Bullet Seating Depth Measuring Problem - Touch, Jamb, or ?

[beartooth91]

I've had a lot of problems, with my 30-'06, determining where the bullet meets the rifling. I'm using the Hornady LnL tool, with the comparator. The problem is that I get two distinct groups of measurement, with any given bullet, in this particular rifle. This morning, I was trying to find the depth - touching the lands - for the Sie 168 MK. This included multiple measurements for four 168 SMK's. I get a group of measurements around 2.661" and another group around 2.687" - with all 4 bullets. I've had this same problem with every bullet I've tried, in this rifle. I know its partly due to the amount of push I give on the LnL rod. There's always a first bit of resistance, and with firm pushing, a bit more give. In every instance, I get very light scoring on the upper side of the bullet - not all the way around - just on the upper side. This leads me to believe the bullet isn't going in exactly straight. Of course, as I re-measure each bullet, the scoring progresses around the bullet.
I do not have this issue with my other five rifles and get more accurate measurements. Somewhere, I'm going wrong.......please advise.
Thanks

[stangfish]

I always suspect lack of concentricity when that happens to me. sometimes I find the modified case to have ad drag as well. Is there a certain purpose for putting the SMK in/at the lands?

[missed]

I typically push my LNL tool in push lightly till it stops then tap it two more times and lock the set screw down. I have had times where I have gotten some random numbers. I usually take an average of 5 measurements, I also do mine with a clean chamber and bore.

I measure all my different bullets with them at the lands as my base point for all my loads. A little different bullet shape has made a big length change.

having a .026" spread would be unacceptable for me. Was this with multiple bullets or all the same bullet?

[DT400]

I have found that a very light touch is all that is needed. If you are getting ANY scoring on the bullet you pushed way to hard and are actually into the lands. You should be pushing light enough that after your measurement if you turn the rifle muzzle up the bullet should come out of the chamber in the case and not stick in the rifling. I do a minimum of 10 measurements and you will find you will develop a "touch" and get consistent readings....a very light touch is all that is required. You are trying to just contact he lands and go no further.
HTH
Darrell

[beartooth91]

Was this with multiple bullets or all the same bullet?
- Seven, different bullets - all 168 Sie MK's. 24 total measurements were taken, spread among the seven bullets.

- With regards to the light touch, there are differing opinions. Here is an excerpt from German Salazar (The Rifleman's Journal), regarding using the LnL tool and the force required:
"Push forward on the rod with the heel of your hand while pushing forward on the tool with your thumb and forefinger. You should feel the case seating firmly in the chamber. Then, as you push the rod forward, you will feel some resistance to the bullet's movement as it enters the throat and then you will feel it come to a stop as it contacts the rifling. Try this a few times when you are first using the tool; depending on the dimensions of your chamber, the resistance in the throat may be somewhat high and can fool you."

- I've always assumed - with this rifle, the two groups of differing measurements has to do with the last sentence in the quote, above.

- Again, I seem to have this problem with only this, particular rifle. My other five tend to give easier, accurate, measurements.

So, still don't see any smoking guns with what I'm doing wrong........

(late entry) As indicated in my original post, the measurements recorded, with the 168 SMK, when the bullet won't go any further, came out to 2.687". Interestingly enough, when I got into my Excel spreadsheet, to record those measurements, I found I'd came up with 2.686", months ago, for the 175 Sie MK........

[thermaler]

I recently ordered two 300 win mag modified cases made by Hornady--and they have different neck tensions--almost as if one had been partially neck sized. They yield different measurements for some reason--don't know if that might be something to consider.

[DT400]

- Seven, different bullets - all 168 Sie MK's. 24 total measurements were taken, spread among the seven bullets.

- With regards to the light touch, there are differing opinions. Here is an excerpt from German Salazar (The Rifleman's Journal), regarding using the LnL tool and the force required:
"Push forward on the rod with the heel of your hand while pushing forward on the tool with your thumb and forefinger. You should feel the case seating firmly in the chamber. Then, as you push the rod forward, you will feel some resistance to the bullet's movement as it enters the throat and then you will feel it come to a stop as it contacts the rifling. Try this a few times when you are first using the tool; depending on the dimensions of your chamber, the resistance in the throat may be somewhat high and can fool you."

- I've always assumed - with this rifle, the two groups of differing measurements has to do with the last sentence in the quote, above.

- Again, I seem to have this problem with only this, particular rifle. My other five tend to give easier, accurate, measurements.

So, still don't see any smoking guns with what I'm doing wrong........

(late entry) As indicated in my original post, the measurements recorded, with the 168 SMK, when the bullet won't go any further, came out to 2.687". Interestingly enough, when I got into my Excel spreadsheet, to record those measurements, I found I'd came up with 2.686", months ago, for the 175 Sie MK........


Interesting. I had never heard of doing it this way. I will recheck my method and try it this way and see what happens. I do force the case in against the shoulder with one finger while lightly pushing the measuring rid in with another. Might just be a difference in the way the throats are done from make to make. I have only used these Gage's on my Sakos so far.

Darrell

[82boy]

I must say I have never been impressed with the old Stony Point seating depth measuring device, that is now called the Hornady LNL device. There is many tolerances that can skew measurements as you are finding out. IMO the best thing you can do is sell this tool. The Sinclair depth finding device is not much better, though it takes out many of the variables found in the Hornady device, my experience is that it just doesn't come up with a correct seating depth.


What I have found to work best ot using a fired case that has been sized, and will tightly hold the bullet. One variable you may be seeing is you need to segregate your bullets by Ogive length. In a typical box of 100 Sierra bullets it is not uncommon to find two different ogive length bullets. Once you have this figured out you can proceed, to find actual seating depth is a tedious and time consuming process. You want to start with the bullet seated just into the case, (WITH NO PRIMER OR POWDER!!!!) and then place it into the gun, and close the bolt. then remove the case, and measure it. Now place your seating die to that measurement, and then taking the bullet clean the marks off with some 0000 steel wool. now move the bullet in at .002 increments, and watch the marks. At first the marks will be rectangular, and this is a hard jamb. when you back the bullet out you will see the marks change, when the marks are square, this is close to jamb, then as you move out you will see the marks be crisp at the top, and fad at the bottom, this is close to touching. It takes many times of moving the bullet in the case and reinserting the case to find this measurement. When I look for is at the point where the marks are hardly visible, this is just touching, and this is where I start looking for a seating depth. From this point I will make loads with the bullet .005, .010 , .015 , 1nd .020 off from this measurement.

Bullet seating depth is THE most curtail thing to accuracy, and spending time to get it right is well worth the effort.

[stomp442]

+1 This is exactly how I do mine too 82boy.

[thermaler]

I must say I have never been impressed with the old Stony Point seating depth measuring device, that is now called the Hornady LNL device. There is many tolerances that can skew measurements as you are finding out. IMO the best thing you can do is sell this tool. The Sinclair depth finding device is not much better, though it takes out many of the variables found in the Hornady device, my experience is that it just doesn't come up with a correct seating depth.


What I have found to work best ot using a fired case that has been sized, and will tightly hold the bullet. One variable you may be seeing is you need to segregate your bullets by Ogive length. In a typical box of 100 Sierra bullets it is not uncommon to find two different ogive length bullets. Once you have this figured out you can proceed, to find actual seating depth is a tedious and time consuming process. You want to start with the bullet seated just into the case, (WITH NO PRIMER OR POWDER!!!!) and then place it into the gun, and close the bolt. then remove the case, and measure it. Now place your seating die to that measurement, and then taking the bullet clean the marks off with some 0000 steel wool. now move the bullet in at .002 increments, and watch the marks. At first the marks will be rectangular, and this is a hard jamb. when you back the bullet out you will see the marks change, when the marks are square, this is close to jamb, then as you move out you will see the marks be crisp at the top, and fad at the bottom, this is close to touching. It takes many times of moving the bullet in the case and reinserting the case to find this measurement. When I look for is at the point where the marks are hardly visible, this is just touching, and this is where I start looking for a seating depth. From this point I will make loads with the bullet .005, .010 , .015 , 1nd .020 off from this measurement.

Bullet seating depth is THE most curtail thing to accuracy, and spending time to get it right is well worth the effort.I'm having a bit of trouble following the rectangular/square marks thing--any illustrations/photos to help more easily understand? thnx.

[BillPa]

I'm having a bit of trouble following the rectangular/square marks thing--any illustrations/photos to help more easily understand? thnx.

Sure, some chamber casts.
http://i29.tinypic.com/2ynkqdh.jpg
The cartridge in top is my 25 Imp with a 100 seated 10 off. The cast in the middle is one of it's chamber. The lengthwise "grooves" in the cast is a mirror image of the lands, the start of which causes the square marks.

Bill

[thermaler]

Sure, some chamber casts.
http://i29.tinypic.com/2ynkqdh.jpg
The cartridge in top is my 25 Imp with a 100 seated 10 off. The cast in the middle is one of it's chamber. The lengthwise "grooves" in the cast is a mirror image of the lands, the start of which causes the square marks.

BillSomehow I missed the chamber cast part in your first post. : ) Thanks.

[82boy]

No chamber cast, when the bullet hits the lands it engraves a mark on it. When the bullet is jammed hard into the lands it will show a rectangular marks around the bullet, on for each land. So in a 4 groove barrel you should see 4 marks. This is also a way to tell if the chamber is straight or crooked. If it is crooked you will only see engraving marks on one side of the bullet. When you back off the marks get smaller and lighter.

[sharpshooter]

The biggest problem with the LnL or Stoney point tool, is the modified case. Most of the case necks are expanded bigger than the neck diameter in the chamber. When inserting the tool in the chamber it does not seat all the way, giving a false reading.

[thermaler]

The biggest problem with the LnL or Stoney point tool, is the modified case. Most of the case necks are expanded bigger than the neck diameter in the chamber. When inserting the tool in the chamber it does not seat all the way, giving a false reading.Funny you mention that--I was just looking at the cast vs loaded case and it looks like the chamber has room to spare in the neck compared to the sized case. I'm assuming most chambers (conventional) are made to SAAMI specs with perhaps a tad bit room to spare?

[missed]

The biggest problem with the LnL or Stoney point tool, is the modified case. Most of the case necks are expanded bigger than the neck diameter in the chamber. When inserting the tool in the chamber it does not seat all the way, giving a false reading.

I have run mine through my collet dies with them backed out to the point where I have some more resistance than it came with and I have gotten more consistent measurements.

[DT400]

The biggest problem with the LnL or Stoney point tool, is the modified case. Most of the case necks are expanded bigger than the neck diameter in the chamber. When inserting the tool in the chamber it does not seat all the way, giving a false reading.

While this may be the case in some guns you could always see how easy the modified case drops in and chambers in your gun. I have the Hornady modified cases for 4 different calibers and 3 different manufactures of guns and have not experienced this (2 Sakos, Savage, Remington).
YMMV
Darrell

[mike21]

This is a very timely thread for me as I am fairly new to this topic. Like some other posters, I became a little concerned about the consistent accuracy of the L&L. One of my concerns was the modified case which, as far as I know, is basically factory brass. My internet research revealed some folks were making their own modified cases from fireformed brass to improve chamber fit.

Seemed logical to me so I acquired the correct tap and made my own modified case from fire formed brass that fits the L&L. I'm really not sure if this will help, but I plan on trying it on 4 different bullets for my newly acquired M12 FV.

Seems to me 82boy and stomp442 have described the most accurate method. I plan on trying both to see if there are any significant differences. That is, if I can read the marks correctly and don't get a bullet stuck in the barrel.

Not sure this will help our OP with his 30-06 problem, but thanks for the excellent discussion beartooth.

http://i1210.photobucket.com/albums/cc418/mswill1/IMG_0560.jpg (http://s1210.photobucket.com/user/mswill1/media/IMG_0560.jpg.html)

[beartooth91]

This is a very timely thread for me as I am fairly new to this topic. Like some other posters, I became a little concerned about the consistent accuracy of the L&L...... Seems to me 82boy and stomp442 have described the most accurate method. I plan on trying both to see if there are any significant differences. That is, if I can read the marks correctly and don't get a bullet stuck in the barrel.

Not sure this will help our OP with his 30-06 problem, but thanks for the excellent discussion beartooth.

http://i1210.photobucket.com/albums/cc418/mswill1/IMG_0560.jpg (http://s1210.photobucket.com/user/mswill1/media/IMG_0560.jpg.html)

Yes, Thanks to all who have replied. I am particularly intrigued with the method using the long seated bullet and plan to try it, comparing my LnL measurements. I have a bag of fine steel wool. Is this the same as the "0000 steel wool" described?

[beartooth91]

Lord of the Idiots, here, trying to resurrect this thread.
I tried the seating/measurement method, mentioned above, from 82boy and stomp442. The results confuse me.
So, for reference, I measured 3.693" and 3.692", respectively, for the 168 SMK and 175 SMK, with the Hornady LnL tool. (This was from my records and was based on several bullets of the 168 and 175 SMK, taken when I made the original post.)
Today, I took 3 bullets - two 168 SMKs and a 175 SMK, seated them way out, inspected/measured them, and progressively seated them deeper. Observations as follows:
1. For the first 168, I started with a length of 3.706". Chambering felt normal and a complete scoring ring was observed around the ogive. As I seated deeper, in .005 or .010 increments, the scoring ring thins and breaks (not complete) around 3.670 to 3.676".
2. For the second 168, I started with a length of 3.740". Chambering difficult. After extraction, I remeasured and the length was now 3.696". Again, as I progressively seated deeper, the circular ogive scoring ring got thinner and became broken around 3.670 to 3.676, as above.
Chambering force became "normal" around 3.691 or so.
3. For the 175 SMK, I started with a length of 3.716". Again, chambering required excessive force. As I seated deeper, the force lessened and became "normal" between 3.691" and 3.697". The circular scoring ring became broken at the 3.691" measurement.
4. I never did see the vertical or square or rectangular marks, mentioned above.
5. All of the above measurements are with the Hornady comparator.

So, thoughts on what I found today? Thoughts on today's measurements vs. the ones I made with the LnL tool? Thoughts on any of the above?

Mark