Heat
of Explosion and Vihtavouri N120
This travels into an area
that is not of vital importance to some; however there are a few
misconceptions about properties of smokeless powder that I'd like
to set to rest. I have a few senior ballisticians to thank for both
reviewing and confirming this information.
Nitrocellulose based
smokeless powder requires pressure in order to sustain ignition.
It is this characteristic that helps make nitrocellulose-based propellants
safer to handle, use and store than blackpowder and many so-called
substitutes. Lacking the required pressure, incomplete combustion
occurs-- meaning a misfire or a blooper. Directly put: it is flame
out. That is why, in example, you cannot reliably shoot a sabot
out of the Savage 10ML-II without a bullet in it. With an explosive
such as blackpowder, you can. Or, you can entertain your friends
over the holidays by shooting flaming pellets out of a muzzleloader
with no sabot or bullet at all.
Contrary to some misinformation
drooled out elsewhere the sustaining of combustion has nothing directly
to do with peak pressure at all. The precise pressure that must
be maintained throughout the bullet's travel through the barrel
varies by powder. However, the rule of thumb is 2000 PSI for single
base extruded rifle powders; 5000 - 6000 PSI for ball rifle powders.
Difficulty in ignition, perhaps more correctly phrased as difficulty
in sustaining ignition with low coefficient of friction loaded-from-the-muzzle
sabots is one of the reasons ball powders are considered unsuitable
for the 10ML-II application.
Heat of Explosion
values are not commonly available for today's powders but are relevant
to the Savage 10ML-II application. Heat of Explosion is the "caloric
energy of powder substance per unit of mass." Heat of Explosion
values are recorded via calorimetric bomb tests. It varies according
to the nitrogen content of the powder and surface treatment of the
powder. A powder with a lower Heat of Explosion produces cooler
temperature propellant gas and is FAR easier on sabots and ventliners
alike-- it decreases barrel erosion as well; dramatically so.
Of the Savage-compatible
propellants I have tested, there is one standout in this regard:
Vihtavouri N120. Vihtavouri N120 has a relatively low Heat of Explosion
of 3680 KJ/kg.
That number may not
be meaningful to you, however it is significantly less than 5744,
SR4759, IMR 4227, and N110. It is also less than even slower powders
such as N130, IMR 4198, H322, Reloder 7, and Reloder 10X.
It is for this reason,
coupled with the excellent velocity, bughole accuracy, and reasons
discussed elsewhere when used with 300 gr. bullets
. . . that I believe Vihtavouri N120 is the very best propellant
you can possibly use in the Savage 10ML-II.
If you need any
help in finding this outstanding 10ML-II propellant I'm advised
that you are welcome to call Jeannie Bolda @ 630-350-1116 Ext. 106--
they are happy to help!
NOTE:
I use 55 to 57 grains, and never exceed 60 grains by weight.
I do not use heavier than 300 gr. saboted bullets, and do not condone
their use.
©
October, 2005 by Randy Wakeman
