about 12 foot-pounds at fifty yards.  

Thus all the testing.  Ultimately,  I don't know how serious I'm going to get or be about maintaining a statistically tight spread over those 10-15 shots, but I do want to see the data myself and maybe start to develop a spidey sense with it.  At heart I'm a functional guy:  I'll obsess over data just long enough to find the pattern I want.  And here, what I want is:  1) enough field accuracy to hit that 1" squirrel brain at 50 (yes, that's gonna be through glass), 2) enough power to anchor a snowshoe hare at the same distance, and 3) enough consistency from shot to shot that I can learn one trajectory and lean on it.  I suspect that the TalonP is going to provide multiple pellet options that can do a half-inch at 50 off the bench, leaving me a little wiggle room to guarantee the inch from a field position when it counts. 

_____________________

I also ran a string through the Bronco with the half-pint-milk-box wadcutters from Crosman (mostly to test the chrono before firing the .25s over it) and learned only afterward that the otherwise nice iOS app for the "Ballistic Precision" chrono does not allow you to capture and save a string in arrears--you have to declare that you're going to save the string before you shoot it!  Okay, so this is a minor matter and I'm glad I figured it out now rather than later, but you should have seen this string!  Other than a few errors when I got the tiny pellet too far above the screens (this is becoming a consistent pattern), there were probably 20 shots in the string and the extreme spread was less than 5fps (first standard deviation was under 2!)  I was impressed, and will have to try that again to see if it was a fluke.

I'd like to construct/fashion, if I can, a "plug-and-play" bench for doing chrono testing with the airguns, since I plan to do a lot of that:  something that I can quickly lay the chrono and the gun on and have their alignment be very close to ready-to-go.  The initial thought was a simple board that would "mount" the chrono, on a small tripod, at a height in the middle of the tripod's adjustment range, and at the other end perhaps mount my "Site-N-Clean" cleaning vise/rest to match it.  In theory, small elevation adjustments for different guns could be handled by the tripod's vertical crank, and I would just point the aligned shebang at a suitable target, permitting me to do both accuracy testing and chronography at the same time.  (Not so much an issue for the Bronco, where pellets and powerplant are both cheap, but right now at least--still looking for work--.25 pellets do cost noticeably more, and as marvelous a device as that Hill pump is, I'm not going to be able to do hundreds of rounds at a time with a hand pump only.  :-)

Nothing like a few quick shots off the porch to brighten your day.

Took a few minutes this morning to reconnect with the TalonP carbine I put together last November, which has apparently been on back-burner for a while.  

Click for more bigger awesome.

Just a few offhand shots on the 25y rimfire spinner, off the front deck, followed by a top-off fill to 3000psi.  Total time from the first thought of "hey, I should work the airgun" to refilled, clean, tightened piece and accoutrements all put away, was probably twenty minutes.  And this is the complicated pellet gun, which trades a few operational conveniences for the potential of nearly half the power of a .22 Long Rifle.  (I could have put the same number of shots downrange with the breakbarrel AV Bronco in under half that time, from first-thought to all-put-away.  The Bronco is not about power at all, but rather about easy, high-volume practice shooting--and it is very, very good at that.)

Yeah, I have become a fan of airgunnery as a valuable personal training tool.  :-)

Confirmed:  I really do like this piece, and look forward to learning more about it this year with working chronography, a goodly supply of .25 caliber pellets, and a whole lot of manual pump strokes into the Hill pump.  With a little luck, I'll be able to work with the six-year-old on some select tasks as a school subject (physics, arithmetic, and statistical concepts in chronography and in accuracy testing), and of course work on my own as well.

For whatever reason--maybe it's just warmer now and things have loosened up--I was able to roll the power adjustment wheel with little issue, and so adjusted it all the way down to the bottom of the scale, where I fired the last few shots of the session.  This should set things up well to begin testing how miserly the gun can be in terms of shots-per-fill, and what power it generates at that level.  I suspect even at the lowest setting there will still be plenty of power available for the sort of game I'm most likely to pursue (think spruce grouse and snowshoe hares), and as anticipated I am already beginning to appreciate the effort required to feed a PCP ("precharged pneumatic") airgun with a high-pressure (2000-3000psi) hand pump.  I still love the concept, but it's enough effort that it does tend to keep you from wasting shots needlessly.

Once we get things dialed in for chronography testing and most-accurate-pellet choice, I look forward to swapping out that lovely but huge and heavy Leapers glass for the Walther dot sight, and adding a Giles sling to make the piece more wearable.  The whole plan for this piece in the longer term, after all, is to serve as a knockabout carbine of minimum bulk and weight;  someday I still hope to acquire a "slightly bigger brother" in the form of the AirForce EscapeSS, which features both readily interchangeable barrels (and a reputedly subtler valve) and sound suppression built into the frame.  (That's the piece I think the Leapers glass would be ideally suited for.)  The two guns could share air tanks and parts, and I like the idea of having one set up as a .22 (for higher-volume shooting) and the other as a .25 (for maximum power and range).

I did notice that the top hat came loose again, which was a little aggravating.  I may have to use threadlocker on those tiny set-screws after all.  (If I'm reading things right, the top hat is mostly a set-and-forget item anyway.)  We'll see how a really good scrunch goes.

Functionally, there's still only one thing I have reservations about, and that is fumbling the load in really cold weather.  I seem to notice that every time I shoot the piece, even when (like today) the weather is just fine and there is no trouble at all.  It's as though now that I've thought about it, the brain can't let go.

Very well, then, I'll make it a matter of practice and habituation.  Shucks.  :-)

Functional chronography at last?

The replacement chronograph arrived from Battenfeld Technologies, and today I got to set it up and try it out.  By which I mean "conduct a very rudimentary test";  this was no sort of dedicated session.

However, I'm encouraged at the results.  I had the deck stacked up for it to fail.  To wit:

• Today is the winter solstice, at just about 60 degrees north latitude.  It wasn't fully overcast, but certainly cloudy.  I shot at 3pm, one hour before sunset.  This is not what you'd call "ideal light".  (Temp was 27F and humidity was 64%, for my own documentation.)
• I had the standard screen shades on the unit.  (When they sent me the replacement, they actually sent me the "deluxe" kit, which includes a pair of infrared skyscreen shades intended to improve performance in diffuse light.  I now have that option, but I tried it without first.)
• I tested with the tiniest projectile I will ever shoot over the screens--an 8-grain .177" diabolo pellet.  (Even Airsoft BBs are bigger than this.)

The test string was 18 shots (the capacity of my "pellet pen" loader/seater).  I did record two errors on shots 4 and 5, but suddenly I had an odd hunch that maybe I should cause the pellet to pass lower, closer to the screens.  I tried this and the error, and the "fix", seems to be repeatable.  Interesting.  I'll be curious to see if I get the same effect when I pass a 31-grain .25" diabolo pellet over the unit, or if maybe that tiny little 8-grain pill is just that much harder to pick up that you have to "help" it a bit with proximity.  Or, maybe this is where the IR lights start to become valuable.  More testing, of course!

Still...every time I put a pellet low over the screens (call it the bottom 1/4 of the presented trapezoid, rather than the middle half), even in minimal, flat light and using the standard screens, I got a read.  And the simple interface and export options (this chrony is notable for interfacing with a smartphone) seem quite promising.

All of which makes me pretty happy.  Here soon I'll try to wring it out more thoroughly at the house (using .177" pellets in the Bronco, Airsoft BBs in the gas 1911, and .25" pellets in the AirForce TalonP), both to learn more about those guns themselves, and also to get ready for range testing when the now-completed 03 Springfield arrives. 

I'll keep fingers crossed that this is going to work out the way I'm envisioning it.  And in that vein, today was a much better start than the first time!  :-)