varying CBTO when measuring finished ammo

[CobraCharmer]

Hi there SH folks,
I am absolutely new to reloading.

I had a question about the variance in the OAL length of the loaded round. i am loading 180 gr bergers for my 7PRC.

I am using a RCBS Summit with standard 7mmPRC dies (didnt get the matchmaster set).

I determined the OAL length to the lands to be 2.620 (used the oal gauge) and decided to jump it by 20/1000 and shoot for 2.600" as my OAL as measured from the ogive. I then took a plain piece of brass and through trial and error was able to get the OAL dialed in to 2.599 off the ogive. After i loaded up my 30 rounds, I am getting variances in length from 2.594 to 2.609 inches.

Is this normal?

Sorry if my question is borderline obsessive compulsive.

EDIT: I mean CBTO and not OAL as another member kindly pointed out

 

[simonp]

You should be using a tool (Hornady, Area 419 or Short Action Customs) to measure the loaded round from the ogive, that will give you a more consistent reading.

The way you are doing it, you will never be consistent and will drive yourself insane.

 

[CobraCharmer]

You should be using a tool (Hornady, Area 419 or Short Action Customs) to measure the loaded round from the ogive, that will give you a more consistent reading.

The way you are doing it, you will never be consistent and will drive yourself insane.

I am using this tool below to measure my rounds (i already have a modified 7PRC case):

Lock-N-Load® O.A.L. Gauges & Modified Cases - Hornady Manufacturing, Inc

Lock-N-Load® O.A.L. Gauges Regulating seating depth and the resulting jump to the rifling is widely regarded as fundamental to improved accuracy. A few thousandths of an inch change between the bullet and the rifling can make the difference betw...

www.hornady.com

 

[RegionRat]

CBTO means cartridge base to ogive
COAL means cartridge over all length, some folk say OAL when they mean COAL
Don't say OAL when you mean CBTO.

The typical SAAMI spec will show a COAL of 3.090 MIN - 3.340 MAX, so we know you probably mean CBTO.

When you say OAL but mean CBTO, it makes things muddy. Those of us who know the specs for 7 PRC can assume you got this right but used the wrong terminology, however other folks may not know what you mean.

That said, small variation in CBTO is normal. The definition of small in this context is where the trouble starts...
Some folks will not rest till their tolerance is below 0.001" and others are okay with 0.005"

Your range is on the order of 2.609 - 2.594 = 0,015" and is an indication that you are missing something.
You should be able to hold closer to 0.005" as a beginner, and less as you improve.

Double check your work across the board.

Start with the brass prep and look hard at the neck chamfer and inside diameter.
Are you "over cleaning" the necks?

Squeaky clean metals can stick and gall, and the variation in seating forces can contribute to your issues. Don't over clean the brass. It does look great, but makes things difficult. Try to pay attention to neck details. Get with a mentor if you need help.

Are you gaging the same way each time?

It is easy to get into a debate about handing 5 different people those tools and instruments and getting five different answers.
Measurement on the ogive requires a good touch to keep the gage contact pressure the same.
Practice with just repeating the same measurement over and over on a bullet and study what it takes to get the answer to repeat, then switch to cartridges.

If you look with a fresh critical eye, you will find it. If you don't, get some help.

 

[CobraCharmer]

CBTO means cartridge base to ogive
COAL means cartridge over all length, some folk say OAL when they mean COAL
Don't say OAL when you mean CBTO.

The typical SAAMI spec will show a COAL of 3.090 MIN - 3.340 MAX, so we know you probably mean CBTO.

When you say OAL but mean CBTO, it makes things muddy. Those of us who know the specs for 7 PRC can assume you got this right but used the wrong terminology, however other folks may not know what you mean.

That said, small variation in CBTO is normal. The definition of small in this context is where the trouble starts...
Some folks will not rest till their tolerance is below 0.001" and others are okay with 0.005"

Your range is on the order of 2.609 - 2.594 = 0,015" and is an indication that you are missing something.
You should be able to hold closer to 0.005" as a beginner, and less as you improve.

Double check your work across the board.

Start with the brass prep and look hard at the neck chamfer and inside diameter.
Are you "over cleaning" the necks?

Squeaky clean metals can stick and gall, and the variation in seating forces can contribute to your issues. Don't over clean the brass. It does look great, but makes things difficult. Try to pay attention to neck details. Get with a mentor if you need help.

Are you gaging the same way each time?

It is easy to get into a debate about handing 5 different people those tools and instruments and getting five different answers.
Measurement on the ogive requires a good touch to keep the gage contact pressure the same.
Practice with just repeating the same measurement over and over on a bullet and study what it takes to get the answer to repeat, then switch to cartridges.

If you look with a fresh critical eye, you will find it. If you don't, get some help.

Yikes! I meant CBTO, my apologies

I can see where that may be misleading. I know what you mean by practicing measurements as I do see the change in readings when I change the pressure and how the cartridge sits by a minute amount.

Thank you for the assist.

My brass was deprimed and cleaned for 2 hours in a vibratory tumbler, wiped down, lubed and resized (cases were super uniform post resizing), chamfered and deburred with a Lyman.

While the brass was clean enough, I am not sure as to how to spot over cleaned brass? It looked the same level of shiny (maybe a shade dull?) as a new hornady round.

Lots to learn here. Again, I appreciate the help.

 

[OkieMike]

How many firings on the brass, if any?

Edit: Based on your post above mine, at least one firing.

No burrs/swipes on the base? New primers are seated flush or below flush in the pocket?

Just trying to eliminate the simple stuff first.

Mike

 

[Ffastfreddy]

I believe you will want to use the Hornady Comparator and a digital caliper to consistently measure your CBTO.

Lock-N-Load® Bullet Comparator - Hornady Manufacturing, Inc

Lock-N-Load® Bullet Comparator & Inserts Lock-N-Load® Bullet Comparator Measuring cartridge lengths across the bullet tips is not a reliable (or repeatable) method for meas...

www.hornady.com

The OAL Gauge you linked is used to explore what CBTO you should want to have in your rifle. The Comparator is used to measure what CBTO your round has. I am unclear how you are currently measuring but it may not be consistently to the same datum point on the ogive.

 

[Mike Casselton]

As OkieMike suggested, make sure your primers are at least flush with the base of the brass. Preferably, .004-006 below flush. (Some people like more, some less. It's a different discussion)

Also, dwell time seating bullets can affect consistency.

Some people like to seat, rotate 180° and reseat.


Try different methods

 

[CobraCharmer]

I believe you will want to use the Hornady Comparator and a digital caliper to consistently measure your CBTO.

Lock-N-Load® Bullet Comparator - Hornady Manufacturing, Inc

Lock-N-Load® Bullet Comparator & Inserts Lock-N-Load® Bullet Comparator Measuring cartridge lengths across the bullet tips is not a reliable (or repeatable) method for meas...

www.hornady.com

The OAL Gauge you linked is used to explore what CBTO you should want to have in your rifle. The Comparator is used to measure what CBTO your round has. I am unclear how you are currently measuring but it may not be consistently to the same datum point on the ogive.

I use the comparator to check my CBTO with a set of digital calipers. I have also realized that my measurement procedure needs to be super consistent as well as that can effect the reading by thousands of an inch easily.

As OkieMike suggested, make sure your primers are at least flush with the base of the brass. Preferably, .004-006 below flush. (Some people like more, some less. It's a different discussion)

Also, dwell time seating bullets can affect consistency.

Some people like to seat, rotate 180° and reseat.


Try different methods

How many firings on the brass, if any?

Edit: Based on your post above mine, at least one firing.

No burrs/swipes on the base? New primers are seated flush or below flush in the pocket?

Just trying to eliminate the simple stuff first.

Mike

After speaking with @Sig Marine at length over the phone this evening (what an eyeopener that conversation was), there are several things INCLUDING looking at a proper bullet seating stem for the VLD bullets in addition to the above variables the two Mikes are talking about above.

Its absolutely unreal how much there is to learn.

 

[RegionRat]

While the brass was clean enough, I am not sure as to how to spot over cleaned brass? It looked the same level of shiny (maybe a shade dull?) as a new hornady round.

Some methods can clean the necks to nascent metal. When a squeaky clean bullet gets pushed into a squeaky clean neck, the friction turns into a wide variation from normal to stick-slip- to galling. This isn't good for performance.

If we dry tumble, there is a carbon layer in the neck, plus dust residue from the tumble media.
If we use methods like wet tumble with pins, the inside of the necks and case get scrubbed.
Some ultrasonic cleaners can over clean necks as well.

The most effective way to learn, is to try an inline die with a small arbor press. You don't need to own one, just try your prepped brass on a borrowed one to learn how much effect the details of your prep make on seating forces. The main point being an inline with small arbor gives you the sensitivity that you can't feel in a regular press.

Something in the mix is way off. No way to say of it even has anything at all to do with neck friction, but your 0.015" variation is too large and should be something gross. If you don't find it yourself, maybe have a more experienced friend or mentor come over and have a look.

 

[CK1.0]

IMHO the easiest way to shrink the variation in your CBTO lengths is to just slow down a bit at the handle.

Brass and copper are soft, and as has been mentioned, the friction and press-fit in the necks can vary from case to case depending on one's cleaning/brass prep regime. So when seating bullets, one's stroke/technique matters.

If one runs the handle briskly to a hard stop like a gorilla, the variation will be greater than if one runs the handle carefully and smoothly, sort of sneaking up on reaching full stroke more gentle-like...

 

[CobraCharmer]

Some methods can clean the necks to nascent metal. When a squeaky clean bullet gets pushed into a squeaky clean neck, the friction turns into a wide variation from normal to stick-slip- to galling. This isn't good for performance.

If we dry tumble, there is a carbon layer in the neck, plus dust residue from the tumble media.
If we use methods like wet tumble with pins, the inside of the necks and case get scrubbed.
Some ultrasonic cleaners can over clean necks as well.

The most effective way to learn, is to try an inline die with a small arbor press. You don't need to own one, just try your prepped brass on a borrowed one to learn how much effect the details of your prep make on seating forces. The main point being an inline with small arbor gives you the sensitivity that you can't feel in a regular press.

Something in the mix is way off. No way to say of it even has anything at all to do with neck friction, but your 0.015" variation is too large and should be something gross. If you don't find it yourself, maybe have a more experienced friend or mentor come over and have a look.

I wiped the tumbled brass with a t-shirts and checked the flash hole for media as well. The arbor press idea is definitely new for me. I have a friend coming over this weekend to take a look at the setup etc.

IMHO the easiest way to shrink the variation in your CBTO lengths is to just slow down a bit at the handle.

Brass and copper are soft, and as has been mentioned, the friction and press-fit in the necks can vary from case to case depending on one's cleaning/brass prep regime. So when seating bullets, one's stroke/technique matters.

If one runs the handle briskly to a hard stop like a gorilla, the variation will be greater than if one runs the handle carefully and smoothly, sort of sneaking up on reaching full stroke more gentle-like...

I got so used to the cam over when sizing the brass, i was using about the same amount of force for seating the first few rounds till i realized that i didnt have to use that kind of force atall.

Sure enough, i re-measured and the first 10 rounds are on the shorter side 2.594 - 2.597 while the remaining 20 are on the 2.6 - 2.604 with the only anomaly being the very last one that came in at 2.609.

The irony here is that I lost sight of why I was handloading in the first place. CONSISTENCY CONSISTENCY CONSISTENCY.

I should have been a bit more patient.

 

[Evintos]

I use the comparator to check my CBTO with a set of digital calipers. I have also realized that my measurement procedure needs to be super consistent as well as that can effect the reading by thousands of an inch easily.

If you're not already doing so - when you measure with the comparator, rotate the cartridge a few times in the comparator, it'll help to keep the cartridge aligned between the comparator and caliper jaw. Also don't apply super hard pressure on the thumb wheel or slider.

 

[JoshPutman]

There is a touch you develop using calipers. There is no need to squeeze the shit out of them, they are not an adjustable wrench. Be gentle with them. The force you apply can vary your reading by several thousandths.

I'm not trying to imply that you are ham handing them, just making you aware of the intricacies of using them.

 

[MarkyMark007]

it's the press and the die with inconsistent neck ''tension'', which cause an incosistent length (if you have right seating stem). can be in finished round or at headspace:

Is your seating die micrometer accurate

Is your seating die micrometer accurate, not repeatable/consistent, accurate? When you move the micrometer .003 does it move the bullet depth .003?

www.snipershide.com

 

[OkieMike]

When I seat bullets I try to keep variance to +/- .0005"

Doesn't always work out that way especially if the case is near max fill. Sometimes I have to settle for +/- .001" if I'm trying to just get them done.

The absolute max I will accept is +/- .0015 but that's just me. Probably overkill but it helps me sleep at night.

I've found that applying the "same" amount of force to the ram handle helps... But it's near impossible to do that consistently so that's where an arbor press and force gauge would come in handy. But with practice you can usually keep things pretty close.

Mike

 

[JR1200W3]

Here is a question for the OP.

"Does it matter?"

Everyone is focused on getting the most consistent CBTO. But does it matter? If you're accuracy is dependent on 5 thou of seating depth then that is a picky load you probably don't want to be shooting that anyway.

Try to get your CBTO variation inside of 5 thou and find a seating depth that has a decent window of accuracy so you don't drive yourself crazy tying to get down to the single thou every time.

 

[Baron23]

I use the comparator to check my CBTO with a set of digital calipers. I have also realized that my measurement procedure needs to be super consistent as well as that can effect the reading by thousands of an inch easily.




After speaking with @Sig Marine at length over the phone this evening (what an eyeopener that conversation was), there are several things INCLUDING looking at a proper bullet seating stem for the VLD bullets in addition to the above variables the two Mikes are talking about above.

Its absolutely unreal how much there is to learn.

If you are seating VLD bullets without using a VLD seating stem, that alone will have a negative impact on your consistency, IMO.

 

[CobraCharmer]

If you're not already doing so - when you measure with the comparator, rotate the cartridge a few times in the comparator, it'll help to keep the cartridge aligned between the comparator and caliper jaw. Also don't apply super hard pressure on the thumb wheel or slider.

Yep, I have started doing that now. Force isin't everything is my new mantra.

There is a touch you develop using calipers. There is no need to squeeze the shit out of them, they are not an adjustable wrench. Be gentle with them. The force you apply can vary your reading by several thousandths.

I'm not trying to imply that you are ham handing them, just making you aware of the intricacies of using them.

Ham handing is my middle name. Apparently.

it's the press and the die with inconsistent neck ''tension'', which cause an incosistent length (if you have right seating stem). can be in finished round or at headspace:

Is your seating die micrometer accurate

Is your seating die micrometer accurate, not repeatable/consistent, accurate? When you move the micrometer .003 does it move the bullet depth .003?

www.snipershide.com

I didn't even consider neck tension till I spoke with a forum member last night. I am just using a standard seating steam that came with the die.

When I seat bullets I try to keep variance to +/- .0005"

That is the dream Mike. I will get there, one day, eventually.

Here is a question for the OP.

"Does it matter?"

Everyone is focused on getting the most consistent CBTO. But does it matter? If you're accuracy is dependent on 5 thou of seating depth then that is a picky load you probably don't want to be shooting that anyway.

Try to get your CBTO variation inside of 5 thou and find a seating depth that has a decent window of accuracy so you don't drive yourself crazy tying to get down to the single thou every time.

This brings up a great point, i am looking for a load with a large margin of error within 10/1000 of a variance in seating depth.

If you are seating VLD bullets without using a VLD seating stem, that alone will have a negative impact on your consistency, IMO.

I am going nuts looking for a VLD seating stem that fits a standard RCBS seating die. Where could I find one that I could replace my current one with?

 

[JR1200W3]

i am looking for a load with a large margin of error within 10/1000 of a variance in seating depth.

Part of that is bullet style. VLDs are known to be a bit more picky on seating depth. Generally, longer jumps are more tolerant of variants. When you get closer to the lands, I think you have a higher chance of finding a good seating depth, but the variation window is smaller.
20 - 30 thou from the lands will provide decent accuracy from 90% of the bullets out there but may only provide you 5 thou window of variation. A 77gr SMK loaded to mag length in a .223 Wylde chamber is a great example. Traditional bullet shape. .200"(?) Jump. Fantastic accuracy. You'll never have to mess with seating depth.

 

[OkieMike]

Here is a question for the OP.

"Does it matter?"

Everyone is focused on getting the most consistent CBTO. But does it matter? If you're accuracy is dependent on 5 thou of seating depth then that is a picky load you probably don't want to be shooting that anyway.

Try to get your CBTO variation inside of 5 thou and find a seating depth that has a decent window of accuracy so you don't drive yourself crazy tying to get down to the single thou every time.

That's a good point. I try to keep everything tight because... Well... That's what I learned... and never bothered to check and see if a wider tolerance still yielded acceptable results.

Mike

 

[JR1200W3]

That's a good point. I try to keep everything tight because... Well... That's what I learned... and never bothered to check and see if a wider tolerance still yielded acceptable results.

Mike

I'm driving to the range right now to test seating depth. I previously shot five round ladders of 20 off, 30 off, 40 off, and 50 off. 50 off shot best.

Now I'm shooting 45 off, 50 off, and 55 off to see what my window looks like.

 

[Baron23]

I am going nuts looking for a VLD seating stem that fits a standard RCBS seating die. Where could I find one that I could replace my current one with?

Wow, just looked and I don't see them offering this anywhere. I use Redding dies and they make seating stems that are longer for VLD bullets including my humble Berger 140 Hybrid Targets. Doesn't look like RCBS offers a similar item that I could find.

I do note that if you google "RCBS vld seating stem" there are posts on different forums on this subject and it seems the answer is to contact RCBS customer service. Apparently they can make you one....or something? I would def contact them, tell them caliber/bullet you are using, and ask if they have a VLD stem (though they might call it a seating plug??)

Redding looks like a very different design than RCBS. This is the Redding seating stem. If you put a bullet pointy end down in a standard stem and it bottoms out and cocks to the side, then you need the VLD stem that will allow contact at the ogive and not the meplat.

Best of luck and give RCBS a ring/email and ask them is all I can offer.

 

[MarkyMark007]

I didn't even consider neck tension till I spoke with a forum member last night. I am just using a standard seating steam that came with the die.

did you understand my post which I was linking or you didnt read it ???

you must firmly contact your seating die to your shellholder to have constant dimensions !!! even if you have problems with neck tension, firm contact will surpass that to some extent and you will have quite constant OGIVE dimensions.

and for seating stem:

-if you dont have marks on the bullet:

https://bulletin.accurateshooter.com/2018/09/tip-polish-seating-stems-to-eliminate-ring-marks-on-bullets/

https://bulletin.accurateshooter.com/2018/09/tip-polish-seating-stems-to-eliminate-ring-marks-on-bullets/

-of your tip of the bullet is not contacting your seating stem upper-end, you dont have problems with seating stem and you dont need to change it.

 

[JoshPutman]

If you have a seating die that seats and crimps at the same time, you don't want to do that because you will crush shoulders. I learned that the hard way when I started loading 5.56.

If you bring the ram all the way up every time, even without hitting the bottom of the die, how would you not get consistent seating depth? Unless your neck tension is all over the place, perhaps.

I do, however, use a few seconds of dwell at the top, so maybe that's why I seem to get good results.

If I'm mistaken in my thoughts or methods, I'm willing to be corrected.

 

[MarkyMark007]

If you bring the ram all the way up every time, even without hitting the bottom of the die, how would you not get consistent seating depth? Unless your neck tension is all over the place, perhaps.

I cant have consistent OGIVE dimension if I dont hit the bottom of the die; not with ex Lee Classis Cast press not with present RCBS Summit press... Because of small or large variations in neck tension... I just cant control that by some other way...

 

[CobraCharmer]

Wow, just looked and I don't see them offering this anywhere. I use Redding dies and they make seating stems that are longer for VLD bullets including my humble Berger 140 Hybrid Targets. Doesn't look like RCBS offers a similar item that I could find.

I do note that if you google "RCBS vld seating stem" there are posts on different forums on this subject and it seems the answer is to contact RCBS customer service. Apparently they can make you one....or something? I would def contact them, tell them caliber/bullet you are using, and ask if they have a VLD stem (though they might call it a seating plug??)

Redding looks like a very different design than RCBS. This is the Redding seating stem. If you put a bullet pointy end down in a standard stem and it bottoms out and cocks to the side, then you need the VLD stem that will allow contact at the ogive and not the meplat.

View attachment 8291016
Best of luck and give RCBS a ring/email and ask them is all I can offer.

Reaching out to RCBS worked out. Thank you for that suggestion!

Here is what they said verbatim:
To create a custom plug, we’ll need 3 sample bullets, the diameter of the seater stem, and the caliber. We make seater plugs in 1/4 x 28 and 1/2 x 20. If you need a 7mm or .30 caliber Matchmaster seat plug for your Matchmaster die set, please specify the length of your seat plug so we ensure we make the correct plug for you. Without this information, we cannot start the plug and your order will be delayed. Please include your name, address, and telephone number as well as the type of plug you need (1/4 x 28 seat plugs thread into the die from the bottom and 1/2 x 20 seat plugs thread into the die from the top) in your package.

The cost for the custom plug is $19.95 and $7.50 for shipping, plus applicable sales tax. If you have a Gold Medal seat die or Matchmaster seat die seat plug, the price is $27.95, plus shipping and sales tax. We will contact you for your Visa card or Mastercard details. For expediency, please do not include a check with your package, as we no longer process them. Please ship your package to the following address:

RCBS
605 Oro Dam Blvd E.
Oroville, CA 95965

The process will take 2 to 6 weeks to complete once we’ve received all the necessary information.

Please do not respond to this email unless you need further assistance to decrease our email volume.

KA | Technical Support Representative
RCBS | Champion | Weaver
605 Oro Dam Blvd E
Oroville, CA 95965

 

[Baron23]

Reaching out to RCBS worked out. Thank you for that suggestion!

Here is what they said verbatim:
To create a custom plug, we’ll need 3 sample bullets, the diameter of the seater stem, and the caliber. We make seater plugs in 1/4 x 28 and 1/2 x 20. If you need a 7mm or .30 caliber Matchmaster seat plug for your Matchmaster die set, please specify the length of your seat plug so we ensure we make the correct plug for you. Without this information, we cannot start the plug and your order will be delayed. Please include your name, address, and telephone number as well as the type of plug you need (1/4 x 28 seat plugs thread into the die from the bottom and 1/2 x 20 seat plugs thread into the die from the top) in your package.

The cost for the custom plug is $19.95 and $7.50 for shipping, plus applicable sales tax. If you have a Gold Medal seat die or Matchmaster seat die seat plug, the price is $27.95, plus shipping and sales tax. We will contact you for your Visa card or Mastercard details. For expediency, please do not include a check with your package, as we no longer process them. Please ship your package to the following address:

RCBS
605 Oro Dam Blvd E.
Oroville, CA 95965

The process will take 2 to 6 weeks to complete once we’ve received all the necessary information.

Please do not respond to this email unless you need further assistance to decrease our email volume.

KA | Technical Support Representative
RCBS | Champion | Weaver
605 Oro Dam Blvd E
Oroville, CA 95965

While I’m very glad they have an answer for you, I’m sort of appalled that the don’t make VLD plugs in various calibers as does Redding and, I would suspect, others. Without needing you sample bullets, etc.

I’m not familiar with RCBS dies but VLD bullets are quite common and having them bottom out in your seating due is bad juju. Just baffling to me.

Cheers

 

[CobraCharmer]

Loaded a new batch of ammo and this time it was 30 rounds with the RCBS seating stem and kept the downstroke as uniform as possible across the board:

Distance to lands was 2.620 inches
Target CBTO was 2.6 inches

I measured each of them as uniformly as possible. Here are my numbers.

AVERAGE 2.6005
STD DEV 0.0017
MAX 2.602
MIN 2.595

 

[DeathBeforeDismount]

Here is a question for the OP.

"Does it matter?"

Everyone is focused on getting the most consistent CBTO. But does it matter? If you're accuracy is dependent on 5 thou of seating depth then that is a picky load you probably don't want to be shooting that anyway.

Try to get your CBTO variation inside of 5 thou and find a seating depth that has a decent window of accuracy so you don't drive yourself crazy tying to get down to the single thou every time.

This. How does it shoot.

A few thou variance wont matter unless you are shooting a really bad bullet. Berger hybrids don't care.

 

[secondofangle2]

I discovered this problem myself the first time when I was setting up my Warner tool company seating die for 50 BMG and 750 AMAX

Not only does the 50 Amax Projectile have a variable overall length, the bullet also has a variable base to give. You can measure the unloaded bullets themselves in the same device you would measure your CBTO - but measure just the bullet. I bet they vary by several thou

If your seating stem measures off the tip of the bullet, then you will have consistent COAL but not consistent CTBO. Assuming you’re not damaging the tip with an ill-fitted seating stem

Even if you could find a seating stem that pushed the projectile from the ogive when seating, the ogive appears at a different length along the bullet in the case of the Amax. So then I would have a consistent CBTO but still a variable COAL.

All of this due to bullet to bullet variability, at least w the 750 AMAX

Thankfully, I realized it didn’t matter because I have a long throated 50 BMG and the bullets are jumping 250 thou anyway, so it hardly matters

Have you measured the base to ogive of your unloaded BULLETS?

 

[Holliday]

I always have difficulty with consistent CBTO so I generally sneak up on it with the micrometer adjustment on the die. I end up with +/- .0005 (worst case .001). Using a SAC comparator really helps though. Night and day over the Hornady, in my opinion….Same with the headspace comparators.

The problem is that means not all bullets are moved the same amount of times. I often wonder if this enlarges my SDs……..??

I will say that annealing helps minimize this variance.

 

[secondofangle2]

What exactly does the SAC compared to do that? The Hornady doesn’t or doesn’t do as well?

I don’t want to derail this thread, but just because you can measure something to .0001 doesn’t mean that you should or that it improves anything that we care about

I mentioned above inconsistency in the geometry of bullets, but I’m not gonna put them all on a laser, scanner and sort them

 

[Holliday]

I don’t want to derail this thread, but

So stommpy feet???