Base to Ogive Measurement

[cayennejon]

Today while sorting 123 grain Lapua bullets prior to loading for my 6.5 x 47 Lapua I discovered a marked difference between their base to ogive measurements. The bullets in the first box averaged .717" base to ogive measurement while bullets from a new box measured .738" base to ogive.
I weighed a sample from each box and they weighed the same, 123 grains.
Has anyone else noticed this?

 

[memilanuk]

It happens. Box A comes from one set up, box B comes from another. Different machine, different batch of materials, different setup, etc. Seeing this between lots isn't unusual; some brands you see it somewhat inside a lot... although the manufacturer swears the bullets all come of the same machine

 

[Winchester69]

...some brands you see it somewhat inside [of] a lot... although the manufacturer swears the bullets all come of the same machine.

Monte,
You have a real eye for the pertinent. Your recent Stat course had to have had a lot to do with with SPC.
.

 

[SlowpokeRodriguez]

Unless you have the right tool,eg a Buhay)it is almost imposable to accurately measure base to ogive. How did you take the measurements?

The process of how the lubricant is applied to the jackets before they are placed in the die has a lot to do with this. SPC would have an application in many facets of bullet production but for most bullet makers this is still a touch labor process.

 

[MATSUBOB]

The base to ogive doesn't really tell you what you need to know, it's the tip to ogive that is the important measurement. When the bullet seater pushes down on the bullet it does so from the tip end, not the base end. All reloaded rounds should be the same OAL measured from base of case to the point where the bullet touches the lands.

 

[spclark]

MATSUBOB, that sounds like a contradiction.

Given two batches of bullets that all have a fairly uniform ogive-to-meplat,bullet tip) dimension, if a significant number have longer bearing surfaces owing to a longer base to ogive dimension, seating all to a uniform case head to ogive dimension will seat some deeper than others, yes? Isn't that why some folks sort bullets by weight AND bearing surface?

I agree that bullet ogive / land-contact point to case head uniformity is a worthwhile goal for accuracy in reloading, while unrecognized bullet variations have an effect that can be reduced without too much additional effort.

 

[Cheechako]

The base to ogive doesn't really tell you what you need to know, it's the tip to ogive that is the important measurement. When the bullet seater pushes down on the bullet it does so from the tip end, not the base end. All reloaded rounds should be the same OAL measured from base of case to the point where the bullet touches the lands.

Bob

You are correct that the seater pushes down on the tip end, but a correctly made seater stem doesn't push on the "tip", it pushes on the ogive. Otherwise you'd never have uniform base to ogive seating depth which is the important measurement. Many super accurate Benchrest bullets do not have consistent oal but they do have consistent base to ogive length. For point blank distances the slight variation in bullet oal is not critical but some long range shooters do uniform the meplat on their bullets. It's yet to be proven that meplat trimming is a beneficial expenditure of time, IMHO.

Ray

 

[jb1000br]

Tip-to-ogive is meaningless IMO...the bullet-making die HAS TO make that area the same,as long as the meplats are the same diameter)...that part doesn't move. The LENGTH of the bearing surface is the real variable.

Why would you want to measure the flash on the meplat anyway?

YMMV,
JB

 

[MATSUBOB]

Most bullet seaters do not reach the ogive on especially on VLD bullets but rather touch the bullet somewhere higher. I still maintain the most important measurement for consistant bullet seating in the lands is the distance from where the bullet seater actually touches the bullet and the point that the bullet touches the lands in the rifle. Any variation in that distance of +- .0015 will have a potential impact on accuracy. Check out the following web page under new products:
http://www.greensrifles.com

 

[Bullet94]

I’ve wondered about the variation between the seater stem and the place where the bullet first contacts the lands. Couldn’t the hole in seater stem be,enlarged) to contact the bullet at the same place where the bullet first contacts the rifling and the bullet comparator made to be this same size too? If these were all the same diameter making accurate measurements sure would be easier, but as the barrel erodes wouldn’t the part of the bullet that first contacts the lands change?

 

[jb1000br]

Jon, the newer 123 scenars ARE longer then my old batch,I had to crank my seater down 6thou to get the same seating depth IIRC). I'm guessing the ink-printed numbers inside the lids of your 2 boxes of bullets are different from each other right?

Just went to check....

YES, my newer lot of 123 Scenars is 0.012" longer base-to-ogive than an older lot. Bearing surface ended up right at 0.010" longer and very consistent within a lot,10 bullets for each measurement never went more than +- about 0.0005,half a thou)

I use this to measure bearing surface: http://www.6mmbr.com/catalog/item/1433308/977259.htm Works great...measured thousands with it.

BTW, short of benchrest use, you may be wasting a lot of time measuring scenars...

Most bullet seaters do not reach the ogive on especially on VLD bullets but rather touch the bullet somewhere higher.

Bullet seaters will ALWAYS contact ahead of the ogive...unless you make your own seater plug...but what does that matter as long as your seating depth is within +- 0.001?

If your seating depths are erratic, try lubing up the necks instead,NECO Moly Dry Lube)...does wonders for seating depth consistency...and only costs about 12$ Took my seating depth variation to almost nothing...


RE: Green Rifles Tool:

The whole point of the tool is to get consistent seating depths.

Instead you can simply measure each seating depth and use your micrometer seater to put the bullet where you want it if your OAL's are that variable.,Whole lot cheaper alternative )

Hope he has more evidence to back up his claims than the one group review on the site...not much real evidence there, nor good testing...

With the tapered throat, the tool probably reads different depending how hard you push the bullet in as well...

Also, the reviewer never did measure bearing surface...

The review doesn't prove anything IMO...and I still think that is the wrong path...

Q on the tool:

What determines the front end of the measurement? The bullet tip? Or some specific diameter bushing ahead of the bullet?

Oh, and Measuring bearing surface is meant to equalize pressure/velocities, not seating depth.,That part was missing in the review...)

YMMV,
JB

 

[AckleymanII]

I made bullets for a long time.

There are a couple of possible explanations for this extreme difference in measurements. The best explanation is that the company has several different dies set up on different machines. The second difference is that the point up dies are simply screwed in to point up more or less, which would mean a very slight meplat difference.

In my bullet making experience, I could duplicate the same Base to ogive length with a little trial and error of simply screwing in the point up die a little more or less.

I used a Wax lubricant that gave very little if any difference in thicknesses which would change the base to ogive length. My typical base to ogive length variance would be .001 over a thousand bullets or so which is very typical of today's better BR bullets.

You are learning that lot to lot variations means that you simply adjust your seating depth...no big deal! Make your life easier when you find a bullet that your gun likes and buy as many as you can afford!

 

[MATSUBOB]

Jon, the newer 123 scenars ARE longer then my old batch,I had to crank my seater down 6thou to get the same seating depth IIRC). I'm guessing the ink-printed numbers inside the lids of your 2 boxes of bullets are different from each other right?

Just went to check....

YES, my newer lot of 123 Scenars is 0.012" longer base-to-ogive than an older lot. Bearing surface ended up right at 0.010" longer and very consistent within a lot,10 bullets for each measurement never went more than +- about 0.0005,half a thou)

I use this to measure bearing surface: http://www.6mmbr.com/catalog/item/1433308/977259.htm Works great...measured thousands with it.

BTW, short of benchrest use, you may be wasting a lot of time measuring scenars...

Most bullet seaters do not reach the ogive on especially on VLD bullets but rather touch the bullet somewhere higher.

Bullet seaters will ALWAYS contact ahead of the ogive...unless you make your own seater plug...but what does that matter as long as your seating depth is within +- 0.001?

If your seating depths are erratic, try lubing up the necks instead,NECO Moly Dry Lube)...does wonders for seating depth consistency...and only costs about 12$ Took my seating depth variation to almost nothing...


RE: Green Rifles Tool:

The whole point of the tool is to get consistent seating depths.

Instead you can simply measure each seating depth and use your micrometer seater to put the bullet where you want it if your OAL's are that variable.,Whole lot cheaper alternative )

Hope he has more evidence to back up his claims than the one group review on the site...not much real evidence there, nor good testing...

With the tapered throat, the tool probably reads different depending how hard you push the bullet in as well...

Also, the reviewer never did measure bearing surface...

The review doesn't prove anything IMO...and I still think that is the wrong path...

Q on the tool:

What determines the front end of the measurement? The bullet tip? Or some specific diameter bushing ahead of the bullet?

Oh, and Measuring bearing surface is meant to equalize pressure/velocities, not seating depth.,That part was missing in the review...)

YMMV,
JB

That's what I like about precision shooting everyone has their own opinion about what works best. I will continue to measure as I have outlined,tip to ogive) as since I started doing it that way I have shot my best 600y scores and have eliminated the occasional flyer that I use to get. By the way. how can you condem the Green tool when you have never tried it?

 

[jb1000br]

Bob, I didn't condemn it, I said the review and description were lacking, and asked you a question about the tool.

JB

 

[MATSUBOB]

Sorry, I forgot to answer your question on how the measurment is made. The bullet is seated firmly into the bottom of the tool which has a .0001 dial indicator in the tip end that the bullet tip pushes against. By comparing readings on the dial indicator bullets can be segregated by lenth of where the tool touches the ogive to the bullet tip. If you have technical questions you probably need to contact Bob Green who makes the tool who can probably explain it better than me. I just know it works.