4198 something to consider

[JerrySharrett]

A companion thread discusses the new SPP210 powder. Also, recently there have been comments made about 4198 and its lot-to-lot inconsistency. Look at the picture below and you can see part of the problem of this inconsistency. This photo shows why there would be further complications if volumetric measures are used by their selves.

As you can see there are four different specimens and three different grain sizes.

Left to right-H4198 c. 1997, SPP210, IMR4198 from an about 1980 lot, then, IMR4198 from a later lot. IMR lots are consecutive numbers not date coded.

(Sorry about the framing-I shot this in the dark to kill the glare off the note card)

If you click on the image it will enlarge.

 

[Larry Elliott]

I've always been led to believe that the energy of smokeless powder is per weight, not per volume. As Jerry shows it would be hard to have any of these powders produce the same weight of product if the same volumes of each were used. If one determined the volume of each powder that produced the same weights they may well be very close in energy measured as velocity.

Measuring irregular solids by volume only works well through sheer luck and the grace of God IMHO.

 

[Andy B]

I agree, Last season was my first time running into a noticable velocity change. I left my measure as set from the previous charge. Threw a charge of the new lot of powder on the scale and found .4 gr. difference. This was enough to notice something wasnt right. It now has become my practice to compare each new lot of powder and adjust as needed. One more thing for the to do list that works and saves time. The chronograph proves it.

Andy B