Chronograph instructions and tips

by B.B. Pelletier

I need to be humbled periodically to maintain my perspective on things. Fortunately, for me, I was created with many imperfections that make frequent humbling a certainty.

I was taking a .22 semiautomatic rifle apart several days ago to clean the action, and I got to the part where you remove the last drift pin and all the major and minor parts fly apart like a satellite that’s been hit by a particle beam. No chance to see where everything went because they all got disassociated at the same time.

When this happens, I have several mantras to address the situation. No. 1 is I imagine the item was assembled by a 19 year-old girl named Tiffany, while she is also talking to her coworkers, drinking a Slurpee and texting her best friend. Tiffany can put this thing together in 27 seconds and can spot (without thinking about it) when part 51b has been reversed in its slot, which is good because Tiffany isn’t really into thinking.

If that one fails and I still have parts lying all over the table, I think of Ishmael, who uses no special tools to assemble this item. He has a hole in one of the upright girders supporting the roof where he assembles these items all day long. It was blown through the steel girder 37 years ago with an acetylene torch, and it isn’t quite round; but time and use have polished the edges of the hole, and it’s the perfect assembly tool that was used by Ishmael’s father for the same purpose. With it, he can assemble a pallet-load of these things, whatever they are, before tea time.

When that one fails me, there’s only one thing left — the Machtar chant of assembly (see the movie Galaxy Quest). As it happens all too often, even this potent bit of magic refused to work, leaving me with a pile of parts that purportedly had once been a semiautomatic rifle. Had I not seen it in that condition, I would have doubted it.

I got the gun back together by scrutinizing each part and imagining the relationship it had with the other parts (see, mom, I can use that lump on my shoulders for something other than a hatrack!), but I hate it when that happens. Complex parts should self-assemble, like a wine glass filmed in reverse after shattering.

But this isn’t about me fixing a gun. It’s about me being humbled, so I’ll remember what it’s like to approach something new for the first time. Trepidation, you are my middle name!

So, when a Pyramyd Air customer asked for some pointers on the use of a chronograph the other day, I felt I had to spring into action. Here is his exact request:

I’ve read a good percentage of your BLOGs & articles (plus videos), but no-where do I see the distance specified to set-up a chrono for muzzle velocity for springer airguns, pistols & rifles. I use a ProTach Classic Chrono, with 36″ between “start” & “stop” sensors (originally for hand-loading). I’ve searched the net for an airgun industry std. (like for fire-arms), with no success. One article, on the net, said set the “stop” sensor @ 3 ft. from the muzzle ~ that’s impracticle!! How-about-it, B.B., Tom or Robert B.!! Rich

Where to place the start screen
Rich, if this was five years ago, I wouldn’t have a clue what to tell you. That’s because you’re coming from the world of firearms. I began using chronographs with airguns. Only very recently have I started using a chronograph for my firearms, and only recently have I learned the difficulties of figuring out where to place the start screen.

I typically place the start screen about one foot from the muzzle of the airgun. That’s almost ANY airgun, mind you, except for a big bore and one other exception I’ll mention in a moment. A couple months ago, while I was chronoing some centerfire handloads, I rediscovered why my Oehler 35P came with 15-foot cables. Even when the skyscreens are placed 10 feet from the muzzle, the muzzle blast from a .43 Spanish round will move them like a slinky in Shakeytown!

When it came time to test the Benjamin Rogue, I was prepared to move the skyscreens way downrange from the muzzle to keep from blowing them apart from the air blast. Even though the start screen was situated about 10 feet from the muzzle, the entire skyscreen assembly shook violently every time the rifle fired. So, I understand Rich’s question at the most visceral level.

Rich, a spring gun discharges only the tiniest fraction of pressurized air that a pneumatic puts out, so you can place the start screen a foot from muzzle of the most powerful spring rifle or pistol you can find, which would be a Whiscombe JW80 generating 32 foot-pounds in .25 caliber. Ain’t nothin’ badder than that out there (in spring guns, that is), and your chrono will never miss a beat!

CO2 guns — the other exception
CO2 guns, however, often have a visible exhaust that can fool the skyscreen. Whenever I chrono one of them, I back up about 18 inches from the start screen. This holds true for the weakest pistols as well as the more powerful rifles. You don’t get an incorrect number from them, at least not from my Shooting Chrony Alpha model. What you get is an error message that screen one, the start screen, was unable to detect the passage of the pellet accurately. Back up a few inches, and the problem is solved!

The rest of the smallbores
As far as the other smallbore air rifles and pistols are concerned, 12 inches is all the distance you need between the muzzle and the start screen. This holds true for a catapult gun throwing a 3-grain lead shot at 86 f.p.s. as well as an AirForce Condor belting out a .25-caliber 43.2-grain Eun Jin pellet at nearly 1,000 f.p.s.

Watch where you’re shooting!
A funny story that is directly related. Many years ago, I was running an M203 grenade launcher range for my company at Hohenfels training center, West Germany. The M203 is an underslung weapon that attaches to the bottom of the M16 rifle. It lobs a 40mm grenade out several hundred meters and has been called the hip-pocket artillery of the infantry.


Attached under the rifle, the M203 grenade launcher lobs 40mm grenades out to 350 meters. It uses special high-angle sights, which the firer must not forget to use!

Here’s the thing about the M203. It shoots only a few hundred yards, while the M16′s 5.56mm cartridge can shoot several miles. Naturally, the rifle shoots much flatter than the grenade launcher, so the grenade launcher comes with its own set of sights designed to elevate the weapon to a very high angle to get the needed range. If you were to use the rifle’s sights, the grenade would hit the ground just a few yards downrange — and that would be a bad thing.


This young man demonstrates the correct angle for the M203 grenade launcher.

The firing positions on the M203 range were simulated foxholes with bermed bunkers in front and on both sides of each shooter. These berms were made of railroad ties that held back mounds of compacted dirt. Each firing position was protected from the others so that if anything bad happened, only the one position would suffer the consequences. On this day, I found out why — to my chagrin.

Even though I briefed each relay of shooters before they went to the firing points about using the M203 quadrant sights and not the rifle sights, and even though each firing position had an NCO to watch the shooter, we had an incident where a shooter forgot and used his rifle’s sights to engage a target. The grenade came out of the launcher and hit the railroad ties that were about 12 inches in front of him.

No, he didn’t blow himself up. The designers of the M203 grenade anticipated this event (it’s fairly common) and made the grenade to be armed by spin. It has to travel a certain distance downrange before the centrifugal force of it spinning from the rifling arms it, and 12 inches isn’t far enough. After the range was called cold and evacuated, I went to inspect the firing position, where I found a crumpled grenade lying in the dirt, next to the abandoned weapon. Just from the sheer velocity of the projectile, the grenade had dented the railroad tie about two inches!

Bad things can happen
I won’t tell you how I fixed the situation, but my point is this — when the sights and the bore are not aligned at close range, bad things can happen. The same is true with chronographs! If you’re shooting into a pellet trap that’s three feet away and you sight through the scope, you’re going to shoot your chronograph because the bore is three inches below the scope. Don’t think you’re smarter than that, because everyone who uses chronographs shoots them sooner or later. By sighting through the scope, you’re almost guaranteed to put a pellet through the guts of the electronics package.

Instead, sight by instinct, looking at the orientation of the barrel relative to the target, and of course to the skyscreens. Do this both for the elevation above the skyscreens as well as for the line the pellet takes across both screens.

Downrange problems
People sometimes place a chronograph downrange to calculate the terminal ballistics at a certain distance; or, if another chronograph is used near the muzzle, the ballistic coefficient of the projectile. But they forget that downrange the projectile can go wherever it wants. More chronographs have been ruined this way than any other. Figure that it is only a matter of time before the downrange chronograph is hit.

Lighting for a chronograph
The best light for skyscreens is an even light. A totally overcast day is perfect, as is a day with clear blue sky (as long as the sun does not shine directly on the skyscreens). But a day with puffy white clouds that move around is bad, and you’ll have to use the diffuser filters above the skyscreens.

For artificial light, incandescent bulbs that shine evenly are the best. Bulbs that shine by exciting either a gas or a phosphor, such as fluorescents, cannot be used. They will set off the skyscreens.

I personally have found that by reflecting a 500-watt incandescent light off a white ceiling, I get the optimum in indoor chronograph lighting.

Here’s a small lighting tip. Don’t use strobe flashes near the chronograph, because they will set off the skyscreens. So will the arc from an electric welding torch.

On the level
When you shoot through the skyscreens, it’s important to be as close as possible to perpendicular to the path of light to the screen. If you shoot on an angle — up or down doesn’t matter — the path through the screens will be longer than if perpendicular and the recorded velocity will be lower.

You’re in charge!
Most chronohraphs run on batteries. I should not need to say it, but always carry a spare for when the battery dies. It’s discouraging to be out on a range, only to have the battery die and not have a replacement — especially when the whole reason for going to the range was to use the chronograph.

Chronograph oddities
A few chronographs use infrared sensors in their skyscreens and need infrared light sources in order to work. If you lose one of these special-purpose bulbs, all the bright lights in the world will not make up for it. Keep spares close by.

What about that neat little Combro chronograph that attaches to the muzzle of the gun? How good is it? Well, I once owned one and can comment. It does work and you do get a number from it. And whenever there’s a number, people stand around and believe it.

But here is the deal. Oehler, which is admittedly the leader in commercial chronograph technology, separates his skyscreens (the third one in the middle is the stop screen for a second channel that checks the other one) by at least 24 inches. The machine’s clock speed (the frequency at which the crystal oscillates) is four megahertz. While the pellet flies between the start screen and the stop screen, the oscillator is counting at the rate of four million cycles per second. At that rate, it can parse time into small packets. The Combro has screens that are only a couple inches apart and a clock speed they don’t publish, but which must be slower than the Oehler. The number you get from this device is at best a close approximation — a best guess.

Aside from that, the Combro uses IR sensors, will not operate well in strong daylight and is difficult to fit to the muzzle of the gun. If it’s misaligned when mounted, it can be hit by the projectile. It’s not suited to use with firearms.

Wrap-up
I answered Rich’s question in one paragraph in this report, then I went on to discuss other common problems encountered when using a chronograph. If you have any other questions or would like to know more, please make a comment to that effect.

48 Responses to “Chronograph instructions and tips”

  • flobert Says:

    Makes me glad I’m stuck with the soft pine chronograph for now.

  • twotalon Says:

    Chronographs…..or……how to fool yourself and/or your friends.

    And of course, if nobody is watching, you can lie about the results. You don’t even need a chronograph ….you can lie about the whole thing.

    Wonder how many were sent back because the user did not read the instruction manual. Made every mistake possible when trying to use it. Maybe believed that their rifle simply could not shoot that slow because the manufacturer says their rifle shoots 1500 fps. The chrono obviously must be bad.

    twotalon

    • Alan in MI Says:

      twotalon,

      While I agree with you in many ways, I still am glad I have one. They are pretty essential for adjusting a PCP, and if you shoot springers, you only can go by the manufacturer’s lies without one . . .

  • Barrika Says:

    I’ve made it a point to “Chrony” all my airguns and rifles, and have found a LOT of rights & wrongs in the process (my old 1st Chrony will attest to that!):
    Indoors tests with airguns is best, assuming you’ve got a great backstop, & ~100 watt incandescent lighting about 20″ or so above the diffuser.
    I’ve made a large ~20inch squared framed paper diffuser that is held overhead by cord: works great.
    I also rigged up small steel plates in front of BOTH diffusers, to deflect possible stray pellets, and likely some .22s and possibly .222s. Anything bigger than .222 may or may not be deflected enough to protect the sensors!
    Outdoors testing (centerfire mostly) CAN be done without diffusers, but due to tree leaves, varying clouds, I’ve found it far better to use that same large diffuser and that same light, even in broad daylight. Sun angle shifting, leaves & clouds blowing induce errors, with some hideous and some marginal enough to confuse you. (Factory Techs say too MUCH light causes high readings, and I can confirm that!)
    Moderate calibers (say .30-30 and lower, with moderate charges) are tested with the Chrony 9′ from the muzzle. Bigger charges require ~12′-14′, to avoid gas effects, which are slightly increased too by higher humidity.
    IF IN DOUBT, shoot at an expendable target, at SAME site, angle, etc, to be sure you’ve got the rifle (& scope?) sighted in correctly. Then I test the actual Chrony set-up with an air rifle, to verify system performance: I don’t like to troubleshoot the Chrony with my centerfire $hot$! –Barrika

  • Slinging Lead Says:

    I would like to ask other chrony users what method they use to protect the front from errant shots. I purchased the model with the remote display for this very reason, but I don’t want to be shooting apart the front sensor either.

    I was thinking about buying a metal junction box, like you would install a wall switch in, and putting it in front of or around the front of the chrony. I thought I might find some better ideas here.

    • kevin Says:

      Slinging Lead,

      I wouldn’t suggest using anything to protect your chrony that could result in a ricochet back at you.

      Several pugs of duct seal, still in their wrappers, mounted on a cheap tripod work well for chrony work with an airgun.

      kevin

      • Slinging Lead Says:

        Kevin

        Thanks for the tip. My reflexes are not what they used to be.

        And I happen to have one loaf of ductseal leftover, still in the wrapper.

    • Alan in MI Says:

      SL,

      Real easy, at least for pellets – not sure what I would do for bullets. I use a 2×4 cut and glued together to fit over the chrony using a 3 pieces – 2 long ones that go outside the unit along the sides, and then one across the front connected to these two pieces on the side. I then cut two strips of 1×3 that fit inside the open rectangle to rest on top of the chrony to hold it on place, and to protect the rear screen too. It just rests on top of it and all is well. You could add more wood to the front one if you want more protection, but I find just like with insurance, if you are well covered, you are not likely to need it – never shot is once wince I started using that (I had hit the rear screen once before I made this).

      Alan in MI

      • Fred PRoNJ Says:

        SL,

        I used experience. After shooting my first Chrony right in the LCD (I don’t mess around with those pesky skyscreens), I now position the Chrony about a foot to 18″ away from my air rifle and my pellet stop (two heavy foam pillows in a cardboard box with a plywood backing on the outside for cheap insurance) another two feet from the Chrony. As BB says, sight the rifle by eye and approximation while holding it at chest or even hip level. I understand that Chrony has a replacement policy if one needs to fix a casualty of testing. Downrange readings? Not for me – I’m not that good. I almost always hit what I’m not aiming at.

        Fred PRoNJ

  • Joe in MD Says:

    I have tested my Combro with an external chrony and found it to be within a few fps when using my Steyr LG100 with a anti-flip tube.

    On the other hand, my 2240 would not work with CO2 (I have since converted the 2240 to PCP and the Combro works fine).

  • David Enoch Says:

    BB,
    My father in law has some rules for fixing things. I find that they are very helpful.
    Rule #1: There’s nothing wrong. Don’t fix it because it ain’t broke.

    Rule #2: It’s the simplest thing it could be among possibilities.

    Rule #3: It’s the cheapest thing as a matter of cost.

    Rule #4: What did you do last in “repairing” the machine? (You might add to this, what did someone ELSE do last on your machine.)

    Rule #5: For baffling situations, try everything backwards.

    Rule #6: Find a well-functioning machine (car, washing machine, etc., and observe it.

    David Enoch

  • Andrew Says:

    I hate to ask a newbie question but can you just slap a peep sight on any gun? As long as it fits on the rail I can’t see any problem. My only worry is maybe the front sight post is not high enough.
    I want to put one on my daisy powerline 901 because the rear sight on it now is very loose, rusty, and imprecise.

    • Matt61 Says:

      Andrew, my answer to your question based on my experience and others that I’ve read about is that yes you can slap on a peep sight, but getting it to fit properly is the problem. Some will not adjust to your point of aim, and some will not lock on properly. It can be quite a hassle to getting everything to fit if the peep sight was not designed for your rifle.

      Matt61

      • Andrew Says:

        Ok thanks! I think the problem is more likely to be that the rear sight is too high rather than it being too low so don’t think I’ll need a riser. The rail and area around it on a 901 is pretty bare so I don’t think I’ll have too much trouble mounting one. The one daisy makes and the Air Venturi both look very promising.

        • Victor Says:

          Andrew,
          Yeah, sorry about that. Missed that one little detail about the front sight being lower.
          Then it seems that your choice will have to be the rear aperture sight that sits the lowest. I’m sure that the PA technical guys can help you with that detail. Good luck!
          Victor

    • Victor Says:

      Andrew,
      That’s a good question, and I believe that what Matt61 said is true for the most part. However, I wonder if you can buy a “riser” that will allow you to raise the rear peep sight. You might want to do some searches because I think there are dovetail risers that will solve the front sight height problem.
      Victor

      • pete zimmerman Says:

        The German company MEC makes a nice line of risers. Center Shot Sports in Virginia sells them by mail. They ain’t cheap. And Eric Uptagraff of the Army Marksmanship Unit makes some.

        • Victor Says:

          Pete,
          Yeah, I’ve seen them in lots of pictures, but haven’t really been in the market for one. It’s still good to know that you have that option. Not all front sights sit low, so there may be a need to use a riser if you install a rear aperture sight. Thanks!
          Victor

  • Victor Says:

    B.B.,
    There’s a new Webley Alecto Ultra Air Pistol. It has a longer barrel, giving it a higher velocity. I’m sure this is new to you too, but do you think this longer barrel might improve on the accuracy of the pistol?
    Victor

    • Frank B Says:

      Victor,having “read” BB for several years now…..I actually know the gist of the answer he would give.
      A 2″ barrel and a 222″ barrel offer the same potential accuracy,it is not generally a function of length.
      The only thing about a longer barrel that can improve the situation is the added sight radius offers greater potential to aim precisely.This is assuming that all other things are optimum….

      • Victor Says:

        Frank B,
        I hear you, but I wonder if this changes which pellets would shoot best in this gun. The longer barrel increases the velocity, and I can’t help but wonder if this changes pellet preference.
        With this particular gun, since it comes in two barrel lengths, I see a great oppertunity to do an apples and apples test. For instance, where it might have shot best with a lighter pellet, maybe it will now shoot best with a heavier, but similar, pellet. Just a thought.
        Victor

        • Frank B Says:

          That is a pretty good idea Victor.I seem to remember in the reiew that the accuracy decreased with 2 and 3 pumps compaired with one pump.The only hitch being that we see reports every day of different examples of the same model airgun showing preference for a different pellet,or even credible folks reporting terrible accuracy from a model others get great results with.That being said,I’m afraid any result might be “colored” by that possibility,which tends to explode into more questions than answers.Perhaps if the barrels were put through identical regimens to prepare them for testing the field could be made somewhat level.Things like polishing each crown and lapping each barrel with JB bore compound….as well as matching transfer ports.BB really owns an ideal testbed,his Whiscombe has an array of sized transfer port inserts,allowing very precise control of pellet elocity range. Mine is not so equipped….I have the JW80 he mentioned in the blog today….and I currently have the .25 barrel mounted.Even that as a testbed is not without a “spoiler”! Both of ours have a Harmonic Optimized Tuning (H.O.T.S) system on the barrel.It needs to be tweeked to match both pellet and velocity in order to make the smallest groups.Ain’t airguns great?? Never run out of things to ponder!

          • Slinging Lead Says:

            Frank B

            There is one exception to what you said about short barrels being as accurate as long barrels. As Vince once observed, ‘ if the barrel reaches all the way to the target, it will be more accurate.’ It is hard to argue with that kind of logic.

  • Matt61 Says:

    Well, this blog brings back memories. When I was attending a high school JROTC camp at Schofield Barracks, Hawaii, I got to fire the M203 grenade launcher. I knew not to use the rifle’s sights but I somehow ended up aiming with the notch of a screw at the bottom of the grenade sight assembly rather than the sight itself, so the round as my spotter said, was “way off.” Too bad. That was my one chance to use an M203. On the other hand, I’m sure that I hit everything downrange with my 30 rounds from the 20mm Vulcan anti-aircraft gun.

    As for trepidation, I can relate to that too. I’ve had some trouble seating a primer as I tried out my Autoprime system. Finally, I got the thing seated, and in my joy, completely loss track of the shellholder. Then, I spent a great deal of time rummaging around looking for it until I realized that I had left it in the Autoprime!? Anyway, I’m running out of things to do before actually assembling a complete cartridge. Everything is pretty much in place. Heart rate normal. Respiration regular. I feel sort of like this British paratrooper instructor in an Alan Ladd movie where he was serving in the British paratroops prior to the entrance of the U.S. into WWII. The British method for launching out of airplanes was to sit on the edge of a hole in the bottom of the fuselage and drop through it. The instructor, trying to encourage the trainees who would follow, gets into position and says, “I don’t know why I don’t do this just for fun. It’s as easy as falling off a log.” Then, he pushes himself into space, and through the hole you can see him do a “roman candle” where his chute flutters above him and never fully opens….

    Wulfraed, I’m just passing on what I heard about the CFX. Someone wrote that a CFX was a sub 50 yard gun where the RWS 350 is a 100 yard gun. So, the velocity may not be the same across guns in a given caliber. And maybe there are some other things at work. There is the claim that the Lee Enfield gets more accurate at distance than other 30 caliber rifles based on some convoluted argument about the action design which I didn’t follow. Anyway, if the short range does not explain the rapid demise of the CFX what would be the cause?

    PeteZ, for the polar bears in Scandinavia, I suspect the caliber of choice would be the 7.62X54R. Actually, I don’t even know of European calibers that go higher except for the 8mm which is similar and some exotic British calibers for hunting elephants.

    Matt61

    • duskwight Says:

      Matt,

      7,62x54R is I’m afraid entry level round for hunting polar bear. I would feel myself more comfortable with Russian 9,3×64 or 9,3×62 Mauser gun. Or, better, with a smoothbore side-by-side with 12-gauge slugs – that a sure stopper.

      CFX with its typical 18-21J is quite a 50-m gun. However at this distance its rougher default trigger comes into play, so “smoothed” versions shoot better. It’s even a 100m gun, as I spent some time breaking wine bottles @ 100 m from prone (please take all the shards back to where they belong if you shoot in the forest). Being a much “kickier” rifle D-350 seems to me less useful for 100m shooting as its accuracy is hampered by its power. So it’s a sort of checks and balances system.

      duskwight

    • Victor Says:

      Matt61,
      Regarding the CFX. All I can say is that it’s the most accurate rifle that I own, outside of my FWB 700 ALU. At 10 meters, I can dam near shoot single pellet whole size groups. Mine is very smooth, and has the GRT-III trigger (as all my Crosman and Gamo’s do). It does not seem to be particularly hold sensitive, which makes it easier to shoot well than my other springer’s. However, it does appear to shoot slower than my others too (yeah, I know – I need a chrony). There’s more of an apparent delay between the shot being fired, and the pellet hitting the target at 20 yards.
      Victor

      • Loren Says:

        Victor
        I have an accurate Gamo, it is the Gamo shadow NRA model. I was very unhappy with the trigger so I installed the GRT 3 and had a great time with it untill the spring broke. Then I had Pyramyd install the gas nitro spring. Now all I can say is WOW! Allso I should mention I filled the hollow sections of the synthetic stock with a mixture of expanding foam and lead shot.
        Now about Gamo’s replacement for the CFX I think the CFR looks good ,the adjustable stock comb should work for someone trying to get into field target, especially with the Pyramyd installed gas spring. Charlie da tuna has the trigger for late model Gamo rifles it is the GRT 4G TRIGGER.

        Loren

    • Wulfraed Says:

      Wulfraed, I’m just passing on what I heard about the CFX. Someone wrote that a CFX was a sub 50 yard gun where the RWS 350 is a 100 yard gun. So, the velocity may not be the same across guns in a given caliber. And maybe there are some other things at work. There is the claim that the Lee Enfield gets more accurate at distance than other 30 caliber rifles based on some convoluted argument about the action design which I didn’t follow. Anyway, if the short range does not explain the rapid demise of the CFX what would be the cause?

      Based on the PA print catalog, the CFX was a .177 claiming 1000fps lead, 1200fps with PBA. The RWS 350 doesn’t state dual velocities, but is claiming 1250fps in .177 — presuming that is for PBA equivalents the RWS is a slightly faster gun (though 50fps is probably within manufacturing tolerances between the models). If that is for lead, it would be a significantly faster model (though unlikely — the .22 version is listed as 1000fps, but PA tests got 850 with lead).

      Catalog also states the CFX is plastic stock; the 350 is available with wood or plastic — wood may behave a lot differently under recoil (different flexure, etc.)

      I wouldn’t accept any claim of 100yard from any spring airgun… Unless they are lobbing the pellets quite high and foregoing hitting anything in mid-ranges.

      I’d have to ask the same criteria for the Lee Enfield report… Are we talking same weight/style bullet loaded for the same velocity (using same powder?), from the same length barrel? May not be as easy a test to control for — as a large case may not burn properly using the same volume of powder; or conversely, one may be compressing the charge in a small case.

      If the bullet style and/or weight differ, they’d have different ballistic properties. If the velocity differs, the faster one has less flight time in which to be perturbed. If the rifling rate differs, the bullets would have different degrees of stabilization.

    • Victor Says:

      Matt61,
      One last comment about that barrel twist problem. I think you’re math professor friend loved the problem because it will make a good mid-term question. I hope it doesn’t make too many students hate guns. lol
      Victor

  • Wulfraed Says:

    If you’re shooting into a pellet trap that’s three feet away and you sight through the scope, you’re going to shoot your chronograph because the bore is three inches below the scope. Don’t think you’re smarter than that, because everyone who uses chronographs shoots them sooner or later. By sighting through the scope, you’re almost guaranteed to put a pellet through the guts of the electronics package.

    And if it’s a scoped AirForce model, the scope is closer to 6 inches above…

    My Beta Master model now sports a lovely quarter inch concavity on the front sheet metal; right where the plastic control panel would be on the non-Master editions (Shooting Chrony Master versions put the control panel into a palm-size box with some 15+ feet of telephone RJ-11 cable).

    The instructions for the units do recommend putting bright red tape or paint on the screen support rods to give a minimum aiming height for open/scope — but the Condor (and many modern military rifle designs) are so tall one almost needs to aim over the top of the screens).

    The best light for skyscreens is an even light. A totally overcast day is perfect, as is a day with clear blue sky (as long as the sun does not shine directly on the skyscreens). But a day with puffy white clouds that move around is bad, and you’ll have to use the diffuser filters above the skyscreens.

    I’ve got the newer Shooting Chrony red LED lights for mine, for indoor use. But even with that, I found I had to close the apartment door as the afternoon sun was throwing enough shadows to result in false triggering.

    I personally have found that by reflecting a 500-watt incandescent light off a white ceiling, I get the optimum in indoor chronograph lighting.

    Yeah, but photographers don’t call them “hot lights” for nothing… (I’ve go a pair of, Smith-Victor I think, quartz-halogen 600W photolamps. I’ve never had both up at once in my apartment [I'm sure they'd finally overload the wall outlets, considering there are only three circuit breakers between bathroom/kitchen {grounded outlets}, outer walls {living&bedroom -- four outlets}, and inner walls {four more outlets -- and my computer/monitor/printers, surround sound, TV, BluRay, and a 150W torchiere are ALL being fed from one outlet via power strips!}]

    • Loren Says:

      Wulfraed
      If the centers of your scope and barrel on your Air Force rifles are 6 in. apart you need a different mount. Mine are 3.125.

      Loren

      • Wulfraed Says:

        Six inches is probably an exaggeration, but it is still noticeably greater than anything else I own except the HK-91.

        I probably could go to a lower-profile set of rings — I was worried about clearance for the objective bell on the 4-16×56 (there’s an inch of height right there), but it turns out the position the scope is far enough forward that the rear of the objective bell follows the slope of the Condor “handle”

        In contrast, the rubber flip-up cover (on sunshade) of the scope on my RWS m54 actual requires me to depress the rear open sight all the way down (and that’s with the rings on top of the Leapers/UTG “droop” mount base).

  • Lloyd Says:

    BB,
    I was waiting for this blog. I am wondering if there is a way to artificially light a shooting chrony indoors to broaden the sweet spot where it will see the pellets. It’s mainly an issue of my using a loosey-goosey rest bag for a rifle. I have a 12 x18 ” piece of translucent white plastic as a big sky screen and a 60 watt bulb above the plastic over each eye. Are there any tricks of using more light or less light or a higher shot or a lower shot? BB, that 500 watt incandescent off the ceiling may be the answer??

    Also, I’ve got an overhead heater in my garage that is over where the chrony usually is. The fan motor starting up (or stopping, I forget) will trigger the chrony sometimes. No EMI/RFI testing, I guess, LOL.

    Sometimes I’ll use a laser sight (made out of an Office Depot laser pointer) to align the chrony. I just hold a piece of white paper above each chrony eye to get the right elevation and azimuth.

    If anybody has tricks to broadening that sweet spot, I’d love to know. I hate getting those ERR1 and ERR2 screens.
    Thanks,
    Lloyd

    • Wulfraed Says:

      Well… you don’t want to increase the front-back “sensitivity” as that could change the calibration length for the timer circuit. A naked bulb located above and centered would be among the worst offenders, as the projectile shadow will be strongest when it is between the sensor and light; ie, after the front sensor and before the rear sensor, leading to a shorter measured time and hence over-reporting velocity.

      As for the width of the sensors, that’s typically a wedge shape based upon the lens over the photocell. So… the width would be maximum just under the diffusers — but the shadow seen by the sensors will be smaller due to distance, and may not be seen as a shadow against the diffuser background. Shooting lower puts you into the 1-2 inch slit of the sensor, but at that height even a pellet is a significant fraction of the sky screen.

      Are you sure the heater fan /motor/ is triggering the readings, and not a flicker of light reflecting off the fan blades before they get up to speed?

      • Lloyd Says:

        Wulfraed,
        Thanks for you thoughts. Very Interesting about the fan blades. They are bright aluminum and at one time I hung a Halogen flood at a similar height to increase the light level. Too hot to run the heater to tell right now, but a possibility. The chrony had a remote display and I was thinking the low signal levels in the unshielded flat cable between the eyes and the electronics module might have been picking up some stray signals. But maybe not!

        You gave me a hint about the eyes seeing a shadow of the pellet against the skyscreen. The translucent plastic I am using is uniform in appearance, but it is the corrugated flat bottom V-groove type of polycarbonate roofing (sheds and sun porches) with the corrugations running parallel to the pellet travel. Maybe the corrugations are appearing as an uneven background….. clouds in the sky and the outer regions are just not sensitive enough. I guess a perfectly uniform translucent background would be best. Can it be possible to have too much light, which I don’t think is my problem? So i need two nice bands of brightness, one directly over each eye?
        Thanks,
        Lloyd

        • Wulfraed Says:

          I can’t find if you mentioned the model chronograph, but didn’t it come with some sort of diffuser screens? (or was it some high end model where everything was a pick&choose $$$ option <G> )

          I’ll admit the indoor LED screens ( http://www.shootingchrony.com/products_newproducts.htm ) I bought weren’t all that cheap at $120, but they look a lot better than the ugly precursor incandescent design ( http://www.shootingchrony.com/images/lightf1.jpg ). Not that the LED system does not shine through the diffusers; the red beam itself is used for shadow detection.

          • Lloyd Says:

            It is just the regular red alpha master, and it did come with the skyscreens, which I just dug out.
            On my previous chrony (which allowed me to do the upgrade for shot-up chronys, ah-hem) my big bore stuff was always knocking the screens apart, so I just made something sturdier out of frustration. I wonder if I could reinforce the segmented screens with some clear packing tape on top? I will try again with the screens that came with the chrony. My shop has florescent lights, so I will need supplemental lighting, but it has to be sturdy.

            Your comment about “the red beam itself is used for shadow detection.” I don’t understand ???
            Thanks,
            lloyd

            • Wulfraed Says:

              Confusion as I typoed… “Not that” should have been “Note that”.

              If you look at the screens with the LED lights, you’ll see that the LEDs are housed in boxes below the screens. They directly illuminate the sensor with a red beam, rather than the sensor seeing a smooth white surface of the regular screen. The older cheaper incandescent illumination put a long bulb on top of the screen, so the screen was still diffusing the hot spot from the filament.

              Not as easy to store, though, as the screens with the LED unit don’t come apart into three pieces of plastic.

            • Frank B Says:

              The skyscreen junctures are a good place for some alcohol and cyanoacrilate IMHO.I am outfitting mine with some power outage led (white) lights right abvoe my skyscreens to illuminate the plastic thoroughly.I think it might work.At least the angle of illumination will be unchanged.It would be really convenient,they have a retractable plug male and burns 8 hrs per charge.they are even designed to be left plugged in and so can’t overcharge like some cheap rechargable electronics!Sometimes I like Wallyworld.It’s a negative side effect of airgun addiction.Cheap reactive targets called merchandise.

              • Lloyd Says:

                Alright. Sounds like I should stick with the stock skyscreens, except do something to make more robust, and investigate some LED lights. Its a plan!
                Thanks guys,
                Lloyd

    • B.B. Pelletier Says:

      Lloyd,

      My white ceiling trick makes the sweet spot as big as it ever gets.

      B.B.

      • lloyd Says:

        So you bounce the light off the ceiling and still use the white plastic sky screens? I assume that for best results, the white plastic sky screens must always be used so that they provide a uniform background for the sensor to see the pellet contrast.
        Thanks,
        Lloyd

    • twotalon Says:

      Lloyd….

      I use the white cieling trick like B.B. does. Works good.

      My Beta requires more light than my Prochrono does, so I have to raise the 500W halogen work light closer to the cieling with it. I keep all the other lights off in the room, except for one over the pellet trap on the far side. I used a fold out sheet made of thin foam and covered with white paper from Wallymart and stapled it to the floor joists right above where I wanted the chrono. (basement setup)

      I have also used the incandescent lights for the Beta, but there was no difference other than making the chrono top heavy.

      twotalon

      • Barrika Says:

        Again guys, my fairly large 2′ x 2′ paper diffuser, held ~14″ over the Chrony works well indoors and outdoors, and is well-powered by a 60 to 100 watt incandescent bulb about 14″ or so above that. For outdoor use, I hang all from cords from above, and the small, heavy, ANGLED steel plates I installed infront of BOTH sensors keeps it from being top-heavy. Yes, I do have to stabilize this against wind-drift, and yes, it is a small chore to set this all up, so I maximize it’s use when I assemble this rig, about 3-4 times a year. All this is done to get GOOD readings, to avoid wasted shots (E1, E2, E8??), and to avoid nuking this my 2nd Chrony. As they say, shoot enough chrono tests, and its a question of WHEN you nuke the sensors, not IF. (espec. if the lighting is poor and you begin to drop closer to the sensors for any chrono response…)

  • BeeInCognito Says:

    Good Morning BB.Well I need your expertise to help convince my Buddy that the hammer in his gun is more than sufficient as he’s bent on installing an aftermarket hammer and I think it’s Crazy to beat the guts out of his gun.
    How much doe’s the Condors hammer weigh alone,,and then with the weight included in grams?
    The rifle’s is strong right out of the box once you find the right pellet,and I’m trying to convince him that it’s crazy to install an overweight hammer and knock the guts out of her within 6 months to a year.

    Thanks,

    BeeInCognito

    • B.B. Pelletier Says:

      Bee,

      I don’t remember what a stock Condor striker weighs. There is no weight, just the striker.

      Assume around 50 grams.

      I do know that a 75-gram striker will ruin the valve in time.

      B.B.

Leave a Reply


+ 7 = 13

Top-notch springer
Air Arms TX200 air rifle

When it comes to spring-piston air rifles, the Air Arms TX200 Mk III is a favorite of many airgunners, including airgun writer Tom Gaylord. His favorite caliber is .177. While the gun will initially impress you with its beauty and superior craftsmanship, you'll be even more impressed with the incredible accuracy! Tom claims this is "the most accurate spring gun below $3,000." Beech or walnut, left-hand or right-hand stock. Isn't it time you got yours?

All the fun, none of the hassles!
Uzi CO2 BB submachine gun

You've seen tons of movies with guys spraying bullets from their Uzi submachine guns and probably thought it would be a blast. Except for the cost of ammo! You can have all that fun with this Uzi BB submachine gun at just pennies a round. Throw shots downrange for hours on end with all the fun, none of the firearm hassles and a fraction of the cost.

Archives