Distance of OG to Lands?

[DesertDug]

I am reloading .270 Winchester. I have been reloading for my gas guns for some years now, but am trying to get into the bolt action accuracy game. I am finally staring to understand some of the more detailed variables that make reloading your own an improvement in accuracy. In this quest I now have a Hornady case gauge and Hornady OG gauge.

To my surprise my full length and neck sizing dies were already set up for the . 002 (edited) shoulder bump.
So I am good there.

The jump to lands has got me. I think I finally got the hang of the "feel" it takes to get the tool to just touch the lands. My first go of was much shorter in length, but now I am measuring 2.864" for 130g Nosler BT bullets.

Does this seem like the correct number. Is there a way to determine accuracy of this measurement? Is there something to compare this against?

[celltech]

I use a cleaning rod to figure out my OAL. I made a little piece of plastic that screws in and gives it a flat surface. Close bolt and snug rod up against the bolt face...wrap a piece of tape around the rod right at the end of the barrel. Then drop bullet in chamber and lightly push it in with a stick. Use rod to feel that point of the bullet just hitting the lands and put on another piece of tape. Measure between the tape edges...gets close enough for me.

[SageRat Shooter]

I am reloading .270 Winchester. I have been reloading for my gas guns for some years now, but am trying to get into the bolt action accuracy game. I am finally staring to understand some of the more detailed variables that make reloading your own an improvement in accuracy. In this quest I now have a Hornady case gauge and Hornady OG gauge.

To my surprise my full length and neck sizing dies were already set up for the . 020 shoulder bump.
So I am good there.

The jump to lands has got me. I think I finally got the hang of the "feel" it takes to get the tool to just touch the lands. My first go of was much shorter in length, but now I am measuring 2.864" for 130g Nosler BT bullets.

Does this seem like the correct number. Is there a way to determine accuracy of this measurement? Is there something to compare this against?

The only other way I've been able to find where my lands begins is to partially size a case just enough that the bullet will hold and slip just a tad when you use your fingers to push and pull on it. Then I take the bullet and put it in the case (with the bullet seated long). I gently feed it in to the chamber and close the bolt. When you open the bolt, pull it open gently and the bullet should stay seated and will mark where your lands begins. I do that process a few times and measure each time with the OG gauge. That number will be "to the lands".

[celltech]

I tried the cut up bullet case method and just found it to be a PITA. The bullet would slip, the ejector is trying to push the shell around...etc. But to each his own...

[Stumpkiller]

A bit pricey for one caliber (or not) but the Hornady Comparator will give you the ability to measure and compare. (You need the modified case as well).

https://www.grafs.com/retail/catalog/product/productId/7256

[sharpshooter]

To my surprise my full length and neck sizing dies were already set up for the . 020 shoulder bump.
So I am good there.

I hope that is a typo........it should be .002", not .020"

[DesertDug]

A bit pricey for one caliber (or not) but the Hornady Comparator will give you the ability to measure and compare. (You need the modified case as well).

https://www.grafs.com/retail/catalog/product/productId/7256

this is what I have.

[DesertDug]

I hope that is a typo........it should be .002", not .020"

ya sir correct. Not good being dyslectic and a reloader...

[RustyShackle]

I use a cleaning rod to figure out my OAL. I made a little piece of plastic that screws in and gives it a flat surface. Close bolt and snug rod up against the bolt face...wrap a piece of tape around the rod right at the end of the barrel. Then drop bullet in chamber and lightly push it in with a stick. Use rod to feel that point of the bullet just hitting the lands and put on another piece of tape. Measure between the tape edges...gets close enough for me.


^^^ this! I use the same method. Works well enough to get into the ballpark. I used an old cheap plastic jag that I filed flat works like a champ.

So, I’m getting ready to experiment with some Accubonds and seating depth. I’ve been reading guys are seating them deep. And I mean really deep. Like 0.100 off the lands deep. Yes you’re reading that correctly. I just bumped some to 0.070 off the lands and questioning my sanity. Guess I’ll see if it shoots any worse.

[DesertDug]

^^^ this! I use the same method. Works well enough to get into the ballpark. I used an old cheap plastic jag that I filed flat works like a champ.

So, I’m getting ready to experiment with some Accubonds and seating depth. I’ve been reading guys are seating them deep. And I mean really deep. Like 0.100 off the lands deep. Yes you’re reading that correctly. I just bumped some to 0.070 off the lands and questioning my sanity. Guess I’ll see if it shoots any worse.

let us know how that works out.

[Texas10]

I could never get the Hornaday LNL OAL gage and modified case to work reasonably well as intended with bullets smaller than 308. So I took a slightly different path, still using the modified case and tool.

I start by making sure the chamber and throat are clean and free of built up carbon. If you don't own a bore scope or endoscope camera, perhaps it's time to get one to verify your cleaning methods are accomplishing what you expect. You'll need a carbon free throat to perform a good, reliable CBTO check .

Neck size or FL size the Hornaday modified case, and seat a bullet long. If you're not sure where to start, chamber it and close the bolt. The bullet will be pushed back into the case and this can be your hard jam dimension. Record it in your loading notes and remove the bolt for the remainder of the test.

Seat the bullet about .020 deeper and install the case on the tool. Slide it up the chamber with a firm push and retract. If it tends to stick upon retraction, the bullet is in the lands. Remove and seat the bullet another .010 deeper and repeat the test until no tendency to stick upon retraction. The bullet is out of the lands at that point so you need to go back out to your last "stick" dimension and work your way in by .002 increments until you can just feel the bullet touching the lands. Record that as your touch dimension.

Regardless of the method you use, CBTO is just a starting point. You're still going to move the bullet in or out to find the best seating depth. This method gives precise, repeatable measurements you can use later for documenting throat erosion.

Some cautions: Since you're not using YOUR fire formed cases for this test, account for the difference in headspace measurements.

Case drag will skew these test results, so before seating a bullet, run the case into the chamber, rotate it around and feel for any tendency to stick. FL size if necessary to get it to chamber drag free. If you want to use your FF case for this test, but don't have a lathe and proper drill and tap to fit the Hornaday tool, simply drill and tap to fit a section of 3 piece cleaning rod, and use it in the same way. Simple, quick, and precise.

I hope this helps.

[Texas10]

^^^ this! I use the same method. Works well enough to get into the ballpark. I used an old cheap plastic jag that I filed flat works like a champ.

So, I’m getting ready to experiment with some Accubonds and seating depth. I’ve been reading guys are seating them deep. And I mean really deep. Like 0.100 off the lands deep. Yes you’re reading that correctly. I just bumped some to 0.070 off the lands and questioning my sanity. Guess I’ll see if it shoots any worse.

I met a guy at the range who was shooting 308win with 125 gr bullets over H-414 and jumping them .180. He was getting phenomenal velocity and accuracy shooting at 300 yds. Don't remember the bullet brand.

[DesertDug]

"Some cautions: Since you're not using YOUR fire formed cases for this test, account for the difference in headspace measurements."

I wondered if this squees the measurements. You are seeming to say it does. In what way? Do I subtract the difference of headspace's of the fire formed and the horandy tool case?

[Orr89rocz]

^^^ this! I use the same method. Works well enough to get into the ballpark. I used an old cheap plastic jag that I filed flat works like a champ.

So, I’m getting ready to experiment with some Accubonds and seating depth. I’ve been reading guys are seating them deep. And I mean really deep. Like 0.100 off the lands deep. Yes you’re reading that correctly. I just bumped some to 0.070 off the lands and questioning my sanity. Guess I’ll see if it shoots any worse.

Hell i shoot 210 vld hunting bergers in my 300 wsm jumping .130 and it has singled holed at 100 yrds during load development but low velocity node. Closer to high end it cloverleafed, well within your thumbnail. So it depends. May like jump. My 180 elite hunter bergers are different style suppose to be more tolerant of jump and it shot .34” at similar long jump. Very happy with mag length repeater hunting loads

[Texas10]

"Some cautions: Since you're not using YOUR fire formed cases for this test, account for the difference in headspace measurements."

I wondered if this squees the measurements. You are seeming to say it does. In what way? Do I subtract the difference of headspace's of the fire formed and the horandy tool case?

I had to scratch my head over this one a few minutes and in the end, I made a bunch of "modified" cases using my FF brass so I didn't have to re-calculate every time I wanted to check my CBTO for a new bullet, or lot, or whatever. I keep those dummy cases with bullet seated to touch, labeled with bullet, date, CBTO etc. for future reference.

If your fully fire formed case measures (for instance) .004 longer from base to shoulder (datum) than the Hornaday modified case you're using to get the CBTO measurement, ADD that .004 to your CBTO dimension and that becomes the distance to lands in YOUR CHAMBER with YOUR fully fire formed brass.

When I want to double check my own answer, to add or subtract, I use extreme examples to demonstrate the concept. Imagine the Hornaday case measures 1.000" from base to shoulder. But my FF case measures 3.000" And in both cases the bullet ogive is .500 forward of the shoulder. So CBTO of the Hornaday with bullet seated is 1.500" and the Fire Formed case is 3.500". Now it's easy to know which way to go. You add the difference (2.000") since you can't very well subtract.

Of course, if you don't mind the wait, you can send your FF cases to Hornaday and they'll drill and tap them for you, for a fee of course.

[Marine]

I take a fired case and drill the flash hole to the primer size and then I use Lees collet die and carefully bring the neck down to where it just holds the bullet but can be moved by hand. I then get a 4'' threaded screw that will go through the primer pocket and a brass knurled nut for a stop and insert the case w/bullet into the chamber seating it as far as I can with my finger. I insert screw w/nut into the case and push the bullet to the lands and then run the nut down to the case. Remove screw/nut keeping the nut at the stop point and remove case and bullet. You might need to use a cleaning rod to get the bullet off the lands and then reassemble case and bullet holding bullet with the screw/nut in place and measure with calipers. This will be your .00 jump to lands. You can double check this with another once fired sized case seating the bullet to your .00 number and then place round into chamber and close the bolt. When you extract the round remeasure to make sure the coal has not changed and look for marks on the bullet from the lands. I always keep the 1st bullet so I can measure throat wear as it increases. Repeat until the numbers don't change.

[Jester560]

I am reloading .270 Winchester. I have been reloading for my gas guns for some years now, but am trying to get into the bolt action accuracy game. I am finally staring to understand some of the more detailed variables that make reloading your own an improvement in accuracy. In this quest I now have a Hornady case gauge and Hornady OG gauge.

To my surprise my full length and neck sizing dies were already set up for the . 002 (edited) shoulder bump.
So I am good there.

The jump to lands has got me. I think I finally got the hang of the "feel" it takes to get the tool to just touch the lands. My first go of was much shorter in length, but now I am measuring 2.864" for 130g Nosler BT bullets.

Does this seem like the correct number. Is there a way to determine accuracy of this measurement? Is there something to compare this against?Go to youtube and search Wheeler Method. That is the best method to use. No tools required.

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[Robinhood]

I have found this method to be precise.


https://www.youtube.com/watch?v=TWmIwPwLyyg

[Jester560]

I have found this method to be precise.


https://www.youtube.com/watch?v=TWmIwPwLyygThat is the Wheeler method I referred to.

Sent from my SAMSUNG-SM-T337A using Tapatalk

[Orr89rocz]

He mentions taking out the pin and ejector or extractor cuz it may push case forward? Wouldnt you want to simulate actual rifle operation when you do this so when you go to fire the thing you have the exact measurement ? If the ejector/extractor moves case in then this measurement without the ejector doesnt mean much when you load ammo and go to fire cuz it will be closer than you measured.
Or is that being overly complicating the issue and nothing to worry about?