How To Trust Your Chrono!

[Catfish]

Perfect timing for a new forum discussion regarding chronos and how to use them.

This weekend, we had two chronos of different manufacture to shoot our loads over to get ready for the upcoming Arkansas Sectional.

Weather was warmish in the morning, mid 70s, sunny with no clouds. Sun was in the east, and we set up the chronos so that we were shooting north/south.

The chronos would not come anywhere close to agreeing with each other, with a difference of several hundred fps.

We decided to shelve the chronos to start practicing because we were getting a bit frustrated by the varying readings.

Came back mid-day, with the sun more or less directly overhead, perhaps a little bit to the west of the chrono screens. Temps maybe in the upper 80s. Again, massive difference between the two chronos and in addition, both were showing signifigantly faster fps. For example, my loads that were chrono'ing in the 920 fps range in the morning, were well over 1000 fps in the afternoon.

Now we don't know what the hell to do for our loads this weekend!!

So, long story short - how do you know to "trust" in your chrono!!??

Edited May 2, 2006 by Catfish

[.40AET]

Eliminate the "sun" factor. You won't go to a major match and find the skyscreens open to the sun. They are likely using some sort of chrono box.

Who makes the two chrono's that you are comparing?

If you can find someone who has a CED, they sponsor most of the major matches. Trust that. I bought a CED from a shooting buddy and it's +/-.5 PF from the ones that I see at a major match. I feel real confident these days when I go to the chrono. I know that I'm going to be right at 168pf.............It's nice!

[AlamoShooter]

The screan spacing is very important. to + or - 1/8 of an Inch to get a good reading. Teh crono just picks up the shadow of the bullet passing over the first screen and calculates the time differecn when the shadow fo the bullet passes over the next screen. = the old speed distanc thing. most screens are set at 24" so check that first.

JF

[revchuck]

Derrick - My Prochrono works best on a clear day in the shade. The place I shoot at has a strategically placed tree that helps a lot.

[38superman]

Find a known load that you can use as a baseline measurement.

I generally keep some factory UMC 45 FMJ ammo for just that purpose.

The published velocity is 830 fps.

I have shot it enough in various conditions to know that it typically runs about 810 fps in my Edge.

Obviously that will vary a bit with the ambient temperature so do a little experimenting and keep good records.

You need to know what to expect from it under different conditions, i.e. bright sunshine, overcast, cold, hot, etc.

Buy enough to last a while (250) pack? so that the ammo comes from the same lot.

Before you chrono your loads, run five from your known loads and make sure the chrono is giving you the readings you expect.

If so, you can believe the readings from you handloads are relatively accurate.

Tls

Edited May 3, 2006 by tlshores

[benos]

Definitely - Eliminate the sun factor. With everything else the same, that's the single biggest thing you can do for consistent readings, day after day.

At Rio Salado, I learned to always chronograph with the skyscreens in shade, under the metal awnings (on the pistol bays). With the skycreen openings facing the shaded, white metal roof, and the skyscreens themselves in the shade, I never doubted my MKIV's readings.

If you don't have that option at your range, and it's a sunny day, do 2 things:

a. If your skyscreens have the white plastic that snap in place over the skyscreens - use them.

b. Somehow, rig up each skyscreen so that the opening is shaded. Maybe with a target on a stand, by each skyscreen, for example.

If it's a cloudy day, you shouldn't have much trouble getting consistent, accurate readings.

Of course other "variable removing techniques" should always be followed.

Always shoot with the muzzle 10 feet from the first skyscreen.

Always shoot at the same height over the skyscreens.

Always shoot at a 15 round string before you thing you know anything about what just happened.

Two or three 15 round strings should give you a fairly good idea of what's going on with that load, on that day, at that time.

If I was preparing to load ammo for a match I cared about, I'd typically shoot two to three 15 round strings before practicing, and two or three more 15 round strings after practicing before leaving the range. And then after doing that on at least three different days, I'd have a pretty good idea what to expect at the match.

be

[Flyin40]

I have been having trouble also. Bought my first chrono last yr and have been getting varied reading since. Never knew the sun affected it that much. Great info.

Flyin40

[D.Hayden]

I have a long cardboard box lid that fits right on top of the Pact skyscreen supports.. It's about the width of the skyscreens, by about 3'

If it's sunny, it blocks it perfectly, if it's overcast, leave it off.

[Catfish]

great stuff, thanks everyone!!

Hadn't thought about completely putting the gizmos in the shade - I had been under the impression that the sun needed to be involved to get a decent reading across the screens.

[Nebraskan]

One more thing when chronoing (is that a word?):

How much does temp of the gun have to do with velocities? As BE stated, shoot a string of 15. As the gun heats up, does it affect velocity much? How long do you wait between shots or strings? I assume (I will be chronoed for the first time at a match Sunday-four classifier match) that they shoot 3 first thing in the morning from a cold gun.

It also brought up another thought. If you clean a gun right before the big match and the first shots fired are a fresh gun, will it affect velocity? Should you shoot a few shots after cleaning for the fouling shots before going to the match? If this is an issue I can always step outside and blow a few into the creek even the night before the match if it is necessary.

I will be working up loads Saturday and running them on a MKIV. Probably will error on the stout side this first time (172-175) I am a little concerned, as my practice rounds 1.155, 180 lead, 4.3TG were running about 1000fps. Seemed fast for only 4.3g, but this if before I sent in the chrono.

[shred]

Overcast days are best for chronoing if you don't have a box. The 'sun-shields' act as miniature clouds. Oehler has (had) some good information on this in their instruction booklet-- from memory it says something like "although a sunny day looks brighter than a cloudy one, blue sky directly above the sensors is actually very dark and makes readings difficult."

Chronoing in the shade (as in AZ) works because enough light bounces off the ground and then off the cover to provide nice even lighting. Full shade won't work well without light coming from above.

[XRe]

You won't go to a major match and find the skyscreens open to the sun.

You won't??? I've only been to two major matches that used a chrono box, and those were both at Barry - a Nationals and a NA Champs... both chronos run by Greg Lent... Every other time they've been open arrangements...

I won't get into the lunacy of trying to weigh bullets outdoors with an unshielded scale, in the wind....

Edited May 3, 2006 by XRe

[JFD]

The big matches I've been to also had the chrono open to the sun.

Accurate readings can be gotten with cardboard over the screens so the sun is blocked completely??? I'm no chrono expert by any means, but this sounds almost too good (and easy) to be true. Placing a metric target over the screens to get accurate results would be a huge help.

I've got a Shooting Chrony with all the bells and whistles, but I'm not sure how much I trust it. At a big match last year I ended up with exactly 165.0 PF when my average should have been 170. I still haven't proven it was a chrono/technique problem, or because my .40 test loads were resized in a "U" die, but my match loads were sized normally in my SDB. I now run everything through a "U" die just in case (bumped the load up too), but that's a topic for another forum.

If cardboard is the answer, I'll happily drag out 3 chronos and different test ammo and see if I can figure out last year's problem and see if 2 of those chronos are worth keeping.

Knowing EXACTLY what lights to get in order to build a chrono "box" would also be helpful. McMaster Carr part numbers or something like that. I know exactly squat about lighting, and I'm sure I'm not alone.

[Sixgun]

I had exactly the same thing happen to me. 2 Chrono's (one CED and one Competition Electronics Digital) that were about 100fps apart (Well enough differance to put me in minor). Both chrono's were used on an indoor range with the appropriate indoor lighting setups. We noticed on the CED that it was 100 fps slower on my buddies loads from the previous week. My chrono was giving him readings he expected based on previous chrono work.

We ended up getting a third chrono (a Shooting Chrony) and putting my CE Digital and the Shooting Chrony (both with the indoor lighting setups) in "series". Aside from a couple of "error" readings, the chrony's were within 5 fps of each other on all the shots (in most cases only 1 or 2 fps off).

I now feel more confident in my loads. I also discovered that I have a "fast" barrel. I'm using 165 grain bullets and am getting down into the powder charge range of people using 180 grain bullets.

From my experience, would you trust the loads? I want to shoot at least one level 3 match this year and don't want to minor, but also don't want to shoot "pin loads".

Thanks,

Ray

edited for spelling

Edited May 8, 2006 by Sixgun

[.40AET]

You won't??? I've only been to two major matches that used a chrono box, and those were both at Barry - a Nationals and a NA Champs... both chronos run by Greg Lent... Every other time they've been open arrangements...

Thanks for taking the time to point out the my errors. I've only seen a chrono box like Greg uses at a major match. I guess that I need to go to more major matches.

[38superman]

My CED chrono has an option for infrared screens.

This is to assist taking readings in low light.

I wonder if infrared screens would improve consistency and accuracy in bright light.

Tls

Edited May 10, 2006 by tlshores

[Caspian_45]

My CED chrono has an option for infrared screens.

This is to assist taking readings in low light.

I wonder if infrared screens would improve consistency and accuracy in bright light.

Tls

No, they will not work right.

The reason Greg uses a chrono box is so he can use the infared sky screens. The infared sky screens are to be used in total (or almost total) darkness. The infared screens take the "time of day" sunlight variation out of the equation.

[Putty]

I have the PACT chrono and was getting weird readings. Turns out a trash bag near by (bright yellow) was muffing up the readings. Happened today again as well. Once I clear the area around the skyscreens I get good consistent readings.

[CEDUSA]

The spread between the existing brands of chronographs on the market today is aprx. 8.0%. This has a lot to do with the quality of the sensors used and the distance in which the sensors are spaced apart.

Variables that will effect resuls are as follows:

1. Temperature, altitude, & the effects these have on different powders

2. Temperature of the barrel and the ammunition itself. a cold barrel will produce different results from a very hot one. The same with the ammunition.

3. Lighting - MUST be balanced on both sensors. If the sun changes position, you must maintain a balanced condition on both sensors. Whether in bright sunlight (using the top screens) or on shady days (in which the top screen is optional), it is critical to maintain a balanced situation on both sensors.

4. Muzzle blast - If the muzzle blast reaches the first sensor before the projectile, your results will be bad or not at all. If the muzzle blast causes your screens to shake, the readings could be bad. Suggestion - start back and work forward with the handgun or rifle in use until you fnd your closet position.

5. The CED Infrared screens are designed for use when mother nature is not cooperating or for times and locations where insufficient light persists. If they are used under bright sunlight, the sunlight will over power them anyway. Let me reiterate that it is critically important on ALL chronographs to maintain a BALANCED light condition on both sensors.

6. Spacing. Make sure that your sensors are properly positioned and tightened. If they are off by even 1/16" it will cause incorrect readings.

7. Glints - If there is water, sand, snow, or bright concrete on the ground below your tripod / chronograph set-up, the sunlight will bounce (reflect) off the surface shining back up on the projectile preventing the sensors from detecting a light drop (shadow) and thus result in a poor or no reading situation.

8. Indoor - Fluorescent lighting is the kiss of death to any chronograph system. Their light does not allow the sensors to "see" the bullet. Cover the top of the screens if this type of lighting is near your set-up. Also make sure that no additional light is penetrating on one or the other sensor creating an in-balance of light on the two of them. Some ranges are designed with small bays or short distances which cause excessive sound waves and muzzle blasts. These have been known to cause problems with chronograph system results. Last, when using the CED Infrared on an indoor range with AC, make sure the AC itself is a full 110V. If the range is located a great distance from the power transformer, it is possible the output is less than 110V and this may prevent proper performance. In such cases, it is better to use the NiMH Battery Pack instead.

9. Other variables - Depending on the quality of the chronograph & sensors, other variables such as mobile phone transmissions and high tension poles or electrified fencing can all have effects on chronograph performance. Even high static from summer thunder storms in the area of use can result in problems.

I sincerely hope that the above information is of use to many of you and to answering most of your questions.

[mleeber]

I have a CED with Infrared and an Ohler. I monkeyed with the CED for about 6 weeks, sent it back for testing, tried switching parts, and never felt like I was getting valid readings (my 127PF 9mm loads were chronoing in the 400s on the CED with or without IR). I bought an Ohler 35 and it works great.

As a side note, I shot area 6 a month ago. The Chrono stage was 2 CEDs set up one in front of the other in a box with standard screens and white plastic over the open box top. My 40 major loads chrono'ed at about 170PF (my Ohler said 167ish when I tested them). At the GA state match the chrono stage was a single CED and the IR screens (running off of a generator), the same loads, loaded on the same day as the Area 6 ammo barely made major with readings of (1st string) 937, 903, 904 and (2nd string) 940, 901, 902.

I think that each major match should have two chronos back to back and a chrono operator that knows how to set it up and operate it.

[AustinMike]

My Shooting Chrony will start acting up sometimes in the sun. I'll lay the white side of a windshield shade that I keep in my truck over it on top of the sun screens and that usually fixes it. A no-shoot target works too.

[PistolPete]

I had some issues today while trying to chrono a new load I'm working on for .38 super. My previous load was running around 1375 fps consistantly on a cloudy day. I tried the same load today and my results were inconsistant. Today it was very sunny and about 80 degrees. I didn't have any coverage from the sun so I'm guessing that was the cause of my problems. My first string of ammo came in at an average of 1442 FPS. That's quite a big jump without any changes. My next string came in at 1351 FPS. That's almost 100 FPS average from the previous string shot 2 minutes prior. The ammo was produced at the EXACT same time and nothing changed. I'm guessing the sun was the problem. I'll try covering the skyscreens tomorrow and see how things come out.

Pete

[RacerX1166]

How hot was your gun. I've had 30+ fps differences just by chrono'ing at the end of a practice session (gun warmed) versus chrono'ing through a cold gun. Seems to make a bigger difference in my Pro Sx versus my Limited guns. This caused a lot of angst considering I shoot Summer Blast tomorrow!

Other than that, I've been lucky enough to be pretty consistent regardless of time of day I chrono.

I had some issues today while trying to chrono a new load I'm working on for .38 super. My previous load was running around 1375 fps consistantly on a cloudy day. I tried the same load today and my results were inconsistant. Today it was very sunny and about 80 degrees. I didn't have any coverage from the sun so I'm guessing that was the cause of my problems. My first string of ammo came in at an average of 1442 FPS. That's quite a big jump without any changes. My next string came in at 1351 FPS. That's almost 100 FPS average from the previous string shot 2 minutes prior. The ammo was produced at the EXACT same time and nothing changed. I'm guessing the sun was the problem. I'll try covering the skyscreens tomorrow and see how things come out.

Pete

Edited July 7, 2006 by RacerX1166

[9146gt]

Anyone have pic's of a chrono Box.

Thanks

Tom

[PistolPete]

How hot was your gun. I've had 30+ fps differences just by chrono'ing at the end of a practice session (gun warmed) versus chrono'ing through a cold gun. Seems to make a bigger difference in my Pro Sx versus my Limited guns. This caused a lot of angst considering I shoot Summer Blast tomorrow!

Other than that, I've been lucky enough to be pretty consistent regardless of time of day I chrono.

I always chrono before my practice sessions so the gun wouldn't be extremely hot. I tried to chrono today but my batteries were dead. OOPS!!! In your Pro SX are you using N105 or IMR 4756?

I was working a load up with the IMR but don't like it all that much. The dot seems to track 5 times more than with the N105. I bought 8lbs. of it so I'll use what I can but think I'm going to switch back to the N105.

Pete