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denisbeaudry
After inspecting close to 500 different cast BBT’s from .22 to .357 I’ve noticed some irregularities . Now it got me thinking that maybe using a bottom punch /Boattail punch might help getting the tail end of the bullet more uniform . Is there such a devise already out there that would help clean up the bases ? I’ve tried different temperatures ,mixes of lead/ tin and they all have a slight smear where the sprue gets cut off .
denisbeaudry-
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rsterne
Smears due to the sprue cutoff are common to most cast bullets, in my experience…. It is the most destructive to accuracy in a plain base design, where the actual part of the bullet that exists the crown is asymmetrical…. Gas check designs (without the GC), by virtue of the fact that the last part to leave contact with the rifling is the last drive band (which is accurately moulded), rather than the bullet base, are more forgiving, and that is the reason that they are preferred by many airgunners…. The rebated boattail I use for my BBTs shares that feature with a GC bullet…. one of the reasons I chose it…. an accurately moulded drive band, distinct from the bullet base….
If you are using a 2-cavity mould, you can shear the sprue by (gloved) hand, instead of using a mallet, and this helps reduce the distortion of the base from cutting the sprue…. I find that 4-cavity moulds are too hard to open by hand, so I have to use a mallet…. Another thing which I do which helps a lot, is to wait until you see the last sprue harden (a series of concentric circle forms as it hardens, and sometimes a dimple in the middle)…. and then wait 5 seconds before cutting the sprue…. a count of one, one thousand, two, one thousand, etc…. If the mould is opened when the lead is still too hot (soft) the distortion is much worse….
I am not aware of a boattail punch available, and of course they would be different for every BBT design….
HTHs….
Bob
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