Confusion with OAL gage

ElyBoy · Posted: Sun Jan 27, 2008 11:21 am Post subject: Re: Confusion with OAL gage

I have taken a few 100yd shots at deer, aiming through thick Northwoods trees at 20 below zero.
Taking time in the reloading room to get 3/4" groups at 100yds gave me confidence at taking these shots, and bringing home the venison.

Where do you live Wild Man??
You must be in the tropics at above zero.

Where us men live, it has been 30 below and colder for the past month, Shocked

and our snowshoes have been getting a real workout while hunting.

You sure that your aren't catching Tarpon instead of steelhead?? Very Happy

My oldest just came home with his limit of Rainbow Trout.
The other day, Ben and I came home with 8 nice bunnies for dinner.
Don't get much better than that.

Eric

Deleted_User_2665 · Super Member Joined: May 06, 2006 Posts: 380

I live a good ways away from Minnesota..........on purpose.

Dawgdad · Posted: Mon Jan 28, 2008 8:38 am Post subject: Re: Confusion with OAL gage

dakota1 wrote:

Both measurements, COAL, and length of the bullets themselves, was done with a comparator and ogive insert. The tip of the bullet did not come into play. The COAL difference between two bullets was .037, yet the difference between the bullets themselves was only .0046.

Since all results were measured from the ogive, and the bullets being the only variable, why wouldn't the difference between the COAL be the same as the difference between the bullets alone?

I assume ( a dangerous thing ) that the seating die you are using has a donut /hollowed out stem that contacts the bullets near the ogive and is not a flat. Take the seating die out and see how far a bullet goes into the stem. some of the longer bullet designs will bottom out before the stem reaches the ogive. The other variable is the die and press set up. Are you giving the exact same force to each stroke and camming over ? No back lash in the threads on the die or seating stem? All properly adjusted per manufactures instructions? Is the brass all trimmed and sized to be the same? if your neck or shoulder is not set back enough it could impede the sizing step.

I like this kind of problem from a technical standpoint but will agree as others have stated that in most cases, the difference will not be seen in a properly developed load. We call that robustness in th analytical chemistry world. the end result should not be dramatically affected by small changes in key parameters. If you are that close to the edge of poor performance or your performance only occurs in a very narrow band of tolerance, you should work up a different load.

Pumpkinslinger · Posted: Mon Jan 28, 2008 8:59 am Post subject: Re: Confusion with OAL gage

dakota1 wrote:

Both measurements, COAL, and length of the bullets themselves, was done with a comparator and ogive insert. The tip of the bullet did not come into play. The COAL difference between two bullets was .037, yet the difference between the bullets themselves was only .0046.

Since all results were measured from the ogive, and the bullets being the only variable, why wouldn't the difference between the COAL be the same as the difference between the bullets alone?

Maybe I'm catching on (I hope...). You measured the length of the bullet, from the base to a point on the ogive, and then measured the loaded cartridge from the base of the cartridge to the same point on the ogive? Are the shapes of the bases/boat tails exactly the same?

ElyBoy · Posted: Mon Jan 28, 2008 9:18 am Post subject: Re: Confusion with OAL gage

Us Northern Minnesota Iron Rangers have a habit of doing that to people. Very Happy

Eric

MGKelly · Posted: Tue Apr 01, 2008 9:26 am Post subject: Re: Confusion with OAL gage

Hi all,

I too like the technical side of things as I have found the more I understand about any subject the easier and quicker I can achieve my objective. When I was working as a mechanic years ago I found there were many safe "shortcuts" to getting a job done, but only because I understood what I was doing as there are many "wrong" shortcuts that will come back to bite you in the @$$! When I changed occupations and went into electronics and computers I found the same to be true! I salute anyone who is willing to take the time to learn to do things right and/or gain more knowledge, as they can then find an easier way to accomplish their task and still do it correctly. They know just what they can and can't do, they have learned the little secrets that most don't know. Knowledge is a great thing, but only if you use it regularly.

No, I'm not dissing anyone who doesn't want to delve in to the minute details, it's not for everyone. I just like learning new things, keeps the gray matter from turning into mush. Very Happy

An old saying posted in the shop where I used to work goes...

"If you haven't got time to do it right the first time, you don't have time to do it over again!" Embarassed

M. G.

Vince · Posted: Tue Apr 01, 2008 10:41 pm Post subject: Re: Confusion with OAL gage

MGKelly wrote:

An old saying posted in the shop where I used to work goes...

"If you haven't got time to do it right the first time, you don't have time to do it over again!"

Totally correct mate.

A slight twist on yours...my Dad used to say:

"If a jobs worth doing, its worth doing properly, and if you have the time to do it, then you have the time to do it properly".

Cheers, Vince

Dawgdad · Posted: Wed Apr 02, 2008 8:08 am Post subject: Re: Confusion with OAL gage

I think I get it now.... your variation in the bullets was .0046 (base to ogive)but the variation between two loaded rounds was .037 (case head to ogive) after you loaded the bullets.

The first place I would look for that would be the seater stem. You are making you measurements to the ogive but you are probably seating by a point closer to the tip. You may need to reshape your seater to contact the bullets closer to the ogive. remove the stem from the seater die and see how it contacts the bullet surface.

I have ben considering over boring the stem and filling it with an epoxy and molding it to the shape of the bullet I use (after the bullet is covered with release agent). I could do this for each type of bullet and have a full surface contact with the seating stem to more closely control the seating depth.

Thread backlash, inconsistent stroke on the press arm or crud in the seating die can give you error too.

woods · Member Joined: Oct 15, 2005 Posts: 89

dakota1 wrote:

Gun: is a Rem 700 BDL .270 Win
Measuring device: Stoney Point, compariter (sp), .270 ogive insert, digital caliper
Bullets: Speer 130 gr BTSP and Sierra 130 gr BTSP

When I measure the OAL length of the two bullets, in the stoney point gage, I get a difference of .037.
When I measure the length of the bullets alone, I get a difference of .0046.

Since the only variable in the measurement is the bullet, shouldn't the difference in the stoney point gage measurement be the same as the difference when measuring the bullets alone, when measuring, using the same caliper, comparitor and insert?

When measuring with the stoney point gage, I measured 10 different bullets of each manufacturer, threw out the high and the low, and averaged the remaining 8.
When measuring the bullets alone, I measured 5 different bullets of each manufacturer, and averaged the total.

What am I missing?

Perhaps a drawing

There are just too many variables such as the distance from where the comparator contact occurs to the full diameter point or the distance from the full diameter point to the base of the bullet. The differences can get lost in the depth you seat the bullet or elsewhere.

Anyway, it is entirely possible.

sniper · Posted: Tue Apr 08, 2008 6:55 am Post subject: Re: Confusion with OAL gage

wildswalker wrote:

Much voodoo can be conjured up to complicate the process and many thrive on that willingly.

Find your lands, know you mag box max COAL, seat for unihibited function and rock on.....

Ain't hard...............................

Perzackly!

Eschew Ballistic Proctology! Very Happy

WildHorse · Member Joined: Feb 17, 2005 Posts: 184 Location: Nebraska

When I buy a hundred new bullets I usually weigh them. I separate them by weight and then I load them separetly. I usually do not see any appreciable difference in performance. I only do this on my varmint bullets. My hunting bullets are loaded and I do not weigh that bullet.
I usually buy 100 bullets at a time, and I am still loading my 280 with bullets I bought five years ago. I go deer and antelope hunting, and usually don't use more than two or three cartridges. I always sight my rifle in before hunting just to make sure nothing has changed. That ususally takes two rounds. just my 2 cents worth.

sniper · Last edited by sniper on Wed Aug 27, 2008 3:49 pm; edited 2 times in total

Not trying to resurrect this old thread, (not much!) but I have recently replaced my Stoney Point comparator with a Sinclair. Much simpler, but harder to find, 'cuz I no longer need the big box I kept all the Stoney parts in. Razz

Checking my records, (gotta keep records, I can't remember worth beans anymore Very Happy

)I see that a free travel (the distance from the bullet ogive to the beginning of the rifling)of .030, regardless of how I measure, produces the best groups in nearly all loads. OAL is a perfectly serviceable measurement.

The ogive of the bullet is the portion where the base just begins to curve into the point. Proper measurement with either system is from this point.

I find that by splitting a fired, sized case neck down past the neck-shoulder junction, I can use the cartridge case to determine my working OAL. 2, 3, or 4 cuts provide enough neck tension to hold the bullet firmly, but still let it slide.

Slide the bullet into the case mouth just a little, oil it so it won't stick in the barrel, chamber it gently, then just as gently, extract it. Do this several times, resetting the length and measuring each time. COL or comparator, makes no nevermind. This should give you a very close aveage max. overall length. Set your cartridge free travel / COL from this.

It will be some different for each make, style and weight of bullet.

I have heard that bullets tend to vary more from tip to ogive than from base to ogive. That sounds reasonable to me, but you also have to take into consideration cartridge base length dimensions, as it can vary +-~ .002.

Let's face it, .001-.002 is a TINY little amount, hard to duplicate on a consistent basis, and unnecessary in reloading, unless you try to approach zero tolerances closer than what is necessary, or safe.

It is a Fine and Pleasant Madness! Cool

Dawgdad · Posted: Wed Aug 27, 2008 2:50 pm Post subject: Re: Confusion with OAL gage

Oh but you had to open this old sore again didn't you!!! Very Happy

For 90% of handloaders out there you are correct. The performance in terms of group size in a cartridge measured OAL to the tip that has a .030 jump from the lands will not be signifcantly different than those measured to the ogive with the same jump.

But the variation from ogive to tip is more on the order of .008 to .012" even in high quality match hollow points. Varmint and match hollow points are harder to make consistent in this dimension. For the 10% of loaders who are trying to squeeze that last 1/2 moa from a 600 or 1000 yard target load and seating a VLD or Amax type bullet .005 -.010 off the lands that is too much variation. We can still shoot 10s if we load to OAL at the tip but we want X ring so we measure to the ogive. The base to ogive is a much more uniform measurement from bullet to bullet. more on the order of .002 " It is also critical that you have a quality seating die to control the length.

To reiterate this must be done for each type of bullet, brand, weight, profile etc. when you are closer to the lands.

When you are out past .020 off the lands..... load'em and shoot'em.

phill21 · Posted: Wed Aug 27, 2008 4:27 pm Post subject: Re: Confusion with OAL gage

Woods i think you hit the nail on the head there old son. Cool

Dakota1 i once had the same issue with my rounds pondered it for awhile went out shot something and promptly gave up on as it made no differance to my kill shots. Smile

The wife just said whats life without a few mysteries bit of an understatment as women of all ages are a mystery. Very Happy

Keep on keeping on

phil

wncchester · Member Joined: Apr 08, 2006 Posts: 160

"... shouldn't the difference in the stoney point gage measurement be the same as the difference when measuring the bullets alone, ..."

Only if the curve of the ogive forward of bore diameter is the same. That's rare.