Aside from shooting your chronograph...

BenKK

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What have you seen or done to ensure accurate readings?

I haven’t shot my chronograph yet!

Anyway, today I loaded eight 180 grain CEB Safari Solids in new Norma .300H&H brass using 62 grains of 2209 (one of my go-to loads using Hydros or TSXs - I’m not a speed demon). I went out-bush with my chronograph. First I fired-off a cartridge just to “feel” it - haven’t used this projectile before. Then I tried to balance my chronograph on an ant hill, but I could see it would only end in tears. So I looked around a bit further and tried a nearby borrow pit beside the track, but the main dirt heap was too tall and too grassy. So I settled for a plateau just in front of the little mound, and I popped down into a dry depression about five metres away. From a sitting or crouching position I could shoot through the chronograph. My three shots were extremely disappointing even though they all felt good and the rifle seemed to like them: 2331fps, 2559fps and 2737fps. Not cool! Of course, I instantly blamed the bullet. My loads were perfect, all between 62.0 and 62.2 grains. I puzzled about it and eventually wondered if dust from the muzzle blast (or, less likely, some dust being blown back through from the mound just behind) could be the culprit. It didn’t seem too dusty by Australian standards, but to be honest dust was present. So I decided I needed to eliminate the positioning of the chronograph as a problem by going and finding my tried-and-proven 44-gallon drum. Using this taller, steady platform from a standing position, my next four shots were very pleasing, and made sense: 2807fps, 2818fps, another duplicate of 2818fps and 2830fps. I’m happy with this and hope to test it on buffalo soon.

Has anyone else buggered things up with a chronograph?

Cheers!

IMG_0962.JPG
 

mark-hunter

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Hmmm... this one could go also under thread on sabots.

I was on a city range, doing some training. When I was about to finish, a guy came, and he wanted to test his rifle.
He had a rifle, and his ammo, but not much of other equipment. (no range bag at all).
He was friendly, and we started talking.
He wanted to try sabots in 30-06. It was .224 bullet, wrapped in plastic sabot and loaded in 30-06 casing.
I was also interested and offered him to try shooting trough my chrony. (bad decision)
I set up chrony on good distance from muzzle, as I set up for my shooting as usual.

He fired a shot, i saw dust in good line 150 meters at sand bank.
But, when I went to check the chrony - it was busted.:E Horrified:

What happened is, plastic sabot disengaged from bullet maybe 2 meters from muzzle, the bullet went properly as aimed, and tumbling sabot plastic hit my chrony display, destroying it.

I thought chrony was lost for ever.

But,... I have a friend who is electronic freak... :E Excited:, and he found replacement spare chrony display (made in China) on the vastness of ebay.
He ordered two pieces for few euros , and when it was received, he replaced display, bringing new life to my chrony. :E Dancing:

Second display, I keep for spare, just in case.

Lesson learned:
If shooting sabots through chrony, protect the chrony by some would planks, because you dont know where plastic sabbot will end up.
 

mark-hunter

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I don’t even know what sabots are! I’ll look them up.

Dont expect too much. I think it is failed design.
For accuracy: There is also question of twist rate for .30 cal barrel, and this bullet weight... etc.
They should be fast, certainly. They dont have reputation for accuracy.
But i dont see much practical purpose. Better is to buy a rifle in 223 rem caliber, then to waste time with this.

See this:
https://en.wikipedia.org/wiki/.22_Accelerator

upload_2020-4-17_10-37-4.jpeg

YKhJ7eASb6pngEnu_2nmmVFqpBlNn6hubbSCl_OlF31ns99tidCMy9do1UCfVZEqvNwqz1wAipyGfVbWrhwJQtlIvZkbeBvxM-lNTdDUwKDyusp8QQ8
 

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mark-hunter

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What’s their purpose? Small game from a larger calibre?

You guess is as good as mine.

I think, that the purpose is extended range for varmiting, but they fail in accuracy department.

You can have fun with it as well.
Like having a bet with your friends, that your 30-06 can make up to 4.000 fps, or so. (better then their 300 win mag... LOL)
 

fourfive8

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Sabots have been around along time. Back in the 70-80s +/-, one company decided to put plastic sabots on 22 bullets and load them in the '06. The idea was to get a really fast velocity to sell, so.... yep 4000 fps marketing :)

More recently the inline semi-smokeless and smokeless muzzle loader crowd has jumped on the sabot wagon. Some larger military projectiles have been used with some form of sabot since at least the 1850-60s or earlier.

And yes they will ding or destroy a chronograph. As well as gas checks off of cast bullets, wads used for some blackpowder and/or muzzleloader applications and shotgun wads.

Setting up a chronograph graph for reliable and trustworthy readings is a chore sometimes. I've discovered over the years that false readings can have many causes.

A sturdy platform is handy, a drum is good of course if it is right height for the bench rested rifle, a decent tripod is very handy also. A small table will work. So yah- little doubt dust will cause problems. Both muzzleblast and the bullet's wake can "gather" dust and carry it though the sensor zone and cause problems.

For reliable readings most common high power rifles require the chronograph to be at least 15 feet from the muzzle and usually the best readings are from bullets passing squarely over and 2-4" above the sensor slits. The large cloud of gas and debris is actually traveling faster than the bullet just after the bullet exits. The bullet is flying within that cloud for a short distance. That compressed gas cloud dissipates very rapidly but if the chronograph is too close to the muzzle the unit will either be buffeted by the gas cloud (not good) or high density gas or particles in the cloud can "fool" the chronograph. The average chronograph has two sensor slits and they only "want" to see a single bullet shadow as it passes over them. Even insects flying around the sensors during a shot will mess with readings. Wads, ball patches, globs of bullet lubricant, powder particles, sabots, gas checks, anything other than a solid bullet casting a clean shadow over the sensors can foul up readings. The best shadow is cast during complete cloud cover. The next best is a high sun angle with the screens providing the shadow producing "cloud cover". Low sun angles are not good because light reflections onto the sensor slits or direct sun light on the sensors can wreak havoc with reliable readings. In low sun angle use the sky screens for the shadow but use something like stiff index cards taped to the side of the unit or screen supports to block direct sunlight from hitting the sensors. After much frustration, several years ago I discovered that trick while troubleshooting odd readings.
 
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Tanks

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One of the reasons I have switched to LabRadar with its own tripod. No need to worry about shooting it and no need to worry about sun etc. and easy to set up.
 

Dirtdart

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I don’t even know what sabots are! I’ll look them up.
One example where a sabot is quite useful is if you want to use a bullet in a muzzleloader that you would not be able to push down the bore because of how hard it is were it bore size. I have used 300 grain hard lead .45 caliber bullets in my .50 caliber to get pass throughs on shoulder shots on animals like zebra and gemsbok. With a full bore conical that is made of pure lead (or close to it) in a front stuffer as small as a .50 caliber penetration is not nearly as good. Even though I have not used jacketed bullets in my muzzleloaders the same principle applies I would assume.

DSC02687 (1).jpg
 
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Ridgewalker

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I watched a kid shoot right through his brand new first shot Chrony! I felt badly for him, but he laughed a long time afterward.
I have never used a Chrony with the built in sky screens. I have had a Pact for many years that has separate sky screens you mount to a tripod. If it is sunny and the sun is mostly overhead, it works well. I purchased a MagnetoSpeed a few years ago to use if the sun wasn’t out and it works OK except on rifles with muzzlebrake or with suppressor adapters. Figuring this out, I now have a LabRadar, but if you are in close proximity to another shooter (next bench) it can get confused with yours and their bullets or muzzle blast. JME&O
 
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What have you seen or done to ensure accurate readings?

I haven’t shot my chronograph yet!

Anyway, today I loaded eight 180 grain CEB Safari Solids in new Norma .300H&H brass using 62 grains of 2209 (one of my go-to loads using Hydros or TSXs - I’m not a speed demon). I went out-bush with my chronograph. First I fired-off a cartridge just to “feel” it - haven’t used this projectile before. Then I tried to balance my chronograph on an ant hill, but I could see it would only end in tears. So I looked around a bit further and tried a nearby borrow pit beside the track, but the main dirt heap was too tall and too grassy. So I settled for a plateau just in front of the little mound, and I popped down into a dry depression about five metres away. From a sitting or crouching position I could shoot through the chronograph. My three shots were extremely disappointing even though they all felt good and the rifle seemed to like them: 2331fps, 2559fps and 2737fps. Not cool! Of course, I instantly blamed the bullet. My loads were perfect, all between 62.0 and 62.2 grains. I puzzled about it and eventually wondered if dust from the muzzle blast (or, less likely, some dust being blown back through from the mound just behind) could be the culprit. It didn’t seem too dusty by Australian standards, but to be honest dust was present. So I decided I needed to eliminate the positioning of the chronograph as a problem by going and finding my tried-and-proven 44-gallon drum. Using this taller, steady platform from a standing position, my next four shots were very pleasing, and made sense: 2807fps, 2818fps, another duplicate of 2818fps and 2830fps. I’m happy with this and hope to test it on buffalo soon.

Has anyone else buggered things up with a chronograph?

Cheers!

View attachment 342613
@BenKK
I was at the range with a friend to sight in his 30/06 long story short. First shot was thru the LCD read out, thru all the out he electronics and out the back of the Chrony. The bullet impacting the target 2 inches high at 100 yards with a perfect 30 cal hole. End of velocity testing. He did pay for a new chronograph tho.
Bob
 
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Same chrono I have, I’ve found it must be sunny when using it or I get funny numbers.
@ Wyatt Smith
It's got to be far enough away as well or you get very funny velocities as well from the muzzle blast and the unit can fall over. I set mine at the recommend 9 feet and got velocities over 4,000fps from my 25. Had me scratching my head and checking cases and rifle, 3rd shot and the Whole unit on the ground from the blast.
Bob
 

meigsbucks

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As others have stated, place it 15’ from your muzzle. I’d mount it on a camera tripod. Also, I tend to get the most accurate readings early on a sunny day. Even with the diffusers, a direct overhead sun seems to give me some weird readings.
Years ago, I had one of the very old Chrony’s that had the cardboard windows to shoot thru. A guy with a muzzleloader asked if he he could shoot a round thru for speed. The shed sabot wiped out the cardboard windows.
As a side note on sabots. A friend I used to deer hunt with shot a Remington 760. The Remington Accelerator rounds gave great accuracy in his rifle; better than the deer rounds.
 

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I have shot one chronograph with a .30-06 and another time I shot in half one of the cables that holds the tailgate on a dodge truck. Was using the tailgate as a shooting table both times.
I like to shoot milk jugs filled with water to test bullet performance. Never had any trouble until this past spring when I was working up a load for the .375. Hit the jug center enough and in line with the five behind it-BUT the energy blew that first jugs bottom right through the cardboard table, leaving a ragged hole. No worries, bought my wife a new one at Costco. . .
 

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