Flash hole diameter for .357 brass?

Vince from MO

What is the maximum diameter of flash hole for this brass? A friend was given some once fired(?) brass and the flash hole looks large to me. He loaded a few of the with a stiff load and could not eject them. I think this might be the problem. Any thoughts?

Thanks,
Vince

bpost

{COPIED FROM ANOTHER FORUM}

The SAAMI spec. for rifle cases using the large primer is 0.078-0.082. It is fine to ream them all to the maximum size of 0.082" using a No. 45 drill.

Small primer pocket rifle and pistol cases use a smaller flash hole size of .074-.078, but some European CIP brass, such as Sako and Lapua uses 1.6-1.7mm flash holes.

Standard decapping pins are 1/16" needle bearings, or 0.0625, so smaller flash holes may yank the decapping pin from the stem.

Pistol cases intended for use with lead-free primers is sometimes found with large flash holes up to 0.12" in diameter. In my testing of Win-Clean (.12 flash hole) vs. standard Winchester cases (0.080 flash hole) in .45 ACP, there was no significant different in velocity, using 230-gr. lead cowboy bullets and a charge of 5 grains of Bullseye.

Use of enlarged flash holes eliminates the primer blast shoving the case shoulder back, shortening headspace when rimless cases are used with very light gallery loads. However, such modified cases should never be used in loads generating more than about 20,000 psi. because doing so increases the risk of blown primers and could result in a case failure, with dangerous release of powder gases.

76k20

First question, what componets make up this "stiff load"? Powder brand/type/charge weight, primer, bullet weight/brand/diameter, brass manufacturer, etc.

Probably not a good idea to start with a "stiff load" when trying to determine if the cases have an overly large flash hole. Compare these questionable cases to a known once fired factory case with the primer removed and see if there is a difference.

One thing that comes to mind regarding flash hole diameter is loading for plastic bullets that Speer sells for indoor practice. Speer does mention enlarging the flash hole when using these, but the cases are NOT to be used when loading real ammo.