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 Using Calipers to Measure from the Ogive? or just COAL 
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with regular calipers? There are a few companies that sell attachments for calipers to measure from the ogive. Even this has challenges as bullet shapes aren't all the same. So it will always be a relative measurement and applicable to YOUR gun and the types of bullets you commonly use...

So anywayz on that...The HP's get dinged up just being in the box and the nylon(?) ballistic tips in some hunting ammo get jacked for whatever reasons too, even before being loaded...(I don't use that kind of bullet though) so what are your thoughts about measuring from the ogive to counter those irregularities?

I'm not sure, with a semi-auto gun, that this this kind of accuracy will benefit me, but if I ever get a bolt gun...

But... I just don't know enough to say... you?

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Thu Dec 21, 2017 4:20 pm
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This is still an area where I'm actively learning. My interwebs research indicates a lot of benchrest shooters seat the bullet until it's right in contact with the lands or may back off from 0.0010" - .0015" on the theory that this provides the best accuracy.

There's a lot of caveats here. Some cartridges employ a lot of freebore requiring bullet jump from cartridge seating to the lands, in some cases so much that it's not possible to seat to the lands or that close.

Also most folks indicate that once you have a promising load then run some additional tests loading rounds at various distances off the lands then measure the resulting group sizes to check the effect of seating depth on accuracy. The premise being that every gun will run differently.

One thing to be careful of here is that seating on the lands or very close can cause increased chamber pressures. So employ caution if working with hot loads.

And of course this is for bolt action rifles or single shot rifles/handguns like an XP-100 or T/C Contender. My understanding on semi-autos is that magazine box length is the determining factor to ensure proper feeding.

My personal experience on my XP-100 in 7mm Rem BR is that I have to seat very far out to get close to the lands. Not sure if this is a result of throat erosion since the barrel history is unknown to me. So on that particular gun I've just started seating to the bullet cannelure instead.

Hornady makes two tools to help with seating depth measurements:

OAL Gauge
https://www.hornady.com/reloading/precision-measuring/precision-tools-and-gauges/oal-gauges-modified-cases#!/

Bullet Comparator Kit
https://www.hornady.com/reloading/precision-measuring/precision-tools-and-gauges/lock-n-load-bullet-comparator

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Last edited by GeekWithGuns on Thu Dec 21, 2017 5:01 pm, edited 1 time in total.



Thu Dec 21, 2017 4:53 pm
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Moved to the reloading discussion area.

Yeah, I'm sure that measuring to the ogive is more meaningful. However, for me it comes down to what you're loading for, and for me personally I'm not getting down to the gnat's ass even for my most snipery rifles.

I adjust the seating die to give me the OAL that I want, and then I start cranking the press. I don't measure each round, and once a round is loaded I don't tweak the OAL. (Not counting the initial rounds loaded during setup.)

So if I get a bullet with a mashed ballistic tip or soft point, it doesn't matter. The seating die works on the ogive anyhow, so this bullet will get seated to the same depth as all of its healthy cousins.

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Thu Dec 21, 2017 4:57 pm
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I'm using the Hornady guages for checking ogive.
I'm still learning too!
I created a spreadsheet for tracking purposes and have been experimenting.
One thing I've summarized....EVERY RIFLE IS DIFFERENT regarding jump or jam on ogive.
Matter of fact I have one rifle that liked .150 jump better than .050 jump which makes no sense to me, but field tests told me "go with .150" for that particular rifle.


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Fri Dec 22, 2017 6:27 am
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GeekWithGuns wrote:
This is still an area where I'm actively learning. My interwebs research indicates a lot of benchrest shooters seat the bullet until it's right in contact with the lands or may back off from 0.0010" - .0015" on the theory that this provides the best accuracy.


Sorta but that's not the full story. They (or any other serious shooter developing a precision load) test and test and test until they know what seating depth gives the best accuracy, there is no guessing based on any theory. If the bullet isn't jammed into the lands, you generally want at least .005" jump to avoid inconsistencies. The .001" you cited leads to some bullets being jammed and some jumping, which is obviously bad for consistency.

Yes, measuring from the ogive is more accurate, and it's not any harder to do if you have the tool. Semi auto AR rifles can (and usually are) accurate enough to benefit from developing a precision load, but only if you're shooting it that way and not just blasting away in a gravel pit. Obviously measuring to the ogive is only a small part of developing a precision load, just measuring by itself doesn't do anything to make your ammo more accurate.


Fri Dec 22, 2017 11:56 am
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Yondering wrote:
Obviously measuring to the ogive is only a small part of developing a precision load, just measuring by itself doesn't do anything to make your ammo more accurate.


Right. So it is a process (I'm fishing here) of finding the right powder/bullet and grain weight of the powder load... then starting to play around with seating/COAL and then re-adjusting the powder load since seat depth will impact internal pressures? rinse, repeat?

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"The said Constitution shall never be construed to authorize Congress to prevent the people of the United States who are peaceable citizens from keeping their own arms." ~ Samuel Adams

“A return to First Principles in a Republic is sometimes caused by simple virtues of a single man. His good example has such an influence that the good men strive to imitate him, and the wicked are ashamed to lead a life so contrary to his example. Before all else, be armed!” ~ Niccolo Machiavelli

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Fri Dec 22, 2017 12:11 pm
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Yondering wrote:
GeekWithGuns wrote:
This is still an area where I'm actively learning. My interwebs research indicates a lot of benchrest shooters seat the bullet until it's right in contact with the lands or may back off from 0.0010" - .0015" on the theory that this provides the best accuracy.


Sorta but that's not the full story. They (or any other serious shooter developing a precision load) test and test and test until they know what seating depth gives the best accuracy, there is no guessing based on any theory. If the bullet isn't jammed into the lands, you generally want at least .005" jump to avoid inconsistencies. The .001" you cited leads to some bullets being jammed and some jumping, which is obviously bad for consistency.

Yes, measuring from the ogive is more accurate, and it's not any harder to do if you have the tool. Semi auto AR rifles can (and usually are) accurate enough to benefit from developing a precision load, but only if you're shooting it that way and not just blasting away in a gravel pit. Obviously measuring to the ogive is only a small part of developing a precision load, just measuring by itself doesn't do anything to make your ammo more accurate.


Agreed. Also in my post just below that:
Also most folks indicate that once you have a promising load then run some additional tests loading rounds at various distances off the lands then measure the resulting group sizes to check the effect of seating depth on accuracy. The premise being that every gun will run differently.

Thanks for the correction of at least .005" jump when seating off the lands. I had my numbers all wrong.

On my guns for IHMSA they are all iron sights or aperture sights. I don't expect to get consistently repeatable groups at 100 and 200 yards with those kind of sights so this exercise on those guns is a moot point because I can't develop repeatable data for different seating depths. So on those guns I've just started seating to bullet cannelure and not worry about seating depth at all.

On a scoped gun it's a whole other story because that opens up the possibility of repeatable, precision shooting at distance.

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Fri Dec 22, 2017 2:18 pm
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jukk0u wrote:
Yondering wrote:
Obviously measuring to the ogive is only a small part of developing a precision load, just measuring by itself doesn't do anything to make your ammo more accurate.


Right. So it is a process (I'm fishing here) of finding the right powder/bullet and grain weight of the powder load... then starting to play around with seating/COAL and then re-adjusting the powder load since seat depth will impact internal pressures? rinse, repeat?


More or less. There are different approaches, but here is the easiest:

- Determine max OAL for your rifle (it'll be limited by either magazine length or chamber throat dimensions).
- Work up powder charges to find max at that OAL.
- Adjust seating depth deeper to find the most accurate load. (pressure drops as the bullet is seated farther from the lands)
- Shoot it.

Of course you can play around for ages trying different powder charges and seating depths if you want. Everybody's got their own way of doing it.


One of the uses of measuring ogive length is discovering when a new batch of bullets has a different ogive length even though the OAL is the same. That changes the jump to the lands, and you'd never know by just measuring OAL.


Fri Dec 22, 2017 11:55 pm
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^^ extremely helpful, thanks!

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“Finding ‘common ground’ with the thinking of evil men is a fool’s errand” ~ Herschel Smith

"The said Constitution shall never be construed to authorize Congress to prevent the people of the United States who are peaceable citizens from keeping their own arms." ~ Samuel Adams

“A return to First Principles in a Republic is sometimes caused by simple virtues of a single man. His good example has such an influence that the good men strive to imitate him, and the wicked are ashamed to lead a life so contrary to his example. Before all else, be armed!” ~ Niccolo Machiavelli

Láodòng zhèng zhūwèi zìyóu

FJB


Sat Dec 23, 2017 10:08 am
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