Dear Mr. Rawles,
Here is the definitive test to determine whether ammunition is corrosive or not. The procedure is credited to Small Arms Review publisher Dan Shea. This test is simple, quick, cheap and conclusive.
THE BRITE NAIL TEST
1. Take a suspect round, pull the bullet and dump out the powder. I like to also take a known corrosive round as well for a benchmark.
2. Take a few brand new “brite” (i.e. non-galvanized) steel nails with a head size just large enough to fit into the case mouth. Degrease the nails in acetone or other and roughen them slightly with sandpaper. Drive the nails into a block of wood.
3. Slip the empty cartridge cases over the nail heads, and taking appropriate safely precautions (shielding, eye protection, gloves, etc) pop the primers with a punch and hammer.
[Dan Shea recommends the following additional safety precaution: Take a piece of wood and drill a hole large enough diameter to accept the case head, about 1/2″ deep and not all the way through the wood. Then drill a small hole (to accept a small nail or punch) in the center of the larger hole, all the way through the piece of wood. Place the larger hole over the case head and insert the punch or nail through the smaller hole. Use this assembly to pop the primers.]
4. Leave the cases undisturbed on the nails for 24 hours in a warm place (I usually leave them on top of the water heater) and then examine the nails.
If the nail looks black and smoky, then the ammo is noncorrosive. If the nail has red flecks, then the ammo is corrosive. It will be obvious – but doing a known corrosive ammo as a control is helpful.
Cordially, – John N.
JWR Replies: Thanks for sending that. For some important priming data on U.S. military arsenal loadings, see this SurvivalBlog reference page. (It provides the lot numbers and cut-off dates to determine if military ammo has corrosive (mercuric) or non-corrosive (styphnate) primers. If in doubt, then use the brite nail test.