How do you guys know how far a bullet is "seated off the lands"?

[VaniB]

I often hear somebody on these forums say "My bullets is .037 off of the lands", or, "My bullets has .065" of jump. Just how do you guys come up with such precise measurements? The only measurement I know to take, is to measure the proven handload from the case head to the ogive and save these notes for future handloads.

After experimenting with carbon blackened bullets, I have observed that the cartridge and black bullet can be pushed into the chamber throat a good ways with the bullet contacting the bore and getting scratch marks over a good length of the way.The scratches start out light and get more defined the further you push the bullet into the throat. So it's not like the bullet is pushed into the bore a certain distance where it suddenly reaches the lands and stops there abruptly.

So, I've never quite understood how to use the exact measurements you mention.

 

[DennisH]

Just how do you guys come up with such precise measurements?

I use a hornady COAL guage on my rifles. Use the correct bushing for the bullet being measured. You have to buy the Hornady COAL brass that matches your gun. Screw the brass on the Hornady tool. Insert the bullet to be measured, push the tool into the chamber until it stops, then you push the rod that pushes the bullet to the lands. Tighten the screw and pull it out, you are ready to measure your exact distance to the lands on your gun. You have to do this for every bullet and every gun you own.

Read the instructions, its very easy. If you have trouble, don't hesitate to ask another question.

But this tool will let the bullet hit the lands, you pull the guage out along with the bullet being measured. Take a measurement and you will have your COAL to the lands. Then you decide where you want to seat the bullet when loading. Sometimes you have to experiment to see what your gun likes.

I have some rifles that like being in the lands .010, and one .050 off, and some inbetween these two!

Watch this YouTube video, sometimes pictures are better than words.

http://www.youtube.com/watch?v=llvsEsaK8-M

 

[Zia Hunter]

I use a Sinclair tool to measure the point where the bullet touches the lands. Very simple tool to use for bolt and single shot rifles. Takes a little practice at first the get consistent measurements. It will give you a maximum COAL for a particular bullet to which to work off of.

 

[BoydAllen]

The Forum Boss has tested the repeatability of his measurements with the Hornady (formerly Stoney Point)tool that is designed for this task, and finds that he is able to get consistent results.

I have spent less time with that tool but quite a bit using the Sinclair tool that has an action adapter, rod and stop collars. With that tool, I apply firm pressure on the back of the rod, with my thumb, and I use that as my reference for touching.

For my benchrest rifle, I have gone to working with the appearance of the marks on a bare bullet, that has been made easier to read by turning it (after loading) in a wad of 0000 steel wool under the pressure of my thumb and index finger, lightly marking it with tiny striations that run at right angles to the axis of the bullet, which make marks made by its contact with the lands much easier to see.

Given the variations that result from different amounts of pressure, I doubt that any written specification can be reliably produced by someone else to three decimal places, but if a good description of technique is included with the numbers, I think that the information can be useful.

 

[necchi]

Yup, like DennisH said, it's another needed tool for the bench

There are hand methods, but they all seem a bit unreliable for that precise measurement, their not bad,, $35-40,,

Here's the read,,
http://www.6mmbr.com/catalog/item/1433308/977259.htm

 

[VaniB]

Now I undersand how you guys are coming up with a given length. Using the Hornady/stoney point tool or the Sinclair tool will produce a reliable and repeatable given length for which to work off of.

Originally, I believed that as a sustitute I could push a dummy cartridge with a less then tight bullet into the chamber. While this method might work for my own use with the carbon black bullet tests I was doing, it does not provide as uniform or consistant way to measure.....especially if trying to share such measurements and info with others.

Thanks for the info gents. Now I understand.

 

[Medic07]

Are there any "reviews" for the RCBS precision mic for measuring coal? I have used my StonyPoint/Hornady COAL guage for years with resonably repeatable measurements and accurate loads, but I do agree with BoydAllen that any variation in pressure exerted to the "pushrod" before locking it in place results in slightly varying readings. I believe that with the RCBS mic (yet another tool/toy I will be purchasing), the pressure is exerted by the closing of the bolt, therefore SHOULD be repeatable time after time...is this true?

 

[jcampbellsmith]

... I have used my StonyPoint/Hornady COAL guage for years with resonably repeatable measurements and accurate loads, but I do agree with BoydAllen that any variation in pressure exerted to the "pushrod" before locking it in place results in slightly varying readings...

I try and take 6 measurements with 6 different bullets and then average the measurements. That gives me a number to work with each time I load those bullets. I know that with time and effort and super precise tools I would get a different measurement back to the bolt face. Regards JCS

 

[CaptainMal]

Using the Hornady tool you just do it a few times until you feel it's repeating accurately. It works well as you can feel how much pressure you are using to push on that bullet.

Now, if you wanted to color mark a bullet in a case you have NO CONTROL of the neck tension and how hard that bullet is jammed into the case. Then you also cannot tell if it's pulled out a bit when opening things up to eject the case. Forget it.

Buy the Hornady or Sinclair tools and the inserts for various calibers to use with your micrometer.

 

[243winxb]

Originally, I believed that as a sustitute I could push a dummy cartridge with a less then tight bullet into the chamber.

Use a flat base bullet, backwards.

 

[lpreddick]

i have used the hornady tool for years and it works...usu. recently i'v tried something similar to what BoydAllen describes, with a little twist. use a sized case fired in the gun. seat a bullet "long"...having polished it with 0000steel wool. chamber round (no powder/primer). remove and with appropriate light find the 4 polished marks from the 4 lands. polish again and seat bullet .005 deeper and repeat. after several seatings the marks get shorter and then disappear. i go back .005 and declare this measurement as the "lands" and seat loaded rounds with jump or jam accordingly. after enough shooting the lands recede and i repeat the process. i must admit these measurements come very close to the ones determined with the hornady tool.

 

[VaniB]

i have used the hornady tool for years and it works...usu. recently i'v tried something similar to what BoydAllen describes, with a little twist. use a sized case fired in the gun. seat a bullet "long"...having polished it with 0000steel wool. chamber round (no powder/primer). remove and with appropriate light find the 4 polished marks from the 4 lands. polish again and seat bullet .005 deeper and repeat. after several seatings the marks get shorter and then disappear. i go back .005 and declare this measurement as the "lands" and seat loaded rounds with jump or jam accordingly. after enough shooting the lands recede and i repeat the process. i must admit these measurements come very close to the ones determined with the hornady tool.

Instead of polishing the bullet (I tried that), I preferred to hold the bullet over a candle which covers it in dark black carbon soot. (It's easier for my eyes to see) But your trial and error method as you describe it is exactly what I was doing. It works well enough for the shooter to determine the preferred seating depth for his handloads. But unlike using the Hornady or Sinclair tool it does not translate to a quick and uniform measurement that can be duplicated by others. In other words, while many of us might be able to use the Hornady tool to duplicate a more uniform reading that we can share with others on the forums, pushing a polished bullet (or blackened bullet)to derive the measurement will likely not translate to the same numbers.

 

[DennisH]

I try and take 6 measurements with 6 different bullets

PS: I try several bullets when taking measurements. Usually you will find a consistant measurement.

4 of 6 will measure the exact same length with 2 being .001 off (in or out).

 

[lpreddick]

forgot to mention...when i use the hornady tool i'v had my gunsmith thread a case that was fired in the chamber and sized (fl or only shoulder bump) since the one size fits all generic cases may give different results. i'll have to try the smoked bullets...almost sounds appetizing.

 

[Beau]

Funny this should come up, I was just measuring the other day.

Used my Stoney Point to get an OAL. Longest measurement was 2.990" with NO marks on the bullet. I wanted to be .010" in, so I seated to 3.000". Chambered the round, ejected, and found that the rifling had engraved the bullet for .080". How does that happen? I guess it depends on your lead angle, but it is sometimes difficult to get a good reading. I measured several other times and got readings like 2.970", 2.950". On an earlier occasion (about 44 rounds ago), I got reading pretty consistently at about 2.910".

I ended up seating to 2.930" and calling it good, I'll see how it shoots.

 

[BoydAllen]

Although there is no harm in doing so, it is not necessary to use a case that has been fired in the chamber of your rifle. Instead, all that needs to be done is to use something like the Hornady headspace tool to measure a fired case and the case that is supplied by Hornady for the seating depth tool. Subtract one measurement from the other, and add the difference to every reading that you take with the unfired case. That will put you spot on.

 

[Ed333]

newbie followup question: if you use different bullets (with a different profile), will that not give you a different COL? I don't understand how the reloading manuals give a fixed COL, without taking into account the differences in bullets.
I have been loading to the COL designated in the manual, but with no idea how much I am 'jumping', or even if I am jumping. (Sounds like I need one of these tools.)

 

[MNFinn]

newbie question also. I have the Hornady OAL tool, I feel slight resistance at one point, and a hard stop a little further in, which point should I use for my measurements?

 

[BoydAllen]

Manual COLs are not specific to your rifle. They are just telling you where they loaded the bullet to get the velocities and safe pressure levels. All that I use a manual for is to come up with a safe starting load from which I can start my own testing, that is all. On the other hand, if someone is just starting out reloading, following the manual should keep him out of trouble....a good thing.

 

[BoydAllen]

emn83,
Use the point that gives the most consistent readings.