I am using the Saeco 315. I'm not casting them myself at this point. I'm buying them from Meisters. The forward bands measure 0.310 and the rear band measures 0.312. So, other than the PITA part of lubing without using my sizer, I can try that bullet unsized to see if things improve. My first session at the range had a significant amount of vertical stringing.
The throat is 0.400 long. So, I would have to seat the bullet longer than the magazine would permit to engage the rifling. When I measured the chamber casting, the groove diameter actually measured a tad larger than the throat at 0.3125. I probably should do another casting and pay closer attention to any tape in the throat leading up to the start of the grooves. This stuff is all new for me and sometimes my reading on the subject lags behind my efforts in the shop. This is the first time I've cast a chamber and curiosity was driving things as much as the need for info.
Last night I looked at the various bullet styles offered by NOE. They used to offer the 315, but I did not see it. A friend has one of their molds in that bullet. He recommended I try that bullet which is why I ordered 500 from Meisters. A few articles I've read and some posts here indicate that a bore rider might be a wiser choice. With 0.310 front lands on the 315 Saeco, I would estimate it at about 0.002" over the bore size if my grooves are actually 0.004". So, I don't think it fits the definition of a bore rider. But I have have no feel for this so might be wrong. Yes, I realize I need to slug the barrel and perhaps make a casting of the muzzle area. I also need to put a small hole gage in the bore. Time has been at a premium lately, unfortunately. So, I'm a little ahead of myself, perhaps.
Sizing them at 0.311 was not a disaster at our local match. Shot a 38 and the am pretty sure that the two flyers (they landed a good foot over the target.at 300 yds) were because I forgot to reset my scope. But this is a gong match with 6", 9" and 12" plates at 100, 150 and 200 yds respectively and a pig at 300. So, these are pretty big targets which removes the requirements for MOA accuracy. I really want to make this rifle shoot as good as possible. It was never rebarreled after WWII and still has its original SA 1921 marked tube.
Not looking to push these hard. Accuracy out to 500 yds is the goal. Nominal 1600 fps is where I'd like to be. I'm using gas checks, but in reading some other articles, it appears that GCs might not be required at these bullet speeds.