The Accurate Reloading Forums
Distance for crony
17 December 2007, 04:18
wrightboyDistance for crony
How far do you put your crony out to get a reading. Wanting to get muzzle velocity. Got mine too close today I guess. It died. Screne is blank. Directions said 15 feet(mine was closer). Will this give a true muzzle velocity?
17 December 2007, 05:12
Ol` JoeI`d go with the directions.
Too close and the muzzle blast will screw up the readings. I set mine ~10-12 ft from the muzzle and have had no problems with it. The difference in velocity at 15 ft from the true muzzle velocity is likely less then the SD of the 1st 5 rounds you will fire over the screens. Don`t sweat it, it will be extreemly close. I saw a formula once to correct for the distance but don`t remember where, it generally worked out to something like 1 fps/ft distance.
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17 December 2007, 05:23
wrightboyThanks
17 December 2007, 07:44
RicochetThey die when bullets go through them, too. Don't ask how I know...
"A cheerful heart is good medicine."
18 December 2007, 20:53
butchloci know, i know
18 December 2007, 23:30
Bear in FairbanksWrightboy:
I too set mine at about 15 ft. from the muzzle. It's a Chrony and that distance seems to work for me pretty good. I usually figure a 10 ft./sec. loss in velocity @ 15 ft. I run my measured vel. thru a ballistics program then work it back for the 15' distance. That's how I usually come up with a 10 ft./sec. difference between the location of the chrony & the muzzle.
Bear in Fairbanks
Unless you're the lead dog, the scenery never changes.
I never thought that I'd live to see a President worse than Jimmy Carter. Well, I have.
Gun control means using two hands.
19 December 2007, 00:13
Reloader12 to 15 feet for me.
I once blew the sky screens off with a 7 Weatherby at around 12'. Didn't hit them, just the muzzle blast. Certainly turned a few heads at the range
Have a Good One,
Reloader
19 December 2007, 01:50
RicochetCloser than about 15' you'll have problems with partly burned powder grains punching holes through the screen on the front.
Gas checks coming off bullet bases have taken out chronies, too. Or sabots with muzzleloaders.
"A cheerful heart is good medicine."
19 December 2007, 02:48
robzI have a length of cord around 15 feet tied to the chrony tripod. run out the cord and its done.
"the older I get, the better I was"
19 December 2007, 03:24
Alberta Canuckquote:
Originally posted by Ricochet:
They die when bullets go through them, too. Don't ask how I know...
But not always, thank God!! My buddy put a .300 WBY 200 gr. bullet through my Oehler at about 3.300 f.p.s. when we were testing a commercially unavailable powder in some warmish loads... That was in the mid-1980s and it is still working!!
Now when I let other folks fire shots over my chronograph, I make sure to just set up the Chrony...
My country gal's just a moonshiner's daughter, but I love her still.
19 December 2007, 05:07
jjmpmy 10 feet equal closer 2 ...12 feet no problems to date .
regards
19 December 2007, 05:15
hawkinsAn easy check is to back off another 10 ft and see if the readings change. If no change you are good.
Take Care!
19 December 2007, 07:40
1 Shot HunterTo make setup easier and give you more tolerance in moving your rifle around on the bench, I'd recommend setting it up at 10 feet. (Think about 10 feet vs. 15 feet - you get a 50% bigger window...)
I had a great experience about 10 years ago, whilst shooting with a very inexperienced (and anal) newbie friend... He was shooting his new 270 over his new Chrony. I wanted to try my 7mm RM and he kept hedging. Finally, he relented. I assured him I was SURE I couldn't possibly hit the Chrony... Squeezed the trigger and the screens went FLYING!!! His look and attitude were priceless - he didn't know what to say... When they finally called a cease fire, he went out and picked up all the scattered pieces. Spent 5 or 10 minutes inspecting every piece and just couldn't find where the bullet hit. I kept reminding him there was NO WAY I could have hit it. He figgered maybe he didn't have the screens on properly. He set it up and fired a bunch of 270's through it, which convinced him that I hadn't hit it, so he let me try again. 1 shot and the thing flew apart again! Such is the difference in muzzle blast. We taped the screens on and everything was fine.
19 December 2007, 08:06
fredj338I set mine 15ft+/-. 10 feet often causes erradic readings due to muzzle blast, you may even blow a screen shade off. You might get bye w/ 10ft on small bores but magnums need abit more room IMO.
LIFE IS NOT A SPECTATOR'S SPORT!
19 December 2007, 16:23
jeffeossoah, the right question is distance ABOVE chrony....
19 December 2007, 16:45
boltmanI set mine up at about 15 feet, 10 is too close for me because I've had erratic readings from the muzzle blast. If you're really concerned about getting the exact muzzle velocity then add 15 fps to your reading if your chrony is at 15 feet. A bullet from the average hunting rifle caliber decelerates at about 1 foot per second.
19 December 2007, 19:10
Mike_DettorreI regularly loan out my chrony...
That is how I have gotten two new one in the last 5 years
MikeLegistine actu quod scripsi?
Never under estimate the internet community's ability to reply to your post with their personal rant about their tangentially related, single occurrence issue.
What I have learned on AR, since 2001:
1. The proper answer to: Where is the best place in town to get a steak dinner? is…You should go to Mel's Diner and get the fried chicken.
2. Big game animals can tell the difference between .015 of an inch in diameter, 15 grains of bullet weight, and 150 fps.
3. There is a difference in the performance of two identical projectiles launched at the same velocity if they came from different cartridges.
4. While a double rifle is the perfect DGR, every 375HH bolt gun needs to be modified to carry at least 5 down.
5. While a floor plate and detachable box magazine both use a mechanical latch, only the floor plate latch is reliable. Disregard the fact that every modern military rifle uses a detachable box magazine.
6. The Remington 700 is unreliable regardless of the fact it is the basis of the USMC M40 sniper rifle for 40+ years with no changes to the receiver or extractor and is the choice of more military and law enforcement sniper units than any other rifle.
7. PF actions are not suitable for a DGR and it is irrelevant that the M1, M14, M16, & AK47 which were designed for hunting men that can shoot back are all PF actions.
8. 95 deg F in Africa is different than 95 deg F in TX or CA and that is why you must worry about ammunition temperature in Africa (even though most safaris take place in winter) but not in TX or in CA.
9. The size of a ding in a gun's finish doesn't matter, what matters is whether it’s a safe ding or not.
10. 1 in a row is a trend, 2 in a row is statistically significant, and 3 in a row is an irrefutable fact.
11. Never buy a WSM or RCM cartridge for a safari rifle or your go to rifle in the USA because if they lose your ammo you can't find replacement ammo but don't worry 280 Rem, 338-06, 35 Whelen, and all Weatherby cartridges abound in Africa and back country stores.
12. A well hit animal can run 75 yds. in the open and suddenly drop with no initial blood trail, but the one I shot from 200 yds. away that ran 10 yds. and disappeared into a thicket and was not found was lost because the bullet penciled thru. I am 100% certain of this even though I have no physical evidence.
13. A 300 Win Mag is a 500 yard elk cartridge but a 308 Win is not a 300 yard elk cartridge even though the same bullet is travelling at the same velocity at those respective distances.
20 December 2007, 06:34
wrightboyThanks guys. Sounds like 15ft is the right answer, but I thought of something else. My shooting bench is 4 ft long. What do you think if I mounted it below the benck to try and shield any muzzle blast with just the guides above the bench for aiming. Just a thought.
20 December 2007, 12:26
Robert_in_mtThat would only measure muzzle blast if it didn't kill chrony right off. Put it at 15 ft or more, you have a 6 inch min. hole to shoot through. I've set mine at 300 yds to check SD at that range and have never shot it "yet", You just have to walk out there to get results. Out at 100yds you can read it with scope.
RC
20 December 2007, 22:38
Dr.KI know what a " New " set of sky screens cost !.
I didn't even set it up my shooting partner did and I was using his 7.62X54 Russian what ever sniper rifle W/Scope and he had it on the bull bag already to go . Boy did it go !!!!!.
Shoot Straight know Your Target . ...
