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Hornady LNL OAL gauge question

 
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  #1  
Old 07-05-2011, 07:33 PM
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Hornady LNL OAL gauge question

I will try to make this as brief as possible. I ordered a Hornady LNL OAL gauge to help me more precisely measure my handloads. I may be doing something wrong, (as I am known to do from time to time), but I need a little help here. First off I measure my OAL (from the ogive) with this tool using my SMK 168gr bullets that I have been using for my rifle. I get a little variation in my measurements, but I feel like it's probably just me getting used to the tool and putting varying amounts of pressure on the ram driving the bullet to different depths into the lands/touching the lands etc. So I make about 8 measurements until I can can get a good idea as to where the lands are. For example, I may have some measure a few thou one way or the other, but I see the same repeating number on the calipers for several measurements and determine that is my OAL. Now I try some Berger 168gr VLDs that I just ordered. (They were on sale at Midway and I thought I would give a box a try.) The thing is, I would expect that since I am measuring from the ogive (with a bullet comparator) the OAL would be the same. Makes sense to me. But I am getting a different OAL value from the SMKs. After measuring multiple times, I have determined that the OAL of the SMKs is 2.720". The Bergers however measure 2.750". It seems like a HUGE error to me. Maybe I'm doing something wrong? Or maybe I just can't wrap my mind around why they would be different? Any insight here would be greatly appreciated.
Steve

Last edited by CRNA; 07-05-2011 at 07:48 PM.
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  #2  
Old 07-05-2011, 09:31 PM
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Re: Hornady LNL OAL gauge question

The context of ogive is often assumed as the point where lands would first contact a bullet nose. That's the datum desired.
But a bullet ogive is not a datum point. 'Ogive' is really a term to define the curve of a bullet nose, rather than a specific place on that curve.

That desired datum(first contact) varies with angles, both related to the nose curve, and the bore leade angle. And while a datum can be calculated, your tool will not match it.
The only matching tool that I know of is a barrel stub throated with the same reamer used to cut your chamber('gizzy').
Without this, you still have a relative datum provided by your tool. It is simulating land contact.

But no matter the tool, the datum provided will change with each different nose curve, cuz different nose curves actually do contact lands differently.
Same lands(simulated or not), but tangent ogive curves(SMK) are way different than secant ogive curves(VLD), so the datum moves.

All that matters is that you determine ogvOAL for EACH bullet type you intend to use & log it.
Focus on reproducing these lengths based your measurements, with your tool.
Hell, I use is a Sinclair 'nut' (nothing fancy). But as long as I can reproduce the exact seated measure with that tool, I'm good to go.
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Old 07-05-2011, 10:39 PM
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Re: Hornady LNL OAL gauge question

Mikecr speaks the truth. You must measure every type of bullet you shoot because they will all be different.
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Old 07-06-2011, 05:38 AM
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Re: Hornady LNL OAL gauge question

So in short, I am measuring correctly and the measurements for the two bullets will be different?
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  #5  
Old 07-06-2011, 07:25 AM
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Re: Hornady LNL OAL gauge question

CRNA - Yes, different bullets will have different measurements.
Just a thought: Usually bullets from the same lot\box have little variation so no real consideration needed... Double check on new lot\box in case considerations are needed.

Mikecr. Excellent explanation.
Sometimes I agree with you.. sometimes maybe not so much... but you have some great head knowledge and this explanation was super and greatly appreciated.

For all my rifles I most often get a deviation of .0005. An occasional deviation of +- .001 happens but rarely now that I am very familiar with my Hornady gauge and how to use it on each rifle. Bottom line as Mikecr states... one can use most anything to acquire a base measurement as long as it is consistent.

"... Focus on reproducing these lengths based your measurements, with your tool."

Thanks Mikecr and good topic CRNA

Last edited by 338winmag; 07-06-2011 at 07:37 AM.
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  #6  
Old 07-06-2011, 09:39 AM
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Re: Hornady LNL OAL gauge question

Thanks guys. I saw variation between the SMKs and Bergers, but I didn't see any variation between the individual boxes of bullets.
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Old 07-08-2011, 10:01 AM
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Re: Hornady LNL OAL gauge question

Also I noticed that I really had to make darn sure I had the modified case perfectly strait to get consistent readings. Still waiting on my Micrometer adjuster for my seating die to come from Hornady. Turn 1/8 turn, measure, repeat. Is a pretty tedious process every time I wan to change the Amount of jump I have.
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