hello ,
i was reading some posts regarding the hardness of the castboolits used.
most of them was trying to get the alloy harder by dropping WW in cold water , age hardening and different additives.
i do believe these "hard cast "boolits have a place in reloading , if one is a commercial caster and the boolits have to be shipped
the hardness will help to get the boolits undeformed to the customer.
another reason would be if one shoots these boolits at high speed [ read high pressure ] naked and lubed .
the soft alloys would loose grip and skid through with no rotation because they would be to soft to firmly hold the rifling.
but....
we are no commercial casters , and we don t shoot our boolits naked and lubed .
we paperpatch our boolits !
i am very sure that our paperpatch follows the rifling perfect if the patch is firmly compressed
i have done some experimenting with different coresizes in the 6,5x55 mm cartridge , the rifles in this caliber have a fast twist.
my alloy of choice is a pure lead with some tin mix , i think the BHN would be somewhere about 8 or 9 BHN .
this leaves me a soft and ductile core that i run through my sizer ... 0.264 , thats full diametre for this caliber.
then i wrap them twice in chainbar printerpaper , and when they dried i run them through the same sizer again.
the patch gets "ironed" really thight to the core this way and is more than capable to grip the rifling.
now for the ductile part , wich is a great bonus in my opinion.
cores in these soft alloys are easily bent by hand , but wil not tear or break , one could twist a circle with them if wanted .
so , when the primes fires and the powdercharge ignites there will be a sudden pressure spike.
our boolit has a certain mass and due to inertia it doesn t want to move instantly , the base of the boolit wants to move faster than the nose , and will continue to do so as long there is pressure behind it.
this leaves the conclusion that the soft boolits will deform under pressure .
this deformation can only be in diametre and is restricted by the barrel , wich is exellent for our purposes.
the boolit will form itself to the barrel and rifling under this pressure , and will continue to do so untill it leaves the barrel.
our very compressed paperpatch is though enough to follow the rifling and not skid through it , and is assisted by the fact
that the boolit grows in diametre thus is pressing hard against the walls of the barrel for an exellent gassealing .
to a certain point this thinking would suggest that the bigger the pressure behind the boolit is , the harder the boolit
will press against the walls in the barrel .
so , now the speed-limit of this bullet will only be restricted to the point that our heavily compressed patch would loose its grip
on the rifling and skid through.... and this is a very strong patch .
oh... one more thing
if our boolit is deformed and this deformation is restricted [ barrel-walls ] our boolit material gains strenght , because the molecules
of our alloy get compacted together...
don t know if i put that correctly , in dutch language i could describe it better ...
what would you say .. am i thinking in the right direction ?