U on REM-UMC Primers


#1

I know it’s been discussed a hundred times, but the forum Search function still resists all of my efforts to actually search for simple things like that. So, what is the meaning or significance of REM-UMC primers marked with the “U” ? Is the meaning the same for both rifle and handgun cartridges?

THX

Ray


#2

RayMeketa:

U.M.C. AND REM-UMC PRIMERS MARKED WITH THE LETTER “U” WERE FOR SMOKELESS POWDER CARTRIDGES, RIFLE OR PISTOL DEPENDING ON THE MANUFACTURER’S DESIGNATION. PRIMERS LISTED IN THEIR CATALOGS THAT HAVE THE 1/2 IN THEIR NUMBER ARE ALWAYS BRASS RATHER THAN COPPER.
IF I GOT THIS WRONG, I WILL COUNT ON 30army TO CORRECT ME.


#3

GWB is absolutely correct. UMC began the practice of using an impressed U on primers in the early to mid 1890’s to denote a cartridge loaded with semi-smokeless or smokeless powder. Usually on cartridges that formerly were strictly black powder and had “graduated” to smokeless. With cartridges that were introduced as completely smokeless, like the .30 Army, the first primers used were un-marked brass. Later, this caliber and others were loaded with “improved” primers, copper cup, impressed U, and I believe this was done to denote the improved primer. REM-UMC continued this practice, but by the time they came into existence, all of this was sort of passé, and I believe REM-UMC did this to indicate that these cartridges were loaded at the factory and not by “outside parties”…???
Randy


#4

I have noticed that rifle loads don’t have the U underlined and that on handgun cartridges it is underlined - is this an “official” differentiation?


#5

Will…

I have both U and U (underlined) in .30-40 Krag and 7.65mm Mauser…

Randy


#6

Will - not all the pistol “U” primers are underlined. I would say, off the cuff, that the norm for pistol calibers is the same as that for rifle calibers, without the underlining of the “U.” That are some underlined ones in pistol, of course, and usually they also exist, in the same caliber, without the underlining.