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Measuring Base to Ogive Length w/ Hornady OAL Gauge

 
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  #8  
Old 06-02-2013, 03:29 AM
Zep Zep is offline
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Thanks woods.

But I still don't have a grasp of the RP Tool. Would you please give us an explanation of how to use it again. Do you actually take one of the collets off the rod for the first measurement and then put it on for the second?
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Old 06-02-2013, 09:14 AM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Sure, but I like pics and it may take 2 posts since this site only lets you post 6 links in any one post

The RP tool is a 30" long .187" diameter stainless rod, threaded at the end to take a .250" brass tip




with 2 well made allen head collets



The tip can be removed for any caliber below 257 but will won't work for 17 calibers

First step is to insert the rod WITH COLLETS attached but out of the way down to the bolt face (make sure the firing pin is in the retracted position, don't ask me how I know) and lock the outermost collet



NOTE that the innermost collet is already part of this dimension so it is "allowed" for in the final measurement

Remove the bolt and insert bullet to the lands. This is the only step subject to variation as has been discussed. I use the Hornady tool but a dowel rod will work if you don't push on it too hard



Insert the tool back down to the bullet tip and lock the innermost collet





(continued)
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Old 06-02-2013, 09:22 AM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Measure BETWEEN the collets



Now like Mike said, take that bullet out and keep it separate. You want to use that bullet when setting your seating die, set it for the OAL desired. IOW seat the bullet to the OAL (to the tip) where you want it (measurement minus jump) and then take a comparator measurement on it. That will allow you to use the comparator to check seating throughout the multiple load seating process and be checking close to the ogive and take the error induced by variations in bullet tips out of the process.

The tool can be used for any caliber except the 17's and you will find other uses for it. It is the only way I have found to check headspace on BELTED cases. Like pin gauges very useful to have around
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Old 06-02-2013, 02:05 PM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Thank you Woods
Awesome explanation
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  #12  
Old 06-02-2013, 04:25 PM
Zep Zep is offline
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Yes! - Thanks Woods!!
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  #13  
Old 06-02-2013, 04:26 PM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Woods explanation is a good one for the tools used.

I don't know what cartridge is the one used in this thread, but if it's one that headspaces on the shoulder, that's the control point for measuring where a given diameter on a seated bullet's ogive is. The case shoulder's hard against the chamber shoulder when its fired. The case head will be somewhere between almost zero to a few thousandths inch away from the bolt face depending on how much spread there is between the case head and shoulder across all the loaded rounds. A few thousandths is normal with full length sized cases.

So, if one wants the seated bullet to be exactly the same distance off the lands on all rounds when fired, the bullet seater has to use the case shoulder, not the case head, as its reference.
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Old 06-02-2013, 04:45 PM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Quote:
Originally Posted by Bart B View Post
The case head will be somewhere between almost zero to a few thousandths inch away from the bolt face depending on how much spread there is between the case head and shoulder across all the loaded rounds. A few thousandths is normal with full length sized cases.
So you're saying that if you set your FL die to size the case body and push the shoulder back, lock it down and size your cases, that there will be a "few" thousandths (in normal conversation construed to be >.002" & <.006" or so) difference between the dimension between the case head and shoulder??!!

Uhhhh in what press?
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