Best method for measuring COL

[ArmyJerry]

I reload a lot of 308 and 223, AMAX and SMK in win brass, some lapua and norma, I cant get consistent measurements on the COL. I am using the Lee seating die and a digital Micrometer. I will set the die to the correct length and lock it down, but the measurements differ from case to case by 5 - 10 thousandths. I suspect its the method I am using to measure, is there anything I can use to get a better measurement, if so what equipment do I need?

 

[doc76251]

You will never get a consistent COL until you have consistent length boolets. While Amax's are probably the better of the bunch Sierra's are all over the place in length, it's a part of the mfg process. How to fix? Stop measuring COL and measure the Ogive length, it's the only length measurement that is really repeatable and therefor worth something.

Cheers,

Doc

 

[0311@LAR]

Yep, buy a comparator tool or you will end up pulling your hair out. Measuring off of the ogive is the way to go.

 

[ArmyJerry]

Which comparator tool?

 

[0311@LAR]

The Hornady one is pretty nice for not a lot of money.

 

[damoncali]

The RCBS Precision Mic is nice. The downside is that its expensive, and not as well made as it could be*. And you need one for every caliber you shoot. On the up side, it's very easy to use and very consistent, and you can also use it for cases.

*The numbers are hard to read, and I've had the graduated rings break free, which requires that you figure out some way to re-zero the thing.

 

[ArmyJerry]

I am okay with the buy once cry once philosophy in this area, the RCBS one sounds a little troublesome. Any other suggestions gents, thanks for the input so far you guys put me on the right track.

 

[Fuzzball]

Advantage of RCBS' Precision Case Mic is ease of use and repeatable consistancy between uses but it is cartridge specific and the dummy cartridge device is nearly worthless. Value of the Hornady "headspace" and bullet seating comparitors (and the similar Sinclair tool) is wide versitility at a modest price while providing all the useful information we actually need.

 

[garandman]

The Hornady one is pretty nice for not a lot of money.

^^^^ THis.

 

[damoncali]

...and the dummy cartridge device is nearly worthless.

They could save a couple bucks and just not provide those. Totally and utterly worthless.

 

[damoncali]

I am okay with the buy once cry once philosophy in this area, the RCBS one sounds a little troublesome. Any other suggestions gents, thanks for the input so far you guys put me on the right track.

If it's a caliber you shoot a lot of, it's worth the 50 bucks or whatever they cost for a Precision Mic. Otherwise, I'd stick with Hornady. They work well - they're just a little more fidly, but a lot more flexible.

 

[ArmyJerry]

Is this the one?
Hornady Lock-N-Load Bullet Comparator Complete Set 14 Inserts

 

[ChrisGarrett]

Is this the one?
Hornady Lock-N-Load Bullet Comparator Complete Set 14 Inserts

Yep, that's the one, but they also package it with five, or six of the common calibers at about half that price here:

Hornady LNL Comparator Set - 22 6mm 25 270 7mm 30 cal | Sinclair Intl

You might be able to get away with buying just the anvil and then buy the particular inserts that you might need going down the road, if you're on a budget.

Here's the Sinclair version, that I picked up on a whim:

Sinclair Hex Style Bullet Comparators | Sinclair Intl INTERNATIONAL

Chris

 

[MikeEzell]

A barrel "widget"...It's ideally made from YOUR barrel stub, with the reamer used on YOUR barrel, but since we are looking for repeatability and not so much the actual chamber being precisely imulated, it can be made from any reamer with the same or bigger neck diameter and a free bore that is not longer than yours. Many smiths don't charge anything, or very little for including one with a build. The smith simply runs the reamer in far enough to form part of the shoulder. This allows for a tool that is very precise for both shoulder bump and seating depth. I've also made them for customers that are comparators that use a dial indicator and can be used for several different cartridges and/or calibers.