Seating depth problem...

[hardly]

I am trying to measure length to lands and can not get it right.  Even using the same bullet I am getting different measurements every time, as much as .120".  Is this normal?   The equipment is Rem 700, 22-250, Hornady OAL gauge and comparitor.  I am obviously doing something dumb.

[charles p]

Are you using an empty unsized case and a smudged bullet, or something like a Stoney Point guage?

[hardly]

it's the same as the stoney point gauge as far as i know.  uses the modified case that screws on.  remove bolt, drop a bullet into the case, insert into the chamber, push the bullet forward with the rod til it touchs the lands, tighten the set screw, remove and measure with a caliper and bullet comparator.

[AtlLaw]

I am getting different measurements every time, as much as .120".  Is this normal?

I went back and read you post and I can give you a definite yes and no answer!     I encountered this when I started using the SP.  Being a handloader, which means I'm a tad bit anal  , I'd measure and remeasure a few dozen times and finally decided to use an average of a few measurements, say 1 or 2 hundred, then deduct .005 just to be safe... I live in fear of a bullet jammed into the lands!     There are so many reasons the measurements could vary, not the least of which is the amount of force used to push the bullet into contact with the lands, that I don't remember the measurements coming out exactly the same every time!

However, differences fluctuating up to .120 is NOT normal.     I'd examine my technique, after you check the gauge over for any defect that is  i.e.: make sure the case is fully seated in the chamber, try to use the same amount of pressure on the bullet to make contact with the lands, stuff like that.  The differences should only be a few thousandths.

[SHOOTALL]

i have seen several people seat a bullet so they contact the rifling when they close the bolt . often the bullet will stick if the round is not fired . This was done on rounds like 7TCU when used in a bolt action . accy was good .

[Ladobe]

 
... I'd examine my technique ...

Short, sweet, simple and the correct answer IMO.

I've used all the SP measuring systems for years (OAL, headspace, comparator) and they are all about technique.   Consistency in your readings takes a light touch.   You will get better at using the system with use (practice).   I've never had a problem getting repeat readings within a few thou.   Important to me because unlike AtlLaw, I lightly jam the bullets in every rifle and specialty pistol I reload for.

[AtlLaw]

i have seen several people seat a bullet so they contact the rifling

I'm not saying that's wrong mind you, just that it makes me nervous so I avoid it.     I've heard of a number of people that believe in it and I know it was a practice with BP cartridge rifles.

[OR-E-Gun Bill]

Kinda hard to imagine a measurement difference of .120" ( .005" under 1/8" ), even for someone not familiar with using the Stoney Point/Hornady OAL Gauge.
I could understand if better if it were .0120" difference and am hoping "hardly" may have left out a zero in his measurement reporting.

Bill

[wncchester]

I can't imagine anything that would cause an inconsistancy of an eight inch with any method of locating the lands. 

The concept of seating to the lands for accuracy (myth) began with benchresters who seat to the lands for accuracy (fact) BUT they are usually using virtually NO tension on their bullets so the land contact gives enough resistance for pressure to build as it should.  WE don't load that way. 

No ballistic rule applies to all situations so accuracy "rules of thumb" are best left to measureing thumbs and ignored at the loading bench.    Almost ALL factory sporting rifles will shoot better with a jump to the lands of anywhere from .020" to as much as .100".  Or, maybe, even .120"!

[Kurt L]

I have found with this tool a stoney point same as the new lock n load to be as you say BUT!
the trick is to
have the set screw loose
put your bullet just inside the case just enough to hold it and push the the inner cable out to the bullet.
then push it all the way in the chamber and hold it and tighten the set screw.
after you take it out you may notice the bullet will go back in the case a bit this is becouse it tried to stay in the throught. but you are ok as you set it at the rifling.
this method will get you the same reading every time vrs trying to push the bullet to the lands do as I said above and its very consitant.
the only thing NEED TO WATCH FOR is chamber lenths. if you have all the stoneypoint or lock n load tools
measure the base to the shoulder on a fired round from that gun than measure your dummy case head to shoulder if they are the same or VERY close your good.
I try to get nickle cases to make my own from and shoot it then drill and tap it and it is a perfect measurement. I like the nickle cases when I can use them as they stay clean and don't tarnish,that's the only reason for nickle.

[hardly]

OR-E-Gun Bill

I tried two methods, with gun on bipod and pushing the rod forward until I felt it touch.  Second, inserted the bullet into the modified case and pushed the rod forward until the bullet tip was just at the case opening and tightened the set screw.  inserted the case into the chamber and tilted the gun barrel muzzle to the floor and released the set screw to let the rod drop on the bullet.  Maybe that is enough to drive the bullet into the barrel enough to give me the .120 difference in the first method.  Looks like i'm not doing anything that wrong, just need to practice.  thanks.

[Glanceblamm]

I lightly jam the bullets in every rifle and specialty pistol I reload for.

Ditto...Lightly jam equals not enough force to make a mark on the jacket but firm enough to get a good reading.

[TOWCOBRA1]

Before I use my stoney point OAL tool, I cycle a cleaning rod w/dry patch through the chamber and throat area several times to remove any powder residue (burnt and unburnt) that might affect the lenght measurements. Some powders burn clean, some do not. A clean chamber and throat area will give more consistant measurements than a filthy one.
John A.