From: andrew, [EMAIL PROTECTED]
Temperature is irrelevant, it is thermal capacity that
matters. Thermal capacity is the quantity of heat energy
required to affect a temperature change. Look at it this
way; the heat from a candle flame is around 1000 degrees
Centigrade, more than enough to give severe burns and yet
you can pass your hand through the flame and not feel a
thing. Conversely you can spill just a little bit of
molten wax that is at less than 100 degrees get a
serious burn. Two other examples of thermal capacity
versus temperature involve ice; drop an ice cube into
boiling water, does it melt straight away? If you are
still in doubt treat yourself to a baked alaska where you
actually cook an ice cream desert in the oven.
You might also want to try putting a plastic wad under a
bullet and seeing how much that melts.
What has pressure got to do with anything? Are you saying
that if I pressurize my lead pot that I can cast at a
lower temperature? I dont think so. Yes, if you put
enough pressure on a solid it will flow like a liquid but
it is not molten.
I presume your reference to HPBT bullets has to do with
their bases being part of the jacket. The reason why
they are considered more accurate is that the hollow
point puts the centre of mass further to the rear so
helping with stability and the boat tail reduces drag,
helpful for long range shooting. The boat tail can
cause stability problems at short range, below 300
yards, though which is why makers of match bullets
like Berger offer both boat tail and flat base
versions of the same bullet. Also it is easier to get
an accurate base by forming the jacket from the base up.
Fire a round of 7.62 and see how much lead is in the
barrel, you wont see any. Examine the base of a fired
bullet you wont see any evidence of melting. And BTW,
The melting points and thermal capacities of lead
alloys and copper alloys are not sufficiently
dissimilar to make any difference in this application.
--
I spoke to Rob Leatham about this, I think it was
at the Sportsman's Team Challenge. I asked him why
he used JHPs in 9x25 Dillon, he told me the FMJ
bullets melted at the base. A lot of people
thought it was to get a shorter OAL but I am
merely repeating what I was told. I personally
think they do melt, you can easily put the centre
of mass to the rear of an FMJ bullet, but they
still use HPBT. Perhaps it has to do more with
that you can get a more consistent base with
HPBT than FMJ. What we're talking about here is
not wholesale melting, more a very slight change
in the base of the bullet which can affect
accuracy.
Steve.
Cybershooters website: http://www.cybershooters.org
List admin: [EMAIL PROTECTED]
___________________________________________________________
T O P I C A The Email You Want. http://www.topica.com/t/16
Newsletters, Tips and Discussions on Your Favorite Topics
