Lapua brass wall thickness

[Kasimir58]

I find it hard to accurately and reproducibly measure brass thickness at the neck using a micrometer. I know that when I load new brass I get .290 neck diameter with 6.5 Grendel and .291 with 6.5 Creedmoor. So it could be that the Grendel case uses slighter thinner brass but, as I said, I can't really confirm it by measuring wall thickness.

I would be surprised if all Lapua brass had the same wall thickness. Different calibers have different requirements, powder loads and max pressures are different. Anybody have more specific information about this?

 

[Webster]

I find it hard to accurately and reproducibly measure brass thickness at the neck using a micrometer. I know that when I load new brass I get .290 neck diameter with 6.5 Grendel and .291 with 6.5 Creedmoor. So it could be that the Grendel case uses slighter thinner brass but, as I said, I can't really confirm it by measuring wall thickness.

I would be surprised if all Lapua brass had the same wall thickness. Different calibers have different requirements, powder loads and max pressures are different. Anybody have more specific information about this?

A top shooter on this website said he got 1-1.5 thou variation on new Lapua brass necks. What do you need the info for? Turn the necks for uniformity. Bullets are vary uniform. I assume you are measuring the necks with a bullet in the neck.

 

[Dkk37058]

223 6.5x47 and 6br seem to average around .014 thick on mine

 

[amiabledave]

For what its worth. My Lapua 6BR brass before I turn the necks on this Lot, #LPT04705 are:

------------ .0120 to .0123 ------------

A micrometer or two and a ball anvil micrometer goes a long way

 

[shoot4fun]

I find it hard to accurately and reproducibly measure brass thickness at the neck using a micrometer. I know that when I load new brass I get .290 neck diameter with 6.5 Grendel and .291 with 6.5 Creedmoor. So it could be that the Grendel case uses slighter thinner brass but, as I said, I can't really confirm it by measuring wall thickness.

I would be surprised if all Lapua brass had the same wall thickness. Different calibers have different requirements, powder loads and max pressures are different. Anybody have more specific information about this?

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First, if you don't have a ball (tube) micrometer you will never get neck wall thickness measured.
If you do and, like many people I know, not very confident of your ability to get a consistent measurement with any micrometer then the best way I know of to get a "feel" for using the micrometer correctly is to practice on a sett of feeler gauges. They are already marked to correct sizes and you can immediately know when you get that "feel" for consistent and correct measurements.
Almost forgot! These are great for measuring those neck thicknesses. You can hold the brass and not have to worry about trying to hold the mic.

Micrometer Stand - Grizzly Industrial

Ease micrometer use and increase precision with this micrometer stand. Cast Aluminum stand features convenient adjustments for optimum reading and part orientation. Fits most inside and outside micrometers. (Micrometer not included).

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[Chris Edmondson]

Measuring neck wall thickness is mostly science, and a bit or art. The 6.5 Creedmoor Lapua brass I use measures about 14 thou neck wall thickness.

Using a standard ball mic should give more consistent results since it averages the outside of the neck on the flat spindle. Using a double-ball mic with a spherical spindle and spherical anvil will be more accurate per se, at a single point on the neck, useful for checking taper.

One thing worth checking is the instrument itself; clamp the mic and something to measure, then measure it 5 or 10 times to make sure the result is the same.

It goes without saying, cleanliness is important.

 

[Straightshooter1]

I find it hard to accurately and reproducibly measure brass thickness at the neck using a micrometer. I know that when I load new brass I get .290 neck diameter with 6.5 Grendel and .291 with 6.5 Creedmoor. So it could be that the Grendel case uses slighter thinner brass but, as I said, I can't really confirm it by measuring wall thickness.

I would be surprised if all Lapua brass had the same wall thickness. Different calibers have different requirements, powder loads and max pressures are different. Anybody have more specific information about this?

Correct me if I'm wrong, but that .290 and .291 sounds like a measurement after sizing before seating a bullet??? And You're using a micrometer to measure the outside diameter?

I'd say the easy way to find the neck thickness would be to seat a bullet and measure the OD of the neck with a caliper, subtract the bullet diameter (.264) from that, then divide by 2. That'll be your neck thickness. But if you want something more precise, then you need a tube micrometer and measure the thickness directly where you can get values down to within .0001".

Wall thickness does tend to vary from one caliber to another, but it can also vary from one lot to another within a single head stamp. The Lapua 6.5 CR's that I've measured were usually around .014". That would mean the OD of a seated neck would be at .292". . . assuming that .014 is uniform around the whole circumference of the neck.

 

[Bill K]

Wall thickness does tend to vary from one caliber to another, but it can also vary from one lot to another within a single head stamp. The Lapua 6.5 CR's that I've measured were usually around .014". That would mean the OD of a seated neck would be at .292". . . assuming that .014 is uniform around the whole circumference of the neck.

Laupa is like most all brass. The neck will have very slight high and low spots and will change from lot to lot.
It seems to average around .014 to .015 so you could first trim the neck ever so slightly and remove the high and low areas, then measure the neck thickness and trim, if needed, to around .013-.014 for consistent thickness.

 

[Bill K]

In fact on todays tech section. There is information on neck tuning.