H4350 velocity testing - velocit versus consistency

[carswellb58]

Using a LabRadar chrono, I tested 4 different lots of H4350 all with exactly the same charge and all with brand new Lapua brass. As you can see, the velocities varied somewhat. While I was tend to favor the lot with the higher velocity (Lot 5672) I do wonder if selecting the batch with the best SD (Lot 5666) will give me the best chance at tighter groups.

I'm interested in whether SD (Standard Deviation) difference is large enough to be meaningful? Or is it pretty much inconsequential?

BTW - ES stands for Extreme Spread in case you were wondering.

 

[dmoon]

I don't personally see that the speeds or SD's are different enough to be meaningful. I've seen changes as big as what you are showing over a mornings worth of shooting as the temperature and pressures change. I think I'd just load up any of them and hit the range.

 

[dsculley]

Base on this information, your true ES (SD * 6) for the loads are:

SD ES
6.5 39.0
7.4 44.4
6.9 41.4
5.6 33.6

A difference between min and max ES of 10.8.

Which of the loads did your target say was the best? That is the final arbiter for me. If it were me, I would load these again and shoot them at extended range and let my target tell me which is best. Based on the data, I would expect lots 5610, 5593 & 5666 to have similar results on target. Did the small increase in MV make a difference on target?

Interestingly, if you combine all the shots from lots 5610, 5593 & 5666 you get SD of 6.3 & average velocity of 2898. It appears those three lots are very nearly identical and could be interchanged. How much of each lot do you have and can you get more of the lot you choose? That would be a consideration as well.

Just my thoughts FWIW,

 

[Beneviolence]

Seems to me like the differences between the sampled ES would be approaching the measurement error unless you've got a $$$ setup. How much of that can be attributed to fouling buildup (or other sources) vs. powder lot variation?

 

[Barrelnut]

I'm with Beneviolence.

Did you shoot the round robin or sequential? That might affect the out come too.

How big are these lots? 8 lb. each? Or 2 lb. each?

If they are small lots, I would mix it all together and not even think about how each performs individually.