I made a pure lead piece with driving bands to use when I slug the barrel of a new 470 Nitro Express rifle that I expect to receive soon.
Do I need to lube the lead before driving it through the barrel.
My plan is to use a wood dowel or brass rod to drive the lead piece from breech to muzzle.
Afterward, I will do a set of measurements that should give me enough information to specify the major and minor bore diameter measurements which will allow me to finalize designs for my own bullets.

I have found that lube helps. Additionally, I would recommend using the largest (and I use wood) dowel that will fit down the barrel without resistance. Using too small a dowel tends to drive make a depression in the lead, and that can skew the measurement...

Use a steel dowel. After you've firmly stuck (and broken) a wood dowel you will have learned your lesson. Not being a smart ass. Steel is better, it doesn't break and if the proper size and used correctly it's better. Brass would be fine if you can find it in the correct size.

I always put a little lube on the bore or lead slug when doing this.

Bob; Yes lube your slug and run an oil soaked patch through the clean barrel. Personally I would drive a slug in from the chamber about an inch and drive it back out from the muzzle, then drive one in the muzzle and drive it out from the breech. 7/16 Hardwood dowel should be fine, cut into 6 inch pieces and grind/ file ends square, 7/16 brass probably even better if you can get it. I couldn't bring myself to hammering on a steel rod, NO MATTER HOW MANY TAPE BANDS I HAD WRAPPED AROUND IT, in the barrel of my new 470 NE, it just doesn't seem right!
The barrel should be choked to muzzle end and if you drive slug completely through you will only get a measurement of the smallest diameter. A bullet .001" larger than the groove diameter just infront of the leade should be a good starting place. A 50 cal lead ML ball should be adequate for a slug too. YMMV

If a steel rod has to have tape bands wrapped around it then it's the incorrect size....too small.

I think I know WHAT you're smokin'.

I would lube it. and I would use a brass rod A rod of just under 470 dia well be plenty strong to drive a lead slug .

p dog,

Sounds good. Another thing it shouldn't be so hard to drive a slug through a rifle bore. After all we're not driving a jacketed bullet through it. Make sure you clean the bore first and lightly oil it and the slug. Another thing with the brass rod (even steel) the weight of the rod should be enough to drive a slug through.

Now the idea of slugging the breach end and the muzzle end is to see if there is a taper in the bore. I would be bad if there is a taper and it's larger at the muzzle end. That would hurt accuracy.

Smokin J "after all we're not driving a jacketed bullet through it" That's correct--don't slug your barrel while shooting jacketed bullets through it.

The rifle is being built by Butch Searcy.
He uses PacNor barrels exclusively.
I called PacNor to ask what the dimensions are and they said the barrels they supply to Butch for his 470s have a bore of 0.475 and a minor diameter of 0.4655.
I just want to confirm or clarify the dimensions I end up with.
If I am going to fab my own solid copper 400 grain bullets, I want their diameter to properly correspond to the rifle bore.
Note: In regard to a tapered bore, I never heard of any reputable modern (within last 50 years) barrel maker having such poor barrel fab control that the bore would be tapered.