Home Forums Hunting & Shooting Ask The Gunwriters Chronographs

Having proper light is essential to chronograph function. The challenge is to design the skyscreens to use available light to your advantage.

We won't get into the design and operation of skyscreens. We are talking about trying to measure the effectiveness of the skyscreen/chronograph system. To measure the effectiveness of the skyscreens, we consider that the second velocity reading on the same shot is essential. It is just about in the same league as trying to measure rifle accuracy by firing one-shot groups on various targets at various ranges. When you fire a two-shot group on a single target you at least get an indication of where the third shot will fall. If the first two shots are close together, you then expect the third shot to hit nearby. If the first two shots are widely separated, you have no idea where the third shot will hit. If you can make two chronographs read very similar velocities on a single shot, you can reasonably assume that both chronographs are accurate. (We'll assume that you've eliminated all the gross error sources such as screen spacing, alignment, oscillator frequency, timer resolution, totally inappropriate light, et cetera.)

KenO

Curious what you are running. I bought a prochrono digital to replace the shooting chrony f1 and putting them in front of thr other, 3 diff rifles 2500-3000 fps, the prochrono reads consitantly 50fps slower.

One of the reasons I like my Oehler is because I am always shooting over two chronographs.

Is the ultimate solution to go back to contact screens?

XL5---

The only chronograph I've taken apart is the Shooting Chrony. It had cylindrical lenses in the light path. From the picture of the CED, it appears that their design does not use them. Am I seeing correctly? Does the photo sensor have its own built-in lens?

It is a Prochrono that reads slower (~40 FPS for 2600-2700).

The most absolute and easiest and not to mention least expensive method is to just NOT use chronographs and trust the data in the loading manual. I'm sure chronographs can be of much value but I have handloaded for well over 50 years and hunted with those loads here and in Africa on many species up to and including Elephant. In all those years and rounds I have never had a handload fail to fire and I have never lost a game animal due to anything other than poor shot placement. I'm unsure as to how a chronograph would have made my pleasure any greater,my rifle more accurate or hunting success any better. As I stated I'm sure for those really concerned with data they are invaluable.

In my case i was working up loads for a wildcat based on measured case capacity. A chrono was pretty helpful even if it was +/- 50 fps.

Or perhaps everyone may decide to buy one so that they can talk about any differences between their handloads and the ones published in books.

Owning a chronograph isn't about accuracy or success. It satisfies one's curiosity. You obviously do not wonder about that, but others do.

Equipment is there to be used or ignored as desired, so I understand your post.

For example, I ignore Remington bolts. I have not had a failure to fire or lost game because I ignored the Model 700.

I chrono'ed my 338 Laupa on a bright sunny day with only the diffusers in use, with no additional shade and got 2820 FPS average velocity. My drop were low at 972 yards. I recohrono'ed on an over cast day and I got 2791 FPS avereag velocity and my drop were correct with exbal ballistic software and not low. The difference of only 29 FPS is only important in predicting trajectory at long distance and not so much at 5 to 6 hundred yards IME


I was useing an Oehler 35 in both instances

There are some fairly simple things you can do to limit the damage from unusual lighting conditions, without resorting to buying IR sky screens. When the sun is low on the horizon, most camera tripods have an articulating head, which will let you tilt the chrono so the sun strikes it from close to the same angle as it would if it were directly overhead.

I cut out a small section from an old translucent shower curtain I was throwing out, which I keep in my chrono box along with a couple of black steel binder clips. If my gun-target line won't let me tilt the chrono the right way, sometimes I can clip that piece of shower curtain on the supports for my sky screen so it shades the sensors.

The critical element in loading for long range accuracy is standard deviation of muzzle velocity. If you roll your own, the easiest way to monitor SD -- and the best way to QC your loads -- is to chronograph them. So owning a chrono is about accuracy. And success, provided you define 'success' as small groups at long range. I shoot over a chrono almost every time I shoot at paper, not out of curiosity, but to QC my work by monitoring my loads' SDs.

But my use for it evolved to that. My original purpose for buying one was so I could use the Optimum Barrel Time method of load development, which requires the knowing of MV.

I also shoot coated bullets, not Moly but tungsten (WS2) and boron (hBN), which do the same thing as Moly, only better. But the slickness of coated bullets generates lower chamber pressures, which leaves you to your own devices for fixing a max charge weight because the manufacturer's load data for naked bullets doesn't strictly apply. So I use MV in addition to my pressure reads after the shot is fired for establishing a max safe coated bullet charge weight.

With a chrono I can trust, and with predictably low SDs, I can do my own BC testing, in case I'm using bullets from a manufacturer who based their "predicted" BC on computer modeling instead of range test data. And with two trusted chronos, I don't even need the low SDs.

So, no, it's not just about curiosity. If you bought one just for bragging rights, that's hardly the chrono's fault.


The M2 has two external lenses. The first is visible in the 'floor' immediately above the two bosses with the screw holes. The other should have been in the slot visible in the floor immediately below those bosses. Except when I separated the halves, the smaller, lower lens stayed lodged in the opposite shell. I was taking it apart to dry it out after it got drowned in a thunderstorm, and taking pictures was an afterthought. And I had reassembled it before I'd noticed the goof and haven't yet found the motivation to take it apart again just so I can shoot more photos.



It completely recovered from the flooding, BTW.

Exactly.......

That's your personal experience which I do not believe is shared by the majority of users. Most chrono owners do not shoot long range or attempt to develop and fine tune their loads for long range hunting or competition.

You haven't changed my view of chronos. I'm convinced that it's not about accuracy or success. I see their use as a way to satisfy personal curiosity. Most buy Chrony or Pact models which would not be at the top of anyone's list if absolute precision was required. I'd be inclined to buy one of Dr. Oehler's products if I wanted performance.

As far as that goes, if the shots are out by 30 or 40 fps, I doubt that it matters too much to the great unwashed. They're happy to see something on the display about their loads.

Bear in mind that I am the board's resident stats geek...

A lot of people just aren't curious about the technical side of the hobby. I have absolutely no quarrel with them. There is a lot to be said for keeping it simple, jamming half a box of Super X in your jacket along with some power bars, and a half-frozen milk jug of water, and slipping out of the house early enough to be in place before daylight.

To some of us, this hobby is a grand engineering experiment.

To us, a chronograph is an extremely useful instrument, probably the most accurate and repeatable instrument we can access.

If your loads are exceeding "book" velocity, they are almost surely exceeding "book" pressure. That's a good safety application.

If you are developing longer range loads, it's good to know your MV so you can set your elevation at 100 yards so that it will be close farther on out. That's a time saver.

If you're doing benchrest level shooting, a chronograph is a big help in developing process consistency. That's a competitive advantage.

If all I shot was a 30-06, 270, or other common chambering, and if my only need was to be ready to hunt, I don't think I'd need one. But for the things I like to do, it's a useful tool.

The tone and conceiceness of the last two posts do not stop me from having to wonder what we will quarrel over next?

Ammo wallets - do you use one or don't you.

Which, when, how. And why the others have lost their marbles.

I am one of the two posts and answered XL15. In short, I do not agree with him, but I hardly see what I posted as anything insulting or negative.

Would you have preferred that I called his views idiotic? That's how people start silly arguments.

...the great unwashed..., hardly a "neutral" adjective, but, since I see Denton's point(s) and concur, I shall leave it at that.

Spot on, it is the "unwashed" that doesn't get this

THANKS JWP for going to the trouble of limiting XLs quote......

so I didn't have to......

I do agree in GENERAl. However I've observed 'exceptions to the rule' a little more often than I expected.

I look for low SD and ES BUT I've also had 'better than average' groups from loads with higher SD-ES. Curious to me, but have been unable to explain to my own satisfaction how that happens.

I would be surprised it you or others have not experienced the same.

OTOH I have no place to hunt extreme ranges. 400yds is about maximum area for seeing and shooting. Therefore I've been satisfied with loads from 1/2-1" groups (outside-outside) not center-center. I'm sure y'all understand that diff.

On another subject, I rarely find myself on the same page as Mr Redgwell.

I dunno - I wash regularly and I get it.