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scratchin my head on velocity
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. |
RE: scratchin my head on velocity
Bullet seating depth and temperature will effect velocity but in both cases the differences are too small to make that much difference.Were the powder ,primers and bullets from the same lot #s on both days?How were the light conditions on both days?Some chronographs are effected by lighting conditions.It may seem silly,but is your chronograph a chrony?I have witnessed someone using one that wasn't totally opened up to the stops.The result is noticeably higher readings.
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RE: scratchin my head on velocity
Stubble,
All bullets, primers and powder came from the same can, box, and tray. I am shooting over the gamma master. Monday was sunny without sun shades on the chrony, Friday was later in the day, a little sun on the chrony and no shades, Saturday, sunny with sun shades. "Opened up to the stops" what does that mean? Would the sun shades on during a sunny day give me the same readout as sun shades on during a cloudy day? |
RE: scratchin my head on velocity
Stubble,
"open to the stops" think I got it, The chronograph completely opened up. |
RE: scratchin my head on velocity
ORIGINAL: haugenna One thing I did learn, is that most reloading books are full of it when they talk about powders and velocity. |
RE: scratchin my head on velocity
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 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. |
RE: scratchin my head on velocity
Did you clean your barrel inbetween range sessions? A clean bore will sometimes reduce velocities until it's gets fouled, then the velocities start to come back up.
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RE: scratchin my head on velocity
If you don't use the sun shades on a sunny day,you willoften get high readings with the chrony.As such,I believe that the readings that you obtained on the second and third day are probably more accurate.
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RE: scratchin my head on velocity
As the owner of a Shooting Chrony myself, I tend to agree with stubblejumper.
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RE: scratchin my head on velocity
Stubble and Solitary,
Thanks for the info....As a new owner of a chrony....I need to make sure it is completely open and that I have the sun shades on at all times. Haugenna |
RE: scratchin my head on velocity
Not always. A nice cloudy overcast day, and no shades needed.
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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.
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RE: scratchin my head on velocity
ORIGINAL: bigcountry 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 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....... |
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. |
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.
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