scratchin my head on velocity
04-29-2006, 06:31 AM
#12
Nontypical Buck
Join Date: Jun 2004
Location: A flat lander lost in the mountains of Northern,AZ
Posts: 3,171
RE: scratchin my head on velocity
I use a beta chrony and noticed higher reading too on sunny days with the shades off. Ive also noticed readings to vary depending on the time of day and positioning of the sun. but im not to big on velocity i dont really care how fast the bullet goes, I look more for velocity spread during different tempatures and seasons.
05-04-2006, 07:48 AM
#13
Giant Nontypical
Join Date: Feb 2003
Location: Texas - BUT NOW in Madison County, NY
Posts: 6,270
RE: scratchin my head on velocity
ORIGINAL: bigcountry
I have same issues with my pact and chony F1. What I found was light conditions was the dominating factor. But it doesn't make sense.
I shot over a friends oehler and it was rock solid one day as it was a year before that. You get what you pay for in chronys.
I like you starting suspecting weather and all. But did the tape test. I put clear tape over my sensors to see what would happen. I lost velocity. By 100fps. Sometimes more.
So I started experiementing taking one peice off the front and so on.
I am a EE, so know little something about timers, and photocells. One thing I do know is temp has a big effect sometimes on circuits. But I am having a hard time wrapping my arms around this problem. Light is light, so theorectically, it shouldn't make a difference on timing no matter how cheap the components are for a F1 or Gamma, or whatever. So I conclude it has to be with the timer circuitry. Any of you guys who have went thru physics or Engineering program has probably has to build a crude timing source from a Quartz timer or something and know you can adjust timing by a few factors but not by much.
ORIGINAL: haugenna
I went to the range three times last week and shot over a chronograph. I shot the same load on Monday as I did on Friday and Saturday. All days were calm days, 60-70 degrees and I pushed a 200 Gr TSX 3292fps was avg, hi 3301, lo 3284, with 100 Gr. RL 25.
I went back Friday and Saturday and only achieved 3170 avg. One thing I did learn, is that most reloadingbooks are full of it when they talk about powders and velocity. What could have been the factor? Any advice. Primers, bullet, powder were all the same. Does trim length and bullet seating depth make that big of a difference? COL was 3.777 on Monday and Saturday and 3.770 on Friday. All shots were with warm, not hot but not cold, barrels. Does ten degrees temperature make that big of a difference? Any advice would be helpful.
I went to the range three times last week and shot over a chronograph. I shot the same load on Monday as I did on Friday and Saturday. All days were calm days, 60-70 degrees and I pushed a 200 Gr TSX 3292fps was avg, hi 3301, lo 3284, with 100 Gr. RL 25.
I went back Friday and Saturday and only achieved 3170 avg. One thing I did learn, is that most reloadingbooks are full of it when they talk about powders and velocity. What could have been the factor? Any advice. Primers, bullet, powder were all the same. Does trim length and bullet seating depth make that big of a difference? COL was 3.777 on Monday and Saturday and 3.770 on Friday. All shots were with warm, not hot but not cold, barrels. Does ten degrees temperature make that big of a difference? Any advice would be helpful.
I shot over a friends oehler and it was rock solid one day as it was a year before that. You get what you pay for in chronys.
I like you starting suspecting weather and all. But did the tape test. I put clear tape over my sensors to see what would happen. I lost velocity. By 100fps. Sometimes more.
So I started experiementing taking one peice off the front and so on.
I am a EE, so know little something about timers, and photocells. One thing I do know is temp has a big effect sometimes on circuits. But I am having a hard time wrapping my arms around this problem. Light is light, so theorectically, it shouldn't make a difference on timing no matter how cheap the components are for a F1 or Gamma, or whatever. So I conclude it has to be with the timer circuitry. Any of you guys who have went thru physics or Engineering program has probably has to build a crude timing source from a Quartz timer or something and know you can adjust timing by a few factors but not by much.
I have also noted similar effects when using early models of the Oelhers with Skyscreens.......
05-04-2006, 07:53 AM
#14
Guest
Posts: n/a
RE: scratchin my head on velocity
Thats what I am explaining, is I don't know why that is happening. I have designed some pretty high speed stuff with photocells, and dont' see it in the lab. But then again, its pretty well never outside.
Maybe the leading edge of the pulse is sharper with more current draw.
Maybe the leading edge of the pulse is sharper with more current draw.
05-04-2006, 01:40 PM
#15
Boone & Crockett
Join Date: Feb 2003
Location: Wall SD USA & Jamestown ND
Posts: 11,474
RE: scratchin my head on velocity
I noticed that as well when I used the Chrony. The Pro-Chrono that I HAVE NOW, Just is not fussy about light conditions. It reads the same regardless of light conditions.
