Choosing a cast size

[Rover]

How do I choose what cast size for my 30cal, I have a 308 and about to purchase my first cast, is a .309 the one i want

[tomo]

I am a newbie and have .309 for 30cal too.

A good guy in this forum taught me that the size should be increased a little bit if you find inaccuracy.
I think .309 is nice for first try.

[fredj338]

Cast size will vary with alloy & casting temp. Bigger is better, so even 0.311 can be sized down to 0.309-0.310".

[tomo]

Hello fredj338,
If I can have only one mould for 308, should I choose 311 instead of 309 and have several size of sizing dies?

[dh2]

I started with .309 for 30 cal. it did not take long and I am sizing .310 accuracy inproved

[JWFilips]

I too, would suggest a .311" boolit

[ShooterAZ]

.309 will probably work OK, but.310 or .311 will most likely be the best fit and best accuracy.

[popper]

Mine drop at 312-13 but I size down to 310. The Lee sizers aren't too accurate and alloy/temp make a difference.

[dondiego]

Just because the mold model number is listed as a "308" doesn't mean that the finished cast bullet will come out at that size. As mentioned, the alloy and temp play a role in the diameter.

[Maximumbob54]

As long as the bore is .308" then I prefer them to drop at least .311" and then I size to .310" and that's been the best for me. Also, I like the bullet to start kissing the lands enough that if ejected they leave some teeth marks on the bullet but don't pull the bullet.

[mdi]

http://www.lasc.us/Fryxell_Book_Contents.htm New caster's or lead bullet purchaser's text...

[gnoahhh]

Ignore bore and groove diameter when selecting a bullet size. Determine what the throat diameter is and size to as close to .0005" (that's half a thousandth) under that you can. Right often that'll mean a bullet .3095-.310". A nose diameter that matches the bore diameter to ride sweetly on top of the lands is a big help too. (bore diameter must not be confused with groove diameter here) Seat so as to kiss the bullet into the leade. Refine your sizing and seating methods so that A) the bullet isn't damaged in the process, and B) the bullet is seated dead nuts straight. Little variations you can get away with in jacketed bullet concentricity will trip you up when it comes to cast bullet accuracy. A cast bullet absolutely must be started into the rifling straight, unless so-so average accuracy satisfies you.

[Yodogsandman]

Rover, Welcome to the site! Are you confused yet? There's a lot of good information already posted above. We all seem to arrive at the same solution a different way. Get a bullet sized for your rifles chamber and throat. The bullets bands should be sized to just under the chamber size. A good way to get "close nuff" is to measure a fired cases inside neck diameter. The case must be fired from your rifle. The best way is to do a pound slug of your chamber throat and measure that. There's a sticky here that walks you through the process.

http://castboolits.gunloads.com/showthread.php?218414-FYI-This-is-how-I-do-a-pound-cast

[MtGun44]

Good rule of thumb is .002 to .003 over groove diam for rifles.

Bill

[Thumbcocker]

I start with .311 boolits in .30 cal. rifles and go down if needed.

[JWFilips]

Good rule of thumb is .002 to .003 over groove diam for rifles.

Bill

Yes MtGun44 hit it on the head! Good info in that!