REPOST FOR HELP

[tipper999]

COAL & OGIVE ???

The COAL to the lands very in lenght from bullet lenght. The Ogive COAL should always be the same, but it's not this puzzles me. The lead angle of the lands does not change, but the bullet angle will very some in the same weight bullet & a lot in another weight bullet, where as it does not make contact at the same OD of the bullet or the same ID of the land's. .300 is .300 unless it's bullet OGIVE, HELP is it the bullet angle contact that makes the OGIVE very. ???

 

[Patch700]

If you have trouble with the English language try having a friend more fluent to help you with your wording.. I'm sure this is why you've not yet got a reply in this matter.

 

[XTR]

The tools that measure the "ogive" for 30 caliber bullets are usually at .300±, but they all taper differently and your lands have a lead angle that will cause it to contact the bullet at different points on the curve depending on the shape of the ogive.

Or, just accept that it is a fact and load accordingly.

Now to really drive you crazy think about this one, the only bullets that I've found that have the same base to ogive measurement to contact with the lands in my guns are Berger 200 and 215 Hybrids, but they both require hugely different seating die settings.

 

[spclark]

...is it the bullet angle contact that makes the OGIVE very. ???

Yes.

Bullet ogives are sections of circles. Even if you have a gauge that's calibrated to provide an ID diameter of 0.300" with which you measure seating depth, bullets with longer-radius ogives (think VLD) may very well encounter the lands where they begin in your chamber's throat - the lead ('leed') - at a point significantly different from that of bullets with a shorter-radius ogive (think Minie ball).

 

[spclark]

...but they both require hugely different seating die settings.

Well, yes! For a reason similar to that in my previous post:

Measure bullet seating depth with one gauge, seat them with a seating stem having an entirely different shape / profile where it contacts a bullet's ogive, then chamber it in a throat having yet another, different shape (lead) & you'll need different die settings for each shape of bullet you mess with.

The ideal would be having seating stems cut with the same reamers as your various chambers. At least then you're eliminating one variable. Having a 'gizzy' to measure seating depth (seating gauge made with your reamer) eliminates another one.

 

[asauer]

spclark is exactly right- I'm not sure it's easy to get meaningful data with most setups. I also wonder how much, if any, barrel wear changes the leade angle itself. I'd have to believe it does. Is it enough to matter? I'm not talking about just chasing the lands...
I know my gunsmith says rifling gets partially burned out (or washed out, which ever gives a better mental picture) but obviously isn't eroded clear down to full groove diameter in a neat, progressive fashion. I'd have to believe the leade suffers the same fate- making it impossible to really gauge unless you had a perfect chamber cast and the tools to accurately measure.

That's assuming it really matters. I'm not a good enough shot to care. I know my gunsmith gives me exact data on where my "lands are" when it's fresh off the lathe, which I verify. After the first shot I consider it a guessing game.

 

[Erik Cortina]

First we need to understand what you are asking, so I'm going to break your post down and ask some questions. Answer my questions so we can help you.

COAL - Case OverAll Length - This is the measurement of a loaded round from base to tip.
OGIVE - The arch between bearing surface and bullet tip.

The COAL to the lands very [sic] in lenght from bullet lenght.

Do you mean that the base to tip of a loaded round varies in length due to bullet length? Are you saying that the tips of bullets is what makes this measurement inaccurate? If so, then yes, it's not an accurate way to measure.

The Ogive COAL should always be the same, but it's not this puzzles me.

You mean that the base to ogive measurement should always be the same, but it is not. So you want to know why?
When does base to ogive vary, when you are trying to measure distance to the lands or when you seat a bullet on a loaded round?

The lead angle of the lands does not change, but the bullet angle will very [sic] some in the same weight bullet & a lot in another weight bullet, where as it does not make contact at the same OD of the bullet or the same ID of the land's. .300 is .300 unless it's bullet OGIVE, HELP is it the bullet angle contact that makes the OGIVE very [sic].

The OGIVE on bullets are not exactly the same from one to the next. What will happen is that some bullets will have a bigger diameter ogive than others at the point where the base to ovine measurement is recorded. A bullet with a "fatter" ogive will seat deeper in the case because the point where the ogive measure .300" is closer to the tip than a "skinnier" ogive. Ogive's vary slightly in the same line of bullets and even more when compared to a different line of bullets due to ogive profile.

 

[ARIZONA_F_CLASS]

First we need to understand what you are asking, so I'm going to break your post down and ask some questions. Answer my questions so we can help you.

COAL - Case OverAll Length - This is the measurement of a loaded round from base to tip.
OGIVE - The arch between bearing surface and bullet tip.

The COAL to the lands very [sic] in lenght from bullet lenght.

Do you mean that the base to tip of a loaded round varies in length due to bullet length? Are you saying that the tips of bullets is what makes this measurement inaccurate? If so, then yes, it's not an accurate way to measure.

The Ogive COAL should always be the same, but it's not this puzzles me.

You mean that the base to ogive measurement should always be the same, but it is not. So you want to know why?
When does base to ogive vary, when you are trying to measure distance to the lands or when you seat a bullet on a loaded round?

The lead angle of the lands does not change, but the bullet angle will very [sic] some in the same weight bullet & a lot in another weight bullet, where as it does not make contact at the same OD of the bullet or the same ID of the land's. .300 is .300 unless it's bullet OGIVE, HELP is it the bullet angle contact that makes the OGIVE very [sic].

The OGIVE on bullets are not exactly the same from one to the next. What will happen is that some bullets will have a bigger diameter ogive than others at the point where the base to ovine measurement is recorded. A bullet with a "fatter" ogive will seat deeper in the case because the point where the ogive measure .300" is closer to the tip than a "skinnier" ogive. Ogive's vary slightly in the same line of bullets and even more when compared to a different line of bullets due to ogive profile.

What Erik said. I started measuring bearing surface length and haven't looked back.