Coal/cbto

Clucknmoan

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This has probably already been stated, but inconsistent BTO is usually inconsistent neck tension. If you really pay attention you can feel the difference in seating pressure resistance if one is going to be long. Expanding out to tension with a mandrel really helps with this, pushes inconsistencies in your neck thickness to the outside. The other thing it maybe is if you are seating over a compressed load. That will create inconsistencies too.
 

N2TRKYS

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Had my smith open the mag box up to fit a coal of 3.080”. He made me some dummies but I disassembled them to shoot the bullet and try out my forester bullet puller.
I’m way past mag length when at lands with either Berger or hammer this being the reason I said I’d just hand feed the Berger’s. The hammers jump far less at mag length .035”ish jump but the Berger’s .105”ish jump.
I say “ish” because my modified case was unfired win brass but I’m now using new Norma and they’re slightly different. I need to have one of my 1x fired pieces of Norma bump sized .002” and threaded for my oal gauge so I can know more exactly where the lands are with these components.
However I’m not shooting Berger’s at any game here in California so I can put off development on them until I get drawn for out of state hunt and just shoot the hammers at mag length as they seem to be impervious to differences in jump. (Steve at hammer will agree with this... as wrong as it sounds).
I’ve gotten the answers and info I needed to resolve my issues at the moment and thank those who replied here.
You can just use your cleaning rod to find your distance to the lands.
 

Clucknmoan

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In my experience BTO is much more consistent, and it’s the only measurement I really care about since consistent distance from ogive to lands is what we are after. COAL for me is effected by too many things, bullet tips are quite often buggered up whether they are plastic or not. Doesn’t give consistent Measurements for me where the ogive never changes.
 

Clucknmoan

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If you really want to get down and dirty with you touch, look up The stripped bolt method. Alex Wheeler has a great video explaining it. I use a cleaning rod with collets to get a general idea, but it always turns out that I’m in the lands about 5 thou after I strip a bolt. That much may not matter to some, but being within a half or a thou of accurate is nice when you are checking 2 years down the road to see how much your throat has eroded.
 

N2TRKYS

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In my experience BTO is much more consistent, and it’s the only measurement I really care about since consistent distance from ogive to lands is what we are after. COAL for me is effected by too many things, bullet tips are quite often buggered up whether they are plastic or not. Doesn’t give consistent Measurements for me where the ogive never changes.
Have you measured many distances to the ogive on your bullets(just the bullet, not the loaded round)?
 

N2TRKYS

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If you really want to get down and dirty with you touch, look up The stripped bolt method. Alex Wheeler has a great video explaining it. I use a cleaning rod with collets to get a general idea, but it always turns out that I’m in the lands about 5 thou after I strip a bolt. That much may not matter to some, but being within a half or a thou of accurate is nice when you are checking 2 years down the road to see how much your throat has eroded.
Huh? There’s nothing to strip out with a cleaning rod. What’s your version of this method?
 

mvrk28

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Cahunter what kind of bullet trimmer are you talking about? Didn’t know that was a thing.
I would advise against doing any meplat trimming or bullet pointing. Just seat to CBTO (regardless of what misinformed people may think they learned in their testing, they're wrong) and find a good node in a ladder test. This method has given me sub half moa in countless rifles.
 

Clucknmoan

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Huh? There’s nothing to strip out with a cleaning rod. What’s your version of this method?
I use a cleaning rod, collets and a bullet being pushed into the neck to get a starting point. Re insert the bullet and Measure that 5 or 10 times and you get some variance. Try it with different bullets and you will get even more variance. Might not be much, but you almost always have to take an average to get touch. Take that average to start with.

Then take your bolt and strip the firing pin so there is no tension at all when you close the bolt. It will just fall.

Then you can either remove the ejector (if the action has one) or take a dremell tool and carve out the case head/base so the ejector doesn’t touch anywhere. Make sure you size the case. Set the case in the bolt and slide it in the chamber. You will feel absolutely no resistance, it will just fall.

Seat a bullet in that sacrificed case to the the average length from the collet measurement and again set it in the bolt and run it in the chamber. 99% of the time it will not fall freely with that measurement, which means you are actually in the lands. If the bolt closing is real sticky, keep seating 2 or even 3 thou deeper till you can barely feel a tick or resistance. Then go half or 1 thou at a time. Measure between it depth and document it. Once you don’t feel any resistance on the fall or the rise of the bolt, the last measurement you took is touch. Just take that sacrificed case and throw it in you die box for the next time.

Yes it takes extra time, but it’s very accurate and repeatable every time. 5 years down the road when your rig doesn’t shoot as well as it used to, do this test again and see how much your throat has eroded. If it’s eroded 5 thou then seat you loads 5 thou longer than original and you are back in the money.

Like I said, Alex Wheeler has a great video explaining the process
 

N2TRKYS

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I would advise against doing any meplat trimming or bullet pointing. Just seat to CBTO (regardless of what misinformed people may think they learned in their testing, they're wrong) and find a good node in a ladder test. This method has given me sub half moa in countless rifles.
I can’t help that you don’t like the results from my testing. That’s your issue.
 
Last edited:

N2TRKYS

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I use a cleaning rod, collets and a bullet being pushed into the neck to get a starting point. Re insert the bullet and Measure that 5 or 10 times and you get some variance. Try it with different bullets and you will get even more variance. Might not be much, but you almost always have to take an average to get touch. Take that average to start with.

Then take your bolt and strip the firing pin so there is no tension at all when you close the bolt. It will just fall.

Then you can either remove the ejector (if the action has one) or take a dremell tool and carve out the case head/base so the ejector doesn’t touch anywhere. Make sure you size the case. Set the case in the bolt and slide it in the chamber. You will feel absolutely no resistance, it will just fall.

Seat a bullet in that sacrificed case to the the average length from the collet measurement and again set it in the bolt and run it in the chamber. 99% of the time it will not fall freely with that measurement, which means you are actually in the lands. If the bolt closing is real sticky, keep seating 2 or even 3 thou deeper till you can barely feel a tick or resistance. Then go half or 1 thou at a time. Measure between it depth and document it. Once you don’t feel any resistance on the fall or the rise of the bolt, the last measurement you took is touch. Just take that sacrificed case and throw it in you die box for the next time.

Yes it takes extra time, but it’s very accurate and repeatable every time. 5 years down the road when your rig doesn’t shoot as well as it used to, do this test again and see how much your throat has eroded. If it’s eroded 5 thou then seat you loads 5 thou longer than original and you are back in the money.

Like I said, Alex Wheeler has a great video explaining the process
I’ve had more repeatable measurements with the cleaning rod method than with the tool, so that’s what I go with.
 

Clucknmoan

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Great, then you know that they all don’t have the same measurement.
No they don’t all have the same measurement if measuring from the base of the bullet to the ogive. But that doesn’t matter for CBTO once it’s in a case. Base of bullet to ogive and ogive to meplat is irrelevant to CBTO. At least in terms of accurate seating depth.
 

Clucknmoan

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I’ve had more repeatable measurements with the cleaning rod method than with the tool, so that’s what I go with.
Just to be clear, this method doesn’t use a tool. But yes, there are variances with Hornady s OAL tool.
 

JakeSCH

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This thread is hilarious. Ya'll doing the same thing in different ways. Being consistent with how you do it most important.

However, I'm getting my popcorn out for this one.
 

N2TRKYS

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No they don’t all have the same measurement if measuring from the base of the bullet to the ogive. But that doesn’t matter for CBTO once it’s in a case. Base of bullet to ogive and ogive to meplat is irrelevant to CBTO. At least in terms of accurate seating depth.
So, now they are different. Gotcha, thanks.
 

N2TRKYS

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This thread is hilarious. Ya'll doing the same thing in different ways. Being consistent with how you do it most important.

However, I'm getting my popcorn out for this one.
I’ve been trying to tell them that, but they won’t listen. Lol. Pass the popcorn, please.
 

Brendan

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This thread is hilarious. Ya'll doing the same thing in different ways. Being consistent with how you do it most important.
Not at all the same thing. CBTO and COAL measurements are different and one can introduce error that the other won't in certain scenarios.
 

Clucknmoan

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So, now they are different. Gotcha, thanks.
Lol. I’m not trying to argue with you, I’m trying to help the OP and politely give what years of chasing consistency has taught me.

Please clarify your side of this without trying to run over me with the bus. How does an inconsistent BULLET base to ogive effect Cartidge Base to ogive?
If there is merit to it, I guarantee I will listen.
 
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