Remember the Lyman Data was based on 8" test barrels, I only have a 5" barrel. I have asked JR of Lone Wolf about getting the longer barrel for my G-29 without the ports cut into the barrel, but he said the ports are cut early on in the machineing process. I rather not hae the ports jetting the flash and unburned powders into my line of site.
The bullet's diameter will be the thing which will affect accuracy the most. 0.356" will be better than 0.355", some people like 0.357" to fill the bore...Cast bullets shoot better and lead less usually at 0.002" over the bore diameter. Therefore measuring the bore is important, slugging the barrel is the only way to know for sure.
I found the lighter bullets(90-95 grain) didn't shoot as straight, the 115 grain & up worked better.
Be aware of the sizing of the die, you can't just run it down to the shellholder, you need to adjust so it only sizes the brass down enough to fit the chamber correctly. I originally over sized the brass(used 10mm) with the Dillon sizing die. The new brass from Double Tap is sized correctly to start. You can use the barrel for the cartridge gage.
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