Chronograph ?
10-02-2007, 07:37 PM
#1
Fork Horn
Thread Starter
Join Date: Oct 2005
Posts: 141
Chronograph ?
I received a Pact chronograph from a relative as a gift and finally had achance to try it out. The instructions say to place the starting edge 8 feet from muzzle of rifle and adjust the height so the bullet passes 5-8" above the sensors. I shot 15 rounds and only got one reading. It was at dusk so I'm not sure if the lighting was an issue or if something else was a factor. I also noticed that my groups were slighly right of center while shooting thru the chrony. Once I moved it out of the way I was back to center, Anyone else have any experiences such as this? The one and only velocity measurement I did get wasn't close to what the reloading manuals show as approx. velocity. I'm confused, could somebody Please help me out. Thanks.
10-02-2007, 09:58 PM
#3
Nontypical Buck
Join Date: Aug 2005
Location: S.W. Pa.-- Heart in North Central Pa. mountains-
Posts: 2,600
RE: Chronograph ?
bigcountry's right on. A bright but cloudy day is best. I carry a tape measure with my Chrony and usually set it 10 ft. from the muzzle. The velocity is measured by the time it takes the bullet to pass over the photocells, and if it's too dark, they won't see it well. If it is used in bright sunlight, the same thing can happen Does yours come with the shades for over the photocells? I usually find it necessary to use them on most of the days I shoot.
As far as the windage change, I've never had that happen....
Don't be alarmed at lower velocities than companies publish. A lot of them are taken from barrels longer than the general hunting rifle comes equipped with, and some just plain seem imaginary.
As far as the windage change, I've never had that happen....
Don't be alarmed at lower velocities than companies publish. A lot of them are taken from barrels longer than the general hunting rifle comes equipped with, and some just plain seem imaginary.
10-24-2007, 11:15 AM
#7
Join Date: Dec 2006
Location:
Posts: 80
RE: Chronograph ?
i have the very same cronograph and it did the same thing to me. i have found that dusk is in deed the worst time to try to use it. the best time i have found is mid day with it in a slightly shaded area or cloudy. as for the velocity, i have found that most of your reloading manuals to be different from each other. the book i have found that seems to be real close is the serria 5th eddition. and dont forget to keep a fresh battery (9v) for your cronograph printer. if it gets a little low, it wont print being a laser printer. also keep in mind, trickle your powder to fine tone your loads. you will find it to be more consistant.
10-27-2007, 11:18 PM
#9
Nontypical Buck
Join Date: Feb 2003
Location: Coralville, IA. USA
Posts: 3,802
RE: Chronograph ?
Cloudy days are best, followed by sunny days with the diffusers on the screens. Try to shoot through the middle of the screens as much as possible. Another thing you might want to try is moving the chrony out to at least 10 ft from the muzzle. if you're too close to the chrony the gasses from the muzzle can actually disrupt the reading. Sometime this will cause a wild reading, but since it usually effects the first screen, the chrony will just show no reading at all because the first screen gets tripped twice before the second screen gets tripped. This messes up the timer.
As far as published vs. actual muzzle velocity, well, you're in for some surprises, some good some bad. One thing to note in your manual is what type of barreled action the round was pressure tested in for the published data. Sometimes they use pressure test barrels, sometimes they use factory sporting rifles, sometimes they use longer than typical custom rifles. One thing you'll likely note is that velocities taken from pressure barrels are considerably higher than standard because they use minimum spec chambers and throats with tight headspacing. This tends to give higher velocities. The data from custom rifles will probably be a little higher than what you might see in your rifle because custom guns usually have the chambers tighter than factory rifles, but not min spec. And if you're lucky and the data you're using was shot in a factory rifle with the same barrel length, it'll probably be pretty close, with your rifle maybe even exceeding published velocity. Factory chambers are usually cut on the loose side so that they will reliably and safely feed, chamber and fire all factory ammo. Pressure barrels are intentionally min spec because if the pressure is safe in the test barrel, it'll almost certainly be safe in your rifles barrel.
Mike
As far as published vs. actual muzzle velocity, well, you're in for some surprises, some good some bad. One thing to note in your manual is what type of barreled action the round was pressure tested in for the published data. Sometimes they use pressure test barrels, sometimes they use factory sporting rifles, sometimes they use longer than typical custom rifles. One thing you'll likely note is that velocities taken from pressure barrels are considerably higher than standard because they use minimum spec chambers and throats with tight headspacing. This tends to give higher velocities. The data from custom rifles will probably be a little higher than what you might see in your rifle because custom guns usually have the chambers tighter than factory rifles, but not min spec. And if you're lucky and the data you're using was shot in a factory rifle with the same barrel length, it'll probably be pretty close, with your rifle maybe even exceeding published velocity. Factory chambers are usually cut on the loose side so that they will reliably and safely feed, chamber and fire all factory ammo. Pressure barrels are intentionally min spec because if the pressure is safe in the test barrel, it'll almost certainly be safe in your rifles barrel.
Mike
