Measuring OGIVE

@CW308 - ogive is actually the shape of the bullet, think Gothic arches in medieval architecture. The word ogive dates back long before bullets and even gunpowder. Datum is the correct term but even Berger in some of it's pubs uses the term ogive when determining the distance from the loaded bullet where it first contacts the lands.

I use the term ogive myself but the correct term is datum which is a fixed point on a line used for measuring. That term is also misused quite a bit when referring to the tools used to measure the bullet seating depth. Does not matter a whit as long as you get consistent contact depth reading with the same bullet.

Oh and for Guffy , yes I do measure and record my barrel before I even put it on to determine the seating depth and keep that same bullet to determine the erosion over time. That way I can "chase the lands" as the barrel wears

By the way Guffy you never explained why you slug the barrel to determine the lands and grooves of the barrel before doing a seating depth measurements. Do you also measure the length of pull, trigger pull weight, and overall weight of the gun before doing your seating depth measurement?
 
"...Measuring OGIVE..." For what purpose? Ogives only apply to OAL when fiddling with the off-the-lands distance after working up the load. Said fiddling being 100% an optional trial and error thing that isn't necessary. Even then you really don't need to measure the ogive. Ogives have nothing whatever to do with OAL either. OAL is measured from the pointy bit to the flat bit of the cartridge.
"...ogive is actually the shape of the bullet..." Sort of. It's the arch of the bullet(Gothic vaults aside). A datum is a specific spot on the arch. A datum only applies to the off-the-lands distance too.
 
hounddawg
Thanks for explaining ogive and datum . Meaning the same even though correct is datum , I use ogive for the bullet an datum for the case shoulder. Maybe best as bullet and shoulder datum line . I'm not confused anymore . You can learn different stuff every day . I also chase the lands , usually every lot of 500 bullets I'll measure the wash . I'm not loading hot and single feed giving time between shots , 3000 through the tube 308 seeing some fire cracking but still shooting tight groups. Can never have enough tools . I try to keep it simple . Thanks Again

Chris
 
You can learn different stuff every day
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16 years ago reloaders thought the datum was a line, a lot of reloaders got dizzy and the rest passed out when I informed them the datum was a circle/round hole. And then there is the 'even today' there are reloaders that believe the datum is a joke.

I am the fan of 'datum based tools'.

F. Guffey
 
F.Guffey & hounddawg explain it very well , before saying ogive is a datum confused me now it doesn't. I like learning new stuff , Thanks guys.
 
As noted, you can do the measurement on any point of the curve of the bullet and get a relevant location to seat it to.

Granted I am a technical heretic in this regard but the reality is you don't have to have a Masters in Datumese to make it work.
 
Cover a bullet with Dykem or a markers ink and it is easy to see when it contacts anything including the rifling. It’s not always the fastest method but it is the least expensive.
 
16 years ago reloaders thought the datum was a line, a lot of reloaders got dizzy and the rest passed out when I informed them the datum was a circle/round hole. And then there is the 'even today' there are reloaders that believe the datum is a joke.
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actually a datum is neither. It is a point that is used to begin a measurement which is a abstract concept. The datum can be found at the dumb end of the tape measure

The piece of metal with a hole that you call a datum is the comparator and establishes where the datum point is on the line. The hole is just a hole.

You can take 3/4 inch hex nut and drill a 3/16 " hole through a flat and you have a comparator that could be used from .20 cals and up on any bullet with a tangent or secant ogive and a metplat smaller then 3/16 . Poor mans version of the Sinclair nut that can be made for a less than a buck in 15 minutes
 
Mine was made in about 5 minute with a pre drilled hole, homeless compartor?

Only the individual bullet mfg cares as its a specific to a quality control measurement for them

The rest of us only need or want somewhat better consistency on bullet seating over the more variable tip COAL thing.

As bullet shapes are all different, even an mfg has difference datum points they shoot for (pun intended)

One size fits all does not work for them, but we do use one side fits all.
 
You can take 3/4 inch hex nut and drill a 3/16 " hole through a flat and you have a comparator that could be used from .20 cals and up on any bullet with a tangent or secant ogive and a metplat smaller then 3/16 . Poor mans version of the Sinclair nut that can be made for a less than a buck in 15 minutes
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I remember that; when reloaders realized the datum was not a line but a round hole and they discovered one of the more common datum diameters was 3/8" or .375" they declared it was no Biggy. All a reloader had to do was make a trip to the hardware store to purchases bushings with 3/8" holes complete with a radius.

F. Guffey
 
You are welcome. I hope you are not even more confused.

Frankly it winds up too technical for a simple process of having a device on the curve of the bullet to seat it more consistently than using the tip which varies a lot more.
 
Less confused, lol.

Yeah, I will learn as I go and until I do it myself. Just that I am probably a bit more over cautious as I know reloading can be very dangerous if not done properly, so just want to do things where it won't harm me or people who are with me or the area for that matter.
 
I rather buy the tool , drilling a hole is simple but when using for the ogive/ datum and measuring in thousands just a slight angle would screw your measurements up . Some of you could there's no bought , using my hand drill I don't think so .
 
Could be, some of us like making tools. If we are fooling ourselves........


ND: Reloading is that odd thing that done right its not an issue, done wrong and you see a gun blown up like I was at the range when it occurred.

Modern gun and blown all apart, the shooter got a heck of a dental bill (otherwise ok, sometimes a few teeth are a small price to pay vs loosing an eyeball or two)

I shoot some mil surplus, most are unsupported heads and that's a bigger issue.

They came up with a term to describe breaking safety barriers and getting away with it.

Normalizing Deviation. Coined for the Space Shuttle and the launch under temps the O rings were not intended to seal. They got away with it once, so they did it again at a lower temperature (they as in the authorities got away with it, the Shuttle Crew did not)

I have never been sorry I was safe, but I sure have been sorry when I was not.
 
The brag of the Sinclair hex tool is that its holes are reamed to final size with actual chamber throating reamers, so it should rest on your bullet exactly where the throat touches it as it enters.

My measurements have shown that location is, indeed, a little bit more consistent than a hole that finds the ogive higher up. On 150 grain Sierra MatchKing .308s, the standard deviation for the Hornady tool, which found the ogive an average of 0.524" above the base was about 18% bigger than for the Sinclair inserts which found the ogive on that bullet type at an average of 0.3800" above the base, where a throat would contact it (this is not the hex nut, but the Sinclair caliper adapter inserts, which are stainless steel and have a wider hole than the Hornady). But if all you are doing is comparing the seating depth of bullets, then either is better than OAL, which varied about twice as much, bullet-to-bullet.
 
I have been going to youtube/google to see/read on measuring ogive as this is something that I did not do on a previous load.
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My question(s) are,
1) WHY do you think you need to do this??

Why do you think its important? What are you hoping to gain? Do you think it will amount to anything actually useful?

Or are you just happy to spend money / time on tools and techniques that don't matter outside of a very, very specialized application??

There are some fine folks here who will happily give you detailed chapter and verse on how to do something they do. Whether it is something useful and beneficial to you, or not.

I've been reloading since the early 70s, and have loaded for over 30 different cartridges ranging from .22 Hornet up to .458 Win Mag.

I've never deliberately loaded a round so the bullet touches the rifling, never set any to be "just off" the rifling. Never measured "to the ogive", NEVER worried about "shoulder bump back". Not once, ever.

I find "Measuring to the Ogive" to be a meaningless and irritating phrase. Oh, it has a definition, but it doesn't have much meaning, because it can be something different to every different person, and still be within the "correct" definition.

Ogive is, as was mentioned, the ENTIRE portion of the bullet where it reduces diameter from full bore size down to the point. The flat part of the point is called the meplat.

Datum is a point which you choose as a consistant reference point. It is entirely arbitrary where it is placed initially.

I hear people saying "measure to the ogive", (and buy this or that to do it with), and claiming doing so will give you better accuracy.

Just seems like selling snake oil, to me. And my snakes don't squeak..:rolleyes:
 
44AMP
So tell me how you have been reloading for the last 40+ years . Do you go with whatever the load books tell you . I guess if you do and the rifle doesn't shoot well it's the rifle . I use to load from the books , then I started reading . Using the same bullet and powder , tweaking powder and bullet length , things change , some good some bad . Then even with case prep you will see changes . I'm surprised at your questions especially from a guy who has been reloading for awhile on a post from someone who is just getting into the game . I guess we do what works and pass it on

PS nino all I suggest is read up on reloading , try things that make sense to you , keep asking questions , I think your doing fine . Keep up the good work.

Chris
 
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44 Amp, at a previous thread I was having difficulties where loaded 223 VMAX 60gr did not chamber correctly. I had to force those rounds with the action of course for it to close. I was following case trimming, oal based on the book (Lyman 50) and was having the problem. The projectiles were getting marks. Some were stating that my seating was improper (crimping). So I followed the members instructions and did the same process with Nosler CC 69gr and those worked fine. They chambered right with no resistance. The VMAX was the one giving me problems. My ignorance, I didn't know/paid attention to different bullet shapes. Some were stating measuring ogive would help me seat certain problematic projectiles better to avoid markings. In this case the VMAX. The VMAX I seated a bit deeper vs the NOSLER CC and they were still getting some marks. All brass was trimmed equally for both projectiles.
 
44AMP: Not sure why you even read or post.

Lets do it the same way we did 40 years ago (and yes I am a fairly old dog myself and have been accused of being a stick in the mud)

I do minimum case resize (makes Unclenick happy to use the term) because I dislike seeing my cases crack (not to mention the pesky detail of I shoot mil surplus and its got an unsupported head and I am not keen on a gas release thank you if I can prevent it)

I don't have unlimited funds so I use what I think is judicious new knowledge to not have to replace the brass each 8 rounds. Not a factor when I was hunting, brass did not get used that much, it is now I target shoot.

Like ND, I have seen some odd stuff with the new bullets that the set back made clear that it was an odd bullet.

I too like to play with COAL (or COAO) to tune the rounds to the rifle.

I fail to see where your 40 year old practices really contribute anything to the OP let alone the general intent of the forum.

I look at stuff all the time and I disregard much of it as well as it does not apply to me, its too costly, it does not fit in well with my trains of thought.

But I do know I have not reached the apex of knowledge, there are new things out there and some are worth using for me.
 
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