.309 vs .310

[AJC1]

Fired up the pot and ran my first heat cycle after baking the mold twice for heat cycles. Made a pile of scrap and had 20 keepers. My eye is very critical right now so any flaw sent them packing. Did some measurements captured in the picture below. I believe .310 or .311 would be no issue. I could probably eek out .312 with PC and may try that when I start project arasaka.

 

[GooseGestapo]

Add some 95/5 lead free solder to your mix. The added tin will make bullets fill out better.

 

[Thomasss]

Yep, but you should measure them again after they sit for a day or two. I hate to say this but most of us
have several different sizes because diameters do change over time, due to mix and heat and time of year casting, etc.

Take your best guess. After you shoot some, you might be very happy and then again
you may think, hear or read. I wonder if it would improve if I did this???

Use the Force Luke, the Force...

 

[BJung]

A cast bullet should be .001" larger than the bore size. You can guess but slugging your barrel takes out the guessing. Find some pure lead like some airgun pellets and pour them into your bullet mold. Obturate it a bit but hammering the cast bullet tip with the base on the concrete floor. Then, cut the bullet in half, lube it well with something like Imperial Wax and slug the lead piece through your barrel. Measure the slug with a micrometer and add .001" Another suggestion which I haven't tried yet is slugging the chamber and part of the bore. This is suppose to be the ideal bullet diameter - so I've read. I tend to age my cast lead ingots because the hardness changes and stabilizes. The other option to me is to water drop every bullet and shoot it while fresh. If you're hunting, file off the tip and remove the temper of the tip with a torch while the shank is in ice water. You probably know this but I'm just posting how I'd do it.