ABBREVIATIONS WHAT DO THEY MEAN

[ANDY T]

Hi
I am a English lad and are new to this site and need some advice i am just about to pick up my new well second hand rifle which is a custom 308 AI
I am not new to shooting but are newish to reloading and have been given some reloading data with the rifle but there are parts i don't understand and would like it clarified as to what it means and how to properly use my calipers to reproduse the data given.
The data i have and don't understand is in red.
Is there any videos explaining this.

155 SCENNAR VARGET 45.20 GRAINS FED M PRIMER OGIV 2.165
155 SCENNAR HODGDONS 4895 45.10 GRAINS F M PRIMER OGIV 2.165
NOSLER COAL 2.788
SCENNAR COAL 2.970

Regards
Andy

 

[okie]

coal=case over all length (base to bullet tip) in any reloading manual.... ogiv=ogive--google it--this measurement probably refers to seating depth measured from case base to bullet ogive---you need a bullet comparator to get this distance(sinclair makes one) but if you use different comparators this will differ slightly

 

[Yellow11]

Ogive - where bullet "shoulder" is measured to, rather than the tip.

COAL - cartridge overall length.

The latter is the top to tail measurement, where as the Ogive is the distance to where it touches the rifling

 

[ANDY T]

coal=case over all length (base to bullet tip) in any reloading manual.... ogiv=ogive--google it--this measurement probably refers to seating depth measured from case base to bullet ogive---you need a bullet comparator to get this distance(sinclair makes one) but if you use different comparators this will differ slightly

Hi
I understand COAL now but i dont understand ogive measurement.
When i put my comparator on the measurementS don't make sense they are well above the 2.165 more like 3.000 something.
Andy

 

[RonAKA]

The Ogive may be measurement tool specific. I believe technically it is the point where the bullet touches the lands (not the bore). To make more sense of things, what you are trying to do is two things.

1. If you have a magazine type gun, then you want the cartridges to fit in the magazine. For that reason, factory loads are made to always be short enough. The COAL is the actual base to tip measurement.

2. From an accuracy and pressure point of view, the more important dimension is how far the Ogive contact point on your bullet is from the start of the lands. It can have a jump, or can be jammed into the lands.

In theory the distance from the base of the cartridge to the ogive contact point on the bullet should be measurable, but it may be specific to the method used. However each individual gun is going to have a different measurement from the bolt face to the lands. The difference between the ogive to base measurement and the bolt to lands is your jam or jump.

It does not make sense to me to follow a specific base to ogive dimension based on somebody else's load data. So, I only think in terms of jam or jump. I use the split case method (see link below, and I find only one slit in the case neck and shoulder works best) to establish a COAL that corresponds to the distance from the base to the lands. However, remember that this COAL is specific to your gun, and to the one individual bullet you measured it with. The issue is that bullets even in the same lot vary in length. If you want to reproduce a round that gives you a just touch the lands with that specific bullet you have to load that bullet long, and then incrementally seat it shorter, until your loaded round measure the same. Now you have a die setting that can be reliably used to load bullets from the same lot.

Last loading just to touch the lands is probably not a repeatable or good position, so typically this dimension is corrected, by lengthening it to give a specific jam, or shortening it to give a specific jump.

Hope that helps some. See links below. Hornady sell tools that probably do a better job of the bolt face to lands measurement than the split case case, and that is covered in one link.

http://www.larrywillis.com/OAL.html

http://www.6mmbr.com/catalog/item/1433308/977259.htm

 

[bozo699]

ANDY T,
Hi Andy welcome to the forum! I have never and still don't understand most abreviations, I HATE THEM I understand basic reloading abreviations but most of the abreviations they use on here I have to ask or just guess I am slowly learning and trying to perticipate as much as possible
Andy I think the best advice I can give you is I can tell you are new to it all so with that said, Buy yourself a good reloading manual and read it a couple of times,get as much reading material as you can on the subject. I don't know what part of England you are from but one of the most educated guy's out here on the subject of guns is from your homeland, I have learned alot from his posts here on 6br,His username is Laurie. I hope some of this will help.
Wayne.

 

[hogan]

What abbreviations mean is.... less typing or print space devoted to terms that are continuously repeated. Abbreviations are part of the nomenclature of the hobby, craft, or trade. OD to a machinist, barrelmaker, shooter is different from what a medical doctor (MD) might think of.

Probably a sticky somewhere to discuss all the abbreviations. Try google.
IIRC, lots of articles around about internet posting abbreviations; bound to be one for shooters.

 

[Tozguy]

The term ogive is not an abreviation. It refers to the curvature of the front of the bullet. There are terms for the shape of the ogive (ex: tangent ogive) but giving a length of ogive is quite unusual. The author of the information should be the one explaining what dimension is referred to as ogive.