shooting on a shoestring
06-06-2009, 10:18 PM
I've been following the thread on case neck tension - good stuff. I got excited b/c I've got a NMBH in .357, 4&5/8 barrel that I've not got to group well. I haven't paid any attention to case neck tension on my .357s, so I decided it was time to investigate.
I have 2 sets of 38/357 RCBS dies. Both are carbide. I found one sized my Winchester cases to .355" inside diameter and the other to .354". Upon further inspection the smaller is marked "77" on the top of the die, the larger "79".
I wasn't aware there were different sizes of sizers to be had.
Incidently, the expanders from each set both measured .355" O.D.
After seating and pulling some Group Buy 175 gr KSWC cast air cooled WWs, I discovered the boolits were getting sized by roughly 0.002". The mould drops the boolits 0.359 @ 90 degrees to the parting and 0.357 at the parting. The boolits were run through a 0.359 die (which really measures 0.359) and lubed with Felix Lube, and they were not sized by the die. However after seating and pulling them, the diameters were 0.357 to 0.355, still out of round, but smaller. I didn't expect that.
The cases were sized with the smaller die w/o using the expander, a couple were sized with the larger die w/o expander, and then some were sized using the expander. All sized my boolts to .357 x .355.
Looks like its time to go to harder boolits, and perhaps I should lap the mould to improve roundness.
Perhaps my grouping problem is not the Blackhawk, but its fodder.
I have 2 sets of 38/357 RCBS dies. Both are carbide. I found one sized my Winchester cases to .355" inside diameter and the other to .354". Upon further inspection the smaller is marked "77" on the top of the die, the larger "79".
I wasn't aware there were different sizes of sizers to be had.
Incidently, the expanders from each set both measured .355" O.D.
After seating and pulling some Group Buy 175 gr KSWC cast air cooled WWs, I discovered the boolits were getting sized by roughly 0.002". The mould drops the boolits 0.359 @ 90 degrees to the parting and 0.357 at the parting. The boolits were run through a 0.359 die (which really measures 0.359) and lubed with Felix Lube, and they were not sized by the die. However after seating and pulling them, the diameters were 0.357 to 0.355, still out of round, but smaller. I didn't expect that.
The cases were sized with the smaller die w/o using the expander, a couple were sized with the larger die w/o expander, and then some were sized using the expander. All sized my boolts to .357 x .355.
Looks like its time to go to harder boolits, and perhaps I should lap the mould to improve roundness.
Perhaps my grouping problem is not the Blackhawk, but its fodder.