So I slugged my bore

[gray wolf]

I have been taking it for granted that my 45 a c p barrel was .451.
So I have been sizing to .452. Well I took a soft lead bullet and drove it down the bore muzzle first. I got a nice clean bullet out the other end.
I put the calipers to it and it measured .450. I have .451 and .452 sizing dies.
Have I been using the wrong die? should I be using .451 for the .450 bore?
What can happen if I am .452 in a .450 barrel??
I get leading in the pistol one inch from the chamber. I thought this meant that I may be undersized. but I a .002 over bore size so what up with this?

[45 2.1]

The best thing to do is to try the 0.451" boolits and see what happens.

[Bass Ackward]

GW,

There is a BIG misconception that going larger will ALWAYS prevent leading. In fact, it can be just the opposite and you can actually cause leading sooner if you have a poor lube or the wrong hardness bullet either too soft or too hard.

By the same token, sizing to bore will help prevent galling, but not if you gas cut from not sealing cause you just blew the lube off your bullet.

So it depends on how and where your leading begins. Proper diagnosis will yield the correct path. Essentially it's what kind of leading are you getting. Gas cutting? Or galling?

Bob nailed it for you. Since you got the sizer, ask Professor Gun what he thinks. My bet is that the leading will disappear and in this case, your accuracy is going to improve.

[gray wolf]

OK the last time I shot the bullets were a little soft and sized to .452.
After 10 rounds I could see a heavy build up of smeared lead just in front of the chamber, the front half of the barrel was OK. The best way I could say it was a heavy smearing of lead.
It brushed out with a dry brush and a patch. This happened after every 10-20 shots and I had to stop and clear the lead out.
Here is what was different- I shot a round nose bullet instead of the #68 S W C, The lead was a little softer but not pure. the lube was about the same as I always use.
Like I said the lead was in heavy gobs just in the front of the rifling, heavy smear.
Is this what you call galling?

[45 2.1]

Try waterdropping your boolits straight from the mold. A little antimony and a trace amount of arsenic are required for your boolit to harden (allready present in wheel weights even if cut with soft lead). I shoot 45 ACP 230 gr. RN this way and have excellent results.