Mercuric primers went out of use in the very early years of the 20th century. Chlorate primers took their place in U.S. military ammunition from then until the early-mid 1950's.

Chlorate primers were perfectly harmless to brass, but as we know played hell with gun barrels if cleaning regimens weren't adhered to. Mercuric priming compounds attacked brass cases but that was so long ago that it doesn't bear being concerned about today. 

Why did the gov't insist on retaining chlorate primers long after commercial sporting ammo makers had switched to non-corrosive primers? Simple, the old FA-70 primer (chlorate compound) was dead reliable - it was proven to remain stable in utterly atrocious storage conditions - and was notoriously consistent in nature. Some pretty good reasons when men's lives were at stake. Handloaders guarded their stashes of FA-70 primers long after they were obsolete/discontinued for much the same reasons. I knew old guys who insisted on using them exclusively until supplies finally dried up - one guy in particular I knew kept them running into the 1980's. (I have a small stash of his leftover FA-70 primers and load a couple .30-06 rounds with them now and then as a memorial to that grand old man, with Surplus 4831 powder too, of course.)

If you stumble onto a stash of gov't corrosive chlorate primers and feel the need to shoot with them, go ahead they might surprise you. Just be sure to follow the barrel cleaning protocols our fathers/grandfathers adhered to afterwards and clean your bore religiously. No harm, no foul, and the brass is most definitely re-usable afterwards too.

Phil Sharpe wrote about the FA70's, they're good hot primers however they blow salts into the grains of the barrel steel that need to be washed out with hot water. He recommended making a drilled-out case with a copper tube soldered into the old primer pocket and a funnel on the end. You'd pour a quart of boiling hot water through the barrel to get rid of the salts. If you didn't do that, the salts would rust the barrel even though the barrel was cleaned and oiled.

Cbashooter

Personally, I've never used FA70 primers, but I've always heard that they were excellent primers but corrosive. My father used to tell me that FA70's were the cause for all the dark bores in Krags. This is from the IAA forum; "The F. A. No. 70 primer is a Potassium Chlorate mixture. The FA-70 primer mix is defiantly corrosive. This primer mix was adopted 19 Aug. 1918 and was used until it was replaced in 1952. During the period of 1941 to 1952, experiments with the non-corrosive primer P-4 were conducted, but the corrosive FA-70 continued in use until 1952." This is from the Firing Line forum; "Chlorate primers leave chloride salts in the barrel. Salts attract water and aggressively spread rust. Salts won't dissolve in oil so users of corrosive primers must use a water based cleaner, or water, to get the stuff out of their barrels."

I would gladly put up with the extra cleaning required for some of those $1 per 1000-DCM primers as would many of us.
I found some 7 mm brass and dies for a friend's early Remington RBlock in that caliber.
In return, he gave me a brick of 1000 LR primers.

The GI bore cleaner found in small OD cans contained water in addition to other ingredients. Designed to help  dissolve any salts deposited in bores.

I have an 1885 HW-SS chambered in 45-60 WCF. Made in 1887. The bore is in excellent condition. Someone kept it cleaned and oiled a bit. Keep up the same regimen as 45-60
was one of the rarer calibers in the 1885 SS.

Hopefully this thread will help me out a little. I was given a bunch of -06 ammunition, its in good condition but its military and dated 42,43, and 47. What would the primers be? I pulled one or 2 of them out and seem to be RA stamped.  If they are corrosive primed, can anything be done to save the brass?
TIA
Sam

thank you for the reply. Nice to know the brass will be ok. I have experienced cracked necks before due to old brass. I do have about half a can of the old nasty smelling RBC that I will use and if and when this ammo is shot it will be in a DCM rifle. If it were not for the fact that the primers are crimped in I would consider breaking it all down but the idea of punching out a crimped in primer just isn't really all that appealing to me.
Again, thanks for the info
Sam

My brothers and I used to get our black powder for $0.75/pound in paper bag, or bring your own coffee can.   

George