From: [EMAIL PROTECTED]
The latest comment from Andrew Lambley seems logical to
me as an explanation for the leading problems I experienced.
However, the GECO bullets I used were swaged, not cast,
and appeared to be pure lead - very soft and coated with a
waxy lubricant that was sticky to the touch. The muzzle
velocities I was measuring with my chronograph with N310
powder and these bullets were similar to 'factory' 38 Special
target wadcutter ammunition tested over the same instrument
- and the cases were obturating properly against the chamber
walls (nice, clean brass, not much 'smoking' of the case
mouths). This would seem to indicate adequate pressure was
being generated but, of course, gives no indication of the
pressure/time curve for my loads and so Andrew's explanation
of the problem could still have applied. The hollow base
bullet's journey from cartridge case to barrel is quite a
rough one. Once it has left the case it will upset to fill,
or try to fill, the chamber ahead of the case mouth (357
Magnum chamber). It will then be swaged down to fit the
chamber mouth and will then negotiate the cylinder/barrel
gap (0.005" in my revolver) and be expanded again as it
enters the barrel forcing cone where it will now be swaged
to fit the barrel. Lots of opportunities for lead to be
shaved off.
I must admit that, having experienced the leading problem
with target loads, using a variety of purchased swaged
bullets - and some cast ones too - I did not push the
hollow based wadcutters any faster with N310 and so I don't
know if that would have solved the problem. I didn't really
want my target loads to be any hotter than the ones I was
producing anyway as they nicely duplicated the factory
wadcutter performance. I had no troubles at all with
Silvalube 158 grn round nosed lead bullets - these bullets
seemed to be much harder than the GECO's.
I accept that the problem could still be attributable to my
revolver but it was not limited to just that gun. As I
stated, I got the same problem with my friend's 586 and it
disappeared when I changed to Bullseye powder in both guns.
This leads me to believe that the cause was a property of
N310, not of my gun. Apart from the leading, it was a superb,
clean-burning powder, easy to use in every way. I still have
some!
The term 'velocity leading' is a carry over from the days
when I used to read American reloading manuals and Gun Digest
etc. It refers to the streaks of lead deposited in the barrel
as the bullets pass through it. Jacketted bullets leave
streaks of jacket material in rifle barrels too, hence the
industry that has built up to market cleaning fluids that
will 'safely' remove this fouling without damaging the rifle's
barrel material in the process. The mechanism for this
deposition could be simple (?) friction as the lubricant
breaks down. It was assumed by all in those days (1950'/60's)
that this process was related to the velocity of the bullet -
as well as to its dimensions and other physical properties
such as hardness, surface roughness of the bore etc.- and it
would normally be expected to be most obvious where the
velocity was greatest, i.e. near the muzzle end of the
barrel.
I am rambling again!
Richard Malbon
Cybershooters website: http://www.cybershooters.org
List admin: [EMAIL PROTECTED]
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