Should I Jump Into The Arbor Press World? (To Improve Seating Depth Consistency)

[CarlGeorge]

You are exactly right. Measuring CBTO does not always allow consistent seating. It's where the seater stem contacts the bullet and where the bullet contacts the rifling, which is very often not where typical ogive tools measure.

A fellow LR BR shooter, who also shoots SR BR, has developed several tools that many top competitors use.

He makes a comparator that measures the bullet where the seater stem contacts it (seater ogive or SO), and another comparator that measures where the bullet contacts the chamber (chamber ogive or CO). These two places on the bullet are not usually where a typical ogive tool contacts the bullet. He also make a comparator for a caliper that matches the seater stem (SO) tool.

When bullets are sorted by SO and CO, they all seat the same and all have the same distance from the chamber.

Is there a place one might find these products?

 

[Bamban]

With a tiny arbor press and a Wilson die you can FEEL all the seating tension flaws. A standard press is a barbell by comparison. Being able to feel the problems is the first step to solving them.

Amen.

I still like my 40 yo DIY inexpensive arbor press. Short lever arm can easily FEEL neck tension in/consistency. You can even make it out of hard wood. Sized to fit in a 50 cal ammo can for range work. It is a left over from my stool shooting days.

 

[mikecr]

Is there a place one might find these products?

BGC comparator

Bob Green's Rifles

Complete Bench & Varmint Rifles Precision Barrel Installation Superior Custom Dies and Tooling Specializing in craftsmanship

greensrifles.com

 

[INTJ]

BGC comparator

Bob Green's Rifles

Complete Bench & Varmint Rifles Precision Barrel Installation Superior Custom Dies and Tooling Specializing in craftsmanship

greensrifles.com

This isn't what I am using. It's this:

 

[mikecr]

When bullets are sorted by SO and CO, they all seat the same and all have the same distance from the chamber.

'Ogive' is the entire nose.
'CO' would be Contact Datum, 'SO' would be Stem Datum.
Your tool adds bearing and base length to both measures.
So your CO is what everyone refers to as BTO (base to ogive).
Your SO would be BTS(base to stem)

What's your sorting procedure?

 

[CarlGeorge]

Using above terms.....

I'm going to do an experiment seating and checking grouping of bullets that have same BTO and BTS measurements. Last night I took a group of bullets I'd already sorted by BTO - and I got BTS measurement for each. I need to load up a few. Hopefully I'll have some range time with them next week.

 

[INTJ]

'Ogive' is the entire nose.
'CO' would be Contact Datum, 'SO' would be Stem Datum.
Your tool adds bearing and base length to both measures.
So your CO is what everyone refers to as BTO (base to ogive).
Your SO would be BTS(base to stem)

What's your sorting procedure?

Correct. Put a bullet nose down in on collimator and note the reading. Swap collimators and measure again. You'll get a reading like 50-72. Those all go into one bin, as do the 51-72s and 50-73s.




All of the bullets in a particular grouping will have the same contact point on the seater stem and thus--assuming all the other parts of your seating process are consistent, will seat the same. Additionally, all these bullets CO will be the same distance from the rifling. This ensures maximum seating and jump/jam consistency.

If I am describing this correctly.......With 50 being the CO and 72 being the SO, a 50-72 will seat .001" differently than a 50-73, and the chamber contact will be .001" different. A 51-72 will seat the same as a 50-72, but the chamber contact will be .001" different. A 51-71 should seat the same as a 50-72 with the same chamber contact point, though the ogive is shaped different.

Good custom bullets will sort into 4-5 groupings. Berger's will have 11-13ish.

SO/CO vs BTO only matters with a LR BR rifle shooting in good to excellent conditions.

 

[mikecr]

A 'collimator' is an optical device..
The BGC I posted to does this same comparison, both measurements -at the same time.
Better still, it excludes bearing length variances and base length variances, and focuses on the measure at hand (ogive radius).

 

[mikecr]

Using above terms.....

I'm going to do an experiment seating and checking grouping of bullets that have same BTO and BTS measurements. Last night I took a group of bullets I'd already sorted by BTO - and I got BTS measurement for each. I need to load up a few. Hopefully I'll have some range time with them next week.

I'll go ahead and predict that you'll find no meaningful difference.

 

[INTJ]

A 'collimator' is an optical device..
The BGC I posted to does this same comparison, both measurements -at the same time.
Better still, it excludes bearing length variances and base length variances, and focuses on the measure at hand (ogive radius).

Collimator refers to more than just optics. Just like the phrase "bite me" can be a directive for an action or a sarcastic put down of someone who is overly argumentative concerning irrelevant trivial matters.

For the Bob Green tool to do what the SO/CO tool does, it would need to have custom inserts for each bullet type as well as a comparator that attaches to the caliper that matches the small round machined aluminum device that allows to bullet to center and align much as a collimator focuses a beam of light for the CO measurement.

 

[EdHarley]

Correct. Put a bullet nose down in on collimator and note the reading. Swap collimators and measure again. You'll get a reading like 50-72. Those all go into one bin, as do the 51-72s and 50-73s.

View attachment 1223225
View attachment 1223226

All of the bullets in a particular grouping will have the same contact point on the seater stem and thus--assuming all the other parts of your seating process are consistent, will seat the same. Additionally, all these bullets CO will be the same distance from the rifling. This ensures maximum seating and jump/jam consistency.

If I am describing this correctly.......With 50 being the CO and 72 being the SO, a 50-72 will seat .001" differently than a 50-73, and the chamber contact will be .001" different. A 51-72 will seat the same as a 50-72, but the chamber contact will be .001" different. A 51-71 should seat the same as a 50-72 with the same chamber contact point, though the ogive is shaped different.

Good custom bullets will sort into 4-5 groupings. Berger's will have 11-13ish.

SO/CO vs BTO only matters with a LR BR rifle shooting in good to excellent conditions.

I have one of the Franklin Comparators. I use it to measure BTO like many others. I also find it to be very finicky. In fact I have had to remeasure 100 bullets because I bumped it and is started to measure 0.012” longer on every bullet. I rechecked the previously sorted bullets and they were all measuring longer than before. So... When I use it now I do 500 bullets at a time and after I am set I don’t move. If I have to go take a leak I want to put police tape around it. My question to you is how do you switch back and forth between comparators without losing consistency? My other questions to anyone are similar to those everyone else has. I have been told by shooters much better than me to sort bullets by weight, BTO, Bearing surface and combinations of the above. I would prefer to sort by weight because it is much more repeatable than the Franklin tool. I have not seen any scientific studies done comparing methods. SOme of this doesn’t make a whole lot of sense. If you sort by BTO why does it change accuracy? Is it a surrogate for weight or center of gravity as others mentioned? A longer BTO would just be pushed further into the case so it shouldn’t change jump. Is there a consensus among the benchrest shooters for what makes the most difference? I want to spend more time shooting than sorting like everyone else.

 

[Trevor60]

measures the bullet where the seater stem contacts it (seater ogive or SO), and another comparator that measures where the bullet contacts the chamber (chamber ogive or CO). These two places on the bullet are not usually where a typical ogive tool contacts the bullet. He also make a comparator for a caliper that matches the seater stem (SO) tool.

When bullets are sorted by SO and CO, they all seat the same and all have the same distance from the chamber.

For the Bob Green tool to do what the SO/CO tool does, it would need to have custom inserts for each bullet type as well as a comparator that attaches to the caliper that matches the small round machined aluminum device that allows to bullet to center and align much as a collimator focuses a beam of light for the CO measurement.

I have the Bob Green tool and i think we are trying to accomplish the same thing; determine which bullet is not like the other.

What is not clear is your two comparators SO and CO methodology. It appear the two comparator system measures the same two points as the BGC tool which uses a stem inside the CO comparator.

The one requirement of the BGC tool was to have a comparator which matched my cal (.30cal) barrel
.300 - .308 the BGC comparator need to be 300-308; it does
The other requirement was to have the measuring stem match my seating stem profile or be deep enough that none of my bullet nose profiles topped out the measuring stem.

I use one seating die with the same stem profile to seat various bullets
155 lapua scenars or 187 BIBs or Bergers 168 to 215's

When i measure i am looking for bullets that have the same contact with the comparator stub to the stem. They are all matched according to my spread requirements.

Loaded rounds are checked using a caliber ogive comparator measuring my seating distance from my chamber. BGC makes one or one of the ogive comparators. This number is my seating reference and is simply a numerical value, used to adjust seating depth.


Cheers
Trevor

P.S.


We got side tracked to the ops original question. F class guys are using an arbor press more and more. They are migrating to a press that measure seating force, like the hydro press. Neck tension variables show up on paper. The hydro press give a number value which can be batched or like the bullet sorter identify rounds that fall outside the norm.

 

[CarlGeorge]

We got side tracked to the ops original question. F class guys are using an arbor press more and more. They are migrating to a press that measure seating force, like the hydro press. Neck tension variables show up on paper. The hydro press give a number value which can be batched or like the bullet sorter identify rounds that fall outside the norm.

I don't consider this discussion side tracked.

The root of the Arbor press question was around seating depth consistency - and all of the stem contact point / comparator contact point comments are, IMHO, in that realm of getting consistent seating depth. So this has been extremely helpful for me. It has helped me develop and clarify in my head some mental models. I'm eager to see if I can improve the seating depth consistency with what has come out of this thread (and I agree with the comment there likely will be no impact on paper).

The seating force monitoring is a whole 'nother motivation for use of an Arbor.....and a very interesting one.

 

[mikecr]

The good thing about hand dies/arbor press is that it absolutely removes press slop.
I do a 2-step bullet seating using micrometer top dies.
1st, ~1/2thou short of desired CBTO.
2nd, dialed dead nutz.

I always make sure every round is right on my logged CBTO, as I also make sure every round is bumped to same exact headspace, and every round is seated with same force, and every primer is seated to same crush value, and every charge to the kernel, and loaded runout off bullet bearing is under 1thou TIR.
No averaging or assumptions for me.

With this I guess, it seems odd to me that folks talk about differences on target -as relating to differences in abstract measures. That could not ever happen to me, I will never see that, because I don't leave any differences in play.
If your BTO mess is leaving bullets seated different, just don't leave it that way. Adjust your seating until every round is correct. If your powder dispensing is causing deviations, don't claim it's causing inferior results on target.. It's not, you are, when you didn't act on each and every deviation to correct it.

We can try to predict outcomes till the cows come home, but if your chambering and firing rounds that aren't right -it's your fault.
That said to death, constant need for adjustments can get old really fast.
Here, it makes sense to qualify ogives with a BGC, as a preconditioning of seating. To make accurate seating go a lot easier. Same with an arbor press and hand dies,, it makes things easier.
It's also less expensive. Have you noticed that? Wilson dies cost less than good threaded dies, and arbor presses are reasonable.

 

[INTJ]

I have one of the Franklin Comparators. I use it to measure BTO like many others. I also find it to be very finicky. In fact I have had to remeasure 100 bullets because I bumped it and is started to measure 0.012” longer on every bullet. I rechecked the previously sorted bullets and they were all measuring longer than before. So... When I use it now I do 500 bullets at a time and after I am set I don’t move. If I have to go take a leak I want to put police tape around it. My question to you is how do you switch back and forth between comparators without losing consistency? My other questions to anyone are similar to those everyone else has. I have been told by shooters much better than me to sort bullets by weight, BTO, Bearing surface and combinations of the above. I would prefer to sort by weight because it is much more repeatable than the Franklin tool. I have not seen any scientific studies done comparing methods. SOme of this doesn’t make a whole lot of sense. If you sort by BTO why does it change accuracy? Is it a surrogate for weight or center of gravity as others mentioned? A longer BTO would just be pushed further into the case so it shouldn’t change jump. Is there a consensus among the benchrest shooters for what makes the most difference? I want to spend more time shooting than sorting like everyone else.

Measuring with the SO/CO tool is the most tedious part of my loading process. I too will sort 500 or 1000 all at once to ensure consistency.

Switching the bullet from one comparator to the other is no issue. The key is to be consistent on how you place the bullet into the comparator and to be consistent on how you drop the dial indicators stem on the bullet. In this regard it is exactly like every other precision measurement we do. Developing a consistent process and consistent feel is a must for consistency in measurement.

To me, BTO is mainly for sorting out bullets that are significantly different than the others. SO/CO allows all bullets to be seated the same and to have the distance to the lands. Again, it only shows up when shooting in good conditions, especially if your tuning node has the bullets close to the lands. The larger the jump the less critical the SO/CO measurement.

If all bullets were made exactly the same, then BTO sorting would ensure that they all seated the same. However, there is variation between the seater stem contact point and the chamber contact point. I explained this previously. SO/CO accounts for that.

In LR BR, the consensus is a good tune has both a wide powder charge more and a wide seating depth node. The wider the load the less small variations in seating and chamber contact points matter. I think most agree that BTO will sort out the bad bullets. Most do not do SO/CO. Most do not spin on a Bullet Genie. However, these actions have been shown in a controlled environment to make a difference.

 

[INTJ]

I have the Bob Green tool and i think we are trying to accomplish the same thing; determine which bullet is not like the other.

What is not clear is your two comparators SO and CO methodology. It appear the two comparator system measures the same two points as the BGC tool which uses a stem inside the CO comparator.

The one requirement of the BGC tool was to have a comparator which matched my cal (.30cal) barrel
.300 - .308 the BGC comparator need to be 300-308; it does
The other requirement was to have the measuring stem match my seating stem profile or be deep enough that none of my bullet nose profiles topped out the measuring stem.

I use one seating die with the same stem profile to seat various bullets
155 lapua scenars or 187 BIBs or Bergers 168 to 215's

When i measure i am looking for bullets that have the same contact with the comparator stub to the stem. They are all matched according to my spread requirements.

Loaded rounds are checked using a caliber ogive comparator measuring my seating distance from my chamber. BGC makes one or one of the ogive comparators. This number is my seating reference and is simply a numerical value, used to adjust seating depth.


Cheers
Trevor

P.S.


We got side tracked to the ops original question. F class guys are using an arbor press more and more. They are migrating to a press that measure seating force, like the hydro press. Neck tension variables show up on paper. The hydro press give a number value which can be batched or like the bullet sorter identify rounds that fall outside the norm.

I haven't use the Bob Green tool. The guy the developed the SO/CO tool is familiar with Bob Green tool and says it does not do what his tools do. My guess is that the Bob Green tool uses the standardized ogive measuring point for the CO reading, and that isn't always correct. The CO inserts for the calipers are matches to the CO comparator so what you measure with the caliper is the same as how you sorted your bullets.

 

[mikecr]

To me, BTO is mainly for sorting out bullets that are significantly different than the others. SO/CO allows all bullets to be seated the same and to have the distance to the lands.

This is dead wrong. For one, near entirety of BTO measure(itself) falls BEHIND land relationship. So whether BTOs are matched or vastly separating means nothing to seated land relationship, nor desired/tested best CBTO. And, CBTO like BTO also falls behind land relationship.
What 'allows' all bullets to be seated to tested best CBTO is the reloader (you).

Let's talk about that (CBTO)(what matters).
There is no 'standardized ogive measuring point' beyond your local measure.
This, because no two tools take the same datum on noses, and nothing has been widely accepted as a 'standard' for leade angles, and that will never happen -because it doesn't matter
There is no 'correct point',, and neither you nor anyone else have the tools needed to account for nose angle to leade angle(never have),, so actual land relationship never mattered all.

What matters with seating is that you fully test for best seated CBTO(regardless of land relationship), and log it with ANY local tool that you will always use to reproduce it.

There is no counting on prior bullet sorting to reach CBTO.
Where you want matching CBTO (you should always), then you'll make sure every round you make matches that logged best tested CBTO, using that same local tool, to reproduce what tested as best.

 

[INTJ]

This is dead wrong. For one, near entirety of BTO measure(itself) falls BEHIND land relationship. So whether BTOs are matched or vastly separating means nothing to seated land relationship, nor desired/tested best CBTO. And, CBTO like BTO also falls behind land relationship.
What 'allows' all bullets to be seated to tested best CBTO is the reloader (you).

Let's talk about that (CBTO)(what matters).
There is no 'standardized ogive measuring point' beyond your local measure.
This, because no two tools take the same datum on noses, and nothing has been widely accepted as a 'standard' for leade angles, and that will never happen -because it doesn't matter
There is no 'correct point',, and neither you nor anyone else have the tools needed to account for nose angle to leade angle(never have),, so actual land relationship never mattered all.

What matters with seating is that you fully test for best seated CBTO(regardless of land relationship), and log it with ANY local tool that you will always use to reproduce it.

There is no counting on prior bullet sorting to reach CBTO.
Where you want matching CBTO (you should always), then you'll make sure every round you make matches that logged best tested CBTO, using that same local tool, to reproduce what tested as best.

Base to ogive measurements are good for finding bullets that are similar. SO/CO takes it to the next level by ensuring that bullets seated to the same measurement also have the same jam/jump. It is a PITA to sort this way and it does not show up in the target in every situation.

And there are indeed standardized tools for measuring the ogive. Hornady, Sinclair, and others make these. Sometimes they measure where the bullet will first contact the bore, sometimes they do not. That is the reason for making a custom tool.

So I will keep sorting with SO/CO and spinning on the Bullet Genie. And PLEASE keep arguing against that and trying to convince others that it doesn't work. I like winning matches and shooting small groups.........

 

[Dusty Stevens]

All you need is a barrel stub and reamer and you can measure exactly where itll hit

 

[CarlGeorge]

I'll go ahead and predict that you'll find no meaningful difference.

And......you were right. Shot some tests today. All grouped basically identically. I expected to get some better seating depth results (I did) but didn't see a result on paper.

I ordered the Arbor and bullet seater last night. I'm gonna venture into the world of checking seating pressures.

Thanks all!