[mavericks]

when we say OAL of 2.28, is that from ogive or from tip of bullet? I think i've been using tip of bullet because i didnt buy a comparator for .270 until today. I know tip of bullet changes alot from lot to lot and even within lots. Also if typical oal is 2.28 to ogive and i've been using tip, then i had been loading the bullet short and it would be highly likely causing pressure signs.

I've been reading the "Precision Reloading" book and i'm kinda filling in the missing knowledge.

 

[DDriller]

Measurement if from tip of bullet. Only a few magazines will not load past 2.30. Most Barrett mags only load to 2.25

 

[Daniel]

You are correct

The Overall Length (O.A.L.) most people are referring to is sometimes referred to as the Combined Overall Length (C.O.A.L) by others. The C.O.A.L is what most on this forum mean because it is the length of the entire round from base to tip of the bullet. This C.O.A.L. dimension is important in magazine fed weapons because the C.O.A.L can exceed the internal dimension of the magazine and still be fed into the rifle.

The O.A.L can be measured using a bullet comparator (Hornady Lock-N-Load and Sinclair both make them) that bases the length of the round on the distance from the base to a consistent diameter point on the ogive of the bullet. This O.A.L. measurement makes for a more consistent distance for the bullet from the point to where the bullet will engage the lands of the barrel, keeping the "jump" or "lead" of the bullet the same from round to round.

The O.A.L can also be set using the bullet comparator and tends to but not always keep you within the margin of length necessary to get the round to fit the magazine.

In a nut shell, the best and most consistent means of measurement will be the O.A.L using a bullet comparator and as long as you keep that dimension withing the length of the magazine, you'll have no problems at all.

 

[mavericks]

The Overall Length (O.A.L.) most people are referring to is sometimes referred to as the Combined Overall Length (C.O.A.L) by others. The C.O.A.L is what most on this forum mean because it is the length of the entire round from base to tip of the bullet. This C.O.A.L. dimension is important in magazine fed weapons because the C.O.A.L can exceed the internal dimension of the magazine and still be fed into the rifle.

The O.A.L can be measured using a bullet comparator (Hornady Lock-N-Load and Sinclair both make them) that bases the length of the round on the distance from the base to a consistent diameter point on the ogive of the bullet. This O.A.L. measurement makes for a more consistent distance for the bullet from the point to where the bullet will engage the lands of the barrel, keeping the "jump" or "lead" of the bullet the same from round to round.

The O.A.L can also be set using the bullet comparator and tends to but not always keep you within the margin of length necessary to get the round to fit the magazine.

In a nut shell, the best and most consistent means of measurement will be the O.A.L using a bullet comparator and as long as you keep that dimension withing the length of the magazine, you'll have no problems at all.

This makes sense to me now! Thanks for clearing it up.

 

[Test_User]

Correct:

COAL= Loaded round from tip to base

The issue is its in the context of how it is used. When talking about a loaded round COAL OAL are used interchangeably by most.

Turn COAL only matters for function mag limits and feeding

OGive or bullet shoulder to base matters for distance the bullet will travel before it first hits the lands of the rifling. This is what effects accuracy and along with it pressure and vel as secondary issues. With the AR 6.8 hitting the lands with too long of a round is not a concerv unless you are single feeding by hand as nothing past 2.30 can fit ina mag and not bullet loaded to that legnth is touching.

You want to use the measuerment from the ogive to the base for checking consistency of the rounds and what the actual jump is for tuning the load and also if you set up dummmy rounds to track throat errosion. Bullets can vary if measured to the tip as the tips tend to vary in many bullets where as the shoudler or ogvie junctionto base in modern bullets is very consistent. You use COAL to ensure that even with tip variation no loaded round will be longer than will function in a mag.