How to sort bullets by bearing surface?

[264WM70]

I was told that sorting bullets by bearing surface should be the first sorting step. I have a Sinclair Bullet Sorting Stand with a dial micrometer that I use prior to weight sorting. I don't think this is truly measuring bearing surface. It is measuring base to ogive. If all the boat tail cones were the same then this would be an acceptable method but I have now way of telling if that is true. I never sort by bullet overall length. Should I measure overall length or tip to ogive too? I plan to one day get into bullet pointing. I want to make sure I know what I am doing before going down that rabbit hole.

 

[Mark W]

I would use two of these or something similar.

https://www.googleadservices.com/pa...ahUKEwif8YSU2b7VAhUBcyYKHbQTDFIQwg8IIw&adurl=

 

[KenOath]

I was told that sorting bullets by bearing surface should be the first sorting step. I have a Sinclair Bullet Sorting Stand with a dial micrometer that I use prior to weight sorting. I don't think this is truly measuring bearing surface. It is measuring base to ogive. If all the boat tail cones were the same then this would be an acceptable method but I have now way of telling if that is true. I never sort by bullet overall length. Should I measure overall length or tip to ogive too? I plan to one day get into bullet pointing. I want to make sure I know what I am doing before going down that rabbit hole.

I use the same tool as yourself, Brian Litz was asked in an interview once with Eric Cortina that if he sorted bullets one way what would it be, his reply was base to ogive.
I've found that the Sinclair tool and stand is effective enough to cull the bullets that are out of the main good to go pile.

Cheers Rushty

 

[JohnKielly]

I've found there is a close correlation between bearing surface & OAL of the bullets I meplat & point, so I adjust the Whidden meplatter to fully trim the long ones & sort on point appearance. The shorties, I give a closer trim later.

 

[Ringostar]

I use the same tool as yourself, Brian Litz was asked in an interview once with Eric Cortina that if he sorted bullets one way what would it be, his reply was base to ogive.
I've found that the Sinclair tool and stand is effective enough to cull the bullets that are out of the main good to go pile.

Cheers Rushty

Yes ^^^ Stick with what you have, and measure base to ogive. It will sort out any ones that might be a problem.

 

[mikecr]

Tubb's setup will measure bearing without including bullet base length. http://www.6mmbr.com/medlerTUBBBSC.html
The ogive datums could still affect measure until qualified with a Bob Green Comparator.
Personally, I'm sure bearing means nothing at all to outcome. The most significant bullet dimension for BC, by far, is meplat diameter. And I've seen zero evidence that bearing variance affects MV.

I focus on qualifying ogive radius, and meplat trimming/pointing from those qualified ogives.
Could care less about bearing + boat tail length + base diameter.

 

[GerryM]

I have an idea that might work for you try this get a piece of carbon paper and some paper.
Pace the bullet you want to check on the carbon [paper and roll it with some pressure you should have mark on the paper.
Measure it with a caliper.

 

[dkhunt14]

Tubb's setup will measure bearing without including bullet base length. http://www.6mmbr.com/medlerTUBBBSC.html
The ogive datums could still affect measure until qualified with a Bob Green Comparator.
Personally, I'm sure bearing means nothing at all to outcome. The most significant bullet dimension for BC, by far, is meplat diameter. And I've seen zero evidence that bearing variance affects MV.

I focus on qualifying ogive radius, and meplat trimming/pointing from those qualified ogives.
Could care less about bearing + boat tail length + base diameter.

I don't know who makes them for Tubbs Now but John Buhay used to. The pieces look like mine. He got a new job and stopped making them. He turned everything over to Mark King. Now Mark stopped making them. I would imagine Tubbs just copied Johns and got a machine shop to produce them.

Maybe John Hoover at Acurracy one. All you need is the inserts if you already have the stand. Matt

 

[264WM70]

Accuracy One's website has this one listed:



It looks similar to the Sinclair Stand but with a insert attached to the micrometer stem. Is this what you were thinking Matt?

Joe

 

[mikecr]

The Accuracy One is same as Tubb's.
For bearing, you need measure between two datums. If you go only ogive to base, your deviations will only have you wondering what they actually mean. Are they bearing, or base length, or base angle, or ogive radius?
What does it mean to external ballistics? What does it mean to internal ballistics?
OP's concerns are valid.
But you couldn't begin to predict without separating these attributes into truths from the beginning. Right?
You can't apply math to assumptions, and you can't prove generalizations, because these sloppy efforts are certain to fail tests.

Consider the number of threads here & at other forums where someone buys a toy, uses it, and then asks everybody what they're doing. What it means.. Usually, they're hoping for what they want to hear(that everything is ok).
I guess for me it's too boring to provide that... I am trying to help though

 

[kvd]

If one wishes to know the dimension of the bearing surface for a particular bullet, a few calculations will need to be made. I've only done this with a comparator that is an approximation of the diameter of the rifling lands so I can't say how it might be done with the Sinclair tool. Measure the following:

1. Base to datum on bullet ogive
2. Turn the bullet around and measure datum on back of bearing surface to tip
3. Bullet over all length
​

With these three dimensions in hand, one may calculate the following:

Ogive datum to tip = Dimension 3 - Dimension 1

Base to back datum = Dimension 3 - Dimension 2

Bearing surface = Dimension 3 - (Ogive datum to tip + Base to back datum)

Ken

 

[MFR]

I built a gage to measure the bearing lenght of 7mm bullets. I can make new inserts to measure other calibers. Here is a link to a video that shows my gage.

Mark

 

[dkhunt14]

Accuracy One's website has this one listed:



It looks similar to the Sinclair Stand but with a insert attached to the micrometer stem. Is this what you were thinking Matt?

Joe

Yes that looks the same. To measure actual bearing you need and insert that goes closet to bullet diameter to go on ogive. Then you need another that comes up the boattail far enough to get clost to the pressure ring. That gives actually the bearing that is riding on the barrel.

I am not sure what the Sinclair looks like but I know you can buy matched sets of pieces for your caliber. The granite stand with dial indicator I feel gives more accurate and faster readings then pieces on a caliper. Matt

 

[264WM70]

Here is the Sinclair Bullet Sorting Stand

 

[dkhunt14]

Here is the Sinclair Bullet Sorting Stand

All you need is the caliber inserts. The one that goes on the stem attached with a set screw. Matt

 

[DaveTooley]

I'd suggest you look closely at the irregularities at the junction of the boat tail and body. That area can take a beating during manufacturing, making it difficult to accurately measure bearing surface. I can tell you in all my testing, measuring BC's, I could not measure any significant difference based on bearing surface length. I never measured any significant difference in BT lengths so base to ogive is all you need to do and then your just looking for the odd wild one. I proved the meplat, by a wide margin, is the most important area of concern. Perfect bullets with irregular meplats will have BC variations that will show up on the target at distance.

 

[264WM70]

I'd suggest you look closely at the irregularities at the junction of the boat tail and body. That area can take a beating during manufacturing, making it difficult to accurately measure bearing surface. I can tell you in all my testing, measuring BC's, I could not measure any significant difference based on bearing surface length. I never measured any significant difference in BT lengths so base to ogive is all you need to do and then your just looking for the odd wild one. I proved the meplat, by a wide margin, is the most important area of concern. Perfect bullets with irregular meplats will have BC variations that will show up on the target at distance.

Dave,

This is the information I was looking to get. If I sort by base to ogive and then sort by overall length or use the Bob Green Comparitor to measure ogive to seating stem, then I should be ready to trim the meplat and point. Now which is better? I think the BGC would sort best, but I would like your opinion.

 

[DaveTooley]

OAL leans nothing. The OAL variation comes from the flow of the jacket when it's run into the pointing die during manufacturing. The jacket folds are not always uniform so there will be one side flow further into the ejector pin hole. I have thought about measuring variations in the shape of the ogive but I can't justify the time or expense because in a given lot of bullets it has little to no affect on performance. There is no way to measure any gain in accuracy. Small variations, which I'm sure there are some, mean nothing. Even with the resolution that Doppler radar can provide it would get lost in the noise.

I would sort base to ogive looking for wild ones. Minimally trim meplats, then maybe point depending on intended application.