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Mar 25th, 2012
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questions on terms #6994619
12/13/17 03:11 PM
12/13/17 03:11 PM
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Stratford Texas
BassCat'99 Offline OP
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what is the correct term used when measuring length with a comparator? that is measuring to the ogive. the when measuring the complete cartridge from base the meplat(?), tip if bullet. Any other terms that relate to cartridge/case measurement would help also.


22 Creedmoor
Re: questions on terms [Re: BassCat'99] #6994632
12/13/17 03:19 PM
12/13/17 03:19 PM
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COAL= Cartridge Overall Length, meaning base to bullet tip, or total length. This is most common length used in your reloading manuals and by other reloaders.

Ogive measurement, which is from the ogive of the bullet to the case head (base of the round). The ogive measurement can have different lengths, depending on which tool you use to get the measurement. In my shop, we use the Hex nut. The hex nut is the fastest method to quickly get an ogive measurement. The Hornady tool is fine, but it takes setting up and screwing onto your caliper. It works great, just slower. And both tools will give you a different length, since the hole the bullet rests in can be slightly bigger or smaller. Some people I load for use the Hornady tool, and I use that tool to get their measurements. But for my everyday use, I use the Hex nut.

I prefer to use an ogive measurement, since the ogive stays constant. A lot of hollow point bullets will vary in length due to the hollow point not being even. The HP often has corners and flat edges on the tip, and will vary by .005" to .010", which is perfectly normal. This variance will show up in your COAL when measuring it. That's why I use the ogive measurement. The most important relationship is the ogive to the barrel rifling. I have set ogive measurements I load to in most of my ammo.

Hex Nut tool

Hornady bullet comparator (bullet ogive tool)




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Re: questions on terms [Re: BassCat'99] #6994641
12/13/17 03:31 PM
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And something to pay attention to... From bullet lot to lot, the ogive to bullet tip can change. For example, the 6.5mm Berger 140 Hybrid was famous for having a large swing from lot to lot in their ogive to tip length. This was important, because if you loaded your rounds only by a set COAL, the ogive of the bullet could be too far from the rifling, or jamming into the rifling, depending on the lot. One of the lots of bullets we got had a much longer ogive to tip length, so we had to seat the bullet out further to keep the ogive in the same location. Similar to this picture below.




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Re: questions on terms [Re: ChadTRG42] #6995010
12/13/17 08:45 PM
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Originally Posted By: ChadTRG42
And something to pay attention to... From bullet lot to lot, the ogive to bullet tip can change. For example, the 6.5mm Berger 140 Hybrid was famous for having a large swing from lot to lot in their ogive to tip length. This was important, because if you loaded your rounds only by a set COAL, the ogive of the bullet could be too far from the rifling, or jamming into the rifling, depending on the lot. One of the lots of bullets we got had a much longer ogive to tip length, so we had to seat the bullet out further to keep the ogive in the same location. Similar to this picture below.



Interesting you show this. I used to load 52 grain Bergers for a 22-250 and I noticed they looked much longer than normal when I loaded a new box. Sure enough the hollow point tips were smaller than previous boxes and the ogives were different and that is when I learned to measure off the ogive. Made a big difference.



Re: questions on terms [Re: BassCat'99] #6995028
12/13/17 09:06 PM
12/13/17 09:06 PM
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Stratford Texas
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Thanks Chad, the man that knows! So it would not hurt to measure ogive and the coal to see if you have a bullet length swing?


22 Creedmoor
Re: questions on terms [Re: BassCat'99] #6995061
12/13/17 09:29 PM
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Originally Posted By: BassCat'99
So it would not hurt to measure ogive and the coal to see if you have a bullet length swing?


Almost all of my reload data records both the COAL and the Hex nut measurement (for ogive length). Yes, I would record both. If I am loading for my personal ammo, and I switch lots of bullets (same bullet, but a different lot #), I will check both measurements. I will also generally check the ogive to bullet tip length. When Berger increased the ogive to tip length on that 140 Hybrid, it also increases the BC of the bullet (generally). So you will need to calculate your new BC. This is why I bought like 30,000 of the 140 VLD-H bullets, so I didn't have to change up my ammo and BC calculations. I ran that bullet in my 260 Rem, and now in my 6.5x47L. And it holds a constant .313 G7 BC. It's also the same bullet I run in customer 6.5mm ammo with that VLD-H bullet. I'm down to only a few thousand now. But, I shoot more 308 now than 6.5mm.



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Re: questions on terms [Re: BassCat'99] #6995118
12/13/17 10:13 PM
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Before I began using a comparator to check seating depth, I would record the cartridge overall length in my notes just as I suppose most would. When I began using comparators I started recording the length in parentheses, such as (2.727") so that it would be apparent I had used the comparator. Helps avoid confusion.


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Re: questions on terms [Re: BassCat'99] #7012738
12/27/17 03:34 AM
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Chad, do you use the hex nut for 6.5 creedmoor? Thinking about buying it, but some reviews show it doesn't work great for smaller calibers.

The Hornady is more expensive and seems to be more cumbersome, so I'd like to use the hex nut unless there is a good reason not to.

Last edited by patriot07; 12/27/17 08:15 PM.
Re: questions on terms [Re: BassCat'99] #7013191
12/27/17 04:42 PM
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^ Yes. The hex nut I use has 6 different hole openings, one of them a 26, for 6.5mm. I use this one, with the 26 or 6.5mm hole.

https://www.brownells.com/reloading/meas...-prod83792.aspx



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Re: questions on terms [Re: BassCat'99] #7013455
12/27/17 08:15 PM
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Thanks!

Re: questions on terms [Re: BassCat'99] #7014021
12/28/17 03:26 AM
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The Hornady locks to the caliper, it's not more cumbersome. I find the nut more difficult to use because it's not connected to the caliper. Either works though but you need to pick one and stick with it, because they will not measure the same. I have both.


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Re: questions on terms [Re: BassCat'99] #7015490
12/29/17 01:17 PM
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Chad do you have tools for measuring length of case shouldermto base of the shell?
I have read on the tfl were reloader are moving their die up or down to make the rounds chamber easily.
They are setting the right headspacing for their own gun.

Re: questions on terms [Re: BassCat'99] #7015538
12/29/17 01:59 PM
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Re: questions on terms [Re: BIGDOG1956] #7015548
12/29/17 02:07 PM
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Originally Posted By: BIGDOG1956
Chad do you have tools for measuring length of case shouldermto base of the shell?
I have read on the tfl were reloader are moving their die up or down to make the rounds chamber easily.
They are setting the right headspacing for their own gun.


You can use the bullet comparator inserts for that if you want to. For instance, use the .30-caliber insert to get a reading on a .223 case. The measurement won't be from case head to "datum line" of the shoulder, but who cares? It should work well enough to get repeatability.


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Re: questions on terms [Re: BIGDOG1956] #7015551
12/29/17 02:17 PM
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Originally Posted By: BIGDOG1956
Chad do you have tools for measuring length of case shouldermto base of the shell?
I have read on the tfl were reloader are moving their die up or down to make the rounds chamber easily.
They are setting the right headspacing for their own gun.


Larry Willis at Innovative Technologies makes one which he calls his "Digital Headspace Gauge".

http://www.larrywillis.com/


Re: questions on terms [Re: BassCat'99] #7015571
12/29/17 02:39 PM
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Re: questions on terms [Re: BassCat'99] #7016449
12/30/17 03:21 AM
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BTW, Hornady makes 2 different comparators, not to be confused.

The Bullet (OAL) comparator stops on the round's bullet ogive.

The headspace comparator stops on the round's neck and is an alternative to the Innovative Technolgies Digital Headspace Gauge.

I believe they use the same base though.


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