Inconsistent Readings With Hornady O. A. L. Gauge

In order to establish bullet jump, for a number of years, I have been dutifully using the O.A.L. gauge to determine distance to the lands. To establish confidence in my results, I make make repeated measurements (10) and consider the average as the "true" value. In addition I have used other measurement techniques for comparison which should yield the same value. My frustration is that results are all over the map. As a recent example with my new unfired 22-250 Shilen Match, the maximum and minimum measurements of one set (10) were 1.988" and 1.944" with an average of 1.967" which is typical of my experience with the O.A. L. gauge! I also used a separate technique which involved reaming the neck of an unfired Lapua case until the bullet could easily slip in and out, and then chambering it with some threadlock to permanently attach the bullet to the case while it was in firing position. The result of this measurement was 2.080"! In the many Youtube demonstrations of the O.A.L approach, magazine and book articles and forums I have never seen this issue of inconsistent measurements mentioned. It seems that one measurement is sufficient. My question is why am I getting such a spread in what should be identical results? Any suggestions would be greatly appreciated.

Because of the taper and the softness of the bullet, you need to be " brain surgeon " gentle when you push the bullet out to the lands. If the bullet sticks at all the measurement will be off somewhat.

Yeeerp! What he said. You need to push the bullet with the lightest of pressure, and be consistent. I use a cleaning rod I the opposite end to push the bullet back out. I check often after pushing the bullet to make sure I’m consistent. If you feel resistance pushing the bummer back out, it means you were WAY into the lands. There should be NO resistance at all.

When I 'measured' the seat depth for the .308 155 Berger's I found that I could not determine with accuracy when the bullet engaged the lands. A fraction of an ounce of pressure and it might be .010 or .020 into the lands. So, I just pick one and use it. After all the end result is to have consistent ammo, not know down to .0001" how much you are away from the lands (or seated into the lands).

The key is to have consistent ammo. During load development you will be testing several OAL to see what works best. What difference does it make if they are engaged or not? And, each bullet likes a different 'jump'. The Bergers mentioned perform best for me when lightly engaged. The SMK's I have used do best a bit off the lands (around .020 or sometimes even a bit more).

Here, here.

I was researching this subject and came across this...actually makes a lot of sense.

Chasing the lands is STUPID! Don't do it. - YouTube

yes but first you have to find the lands..and he cannot.
one bullet per lot.
no pressure...touch..is just that touch...not jam nor jump
if the bullet does not fall out, ignore the reading
.062 ERROR in reading, MEANS you need a better TOUCH, a better feel with the TOOL
YOU NEED TO LEARN TO USE THE TOOL...so far you do not.
take your time move the bullet gently, slowly
i seldom take more than three readings...10 is a failure to communicate( with the tool)
does the bullet move freely in the case ?
does the cable move smoothly in the tool ?
is the chamber and throat clean ?
is it a new throat ?
a used burned throat is no place to be learning

What do you do with your reading? Just curious.

For me, I just use it as a starting point to do a series of shots at different seating depths.

I agree with you Charlie.

To the OP, just keep at it bud. Take in what some of us here have said. Don’t get so crazy with OAL. Honestly.... a few thousandths difference in OAL isn’t going to mean the difference between 3/4” groups and 3”-4” groups!! Ya Smellin’ what I’m Steppin’ in? Just keep at it and your technique will improve. Doesn’t matter what rifle you’re doing this on. With practice, the ONLY outcome is increased prowess. It’s not an “IF”, but rather a when.

So have a beer and as my father used to say(God rest his soul), “Don’t sweat the small ISH. And and know what? It’s ALL small ISH!” -Great line.

what are you using as a trimmer for brass, and what brand tool are you using to measure with? I can get a lot of deflection out of some tools. might as well ask what you have for a press?

One little trick with the OAL tool is to insert the bullet and the tool into the action then carefully point the muzzle down allowing the projectile to self center on the lands, snug the push rod to the base of the bullet and tighten the screw. Use your comparator to record the CBTO number and mark that. -0-

I use a "slip case" instead of the wire. Couldn't get a uniform measurement with the wire. Charlie and Dave have it right, at best it is an arbitrary number.

Bill

Quote:

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Originally Posted by South Prairie jim

One little trick with the OAL tool is to insert the bullet and the tool into the action then carefully point the muzzle down allowing the projectile to self center on the lands, snug the push rod to the base of the bullet and tighten the screw. Use your comparator to record the CBTO number and mark that. -0-

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Jim,

Do you repeat that measurement often and adjust your seating depth based on that or is it a one time thing?

I came to the conclusion that measuring touch is a waste of time. While your technique may work 100% of the time with 30 cal bullets, it may not work at all with 22 cal bullets, especially if your barrel's throat isn't sparkling clean.

Since abandoning that method and instead, seating a bullet long in a sized case and closing the bolt on it, my shooting has improved dramatically. The hard jamb method is a very consistent way of establishing a starting point for bullet seating, and that is ALL it is, a repeatable starting point that moves as your barrel wears.

I find the hard jamb position and start my loading .010 aft of that point, moving back in .005 increments.

Hard jam? Wow. I’m noticed some jams to be .040” into the lands! So to me, that sounds like you would be starting DEEP in the lands. Art .005” intervals, that is in deed quite a few test loads. But like you said... only a starting point.

Not really, it’s such an arbitrary number I only need to check on occasion or a new bullet, from there I’m always testing on paper and making small adjustments if neccasary. most of the BR fellas use the stripped bolt method on custom actions because it’s repeatable and universal enough allow information sharing between a smith and a customer for example.

Another point guys can over look and have inconsistencies with is the modified case purchased isn’t fire formed to their chamber so when you insert the tool snug to the chamber shoulder we leave a gap ( headspace ) at the base of as much as .007 . Now put you comparator on the caliper for a base to ogive number and ask yourself how shall I compensate or if I need too ? Do I pull the case back to the bolt face and push the bullet forward ? WTHeck any way.. we somehow get it figured out. Lol

Thanks for that. It is what I expected then. I just use a COAL measurement as a starting point and shooting tells me how to adjust actual seat depth.

Quote:

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Originally Posted by gguinn

In order to establish bullet jump, for a number of years, I have been dutifully using the O.A.L. gauge to determine distance to the lands. To establish confidence in my results, I make make repeated measurements (10) and consider the average as the "true" value. In addition I have used other measurement techniques for comparison which should yield the same value. My frustration is that results are all over the map. As a recent example with my new unfired 22-250 Shilen Match, the maximum and minimum measurements of one set (10) were 1.988" and 1.944" with an average of 1.967" which is typical of my experience with the O.A. L. gauge! I also used a separate technique which involved reaming the neck of an unfired Lapua case until the bullet could easily slip in and out, and then chambering it with some threadlock to permanently attach the bullet to the case while it was in firing position. The result of this measurement was 2.080"! In the many Youtube demonstrations of the O.A.L approach, magazine and book articles and forums I have never seen this issue of inconsistent measurements mentioned. It seems that one measurement is sufficient. My question is why am I getting such a spread in what should be identical results? Any suggestions would be greatly appreciated.

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My suggestion would be to simply take one of your fired proper length cases and full length resize it.
Then without seating a new primer or charging the case with powder, (empty unprimed case) seat a bullet long by backing off on the seating die.
Insert the case in the gun and close the bolt, which will seat the bullet by jamming it into the rifling.
I would then readjust the die by at least one full turn on the seating depth adjustment and reseat the bullet to that depth.
Then use a match to smoke up the bullet and chamber it into the gun.
Rifling marks will appear on the blackened bullet, deeper adjustments can be made untill the marks completely disappear if desired.
Check the final length chosen for magazine length fit if necessary.
No special cases or tools of any kind are necessary.
An alternative method of removing the firing pin assembly from the bolt and seating the jammed bullet deeper until the bolt falls closed with no resistance can also be used.
But for average Joe loader the match smoked system is easy and works very well.
Resmoke the bullet as necessary.

Problem I have with the Hornady tool is you're using piece of plastic to establish a "precise" point for measurement.

I bought one as well as the special tap so I could use drilled and tapped fire formed brass, but, the pushrod is still plastic unlike the original Stoney Point tool which used a metal pushrod.

After several attempts to get repeatable measurements, I went back to my old method, same as Yobuck describes, of marking a bullet and gradually seating deeper until there was just a hint of rifling touching the bullet. Only difference is I use Sharpies vs a smoked bullet tip.

That’s why I made my own tool. NO plastic... ALL & the pushrod is 1/8” diam. Carbon Fiber rod. I did the same thing also Phil. I tapped one of my cases that I sized, trimmed & fired.

Quote:

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Originally Posted by yobuck

My suggestion would be to simply take one of your fired proper length cases and full length resize it.
Then without seating a new primer or charging the case with powder, (empty unprimed case) seat a bullet long by backing off on the seating die.
Insert the case in the gun and close the bolt, which will seat the bullet by jamming it into the rifling.
I would then readjust the die by at least one full turn on the seating depth adjustment and reseat the bullet to that depth.
Then use a match to smoke up the bullet and chamber it into the gun.
Rifling marks will appear on the blackened bullet, deeper adjustments can be made untill the marks completely disappear if desired.
Check the final length chosen for magazine length fit if necessary.
No special cases or tools of any kind are necessary.
An alternative method of removing the firing pin assembly from the bolt and seating the jammed bullet deeper until the bolt falls closed with no resistance can also be used.
But for average Joe loader the match smoked system is easy and works very well.
Resmoke the bullet as necessary.

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This is the easiest and best way... imo