It will depend upon the hardness of your alloy, the softer your alloy the less pressure is required for adequate bullet obtuation to fit the bore preventing gas cutting and resulting leading.This is a question for you cast shooter's..........As a general rule do cast bullets sized .432 generally shoot the best from your Ruger revolvers?
I agree with you. With close to 50 yrs of reloading behind me, I have discovered that oversized bullets do not add to accuracy.Here's some basic "Revolver 101" info. Cylinder throats regulate the size of the bullet when it exits the throats. In other words ... bullets that are larger than throat diameters will get sized down to the same diameter as the throats, therefore it is fruitless to use bullets that are larger than throat diameter. If bullets are slightly smaller they will bump up in diameter (obturate) when pushed by chamber pressure and will be "sized" to throat diameters.
All barrels in US made revolvers conform to SAAMI specifications of +or- .0005". For 44 cal revolvers, that means bore diameter will be .4285~.4295" or an average of .429". Cylinder throats should be .430".
Assuming proper throat diameter of .430", the optimum lead bullet diameter will be .4295 to .430". Again, slightly smaller bullets will bump up in diameter to .430", assuming they are the proper hardness and are matched to chamber pressure.
Lead bullets need to be delivered to the forcing cone slightly larger than bore diameter so they will form a tight seal between the bore and bullet. If the throats are .430", bullets are sized to .4295~.430", and the hardness of the bullet is correct, the bullet will enter the forcing cone at just the right size for a good seal.
What happens when bullets are sized larger than the throats? Four bad things happen starting with chambering. If bullets are larger than the throats, cartridges will not chamber properly because the larger bullets won't enter the throats. The second bad thing is chamber pressure. Common sense ... forcing a large object through a smaller hole will increase chamber pressure considerably ... the larger the bullet, the more chamber pressure will elevate, which could result in over pressure conditions even with "middle of the chart" loads. Next is "endshake damage". When bullets are too large, chamber pressure will force the cylinder to the rear with way more force than normal. Even a light target load with an oversized bullet will push the cylinder back with a lot more force than a full power magnum load with a proper sized bullet. Eventually this "jack hammer" effect from endshake will cause undue wear on the cylinder's ratchet column and the frame's recoil shield. When endshake gets excessive, the cylinder may unlatch when fired and cause a dangerous situation. Last but not least ... the excessive lead from an oversized bullet has to go somewhere. Some may exit the B/C gap (gap spitting) but most will end up in the bore in the form of bore fouling, which in turn causes accuracy to degrade.
So in summary ... there are absolutely no advantages with using lead bullets that are larger than .430". There are four distinct disadvantages.
There's a document in the Forum Library, "Lead Bullets and Revolvers" that has much more detail. Click on this link to download the PDF: http://rugerforum.net/library/19869-lead-bullets-revolvers.html