Hornady OAL Gauge faulty concept??

[drfroglegs]

I had an epiphany today.. And that epiphany was that there is a serious flaw in the measurement of the OAL using the Hornady OAL system with the modified cases (I think). So that is the point of this forum, please correct my thinking if it is incorrect...

Here's my point. If you use the modified cases to measure the OAL (using the OAL gauge) you will get some value of the optimum length. Now say your actual cases have a shoulder that is 0.020" shorter than the modified case (the case on the left in the figure). Now when you make a cartridge that is the optimum OAL, the bullet will actually be protruding further from the shoulder than they were in the modified case.

The cases in the figure have exactly the same OAL according to the hornady OAL gauge. However the case on the left would not feed into your gun unless you cram the bullet into the grooves.

Has anyone else run into this problem? Is everyone adjusting the shoulder of your cases so they are exactly the same as the modified case?

[Creeper]

I have the Stony Point gauge, which is now the Hornady gauge. Stony Point would, if you sent them a fired case, drill and tap it to fit the threaded gauge adapter body.
If Hornady won't do this, you can DIY with a lathe... doing it by hand and getting it dead concentric would be tough.

First... before you do anything, call Hornady.

Cheers,
C

[Brian Pfleuger]

It's not a faulty concept but you have hit on a point that needs to be understood.

The number that you need from the gauge is actually the distance from the shoulder datum to the bullet ogive.

My fired case shoulders are all longer than the modified case, which I assume are set to SAAMI minimum chamber dimensions.

I use my case measurements, base to shoulder, and add the gauge measurement, shoulder to ogive. That gives you the OAL to the rifling with your own brass.

[mrawesome22]

Use a fireformed case with a vertical slit in the center of the neck. A forum search for "hacksaw" will steer you to the thread.

sudo apt-get update

[Brian Pfleuger]

^^^
You can try that method too, for some reason I only have one gun with which I get good results. Others seem to have better luck. Also, if you use Lee collet neck dies, you can custom adjust neck tension to get a perfect fit for that method. Still only works in one of my guns though. I wonder if it doesn't work better with some bullets, or maybe the interaction between some bullets and some rifling. I don't know. I gave up and went to the gauge.

Once you have the gauge, you just need to realize the differences between the supplied, modified case and your own cases. Make the corrections and you're golden.

[drfroglegs]

Originally Posted by Brian Pfleuger

^^^
You can try that method too, for some reason I only have one gun with which I get good results. Others seem to have better luck. Also, if you use Lee collet neck dies, you can custom adjust neck tension to get a perfect fit for that method. Still only works in one of my guns though. I wonder if it doesn't work better with some bullets, or maybe the interaction between some bullets and some rifling. I don't know. I gave up and went to the gauge.

Once you have the gauge, you just need to realize the differences between the supplied, modified case and your own cases. Make the corrections and you're golden.

Thanks, that was my "solution" to the problem. I was planning on using the head space gauge to measure base to shoulder, then use OAL gauge to measure base to ogive. Then use those values to calculate distance from shoulder to ogive. Then I only have to add this value to my fire formed cases to ensure the oal is accurate. Thanks guys!

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[browninghunter86]

Can you explain this again. Seems like that would give a huge number?

My fired brass reads 1.621" using the Hornady headspace bushing. When using the modified case and tool I get a measurement of 2.255"(to ogive of bullet) so you said add those two numbers?

I use my case measurements, base to shoulder, and add the gauge measurement, shoulder to ogive. That gives you the OAL to the rifling with your own brass

Wouldn't you add the difference between the headspace reading of fired case and the modified case?

[Brian Pfleuger]

Measure shoulder of your fired case.

Measure shoulder of modified case.

Measure ogive of bullet using gauge.

Take the distance from shoulder of modified case to bullet ogive and add it to the measurement of the shoulder of your fired round.

For instance, shoulder of my fired case is 1.75.

Shoulder of modified case is 1.68

Gauge ogive measurement is 2.25

Distance from gauge shoulder to measured ogive is 2.25-1.68, which is .57.

Add .57 to the shoulder measurement of your fired case. 1.75+.57, 2.32.

2.32 is you true measurement to the ogive with your case.

[drfroglegs]

Thanks Brian, that was exactly the point I was trying to make. Unless you are going to resize your brass to the exact dimensions of the modified case, you should instead be taking the measurement from the shoulder(datum) to ogive as the important part. Once you calculate this value (0.57 for you), then you can measure each individual case shoulder(datum) and add this value to your case to determine the perfect OAL.

Note: this assumes the shoulder does make contact with the chamber of course, which is certainly the case if you're using fire formed cases and will be the case with the modified cases as well.

Great explanation, let the accurate reloading begin!

[browninghunter86]

thanks. That clears it up.


I had been just using the modified case reading but then again I was loading to SAAMI specs so didn't really matter but now am trying to load closer to lands so this will help get more accurate reading

[impalacustom]

If your shoulder isn't making contact with the chamber you are going to have serious problems if it's too much of a difference.

Browning, some guns like a crush fit with no lead, some like lots of jump. Weatherby's almost always have a big jump to help tame some of the pressure. 22 Ackley Hornets like crush fits and just touching the rifling, at least mine did.

Changing seating depth can help with horizontal stringing.

[tobnpr]

Interesting point, never thought of it...

In Brian's example, seven-hundredths seems like waaaay too much variance. As in, the modified case isn't within spec for the chamber to begin with. I had "assumed" (hate that word) that the modified cases would be within SAAMI specs just as if it were the "real" deal. That doesn't seem to be the case. So, how does this happen?

I would have expected a difference of maybe a couple of thousandth's....not .07. Or , am I missing something?

[FiveInADime]

Originally Posted by tobnpr

Interesting point, never thought of it...

In Brian's example, seven-hundredths seems like waaaay too much variance. As in, the modified case isn't within spec for the chamber to begin with. I had "assumed" (hate that word) that the modified cases would be within SAAMI specs just as if it were the "real" deal. That doesn't seem to be the case. So, how does this happen?

I would have expected a difference of maybe a couple of thousandth's....not .07. Or , am I missing something?

I think he was giving you arbitrary numbers for demonstration purposes.

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[browninghunter86]

my fired case headspace is 0.002" greater than the Hornady modified case

I think he was just using "numbers" for the illustration

[Brian Pfleuger]

I was indeed. Pulled those numbers out of thin air.

[Unclenick]

This has come up in past posts and you can use the search function to find them. I'll add that the radii on the holes in the Stoney Point/LNL system gauges tend to make their measurements a little short of absolute. It really doesn't matter in this instance, though, as you are trying to get the difference between the two measurements. less the jump you want to the throat, to be what you read on your loaded rounds.

Redding's Instant Indicator tool will measure the ogive to shoulder distance directly and could be used with the gauge, then on your loaded rounds to set the bullet jump. I built a version of my own about three years before Redding came out with theirs. Fitted it with a cheap dial indicator, but it works fine. Mine won't do all the different measurements the Redding does, but mine has different caliber adapters.

[browninghunter86]

Nick how did you make that? That is great


Also to be even more precise shouldn't the modified case be the same trim to length as the fired brass?

[drfroglegs]

I don't think the trim length is important for the oal gauge measurement. Using the head space gauge and oal gauge only the ogive of bullet and shoulder are the contact points. A longer case length just means the case will cover a fraction more of the bullet, but won't affect the value your get.

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[drfroglegs]

Originally Posted by Unclenick

This has come up in past posts and you can use the search function to find them. I'll add that the radii on the holes in the Stoney Point/LNL system gauges tend to make their measurements a little short of absolute. It really doesn't matter in this instance, though, as you are trying to get the difference between the two measurements. less the jump you want to the throat, to be what you read on your loaded rounds.

Redding's Instant Indicator tool will measure the ogive to shoulder distance directly and could be used with the gauge, then on your loaded rounds to set the bullet jump. I built a version of my own about three years before Redding came out with theirs. Fitted it with a cheap dial indicator, but it works fine. Mine won't do all the different measurements the Redding does, but mine has different caliber adapters.

Wow that is nice man, how difficult was that to make? How do you change the caliber? Can you link more close up pictures? That is exactly what I need!

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[Unclenick]

That's any old cell phone picture. I should take some new ones.

I turned that from drill rod for use with the then still Stoney Point Overall Length gauge and my seating die to set controlled distances off the lands from the shoulder. I thought about producing it, but with work keeping me busy I didn't get around to it for about three years after making that one. Then one day the Redding Instant Indicator appeared in an ad in Precision Shooting, so I gave the idea up.

There's a plug inside the body for the probe plunger spring in the dial indicator to depress against the bullet. The plug is bored and reamed with the lead and freebore portion of a chamber reamer for the caliber I want it for so the bullet ogive meets a true throat dimension. The knurled part on the bottom is the case body adapter and it just unscrews. I bored it and reamed it with a chamber reamer to get a partial chamber with the shoulder and about half the neck. It's what the plug stops against.

Changing calibers, I just unscrew the body adapter and let the plug fall out and exchange both parts for ones that fit the other caliber. I did have to have a chamber reamer for each one I made, which I've done for the .223 shown, 6.5-284, .30-06, and .308.

[deepforks]

if you were going to modify one of your fired cases to substitute for the hornady case, wouldn't you want to full length resize it and trim to length to get the most accurate info? i'm thinking if you use a non resized fired case to come up with your oal, once you resize the brass and seat a bullet, youre going to end up with a different oal. so if you used a non resized fired case and wanted a .002 jump, after resizing and bullet seating, you'd end up longer jump, correct? what am i missing?

[hooligan1]

Those modified cases should be SAAMI tolerance guages, and if your gages are off .0012 or whatever from mine who cares? I don't load cartridges for you,,,, and you don't load for me, so live life and shoot some rounds downrange and be confident that your rifle is getting the very best effort from you.

[Brian Pfleuger]

Originally Posted by deepforks

if you were going to modify one of your fired cases to substitute for the hornady case, wouldn't you want to full length resize it and trim to length to get the most accurate info? i'm thinking if you use a non resized fired case to come up with your oal, once you resize the brass and seat a bullet, youre going to end up with a different oal. so if you used a non resized fired case and wanted a .002 jump, after resizing and bullet seating, you'd end up longer jump, correct? what am i missing?

If you were making your own case, you'd want to treat it the way you'd treat any other case. If you neck size, you'd neck size it. If you neck size and shoulder bump, that's what you'd do.

That's kind if the issue with the Hornady cases, they're essentially full-length resized and a lot of us don't do that so adjustments have to be made.

[deepforks]

i meant .020 btw i guess that answers my question. the reason i asked is i just picked one up today with a .300 case. reading through the instructions it states if you want to send a fired case to hornady, they do NOT want you to resize it? now why would that be?

on another note, i ran through a quick session using a 168gr berger vld. the bullet just did not appear like it was seated near enough. maybe i'm used to just wedging a bullet in the case vs. now trying to do things with more precision. so the hornady case length was 2.6145. bullet length was 1.261 = 3.8755. my coal is 3.547 giving me a bullet seating depth of .3285 (on the lands). say i bump them off .025 that puts me in .3535 seating depth. i know the coal is not what i'm going for, but i needed to see bullet seating depth. does this seem too shallow?

[TheTinMan]

drfroglegs - thanks for asking this question!

I hadn't thought through exactly what the OAL gauge is measuring. I didn't take the headspace dimension of the "modified case" versus the headspace dimension of my case into account.

Hornady will modify cases for you:
http://www.hornady.com/store/Modified-Cases/