High SD's with PC vs traditional lube

[xacex]

I know that SD's are only one value to look at when reloading, but this interesting. My 223 loads with varget were running a SD of about 16.5 with traditional lube, and into the 30's with pc. The fascinating thing with this is the pc boolits shot a tighter group, and were a smidge faster in velocity. Normally I would say that load is no good because of the high SD, but in this case I don't know what to make of it. There is about 50fps difference between the pc and traditional lubed boolits. Both sets were loaded on the same machine, same powder drop, case, primer ect. The only thing I changed while reloading this set was the boolit lube/coating.

[popper]

I do a histogram instead (total set of the velocities) looking for end points (ES) and other abnormalities. Over several loading/shooting sessions, maybe with (noted) changes to show a trend or pattern. So much more information at a glance than a silly number like SD. Save the SD for production QC where it belongs. Excel or it's clone does a fine job of plotting the data and keeping track of data sets. Who knows, you could have had 2 fps peaks of very good consistency and SD can't see it!

[xacex]

Good point Popper. I will export the data into excel and see if there is a trend. I know some factory loadings have SD's that high as well, but I know that consistent numbers mean consistent groups that are calculable. I just don't like seeing the trend between PC, and lube because it clicked in my head as not that desirable and a negative towards PC application. I did some testing between powders, and different colors of PC in 9mm and saw some interesting things as well. HF black gave lower velocity numbers, but also lower SD. May be because of the flat causing more friction and alleviating some of the pressure differentiations.

[hickfu]

Hmmm, maybe I should have loaded up more rounds... I loaded 5 rounds each of normal cast boolit and powder coated for my 45-70. I made sure that all 10 projectiles were EXACTLY the same weight at 425.7gr as well as the cases and then the powder... I was going to run them across the Chrono to see if there was any difference in fps between PC and lubed. I cant wait to test them out..

Doc

[popper]

Might want to keep track of order of firing to see if lube/coating trends up or down in fps..

[xacex]

Different day, different weather conditions , and a different range with another 20 round over the chronograph.Today I received the results I expected from the numbers. I guess it was a fluke with that one group. I am going to try a larger caliber, and see if there is a higher SD with those as well. This was testing a load that was posted here that shot a small group in 223. Tried several charges and it is a no-go for me. I have to say, outside of jacketed 223 had been a challenge.
I have to shoot some j words today to make myself feel better. Then, more cast 300 Blackout!

[popper]

more cast 300 Blackout

Now that is fun. Excel will calc the SD for you also. Wondered how sun and not shooting right over the sensors affects the numbers.

[xacex]

Popper, I cheated. My chronograph just hooks into my smartphone, and calculated it for me as I am shooting. From what I understand there is an error in the excel SD formula that need to be corrected before you use it for SD of speeds. Honestly I do not know what the error is I just read about it somewhere a few days ago when I was looking at putting together an excel graph for this.
I did get out for a few, and shot several MOA or near MOA groups with jacketed to confirm something wasn't wrong with the rifle or scope.