Bullet "bump up" during ignition

[Naphtali]

What I think I'm attempting to identify is the relationship among smooth relatively force free loading of muzzleloading bullet, obturation during ignition, and accuracy.
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During ignition any bullet base moves first. I have been informed that included in "moving first" the base expands slightly - perhaps the entire bullet, for all I know. I have been informed, again, that this expansion is anticipated because it is supposed to obturate grooves.

If the previous paragraph is more or less accurate when referring to lubed bullets and/or Minié Balls - yeah, I'm aware that patched balls do not completely obturate grooves -

1. What is the "bump up" for solid base lubed bullets in the .58-.69-caliber range in thousandths or tenths?

2. What is the "bump up" for lubed Minié Balls in the .58-.69-caliber range in thousandths or tenths?
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If I am asking the wrong questions, please respond, as though I asked, to what are the right ones.

[59sharps]

What I think I'm attempting to identify is the relationship among smooth relatively force free loading of muzzleloading bullet, obturation during ignition, and accuracy.
***
During ignition any bullet base moves first. I have been informed that included in "moving first" the base expands slightly - perhaps the entire bullet, for all I know. I have been informed, again, that this expansion is anticipated because it is supposed to obturate grooves.

If the previous paragraph is more or less accurate when referring to lubed bullets and/or Minié Balls - yeah, I'm aware that patched balls do not completely obturate grooves -

1. What is the "bump up" for solid base lubed bullets in the .58-.69-caliber range in thousandths or tenths?

2. What is the "bump up" for lubed Minié Balls in the .58-.69-caliber range in thousandths or tenths?

If I am asking the wrong questions, please respond, as though I asked, to what are the right ones.
Can't help w/ solid base. But on minnes we size them .001 to .002 under bore dia. for ease of loading. never reached a point were they would not load. I never let it go more than 20 rounds w/o running a brush down the barrel. (this is for arms designed for minnies). My first shot out of a clean barrel is always high right. after that point of aim.
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[Buckshot]

...............I don't know if total upset with any particular boolit design, whether solid or hollow base is quantifiable as to a particular measurement. The ultimate limit would be the barrel wall. Recovering fired slugs will tell the tale. A slug that doesn't seal with be very obviously gas cut. A HB would obviously be easier to upset due to it's thinner skirt. A barrel having wide grooves would be easier for EITHER type to upset into and seal. Move to a harder alloy with either design and it'd require a heavier charge to fully upset. If the barrel had narrower and/or deeper grooves you'd run into similar problems. I've seen this in a barrel with 3 wide grooves, and the same load not working as well when fired in a 5 groove barrel, especially with a harder alloy.

In BP rifles it was proven more then 100 years ago that obturation takes place at ignition ONLY. Nowhere else along the barrel does the slug continue it's expansion. What happens at ignition is all you get. It is possible especially with enlongated conicals that if it is too small for the bore, that upon ignition the base will upset to the limits of the grooves, yet the nose can remain offest to whatever it's 'Windage' allowed. For short range work this may not be much of an issue, but the farther away the target is, the more the offset (unblanced nose) will play a part in accuracy.

If I've missunderstood the question then the foregoing may not apply.

...............Buckshot

[Tatume]

In one study of revolver bullets and the barrel/cylinder gap relationship (smokeless powder and jacketed bullets), it was shown that bullets upset to fill the forcing cone and are then swaged into the barrel. A spark-photograph of a bullet emerging from the cylinder with no barrel attached to the revolver showed that the bullet was much larger than the chamber throat from which it emerged. In my opinion, it is hard to relate our everyday experiences to the dynamics in a system operating at tens of thousands PSI. Strange things happen under extreme conditions.

[TCLouis]

Patched Round Balls (if properly sized and lubed) do seal the bore completely or you will get burn through on the patches just like the gas cutting on a boolit.

One can differentiate burn through compared to cutting from rough bore on patches recovered downrange.

Re reading your question I will add

I have one 45 caliber frontstuffer that is over sized and I use boolit cast for a 45-70. I engrave the rifling into the boolit as I seat it. It seats with slight effort. I load it with a damp patch on the jag to remove/soften fouling from previous shots.

Concept is not unlike the REAL concept of the Lee frontstuffer boolits (bore is to big for them also or I would use them).

[ml45]

I shoot 40 /45 cal twist 1 in 18 front stuffers . alloys as hard as 10 bhn . Recovered bullets show engraving all the way to nose radius . powder charge /chamber pressure dictates upset . the harder the alloy is the higher the pressure needs to be . 40 cal will push 300 grn to 1920 fps with 100 grn of T7 .45 cal 350 grn 1830 fps 100 grn T7 the best i shoot is 1.5 groups at 100 yds open sights .All bullets are paper patch lube is bear grease . After i read Ned Roberts book 1987 got a cva big bore striped parts rebarreled to 45 1/18 twist and have never looked back .

[DIRT Farmer]

In recovering formerly 530 round balls shot from my 54/28 ga trade gun when using card wads, the sides of the ball will have a ring around it simular to a round ball fired from a percussion revolver where the sides are shaved by the cylinder. the ball is also flattened on the bottom. When the ball is seated on a fiber wad, it still has the flattened area on the sides but appears rounder and they dont seem to drift as much.

Patched round balls that load fairly easy have the impression of the weave on the sides. This is from recovered balls shot into a snow bank several years ago.