Kevin Tinny
12-12-2018, 08:48 AM
Hello:
John Bly modified three 58 RCBS Bagdon style minie moulds for me to see if a larger than stock sprue plate hole and the 54 version's .240" meplat would improve 58 casting results.
I was having 10 grains of weight range with the 58 and 3 grains with the 54.
The only thing that seemed different was the sprue plate hole and resulting meplat.
We have used three modified 58's and ALL with the .240" meplat, which John achieves by cutting back the blocks a bit, have shot as well or slightly better than the stock one.
John also shortened the plug tip the same amount as the nose was shortened.
Casting the .240" meplat Bly version produced a significant improvement in the weight range. Apples-to-apples, the 10 gr range with .170" meplat shrunk to two grains with the .240 meplat! So, it seems the size of the meplat matters, at least for casting weight uniformity. Casting w 775 degree pure lead using Lyman dipper, not a bottom feed pot.
Anyway, first mould cast(ed) great, second cast great for me, but when a friend used it with good accuracy results, the mould opened stiffly at times and made bullet dropping erratic. I sent him a third one. It cast well and shot well for his first batch, but the next day IT started getting balky. We had tried everything to stop the stiffness with no improvement.
Well ... turns out the HANDLE joint BOLT on the RCBS HANDLES was slightly loose! Simply tightening it solved the opening stiffness and bullet dropping issues.
Fifty years of casting and I didn't think of that!
Thanks Papa Lou.
Regards,
Kevin
John Bly modified three 58 RCBS Bagdon style minie moulds for me to see if a larger than stock sprue plate hole and the 54 version's .240" meplat would improve 58 casting results.
I was having 10 grains of weight range with the 58 and 3 grains with the 54.
The only thing that seemed different was the sprue plate hole and resulting meplat.
We have used three modified 58's and ALL with the .240" meplat, which John achieves by cutting back the blocks a bit, have shot as well or slightly better than the stock one.
John also shortened the plug tip the same amount as the nose was shortened.
Casting the .240" meplat Bly version produced a significant improvement in the weight range. Apples-to-apples, the 10 gr range with .170" meplat shrunk to two grains with the .240 meplat! So, it seems the size of the meplat matters, at least for casting weight uniformity. Casting w 775 degree pure lead using Lyman dipper, not a bottom feed pot.
Anyway, first mould cast(ed) great, second cast great for me, but when a friend used it with good accuracy results, the mould opened stiffly at times and made bullet dropping erratic. I sent him a third one. It cast well and shot well for his first batch, but the next day IT started getting balky. We had tried everything to stop the stiffness with no improvement.
Well ... turns out the HANDLE joint BOLT on the RCBS HANDLES was slightly loose! Simply tightening it solved the opening stiffness and bullet dropping issues.
Fifty years of casting and I didn't think of that!
Thanks Papa Lou.
Regards,
Kevin