I decided it was time to load up for my non-varmint hunting guns.

I have two. One is a Pre-64 Model 70 custom in .260 and the other is a .340 Wea. Mark V that I had rebarreled for .330 Dakota.

I went to the new Sportsman's Surplus store too look at the bullets now available. I was most impressed with the new Hornady line of SST bullets in both calibers. 129 SST in 6.5 and 225 SST in .338. I also purchased the new Hornady reloading manual which had extensive new loads for all the new rounds like WSM, WSSM, Dakota, etc.

Since I am intending to load to max in both cases, something I don't do with my target and varmint rifles, I decided to duplicate all the info given by the book including exact same primer as used in development. That was REM 9 1/2 in the .260 Rem Cases and the F215M in the Dakota .330. The book recommended the WLRM in the 7mm WSM.

So I got those primers. Well, it turns out that using a Hornady handheld priming tool with cases and primers shown above that the primers were a light press fit when the primers used were those recommended by the book and also were in most cases the same mfg. as the cases. It appears that these manufactures design forming punches that precisely match their primer size!

Big secret that I didn't know before.

Is that Hornady #8?

The book is Hornady® Handbook 7th Edition, shown below. It perhaps isn't new to you, but my previous one is 20 years old. I have a relatively new Sierra manual which I have used for the last five years or so.

Funny though that any kind of primer will also fit into any kind of brass - even after having treated the primer pockets to a swirl on the uniforming tool...

I meant no disrespect asking if it was #8. I emailed Hornady about the reloading for service rifle pamphlet. When they replied to my email a couple weeks ago saying the pamphlet is no longer available they said #8 would be coming soon and the information from the pamphlet is in #7 and #8. There was no indication if "soon" is next month or next fall. I'm on Hornady #4, Speer #12, and Sierra #5.1 on PC.

[QUOTE]Originally posted by DMCI*:
It appears that these manufactures design forming punches that precisely match their primer size!
QUOTE]

Unplated WW primers will "fall" into Winchester brass just as loosely as they do into Remington and Federal Brass. Federal 215's have to be squeezed into any brand of brass. The difference is in the primers and their cups, not in the brands of brass. Tight-fitting primer fit tightly (or tighter) in all brands of brass, just as loose-fitting primers are always looser.

What Stonecreek said.

I always find the WW primers are a "loose" fit.



.

I find RO primers to be slightly smaller in dia. I use them in RWS cases that have very tight primer pockets. They are often too small for use in RP brass after 1-2 firings.

The unplated WLR & WLRM primers seem to fit loose in good, new primer pockets.

The plating they left off must have made them larger in diameter?

Find the 'blueprint' for large rifle primers.

What you posted are nominal dimensions.

I saw but can't find just now a print with the primer diameter tolerances.

IE: Diameter = 0.210" +- .0005" for instance.

The blue print.

Even if a primer is a "loose fit" in a standard pocket (not known to be expanded/overused), properly seating the primer eliminates any worries about fitment. If you notice that a new primer's anvil protrudes a few thousandths below the edge of the cup-it needs to be seated flush and we do that by seating the cup firmly in the pocket-two things happen- the anvil presses into the mixture and closer to the face of the cup- as needed for proper ignition and the cup walls a forced snugly to the inner face of the pocket, and a bit wider- so insure your primers are seated well- some measure the anvil protrusion and add a few thou for " crush" and call it good. In any case, insuring the primer face is flush or below flush is a good ROT.

High primers/unseated anvils can have two undesirable effects- slam fires in Autos, and poor/irregular/nonignition otherwise.

Best

I know of no rounded head primers made since, over 50 years ago. And you do realize that primer makers are under no obligation to follow SAAMI drawings. I is amazing that everything fits as well as it does. I am not even sure what this thread is about; didn't read it.