Chasing lands

[jsthntn247]

Measured my lands before the last two day match and my measurement was 2.324 to the ogive which is what is been since the gun was new (750 rounds now). Was going to load a few rounds for a match next weekend and my measurement is now 2.336. Checked it 15 times and keep getting the same number . Should I just go .015 off my new number and load them or load some to the old depth and new depth and shoot a few at the range this week?? Never paid this much attention to a gun as I am now so I've never experienced this before, what do you guys do ?

 

[mudduck]

U gained a inch in your chamber ? Something is wrong

 

[jonbearman]

Its got to be a fat finger. I would try both to see if it likes one over the other anyways.

 

[M-61]

I think you have a typo in your numbers

 

[jsthntn247]

Yea, typo it moved .012. I edited the first post. I can't type on this iPhone.

 

[expiper]

If it moves and touching/jamed is where it shoots best ,,,you gota go with the flow,,,Roger

 

[jsthntn247]

If it moves and touching/jamed is where it shoots best ,,,you gota go with the flow,,,Roger

I shot it today to make sure and your right, the load at the new seating depth was definitely better. Gotta check everything all the time to keep up in this game.

 

[amlevin]

How are you measuring the distance to the lands? A Hornady/Stoney point tool using a bullet? An RCBS Precision Mic with the Bullet seating depth tool?

With the RCBS you'll be measuring with the SAME tool each time but unless you're using the same bullet each time in the Hornady/Stoney Point tool you could see some variations due to irregularities in the bullet.

If one wants to insure that they are getting the same readings every time then the tools have to be free of inconsistencies themselves. On the Hornady, the bullet is the variable unless you dedicate ONE bullet for measuring.

 

[BaconFat]

... If one wants to insure that they are getting the same readings every time then the tools have to be free of inconsistencies themselves. On the Hornady, the bullet is the variable unless you dedicate ONE bullet for measuring.

Because of this point, if you are going to be chasing the lands, shouldn't you also sort your bullets from the base to the ogive? How much variation in base to ogive length would you encounter within a box of bullets?

 

[jsthntn247]

How are you measuring the distance to the lands? A Hornady/Stoney point tool using a bullet? An RCBS Precision Mic with the Bullet seating depth tool?

With the RCBS you'll be measuring with the SAME tool each time but unless you're using the same bullet each time in the Hornady/Stoney Point tool you could see some variations due to irregularities in the bullet.

If one wants to insure that they are getting the same readings every time then the tools have to be free of inconsistencies themselves. On the Hornady, the bullet is the variable unless you dedicate ONE bullet for measuring.

I recently bought the Hornady tool and can't get anything repeatable out of it. I have a fired case trimmed to length that I use and shine a bullet with steel wool. I run the case up into a bushing that gives me enough neck tension to hold the bullet but also allow the bullet to slide back in the case when chambering. I shine a bullet then seat the bullet about .040 longer than I need, chamber it then measure. I then seat it down further, re-shining the bullet each time, until I see no land marks. I then seat the bullet out .020 longer then where the measurements are telling me the lands start and seat the bullet with chambering the round. I will chamber it seated out .020 longer several times and it pushes the bullet back in the case .020 each time, I know I have the correct distance to a hard jam in the lands which is the measurement I have been using. I have 3 bullets that I do this with and they all usually come out withing a thou or two of the same measurment.

 

[seymour fish]

Gents, If you chase the lands, in this case roughly .012, Does that increase your usable case capacity enough to take you off the bottom of the node ? Quickload says yes. What does practical experience dictate? Seymour

 

[stool]

yes..it really depends on how wide the velocity sweet spot is.
eventually you will have to start adding powder to get back there.

 

[jsthntn247]

How wide does quickloads say your node has to be before you need a change in powder charge?

 

[Erik Cortina]

How wide does quickloads say your node has to be before you need a change in powder charge?

QuickLOAD does not tell you how wide a node is, it simply will predict the velosity loss by moving bullet out. The OP should know how wide his node is and also weather he needs to add powder, and if so, how much. All this must be verified on target, as quickLOAD is simply an "estimator" of what would happen.

 

[amlevin]

... If one wants to insure that they are getting the same readings every time then the tools have to be free of inconsistencies themselves. On the Hornady, the bullet is the variable unless you dedicate ONE bullet for measuring.

Because of this point, if you are going to be chasing the lands, shouldn't you also sort your bullets from the base to the ogive? How much variation in base to ogive length would you encounter within a box of bullets?

I shoot 175 gr HPBT's. If I have SMK's I can find up to thee different base to ogive measurements. When I use Nosler Custom Competitions then I find the base/ogive dimension differences negligible.

 

[Jet]

Could using a different lot# of the same bullet cause this?

Jet

 

[gotcha]

Jet, Yes, I've found .012" difference in Ogive to base measurements lot# to lot# with Sierra MK's......... Not much difference in group size @ 100 yds. But it shows going further out. It pays to sort if not using custom bullets and shooting longer ranges. Just my experience.

 

[expiper]

OP,,,when seating the bullets "jamed" ~.010" +/- ,,you can feel the slightest bit of cam over when closing the bolt and you can see the lil' square mark on the bullet and this is what counts,,not a certain length with a cumbersome ojive tool/comparator/gizmo,,,,if using enuff neck tension you can extract a live round every now and then when shooting sighters and look for these marks ,,when they become faint or less rectangular and more square ,,it is time to move out a cupla thousants,,,,,,Roger

 

[Raythemanroe]

What caliber are you talking about? I think some are known for fast throat erosion under longer courses of fire..


Ray

 

[jsthntn247]

It's a 308. Not sure how much erosion to expect but .012 after 750 rounds isn't so bad. Too much more and I'll be going to a 200 gr bullet I reakon.