Finding distance from lands

[gilcarleton]

I am starting to work up a load for the 7mm RSAUM I had built. I actually have two questions, first, how do you determine the distance your bullet is from your lands? When I had my barrel reamed I had the gunsmith ream another piece of barrel, not sure if it was some he cut off of mine or not, but it does not seem to work. I inserted an empty piece of brass and took a measurement. I then loaded a bullet, a little long, and measured it. The difference in the measurement should be how much I need to seat the bullet in order to barely touch the lands. After clambering a round, I could see that the bullet had land scrapes on it in the neighborhood of .650. I really did not know what to do at this point so I measured the scrape as well as I could and seated the bullet by that amount. I could easily be off several thousandths using this method. I am looking for some ideas as to how other do this and get an accurate measurement.

Second question, in working up a load, do you first work up the most accurate powder charge for your rifle then try changing the distance the bullet is seated from the lands or do you use one consistent charge and work up the distance from the lands first? This seems like a circular formula and I am not sure what the best way to approach this is.

Thanks so much for the help. There are many on this site who are much wiser than I and is is great to be able to draw on that experience.

Gil

 

[falconpilot]

Everyone has their own theory on the second question.. But the first is easy...using light neck tension, seat a bullet long. Chamber and close bolt. You should feel the bullet being pushed back into case. Now set your seating die to seat bullet deeper 5 thous at a time. Using 1200 grit sandpaper or steel wool, sand the bullet lightly...chamber and bolt down. Look for 4 or 5 marks in the bullet where the lands engraved them....resand bullet and set it back another 5 thous and repeat above steps until you reach a point where your land marks aren't there anymore..record length.

 

[RW]

what I do is take each individual bullet and make sure the inside of the neck and bullet slide pretty freely insert into the
the barrel stub that has been reamed and gently insert bullet and case. You can use a marker pen and after you gently seat a bullet pull it out and look for the and then I super glue it and use it to set my seating die. If you seat a bullet with a lot of neck tension you are jamming it into the lands. You just want to kiss the lands and then adjust from there. Using a comparater of your choice and measure that distance and work from there. RW

 

[rocketron]

Everyone has their own theory on the second question.. But the first is easy...using light neck tension, seat a bullet long. Chamber and close bolt. You should feel the bullet being pushed back into case. Now set your seating die to seat bullet deeper 5 thous at a time. Using 1200 grit sandpaper or steel wool, sand the bullet lightly...chamber and bolt down. Look for 4 or 5 marks in the bullet where the lands engraved them....resand bullet and set it back another 5 thous and repeat above steps until you reach a point where your land marks aren't there anymore..record length.

+1 but strip the bolt & seat deeper by .002 when the marks start getting smaller also use a proper headspaced case

 

[Jet]

Gil

In addiion to info stated above, give Erik Cortina's method a try. Link below.

http://forum.accurateshooter.com/index.php?topic=3814361.0

Good Shooting.

Rich

 

[bsekf]

I use Eric's method but cut a slit in the dummy case neck so the bullet will slide. Take several readings since the bullet may stick in the rifling on occasion. Keep in mind that you are getting a reference measurement. I start out at least .010 longer and then back off .005 to .010, I usually just advance the seating stem 1/4 turn, load 3 each and look for the variation.

 

[Preacher]

Smoking the bullet and checking for land marks works for me...

 

[fguffey]

I drill the flash hole/primer pocket out to a diameter that will accommodate a cleaning rod. I neck size the case then remove the bolt and place the test case in the chamber. After chambering the round I push the bullet out until it contacts the lands.

After pushing the bullet out of the case and into the lands I use the case to adjust the seating die. After adjusting the seating die to the test case I zero the seating stem with a dial caliper of height gage. ZERO is zero off the lands. If I want .020" off the lands I lower the seating stem .020".

I do nothing to reduce the bullet hold of the neck, I want all the bullet hold I can get. I transfer the measurement of the chamber from the rifling to the bolt face to the seating die. I do not want the bullet hanging in the rifling.

F. Guffey

 

[savagedasher]

I like using the stub with the front milled . You can see how long the neck can be along with where the bullet is in the lands. You have a viewing window with the same chamber of your reamer .
If your going to use the chamber all method make the case from a second time fired case out of your chamber.
A milled stub is the best
If you have a case that doesn't fit in the gun correct the stub will make finding the problem easy. Larry

 

[fguffey]

Then there is the Wilson case gage. The Wilson case gage can be used with attachments for measuring from the top of the gage to the lands. Stubbs, I have stubs, I call them chamber gages, a stub can be used with modified tools to determine the distance from the top of the stub to the contact between the bullet and rifling.

F. Guffey

 

[savagedasher]

The window that is milled in does the same. Like where the land is only a starting point. Every shot that goes down the barrel the distance from the lands increases.
how far and how much depends on many of things. Larry

 

[SHootSTraight22]

I am starting to work up a load for the 7mm RSAUM I had built. I actually have two questions, first, how do you determine the distance your bullet is from your lands? When I had my barrel reamed I had the gunsmith ream another piece of barrel, not sure if it was some he cut off of mine or not, but it does not seem to work. I inserted an empty piece of brass and took a measurement. I then loaded a bullet, a little long, and measured it. The difference in the measurement should be how much I need to seat the bullet in order to barely touch the lands. After clambering a round, I could see that the bullet had land scrapes on it in the neighborhood of .650. I really did not know what to do at this point so I measured the scrape as well as I could and seated the bullet by that amount. I could easily be off several thousandths using this method. I am looking for some ideas as to how other do this and get an accurate measurement.

Second question, in working up a load, do you first work up the most accurate powder charge for your rifle then try changing the distance the bullet is seated from the lands or do you use one consistent charge and work up the distance from the lands first? This seems like a circular formula and I am not sure what the best way to approach this is.

Thanks so much for the help. There are many on this site who are much wiser than I and is is great to be able to draw on that experience.

Gil

It isn't important to start exactly at a certain measurement.. In other words if your goal is to start at the lands, just load up an empty case, chamber it as you did, notice the length "downwards" of the land marks located on the bullet, then seat the bullet that amount further in inward... The marks are most likely no more than .030 long so once you seat your bullet that much deeper, then consider that OAL just off/on the lands... Remember in the end you choose by what the "paper" target is telling you... Your just needing a safe starting point right now...

 

[FN in MT]

Or buy one of these....
http://www.hornady.com/store/Lock-N-Load-OAL-Gauge-Straight-1Each/

 

[Brians356]

Twelve replies, twelve different methods. Vive la différence!

 

[jpretle]

variety is good.

 

[Brians356]

"How much is enough, Gordon?"

 

[lpreddick]

Ditto on the technique described by falconpilot. I use the hornady tool to get a good idea of the lands, then seat bullet .025 longer and look for the engraving marks. A new barrel gives nice square marks, equal in length. A worn throat will show rounded lands and may have engravings of different lengths and as you seat deeper, one land disappears, then the second one goes...the uneven wearing of the lands can be dramatic. In this gun seating "to touch the lands" could be a problem.

 

[K22]

I've tried several methods as described in this post, all work but the easiest method I've found is using the Frankfort Arsenal Tool. It's simple, inexpensive and you don't have to go through a trial and error approach using this tool.

The tool is available at Midway.

 

[noload]

FGUFFEY post #7 is pretty foolproof.

 

[lboom]

The way I find the lands is to drop a bullet into the chamber and very lightly check if it is in the lands,then I run a cleaning rod with a flat tip into the rifle till I feel it touch the bullet. I then mark the rod at the muzzle of rifle. push out bullet and close bolt then reinsert cleaning rod till it contacts bolt face,remark rod.remove rod and measure distance between marks and that is your maximum overall length of case and bullet to be on the lands. Do for all different bullet types to adjust for oglive differences between bullets,this is easier than any other way I have tried.