How Big?

[libbyman]

How much over bore size, can you go without leading the barrel?

[454PB]

Oversize does not cause leading, it's UNDERSIZE that causes leading. If the loaded round will chamber, you'd have to go .004" or so before it caused problems.

Years ago, I read an article where a respected gun writer (I think it was Harvey Donaldson) fired .45 ACP rounds in a 30/06. No damage was done to the rifle, the bullet was swaged down to .30 caliber in the barrel.

[Bass Ackward]

How much over bore size, can you go without leading the barrel?


Libby,

The simple answer to your question is that there is no simple answer.

When any thing you do as a reloader "creates" a condition where pressure pushes a bullet down a bore that the base obturation against your barrel, or the rifling impart more rotational force, that causes friction greater than the strength of your lube is to prevent that friction, then lead is going to melt at that point and be left in the bore. And this is why one guy swears by one lube while another curses it till his dieing day. They caused the problem and lube get's the blame.

I know a gentleman that was a clanker and competed and won in the state of Ohio a few times. He used a Ruger Super Redhawk. He shot 4" groups at 200 yards while using HTWW sized to .439 because that was the largest bullet that would chamber in his gun. His bore diameter was .429 or a full .010 less. Said he used RL7 but never said how much. This apparently worked for him.

I, on the other hand can have trouble with PB in a handgun at .001 over if I play with charges of powders that produce a burn rate where pressure comes up too fast for the sizing that has to take place. So what affects pressure? Just about everything. What lube you are using, to bore condition, bullet design, case design and capacity, hardness, and the list goes go on and on. Your mission, should you chose to accept it, is to think .... logically to produce less pressure while attaining the proper ignition for your set of load / gun conditions. This will then produce the resulting velocity that you desire. Then you can reproduce it several times and find which of those is the most accurate load.

And that is why there are no clear cut "rules" for cast and no simple answer to your question.

[Char-Gar]

IMHO you question relates to a non-issue. The chamber throat limits the size of bullet you can use. Too big and the won't chamber. If you can chamber them, you can shoot them without concern about them being bigger than groove diamter.

I regularily shoot .313 bullets down a .308 bore with excellent accuracy and zero leading. I would shoot them .314 but they won't chamber without scraping lead.

[Bret4207]

I agree with Chargar and Bass, with the following caveat- Sometimes a boolit can be too big to the point that the rifling will go deeper than the lube grooves. Sometimes- sometimes- this causes a lube failure and leading. Depends on the gun, throat, boolit design and a bunch of other mystical things. It comes down to try it and see. BTW- Steel wool removes leading if you get it.

[44man]

The only question I have is how Harvey chambered .45 boolits in a 30-06? Did he cut down the cases?

[454PB]

The .45 ACP case was held against the bolt face by the extractor enough for the primer to ignite.