IMR 8208xbr temp/fps

K

Kim Merrill

Guest
Here are my results of average fps at different temperatures.
LV, 20" Krieger, Bat, Bart 65bt.
CEM M2 Chronograph
Acculab Vicon 2/100th scale
Thermo-Hydro meter

31.50gn 8208, avg 6 to 9 shots at each temp.

67 deg 93% 3387
64 deg 98% 3386
59 deg 63% 3398
51 deg 50% 3342
46 deg 49% 3341

As the days get hotter I will collect more data.
 
ES and Lot Numbers

I forgot this one on my first post;
73 deg 80% 3394 ES 11

67 deg 93% 3387 ES 17
64 deg 98% 3386 ES 17
59 deg 63% 3398 ES 17
51 deg 50% 3342 ES 33
46 deg 49% 3341 ES 44

Mike, Is one 9 shot group worth looking at and 3 three shot groups not worth looking at? I do not understand the logic.

Dave, Lot number 4773
 
Kim Merrill said:
I forgot this one on my first post;
73 deg 80% 3394 ES 11

67 deg 93% 3387 ES 17
64 deg 98% 3386 ES 17
59 deg 63% 3398 ES 17
51 deg 50% 3342 ES 33
46 deg 49% 3341 ES 44

Mike, Is one 9 shot group worth looking at and 3 three shot groups not worth looking at? I do not understand the logic.

Dave, Lot number 4773
Click to expand...
es and sd are of value when a large data set is used.
in a 3 shot group...not much use.
a 9 shot group( or a compliation of 3x3) has some value.
yes in shooting we typically look at 5 and 10 shot data, but the value/math is based on a large sample size(1000...)

my opinion is that we use 3 shots cause it it aint one hole at three, five will not make it better. the es/sd on a three shot string has little statistical value. if a load works, shoot 5x5 and use that sd/es.

mike in co
 
Mike,

I don't think your right, I'm not a math whiz, but I think the SD & ES of a three shot group are very valid statisticlly.
 
If I remember my statistics right,

the sample size required for a SD to be considered valid is dependent on the value of the SD. For a group of 3 shots, SD for that group would have to be right at 1.5 fps for it to be valid at the 95% confidence level. Of course, assuming that level of accuracy does not take into account that a 1.5 fps SD is only about 1/10th of the uncertainity of the original measurements of velocity for each of the shots for many chronographs.

And, no, I do not remember enough statistics to calculate what sample size is required for a particular group size, for a particular confidence level, for a calculated SD, given a +- uncertainity (often at least 0.5%) of measurement. :confused:

Someone please correct me if I "mis-remembered" my statistics. :)

Glen
 
Wouldn’t be much simpler to load the powder in the case, seat the bullet, shoot it and see how it groups in 3/5 shot, then go back and put more or less powder in the case and or seat the bullet in a little or out a little, rather than go to MIT and get a math graduate to come to the match with you so he can figure out if you need to put a four barrel carburetor or a supercharger in your loading to get that right MPH for the bullet to reach the target?????:D
 
The unstated topic was not accuracy. It was how the new powder varies with temperature. That was, more or less, the stated goal for 8208XBR.
 
You are entirely correct.

I was off-topic when I made my "tongue-in-cheek" reply on the math behind the significance of a SD. I was following up on what Mike had said earlier because some didn't believe him that a 3-shot SD was a pretty useless calculation. Tom reinforced my point that we can do all sorts of things to measure and/or calculate or add all sorts of bells and whistles to shooting. But, why should we if it's not adding anything worthwhile?

Glen
 
New FINDINGS

SGJennings said:
The unstated topic was not accuracy. It was how the new powder varies with temperature. That was, more or less, the stated goal for 8208XBR.
Click to expand...

I should have said, It appears that this new powder shoots a little slower at cooler temperatures with low humidity than is does at warmer temperatures and higher humidity.

Kim
 
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