Cylinder throat measurements and "Springback"

[Hickok]

I understand the method of measuring the inside diameter of revolver cylinder throat by pushing an oversize lead ball through from the chamber end and out toward the cylinder face, and then using a micrometer to measure the ball. I measure my revolvers this way and also slug my rifle bores in like manner.

I have always wondered if there is any "springback" to the lead slug after exiting the cylinder throat, thereby giving a slightly larger measurement than the true diameter. Also curious as pertaining to barrel groove diameter measurements using a lead slug.

I never see this topic mentioned much, so I take it the amount may be miniscule and not worth considering. Just curious.

[newton]

From what I understand, nearly pure lead will not spring back much if at all. When you use different alloys, there is a potential for it.

I am not sure how you would prove this other than doing a true cast with chamber casting material.

[Piedmont]

Pure lead won't spring back. Harder lead alloyed will. I remember reading a story of barrel maker Harry Pope having a fellow at a rifle factory tell him his way of measuring with pure lead wouldn't work and he said, "Really? Let's see." and proceeded to show him that slugging with pure lead worked perfectly.

[Hickok]

Thanks for the replies, that answers my question!:-D

[tomme boy]

I use gold:kidding:

[Char-Gar]

I have measured the inside of sizing dies, with high quality tools that measure .0001 and then the size of the cast bullet after it was sized. The most "springback" I have even been able to measure is no more than .0001, which is not enough to matter in what we do. This was with the alloys I commonly use. Spring back in cast bullet may exist, but I discount it as any significant factor.

[newton]

I have measured the inside of sizing dies, with high quality tools that measure .0001 and then the size of the cast bullet after it was sized. The most "springback" I have even been able to measure is no more than .0001, which is not enough to matter in what we do. This was with the alloys I commonly use. Spring back in cast bullet may exist, but I discount it as any significant factor.

Good info to know. I'm having an issue with a .451" sizer and the boolits coming out at .452".