C.o.a.l.

[ping]

I am reloading .308 using sierra 168gr HPBT match kings. The coal is 2.775. I use my caliper to check for the coal and once I get the first one done I crank the rest out. I notice though that they all are not the same so I go back and try to get them close to 2.775. I found out that the die really seats from the ogive of the bullet. My question then is how do you really measure with a caliper being that the tip of the bullet might be blunted slightly. So if I get my first one measured with my caliper to 2.775 should I just take for granted that all of them are correct. The die is not moving either so I know it is not that. It is just confusing. I have been doing this for several hundred loads and have not had any problems but I just want to understand.
Thanks!!

 

[Jim Watson]

Even the best of hollowpoints can be a little ragged on the tip. For best consistency don't go by COAL, get a comparator that measures from down on the ogive where the bullets have all been formed accurately. Stoney Point has one sort, available at Midway, etc., Sinclair has others.

 

[squirrelsniper]

The ogive is what you need to worry about, you can't pay attention to the tip measurement (especially on SMKs ) other than just setting a baseline OAL.

If you try to adjust every bullet so that you end up with the same cartridge base to bullet tip measurement, you'll just make things worse, as you'll be moving the ogive for each bullet and the measurement to the ogive is what really matters.

Stoney Point (and a few others) offer a simple attachment that attaches to your calipers and lets you measure from the cartridge base to the ogive of the bullet.

 

[theCZ]

Ping - I tried EXACTLY what you are doing when I first started reloading. Now I know that is what was responsible for my absolutely erratic accuracy in my 22 Hornet. Get a Stoney Point Comparator and a COL gauge by the same folks. Your accuracy will thank you for it!

 

[ping]

Stoney point

Thanks for all the input. I have requested one from Santa. I was not sure there was a tool that would attach to my caliper for the specific purpose. Cool.

 

[30Cal]

You're seating them a little short--I'm assuming you've got a short chamber or something. 2.80" is pretty typical. Ideally, you want them 5-10 thou off the rifling (seat them as far out as you can without touching the lands).

Ty

 

[ping]

My book shows a 168gr Sierra HPBT to be 2.775. I did notice that the other sizes were 2.81. I am new at this so I try to stay right on mark. I am going to try and figure out my best length for this rifle. It is shooting awesome though. I am using varget with 43.5 gr with the above mentioned Sierra bullet and getting 1/4 groups at 100 yards. It is just unbelieveable how well that rifle shoots. Thanks for the info.