LAPUA brass flash hole...

[flatapple]

Do I have defective box of LAPUA 6.5 Grendel brass or do I need to enlarge the primer flash hole?
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[Csitt]

No, Lapua flash hole is smaller. You need a smaller pin for them.

Chuck S.

[Zeneffect]

Normal, smaller hole.

[Old Bob]

What Csitt & Zeneffect said: Hornady flash hole diameter is 0.080" & Lapua flash hole diameter is 0.062". In my experience, Lapua is the only brass I've seen with 0.062" holes. There may be others but I haven't seen them yet. Probably European made brass if there are others.

Are you looking for a flash hole de-burring/uniformer tool? MidwayUSA has K & M tools for both diameters. They're the tools I use on my brass.

[Velocity]

Lapua’s 6.5 Grendel case takes the Small Rifle Primer (SRP).

https://www.lapua.com/product/65-grendel...e-4ph6020/

[Harpoon1]

Lapua’s 6.5 Grendel case takes the Small Rifle Primer (SRP).

https://www.lapua.com/product/65-grendel...e-4ph6020/

The flash hole and primer size are two entirely different things!

[LRRPF52]

The smaller flash hole channels a narrower, deeper-penetrating spark from the primer to initiate better and more consistent ignition of the propellant column.

If you look at some of the fixed artillery cartridge schematics and primer designs, you will often see a very long primer column with perforations to facilitate more instantaneous ignition of the propellant mass.

The Lapua small flash hole seems to be a way of trying to generate this type of ignition profile, without actually complicating the case with a primer shaft inside the propellant column.




When the primer sends its hot spark through a larger flash hole, you get a more widely-dispersed ignition down at the propellant mass base, without as much penetration into the column of the powder.

This is at least how I see it, after discussing it with engineers who have analyzed the Lapua brass small flash hole design.

The short story is that we think there is more consistent ignition behavior with the smaller flash hole, which helps with keeping consistent SDs.

[flatapple]

Thanks for the good info. I just made my depriming pin smaller.