Chronographs?

[Lumber_Jack]

So what's to know before buying one? I looked at the Shooting & Master Chrony's online but can't rally tell much about them. Anything I should look for? Gonna be a month or so before I pick one up so no big rush.

I want a quality piece, but mobility is a big plus. I know most are made to be portable, but wasn't sure of some are easier to set up than others.

[mikegideon]

This and a decent tripod. Real light, big shooting area, and works real well. Note 96 reviews, 4.6 stars. You may want the remote too.

http://www.midwayusa.com/product/852429/competition-electronics-prochrono-digital-chronograph

[leroy]

I've got a fold up Chrony (...the cheap one...). It works just fine. Like Mike said; ya need a tripod to hold it up with. They are handy and settle all the baloney about what what the velocities are.

leroy

[Trekbike]

I had to smile when I read this part in the description...Be careful to prepare adequately for windy conditions. What that really means is, watch out when it's windy otherwise you'll shoot the screens. I've been wondering, will most units work inside and outside or do you need different models?

[mikegideon]

Yep. Sometimes you need to clock your bullets. Mine sure has come in handy

[jcoosi]

This is what I have and like it.

http://www.magnetospeed.com/

[Lumber_Jack]

I had to smile when I read this part in the description...Be careful to prepare adequately for windy conditions. What that really means is, watch out when it's windy otherwise you'll shoot the screens. I've been wondering, will most units work inside and outside or do you need different models?

I was reading on the Shooting Chrony site that theirs needs a special lighting adapter that hooks to both sensors to work correctly indoors. about $50 accessory

http://www.shootingchrony.com/products_ACCESSORIES.htm

Edited November 1, 2012 by Lumber_Jack

[Lumber_Jack]

This and a decent tripod. Real light, big shooting area, and works real well. Note 96 reviews, 4.6 stars. You may want the remote too.

http://www.midwayusa...tal-chronograph

That looks good. The remote is almost as much as the Chrono, but looks like its a nice addition. Do you use the remote?

[mikegideon]

That looks good. The remote is almost as much as the Chrono, but looks like its a nice addition. Do you use the remote?

No. It's easy to read the display from a distance. I just write the numbers down.

[Lumber_Jack]

No. It's easy to read the display from a distance. I just write the numbers down.

ahh good to know. The Digital version seems to calculate Standard Deviation, where the Pal version doesnt, about $20 difference in price. does it just have a button to scroll through various readings, high, low, avarage, SD, etc?

also just a general question, how far from the muzzle should the Chrono be?

[mikegideon]

ahh good to know. The Digital version seems to calculate Standard Deviation, where the Pal version doesnt, about $20 difference in price. does it just have a button to scroll through various readings, high, low, avarage, SD, etc?

also just a general question, how far from the muzzle should the Chrono be?

Depends on the gun. Start at 10 ft. Gotta move it back if there's lots of blast, like with a .458 SOCOM.

[Dolomite_supafly]

I have a Chrony Alpha Master. I really like it because you have the brains and screen at the end of a telephone cord. It makes it easier to see and if you shoot it the cost is supposedly cheaper to repair.

I used to set mine up with the sky screens and every thing. Now I just shoot across it without any screen in place or anything. I put it on a tripod and have it about 6" below the bullet flight. When I did use the sky screens or the goal posts I would put a piece of tape at the top with a dot to aim at. Prevented me from hitting the chronograph I am sure.

Mine seems to be consistent and reliable.

Dolomite

[Guest HCRoadie]

I had to smile when I read this part in the description...Be careful to prepare adequately for windy conditions. What that really means is, watch out when it's windy otherwise you'll shoot the screens.

Or maybe it was something as innocent as the wind blowing his rig over.

[gregintenn]

Thanks for starting this thread. I may be interested in one as well, and know nothing about them.

[mikegideon]

Or maybe it was something as innocent as the wind blowing his rig over.

Yep. Mine is real light, and has a lot of wind surface area because of the screens.

[bvarnell]

Just so happens that Power Factor posted a video this week.

They are talking about shotguns, but same principles apply to bullets.

http://www.powerfactorshow.com/

[Guest Lester Weevils]

I have the shooting chrony model F-1 Master and it works fine. You find user complaints and unhappy campers with all of em, but am guessing the one Mike Gideon has may be the "least risky" to buy because it typically gets higher user reviews and fewer user complaints than the other brands.

Some of them are mostly plastic and easy to blow over in a wind. The shooting chrony models have a steel chassis and perhaps less likely to blow over in the wind, but mebbe thats not a good enough sole reason to pick that brand.

Something that astronomers sometimes do, perhaps photographers as well-- Easy to jury rig though some tripods have a hook already built-in for the purpose-- Put a strap or a bungee on something that weighs a few pounds, nylon bag of lead shot, water filled jug, box of ammo, concrete block, old car battery, junk refrigerator-- Just whatever you happen to have with you that is heavy. Hang the weight from the center of the tripod so it is sitting low, ideally just a few inches off the ground. That will lower the center of gravity enough to make the tripod less likely to wiggle or blow over.

[Guest BungieCord]

All consumer chronos (currently available) except the Magnetospeed use optical sensors. All optical chronos need a tripod to set up properly. They also all are prone to errors caused by stray lighting, some more than others. Some optical units have available add-on infrared lighting, which eliminates the sensitivity to stray light but adds expense, not to mention the need for an additional power source. One of the optical units, the Kurzzeit PVM-21, comes standard with built-in infrared, but it's also the most expensive ($795).

The optical units are either all-in-one or have separate sensors. If you inadvertently shoot an all-in-one, even if some parts are salvageable, you're still stuck waiting until you can send it in for repair and get it back. The separate sensors are user-replaceable and if you should shoot one, you only have to call MidwayUSA or whoever and you can have the replacement sensor delivered (and be back up and running) as quickly as your MasterCard can stand.

Separate sensor units have a control head that sits on the bench with the shooter. This makes its display easier to read than the screen on an all-in-one, which you've deliberately placed some feet downrange, screen and all. Some units house the battery in the remote head, which makes changing batteries a breeze, particularly useful in cold weather.

The Magnetospeed is unique in that its sensors don't use light at all, they detect the disturbance in the magnetic field from the passing bullet. It straps on your barrel, is far faster and easier to set up, and eliminates the need for a tripod. However, it is an arbitrary mass added to the muzzle of your rifle. Some shooters report that it does affect the accuracy of their rifle, while others see no change. Which means it is [u]possible[/u] that you won't be able to shoot to confirm accuracy [u]and[/u] shoot to measure muzzle velocity at the same time.

I've owned five chronos (and used several others) and I rely on them heavily for load development and quality control of my loading process. I currently have a CED M2 and a Shooting Chrony Beta Master but I'm saving my pennies for a Kurzzeit PVM-21.

The Shooting Chrony brand is the best selling but that's because they're also the cheapest. In my opinion, they're no bargain. I've had three of them fail myself, and I've had major problems with their customer service. The CE Pro Chrono Digital ($120) isn't an arm and a leg more than the cheaper Shooting Chronys but it has a far better reputation (plus a slightly more precise timing circuitry). But it is an all-in-one unit with no remote control. If you can stand the extra $80, the CED M2 ($199) is a good choice. It has user-replaceable sensors, plus a remote unit that sits next to you on the bench. It also has the most precise timing circuitry of any consumer chrono. If you can go another $75, look at the Magnetospeed ($275). It's still a fairly new addition to the market, and the product is evolving rapidly (a sign of both active customer service and responsive R&D), and it's getting generally rave reviews. One of the worst aspects of owning/using a chrono is the time and difficulty in setting it up, especially if you're at a public shooting range, and the Magnetospeed next to entirely eliminates that problem. Plus you can't possibly shoot it unless you've gone out of your way to be stoopid.

If you're intent is to use the standard deviation of muzzle velocity (SD) as a statistical quality control of your loads, it's best to avoid the bargain chronos because their timing circuitry's precision is too low. But if you only are looking to find your loads' true MV so you can do custom range cards, or even just to satisfy your curiosity, even the cheapos shouldn't be too far off the mark.

[mikegideon]

Bungie,

Can you send me a link where they discuss precision timing circuitry in Chronographs? I really want to know the answers, because it went right past me in my research. I did read where the M2 had a problem agreeing between two identical units because of the mechanical design (sensor spacing is critical). Not disputing you... just wanna know.

[Guest BungieCord]

Mike, AFAIK, there is no consolidated source. I dug all this up from the different manufacturers themselves, from their documentation or advertisements. By my count there are eight consumer-level chronos on the market. I found the numbers on six of them but I could never find anything on the PACTs, and Magnetospeed hasn't yet put out anything I can find.

I've only found accuracy claims [i]per se[/i] from two of them. Shooting Chrony claims 99.5% accuracy @2000 fps and Kurzzeit claims "Accuracy: < 1% from the shown value". Except the Kurzzeit has considerably better precision than the Shooting Chronys, so they're definitely selling themselves short at "< 1%".

The German defense lab tested the old CED Millennium model and found it to be 99.8% accurate overall on everything from .45 ACP to .223 Rem. They scored the obsolete Millennium model 0.3% more accurate than an Oehler P35 and the newer M2, with two foot screen spacing, has 3x better precision than the Millennium did with eight foot screen spacing. Edited November 3, 2012 by BungieCord

[mikegideon]

[quote name='BungieCord' timestamp='1351983110' post='838510']
Mike, AFAIK, there is no consolidated source. I dug all this up from the different manufacturers themselves, from their documentation or advertisements. By my count there are eight consumer-level chronos on the market. I found the numbers on six of them but I could never find anything on the PACTs, and Magnetospeed hasn't yet put out anything I can find.
[/quote]

Ah. Manufacturers specs? The "hope and change" of the consumer electronics world . Because of the way chrony's work, there is going to be a fixed error in velocity because of the time base frequency error (the CE spec is +/- 1%). Since that error is fixed, all measurements will be off by the same amount, so calculations like SD will be dead nuts accurate. It's real easy to make them accurate. It's much harder to make them read reliably.

By their very nature, chrony's should be real accurate, as long as the spacing between the sensors is accurate. That's why I like to have the sensors mounted in the same piece of plastic. I'm not too worried about shooting mine unless it deserves it

[Guest Lester Weevils]

Yep the magnetospeed looks really neat for rifles. Possibly a cause of puzzlement attaching to some pistols, and then again possibly easy to attach to other models of pistol?

Many trade-offs, price, accuracy, repeatability, ease of use. Frustration. If you have to wait for beneficial lighting conditions then be very careful and "squint just right" to get it to measure a shot then a chrono might be annoying even if the price is right and accuracy acceptable.

The published spec in my F1 Master shooting chrony manual is "at least 99.5 percent accurate between 30 fps and 7000 fps". Given that the clock crystal is 12 MHz, and assuming that it uses a hardware counter on the microcontroller, and given that the sensor spacing is 1 foot, a 19 bit unsigned register could count the lowest velocity. Or a 20 bit signed register. Which seems reasonable in a cheap gadget.

At the upper limit of 7000 fps one would expect the least accuracy and resolution (smaller counts). Assuming the gadget is just counting ticks. Each tick at 12 MHz would count 83.33 nanoseconds. The time of passage thru the sensors at 7000 fps would be 142.9 microseconds. So the counter would count up to something in the ballpark of 1.429e-4 / 8.333e-8 = 1714.29 ticks. Since it is surely an integer register, it would either count 1714 or 1715, or some other number "in that ballpark" depending on how much jitter and slop is in the system.

If there were zero jitter and slop, at 7000 fps the 12 MHz clock would have a native resolution of about 4 fps. A precise count of 1714 would represent 12e6 / 1714 = 7001.17 fps and a count one bigger of 1715 would represent 6997.08 fps. With zero slop and jitter, I think the system would be theoretically accurate in the ballpark of 99.94 percent at that velocity.

At a "pistol velocity" of 1000 fps, the theoretical accuracy would be much better. The minimum resolution would be about 0.083 fps and it would be theoretically accurate to 99.992 percent.

However, because the spec only claims 99.5 percent accuracy, the fella is giving himself a little over 8 ticks of slop and jitter. Maybe he's dividing the clock, or maybe he has to use software to enable/disable the counter. If he's dividing the clock by 8, then the count would fit in a 16 bit unsigned register. That would also get the clock rate slow enough to run with generic CMOS logic chips, in case he isn't using a counter on the microcontroller.

However, if there is "about 8 ticks of jitter and slop" in the system, and that is all that is going on, then the accuracy at 1000 fps ought to be better than the "worst case" at 7000 fps. At 1000 fps with 8 ticks of slop, the accuracy ought to be in the ballpark of 99.94 percent?

[mikegideon]

Lester!!! I have been putting off going thru the math. I love it when you go full geek on us . Fact is, precision in a chrony should be a non-issue. I may actually pick up one of the M2's, even though it has a fairly low rating (3.1) on the Midway site. It does have some sexy features.

[RED333]

Lester, that is way TMI!!! Made my head hurt.
That said, thanks.

[Guest sL1k]

[quote name='Lester Weevils' timestamp='1352046692' post='838885']At 1000 fps with 8 ticks of slop, the accuracy ought to be in the ballpark of 99.94 percent?[/quote]
I'm hoping that question mark was accidental because I'm not sure who here will check your math to confirm this... I bow before Lester lol