Confused on COAL

[Jrb572]

OK i have been reading how to measure it but im not getting what everybody is saying. I have used a once fired round put the Bullet in neck slowy closed bolt GOT a meassuement is that my COAL? The book says make Coal 3.340. For a .300 wm. Should i set my bullet .010 off my measurment or im i wrong. From base to tip is 3.471 If i remember right should i set it back .010 from there or what. Please help im very confused 190 sierra match kings

Thanks
Joe

 

[Downzero]

Re: Confused on COAL

Book cites minimum COAL for their published load.

 

[Jrb572]

Re: Confused on COAL

Ok even though it says max coal 3.340. So I'm I doing it right. Thanks I appericate it very any help is much appericated

 

[Downzero]

Re: Confused on COAL

You won't be dangerous loading long unless you ram the bullet into the lands, which in my experience is unlikely with a factory chamber. It's loading short that is dangerous.

Pressure = force / area. Loading short reduces area, raising pressure.

 

[MAGUA]

Re: Confused on COAL

Get yourself a Sinclair comparator so you can measure from the ogive.

 

[ChrisGarrett]

Re: Confused on COAL

First of all COAL (cartridge over all length,) sometimes erroneously referred to as COL, is just the straight measurement from the bottom/face/head of the case to the bullet's tip.

The books give you a convservative measurement that will chamber in all rifles and fit all magazines, or as close to ALL as is reasonable in an imperfect world. Most all manuals will tell you that 'generally' your best accuracy will be had by seating your bullets just off the lands. They (Sierra, Speer, Nosler) like to throw out the number .015"-.030". I read of one champion 1k yd shooter who liked .017" off the lands in his rifles w/his 6.5mm tips.

VLD type bullets love being jammed into the lands anywhere from .005"-.025", other bullets can stand to jump a little or even a lot.

Anyhow, the question is how do you measure where each bullet hits your lands? Yes, you have to do each bullet type/model, as they're all shaped differently.

You can buy the Hornady/Stoney Point OAL gage with appropriate modiefied cases and just measure it simply enough. I take 3 bullets from a box and measure each 3 times, averaging them, then the three bullets' aggregates and come to a consensus.

Or...

You can take a fired case with no new powder/primer, dent in an edge of the mouth, just barely seat a bullet so it'll stay put and then cover the entire bullet with a dry erase marker or Sharpie pen.

Insert the case and gently chamber and extract the case. If the bullet sticks, gently knock it out and replace it to the point where the ink has scraped off. Do this three times and average each measurement and then do two more bullets and average them out.

That is your OAL, which is a point on the curved surface of the bullet, forward of the bearing surface, where it first makes contact with your specific bore's lands.

Now, you can back off .015"-.030", or you can go closer, or you can jam the lands, but with that bullet and that bore, you have a reference point to go by.

Be careful when seating long, that you can still feed the rounds into your magazine(s).

Chris

 

[jacq220]

Re: Confused on COAL

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MAGUA</div><div class="ubbcode-body">Get yourself a Sinclair comparator so you can measure from the ogive. </div></div>

+1

 

[Jrb572]

Re: Confused on COAL

I have a hornady tool that measures the lenght I guess of the ogive. I was reading other people questions on here about it and my reloader manual and became confused. Thank guys it very appreciated. I was worried I was going about things wrong. Luckly my rounds still fit in the magazine with a touch of room to spare. I groups well with them where I have them set reading other post I started to worry I was doing something wrong. But once again thank you very much

Thanks
Joe