Hi.
Been away from the forum and shooting for some months, now of course, I have time to spare but no chance to do any shooting, similarly neither is there any point in re loading for the time being.

I have therefor been pottering in the workshop 'making things' which maybe, when and if we return to some form of normality, might improve my efforts at hitting the target.

Apart from a couple of automatic case annealing machines,
(one for a friend) and a lead hardness tester I have made a bullet comparator, the purpose of which is to enable the bullet to be inserted into the case the right amount so as to have a constant 'jump' (or none at all), before it engages with the rifling. I'm sure everyone knows what I'm talking about.

(there are several commercial products on the market together with U Tube videos on their use).

My question is, am I right in assuming that the ID of the 'anvil' into which the ogive of the round sits, should be such as to mimic the  rifling lands in the gun. These inserts are commercially available and designated as suited for various calibres to be inserted  in the clamp on the fixed end of the caliper, but do not state the actual ID. I could buy a set, but that rather defeats the object.
My home cast and commercial lead bullets vary in spite of being sold as 45/70, by one or two thou on the bullet nose diameter. ahead of the driving bands and the ogives vary in length. Therefore, measuring the L.O.A. of the round will not necessarily result in the desired 'jump' being constant unless using aforesaid 'comparator'

While I am asking questions has anyone any experience of the Caldwell Ballistic Chronograph.

Stay safe

John D

     I just shove the bullet up into the leade, and measure with a dial caliper the distance from the bullet base to the breech face.   Easy to come up with the OAL to seat the bullet against the lands that way.  Don't make it harder than it needs to be.

CHRIS
RGChristensen

My current 45-70 fixed load features the full floating spring seater system. Patent pending. The modified RCBS, (shortened), bullet is a slip fit in the case. Seating the cartridge in the chamber sets the bullet seating depth. 

Further details about this load cannot be disclosed at this time, sorry, patent pending......

Used this patent pending load couple years ago in my 45-90. Last time used  scored six chickens.  

Best thing since peanut butter. 

Go ahead, send me a hundred bucks.

I believe that what they were telling you, John, is that your rifle is the best "anvil" to determine zero clearance with any particular bullet and once that is determined it would be easy to set an OAL for any particular clearance. Now, if you are buying bullets and expect them to be of any specific consistency you will be chasing your tail. The only way to count on them to match measurements is to cast them yourself. Also I believe you will find that most shooters want zero clearance as a way to guarantee the bullet is centered in the bore before the fire is lit. At least it is probably the best place to start and then can be experimented with to prove it was.

Seat a bullet quite long in the case and push it into the chamber. Run a wooden dowel or cleaning Rod to touch the end of the bullet Mark it with a sharp edge of a knife or very fine pencil. Remove the cartridge and then run that same rod in up against the breech face and make another Mark. measure those two lines that is your max overall length for a start.Chamber the round and see how it engraves.

Just watched this video. 

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Seems to me like an answer to a problem I've never had. 

"My question is, am I right in assuming that the ID of the 'anvil' into which the ogive of the round sits, should be such as to mimic the  rifling lands in the gun."

The anvil appears to be flat. Has nothing to do with bullet ogive or rifling.

If I understand the OP's question, it involves a loaded cartridge length measurement, taken on the ogive of the bullet.  I have one of these:

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It allows accurate measurement of "cartridge length" with respect to a datum point on the ogive of the bullet.  The idea here is that the ogive shape of the bullet is accurately formed in the bullet making process.  This particular tool is for jacketed bullets.  To determine the maximum OAL for a given bullet, I use the technique described above, with the two marks on a dowel (I use two pieces of blue tape on the dowel flush with the face of the muzzle instead of knife cuts.  Same idea though.)  

I then seat the test bullet in a case to the measured maximum OAL and take a measurement using the comparator and calipers.  This gives an accurate reference length for the maximum OAL.  It is not the actual OAL of the cartridge, but a reference number measured with the comparator.  Once the reference number is known the seating depth can easily be adjusted up or down as needed.

I think this process would work with cast bullets from the same mould, as the ogive shape should be quite consistent, if bullet weights are consistent.  I have not tried this, though.

Mike