Measuring OGIVE

[RC20]

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.

[jmorris]

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.

[hounddawg]

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.

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

[RC20]

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.

[F. Guffey]

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

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

[ninosdemente]

Thanks guys for the replies.

[RC20]

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.

[ninosdemente]

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.

[cw308]

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 .

[RC20]

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.

[Unclenick]

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.

[44 AMP]

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.

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..

[cw308]

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

[ninosdemente]

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.

[RC20]

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.

[BBarn]

I can certainly relate to where 44 AMP is coming from. For a bolt action:

I take an empty case fired from the rifle and slightly dent the case mouth until it will hold a bullet in place. Then I measure about 10 bullets and choose the longest one. Next I push that bullet in the case about 0.1” or so. Then I blacken the exposed portion of the bullet with a black Sharpie.

Open the bolt and insert the bullet/case into the chamber with a finger. As the bullet/case is pushed fully into the chamber, you can feel the bullet being driven further into the case by the rifling. Close the bolt. Open the bolt and carefully remove the bullet/case, holding the case against the bolt face as long as possible, and carefully removing the bullet/case from the action without disturbing the bullet position. (This is more difficult on actions with plunger ejectors). If the bullet slips out of the case slightly as it's removed from the chamber/action, there will be scratches through the black Sharpie near the case mouth (and you repeat the process, ignoring that particular attempt).

After removing the bullet/case, measure it's overall length and write it down. Repeat at least 2 more times, or until a consistent measurement is reached, one that is close to the longest length noted. Then I use that as a max overall length of that cartridge in that gun when using that bullet.

As I load the cartridges, I shorten the OAL by about 0.030” or so by seating the bullet deeper (as a starting point). (This also assumes that cartridge length will also fit in the magazine). If I wish to increase the overall length, I will do so, but only up to about 0.010” shorter than the maximum OAL length noted earlier.

No fancy tools. Just a fired case, bullets, a Sharpie, and calipers. Other similar ways to do it. Some probably better. Has worked fine for me since I'm content to locate the bullet about 0.010” or more off the rifling. Perhaps not good enough someone trying to shoot the smallest of groups.

[Unclenick]

44 AMP,

The ogive tools, like most loading tools, are a convenience. Their purpose is controlling bullet jump to the throat. There is almost always another way to do it or a way to improvise that takes another step or two or a little more coordination, so the tools are not a "must", by any means. Just a convenience. Since a lot of bullets (hollow point match bullets, in particular) have significant length variation (I've measured up to 17 thousandths in the same box of MatchKings in one instance) the ogive location is a more consistent locator and most seating die rams (stem tips) contact the bullet somewhere along the ogive and not from the tip, so it coordinates with them a little better.

As to why one wants to control ogive location, there are two reasons: pressure and accuracy optimization. Ninodesmente, in his other thread, found a bullet with a short ogive that was jamming the lands in his gun even at the bullet factory (Hornady) recommended COL. In order not to see throat proximity elevate pressure he needs to be sure that short ogive location (a Hornady V-max design, btw, so, not a rare oddball) and his short throat have about 0.020"-0.030" clearance (see graph below for why). You can also get to this number by making a split neck gauge and finding the bullet jamming COL and then seating shorter by 0.020"-0.030". Again, there are several special tools on the market that try to make this easier, but you don't have to have them. It's just a matter of what you think your time is worth or what helps keep you from trying your patience or what gives you more peace of mind regarding the accuracy of your control.



Group size is something many people don't realize can be further tuned beyond powder charge alone by controlling seating depth. Under item 3 in this old article, an old sporterized 8 mm Mauser with a badly worn throat is turned into a sub-half moa shooter just by getting jump long enough. In this Berger article, it explains it is actually necessary to find the best jump for some of the VLD bullets to make them shoot well at all. In the 1995 Precision Shooting Reloading Guide, benchrest competitor Dan Hackett reported moving the jump in a 40X in 220 Swift from 0.020" to 0.050" shrank 5-shot 100-yard groups from half an inch to about a fifth of an inch.

If you establish a good jump for your gun with one bullet, it often likes others to jump close to the same amount. The cartridge head-to-ogive measurement tools let you quickly set the jump of a new bullet with a different ogive shape to the same depth as another to use as a starting point to find the best jump for accuracy with the new bullet. Again, the specific tools are not essential, as there are numerous workarounds, but they are a convenience.

Now, do you need any of this to shoot to hunting or even basic high power target accuracy? Usually not. Unless you are using secant ogive VLD bullets the standard designs can usually just be set to their maker's recommended COL and they will shoot quite well. These methods are usually just for those of us driven to shave the last fraction of a moa off our groups by whatever compulsion, usually just because it's fun to get some success in this regard. But occasionally you get a situation like Ninodesmente's where the bullet and chamber just don't fit and there is potential for it to be a safety issue. Probably not a catastrophic risk type of safety issue very often, but more often about avoiding primer piercing and bolt face gas cutting and case head expansion or short brass life.