How large a diameter?

[jski]

I'm reloading for my .30 Carbine Blackhawk. Of course its diameter is .308. Now, I've been told many times and repeatedly that I should use at least a .309 diameter when using cast bullets. I've also been told many times and repeatedly that I should be able to easily insert the bullet into the forcing cone at the breach of the barrel. The problem is that .309 bullets do not easily fit into the forcing cone, lest I use a hammer.

So which of the 2 pieces of advice should I go with?

[Yodogsandman]

You should pound slug your barrel with a pure lead slug and measure to find out what YOUR barrel measures. The boolits should fit your revolver cylinders tightly. The boolits should be .001"-.002" over YOUR barrels groove diameter and fit tightly in the cylinders.

[runfiverun]

.310..

[gwpercle]

The Lyman Manual shows them sized .308 in their data.
If you have both .308 and .309 try them and see what your gun prefers.

My 1903-A3 Springfield in 30-06 can't tell the difference, For years I sized them .308 like the old Lyman manual said to. Read how this was sooooo wrong, bought a .309 sizer and guess what , that dumb rifle shot just as well with .308 as with .309. But I gave the .309 a sporting chance, it just didn't perform like "they" said it was going to.
Gary

[jski]

With the headspacing at the case mouth and the tightening of the cylinder throats, I was forced to push the .309 bullet deep into the case ... maybe too deep ... to get it to seat properly in the chamber. It would certainly constitute a compression load.

I used the 50 .309 diameter bullets I had and called Montana Bullet Works and changed my order to .308.

[runfiverun]

wow.
I actually size to....312 for my 30 carbine revolver.

[rhemcla]

I size to 0.311" for all my 308 Win's and 300 blk's. I did notice better accuracy over .308 and 309"

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[badgeredd]

I'm reloading for my .30 Carbine Blackhawk. Of course its diameter is .308. Now, I've been told many times and repeatedly that I should use at least a .309 diameter when using cast bullets. I've also been told many times and repeatedly that I should be able to easily insert the bullet into the forcing cone at the breach of the barrel. The problem is that .309 bullets do not easily fit into the forcing cone, lest I use a hammer.

So which of the 2 pieces of advice should I go with?

Perhaps you are misunderstanding what some call the "forcing cone." In reality your bullet should fit the chamber throat in the cylinder. Some Rugers have a tight throat which doesn't allow a cast bullet of adequate diameter to slide into them. Some throats vary in the same cylinder. GENERALLY, a bullet .002" larger than the barrel groove diameter is best, but that is not a hard rule. I have a revolver that has throats that are .005" larger than the groove diamet but I size the bullets of SOFT alloy .002 over the groove diameter. Alloy hardnes and bullet length can also affect what size works best in YOUR gun. I personally would start with a bullet .002" over groove diameter IF it will chamber.

[jski]

Badgeredd, I would have needed a hammer to push that .309 bullet thru the cylinder. That can't be the better size v. the .308 !

[jski]

BTW, this is the beastie in question:

189152

As you can see it's gas checked and, as you can't see, it has a 22 BHN. I'd like to push the bullet into the case up to but not including the grove. That's not possible with the .309.