Optimal means to measure chamber .... bullet seating depth

[Webster]

guys,
I have been reloading for a while now... but can never seem to get a reliable fix in the exact measurement of my bullet length to the lands ... so that I can optimize my bullet seating depth.

I've tried loose set bullets (dummy rounds) and then chambering the bullet then measuring OAL .... and more appropriately measuring the length to ogive ....... and doing this repeatedly ... but don't feel I get the right precision I need or the repeatability I want.
I have not bought a commercial measurement device.... but seems like that is my next go.
Any suggestions?

I have tried every method and I keep coming back to the below method.

I use a split cartridge neck (cut with a Dremel tool) and make the overall length to cover the range of about touch to 5-50 thou too long. Seems like you have to get the neck tension not to tight or loose. You may have to size the case to get the right tension after about 10 test. Plot the In COAL VS Delta in Excel. Eliminate a few obvious test like when the bullet stuck and got pulled longer or some how got pushed in when extracting. You can tell the good data by looking at how close it comes to a straight line. Eliminate all Zero Delta data. It was too short to touch the rifling.

I have Excel plot the best fit straight line and enter the equation for the line and R^2. You can have confidence in the result because all of the data points are within 2-3 thou of the best fit line. You are not depending on one perfect measurement. If you don't have a zero data point you can guess at it or calculate for zero on the Y-axis. Doesn't matter that all the Out numbers are not identical. Has to be error in the technique.

Added Later: I sorted the data based on the In column. Looks like the longer the starting IN COAL the farther the ogive gets pushed into the lands. Definite trend.

 

[aj300mag]

I believe the best method to find TOUCHING land relationship is the old cleaning rod method. This from the muzzle, provides distance from bolt face to a bullet tip, while that bullet is lightly held against lands.
One version described at 6.5Grendel forum: http://www.65grendel.com/forum/showthread.php?7743-Determining-Maximum-Overall-Cartridge-Length
View attachment 1021522
In no way will knowing touching COAL, or any other land relationship help you in optimizing seating depth. This, because optimum seating depth is not a land relationship, but a tested best CBTO.

Yup. Been using that method for over thirty years and it works! I use that specific bullet to make a dummy round seated the the measurement I got and then measure the CBTO using a bushing that I made with the chamber reamer.

 

[T-shooter]

I have tried every method and I keep coming back to the below method.

I use a split cartridge neck (cut with a Dremel tool) and make the overall length to cover the range of about touch to 5-50 thou too long. Seems like you have to get the neck tension not to tight or loose. You may have to size the case to get the right tension after about 10 test. Plot the In COAL VS Delta in Excel. Eliminate a few obvious test like when the bullet stuck and got pulled longer or some how got pushed in when extracting. You can tell the good data by looking at how close it comes to a straight line. Eliminate all Zero Delta data. It was too short to touch the rifling.

I have Excel plot the best fit straight line and enter the equation for the line and R^2. You can have confidence in the result because all of the data points are within 2-3 thou of the best fit line. You are not depending on one perfect measurement. If you don't have a zero data point you can guess at it or calculate for zero on the Y-axis. Doesn't matter that all the Out numbers are not identical. Has to be error in the technique.

Added Later: I sorted the data based on the In column. Looks like the longer the starting IN COAL the farther the ogive gets pushed into the lands. Definite trend.

View attachment 1021524

Another way with the split case neck. Get the bullet to be a snug fit but loose enough you can move it with your fingers. Put some blue Loctite in the neck, insert the bullet, and gently chamber it. Leave it sit there long enough for the Loctite to set up. The bullet won't stick or move as you extract it and give a false reading.

 

[Webster]

Thats not simple information. Simple information is just testing it and finding it. What you have is a pain in the ass methodology for a flawed method.

It is not a flawed method. It works and I trust it. I only have to do it on a couple bullets every couple years. Takes about 1/2 hour.

 

[Forum Boss]

I have been able to get repeatable measurements to .001" four times out of five, using the Hornady tool. There is a technique:

1. Make sure you have clean chamber and throat.
2. Modified cartridge needs to be screwed on the tool all the way (it tends to unscrew as you take repeat measurements).
3. Ensure the modified case is FULLY SEATED in the chamber.
4. KEY: Push the bullet GENTLY till you have first contact. Then tap the shaft of the tool a couple times (sometimes the bullet is a little crooked and the tapping will center).
5. REALLY Important. With 1 or 2 fingers, push the plastic rod gently (NOT HARD!!) until you get contact with the lands.

This is where most guys screw up -- they shove the rod hard so they may be .005 in lands, .003, .002 etc.

6. Check the bullet -- you should see the tiniest perceptible mark on the jacket. If you see lines or big engraving you pushed too hard.

NOTE: I have reviewed the Wheeler method in the video. That is also a reliable method. But I think it is cumbersome and unnecessarily time-consuming. Doing 1-6 above I can get a repeatable measurement 4 of 5 (I always take five measurements). And most importantly I can hand the tool and modified case to another guy and he can get the same measurement.



The big three mistakes people make when using the Hornady tool are:

1. Pushing TOO HARD on the plastic rod that advances the bullet.
2. Not seating the modified case properly (all the way) in the chamber.
3. Not ensuring the modified case is all the way screwed on before taking measurement.
4. Not attaching the comparator consistently on the jaw of your Calipers.

 

[pburr]

The bullets relationship to where the Lans start is irrelevant to me. With the Hornady tool, I jam a bullet as far as it will go using only the pressure of my thumb. I push on it 10 times and lock the rod in place and remove. I push the bullet out and that is my jam measurement. It is more consistent than trying to "feel" my way against the Lans or pushing a dummy round in. Once I have that measurement, I simply start load development at -.020 off. Once I find powder range, I start seating depth from -.005 off the hard jam to around -.030 off. I let the paper decide where it wants to be.

 

[jimbires]

I use the split neck method .

I have a question on the hornady tool . are you guys using fired brass from your gun ? if not , how can you be sure the brass case is the correct length for the chamber you are measuring ? or how do you make it the correct length ?

 

[savagedasher]

Depending on the bullet and the diameter and the lead angle pushing the bullet you could be .060 in the lands . Larry

 

[pburr]

I use the split neck method .

I have a question on the hornady tool . are you guys using fired brass from your gun ? if not , how can you be sure the brass case is the correct length for the chamber you are measuring ? or how do you make it the correct length ?

Yes. For the two rifles I compete with I had custom gauge cases made that were fired from my chambers x3.

 

[mikecr]

With the Stoneypoint/Hornady system you're taking things to a shoulder datum(the weakness in the system), while CBTO is taken from the case head.
The cleaning rod method directly leads to CBTO at touching.
With it, there is no modified case with headspacing of it's own. The case is eliminated.

 

[Texas10]

If you're loading for large caliber, like 308 many of the above suggestions will do very nicely. If however, you're loading a slim, pointy, small caliber like 223, 22-250 or even 6mm and are using a stock Savage action, your options begin to diminish rapidly.

For those "hard to read" small pointy bullets, ONE way is to take your Hornaday modified case and neck or FL size it and seat a bullet long. Mount it on the tool, and push it up into the chamber and then withdraw. If it sticks, it's in the lands. Continue to seat the bullet a bit deeper until you feel no "stick" upon withdrawing. That is "touching lands" dimension. Extremely accurate and repeatable. If you want more accuracy, drill and tap your FF cartridge and perform the same test. I use a 6-32 tap and put it on a section of 3 piece rod.

 

[Forum Boss]

With the Stoneypoint/Hornady system you're taking things to a shoulder datum(the weakness in the system), while CBTO is taken from the case head.
The cleaning rod method directly leads to CBTO at touching.
With it, there is no modified case with headspacing of it's own. The case is eliminated.

Mike -- It doesn't matter at ALL which datum if the number you have is repeatable. You just take the number you have and find out where the best accuracy is relative to that number. For example if I have a number of 2.255 for repeatable "Hornady tool touch" and I find, by testing, that my best accuracy is at 2.2560 or five thousandths beyond that point -- that's all I need to know, because I can load my ammo to that length and confirm it with the calipers and comparator. You are discovering the ideal seating depth experimentally with your live ammo. You only need the Hornady reference to have a repeatable starting point. Your testing will reveal the most accurate overall length with your working brass.

 

[tenring]

I have been able to get repeatable measurements to .001" four times out of five, using the Hornady tool. There is a technique:

1. Make sure you have clean chamber and throat.
2. Modified cartridge needs to be screwed on the tool all the way (it tends to unscrew as you take repeat measurements).
3. Ensure the modified case is FULLY SEATED in the chamber.
4. KEY: Push the bullet GENTLY till you have first contact. Then tap the shaft of the tool a couple times (sometimes the bullet is a little crooked and the tapping will center).
5. REALLY Important. With 1 or 2 fingers, push the plastic rod gently (NOT HARD!!) until you get contact with the lands.

This is where most guys screw up -- they shove the rod hard so they may be .005 in lands, .003, .002 etc.

6. Check the bullet -- you should see the tiniest perceptible mark on the jacket. If you see lines or big engraving you pushed too hard.

NOTE: I have reviewed the Wheeler method in the video. That is also a reliable method. But I think it is cumbersome and unnecessarily time-consuming. Doing 1-6 above I can get a repeatable measurement 4 of 5 (I always take five measurements). And most importantly I can hand the tool and modified case to another guy and he can get the same measurement.

View attachment 1021554

The big three mistakes people make when using the Hornady tool are:

1. Pushing TOO HARD on the plastic rod that advances the bullet.
2. Not seating the modified case properly (all the way) in the chamber.
3. Not ensuring the modified case is all the way screwed on before taking measurement.
4. Not attaching the comparator consistently on the jaw of your Calipers.

 

[tenring]

Couple other things Boss: After using the Hornady tool 5 times, average the result and prepare a dummy round to about .005" longer than that CBTO. Burnish the bullet with 0000 steel wool or coat with black marker and try in your chamber with the FP removed. You may need a jewelers loupe to see the marks where contact was made.

I do not tap the bullet in.

Some factory barrels have thin lands making observation of the contact marks difficult.

Forum Boss: None of that is necessary. No need to average -- if you do this right, 4 of 5 measurements will typically be to the thousandth or 1.5 thous. I can do it all again and I will get the same number if I toss the one that's typically off. I don't WANT to push the bullet into the lands hard to get engraving marks, because that can actually alter the readings. I'm NOT looking for marks. What I am getting is a REPEATABLE "first contact". Then if I load .010" longer I know I am about ten thou in the lands... but it really doesn't matter if that is .012" or .009" because the number that counts is where the gun shoots best... that could be in the lands, right near touch, or jumping... all depends on the barrel, bullet and powder combo.

 

[Webster]

The bullets relationship to where the Lans start is irrelevant to me. With the Hornady tool, I jam a bullet as far as it will go using only the pressure of my thumb. I push on it 10 times and lock the rod in place and remove. I push the bullet out and that is my jam measurement. It is more consistent than trying to "feel" my way against the Lans or pushing a dummy round in. Once I have that measurement, I simply start load development at -.020 off. Once I find powder range, I start seating depth from -.005 off the hard jam to around -.030 off. I let the paper decide where it wants to be.

Agree: Finding the touch is just a starting point. Need to load up some shorter and longer and try them no matter how accurate your touch number was.

Forum Boss: I think you will get more consistent, repeatable results going for "first touch" rather than trying to hard-jam as you have described (though I know some short range PPC guys like to do that). If you use the same bullet you will actually be altering the jacket with multiple hard jams like that. 10 times I almost can assure you the measurement will be different on 10X vs. the first time.

 

[Barlow]

Mike -- It doesn't matter at ALL which datum if the number you have is repeatable. You just take the number you have and find out where the best accuracy is relative to that number. For example if I have a number of 2.255 for repeatable "Hornady tool touch" and I find, by testing, that my best accuracy is at 2.2560 or five thousandths beyond that point -- that's all I need to know, because I can load my ammo to that length and confirm it with the calipers and comparator. You are discovering the ideal seating depth experimentally with your live ammo. You only need the Hornady reference to have a repeatable starting point. Your testing will reveal the most accurate overall length with your working brass.

That is exactly what I do. I did a test the other day on 100 gr .257 Hornady's, hard push vs soft touch, there was a .006 difference. Barlow

 

[powderbrake]

Can anyone comment on if it's more difficult to determine touch after erosion has worn down the leading edge of the land? Based on bore scope I am getting 0.008" erosion in the land beginning per 1000 rounds. It's a varmint rifle. I am not going to measure or adjust COAL as long as it shoots small groups. If the groups get bigger our I get flyers I will just try 5 & 10 thou longer and see if it helps. Maybe measure COAL touch or a new barrel.

I find it easier to get repeatable results with the Hornady/Stony point tool and the Wheeler method on a fired barrel, compared to a brand new one. The new barrels may have some burrs in the lands from chambering, and make it harder to get a good reading.

I use the Hornady and Wheeler methods and they will be the same within a couple thousands, but you have to let the target tell you the correct seating depth.

Measuring COAL is not precise. Measure the Cartridge Base to Ogive Length (CBOL) with the Hornady length gauge and seat you bullets according to your target results.

For oddball calibers, or to insure you have the case properly seated with the Hornady measuring tool, get a 5/16 X 36 tap and a letter L drill, and thread one of your fired cases.

https://www.amazon.com/dp/B0195UFBUY/?tag=accuratescom-20

 

[fguffey]

I've tried loose set bullets (dummy rounds) and then chambering the bullet then measuring OAL

Dummy round: A dummy should know what it is worth. I have for years drilled the primer pocket/flash hole out of cases for the purpose of making transfers. I understand I am wasting my time because reloaders do not know what a transfer is. After I drill the flash hole4/primer pocket out on a case I neck size the case; there has to be a reason for neck sizing, I want all the bullet hold I can get, there is no such thing as too much bullet hold, reloaders use 'neck tension' they can not measure neck tension and they do not have a tool that measures 'tensions' but they have an infatuation with neck tensions.

After I drill the flash hole/primer pocket and neck size the case I seat a bullet into the transfer, after seating the bullet I remove the bolt and chamber the transfer and then I use a dowel and or cleaning through the drilled hole in the case to push the bullet out of the case and into the rifling. When the bullet contacts the rifling I stop pushing and then remove the transfer from the chamber.

I have all kinds of tools, some are home made. I could measure the transfer, it is not necessary, instead I install the transfer into the shell holder and then raise the ram, after raising the ram I adjust the seating die to avoid crimping, I then secure the die to the press with the lock ring and then adjust the seater plug down to the contact the bullet. After the bullet seating plug contacts the bullet I secure the jam nut on the bullet seating stem.

That is .000 off the lands, If I choose to seat the bullet .030" off the lands I lower the seating plug .030". If I do not want to start over the next day I save the transfer.

And then there are all of the tools that reloaders surround themselves with. I make tools that, most of them are nice but not necessary if the reloader understand the concept of a transfer. I smith called and said he built 4 rifles with Wildcat chambers, he made the reamer, one rifle came back, it had problems. He took it to one smith after another and then called me. He started to tell me this and that etc. and I was not interested, I was thinking by the time he told me the life story I could already checked the rifle. I took one of his formed cases and drilled the flash hole/primer picket, sized the neck and seated a bullet, remove the bolt and then chambered the transfer. The bullet came out of the case long before the bullet contacted the rifling, the bullet traveled over .250" before it contacted the rifling. He wanted to know how something like that could happen, I suggested someone was reading material by R. Weatherby and did not understand what they were reading. He had the rifle bore scoped before he got to me.

I want to know the length of the chamber from the rifling to the bolt face, again, there are tools for that purpose, if I thought it necessary I would make the tool but I find it easier to transfer the dimension of the chamber to the seating die. I have no problem measuring the height of the seating stem above the die.

After the reloader removes the transfer it is possible to measure the length of the case from the shoulder to the case head and from the case head to the contact point on the bullet that was made by the rifling. Datums, I made datums, I do not made datums that are bullet friendly or case friendly.

F. Guffey

 

[fguffey]

Bullet seating is simple. I thought he ask also how is the chamber done . If not my bad .
Larry

Measuring the chamber length is easy and simple... for a very few. I have no problem measuring the length of the chamber from the datum to the bolt face at least three different ways without a head space gage. One of the easiest ways is to modify a go-gage to measure chamber lengths from go to infinity. The 'tuff' part? The tuff part is convincing someone/anyone it can be done.

F. Guffey

measure lengths from go to infinity

or as I say from .005" (Go-gage length for a 30/06) to a practice .016" longer than a minimum length/full length sized case

 

[fguffey]

With the Stoneypoint/Hornady system you're taking things to a shoulder datum(the weakness in the system), while CBTO is taken from the case head.

Weakness of the system? The weakness of the system is the reloader. Reloaders do not consider the Hornady/Sinclair tool a comparator, For years and years I have said there datum is flawed. A datum does not have a radius. Again, I make datums, they are not case, they are not bullet friendly.. The L.E. Wilson is a precision gage, it is a datum based tool, the datum in the Wilson case gage has a radius. Hornady/Sinclair has never figured out how to make an accurate tool.

F. Guffey