Seems like the primers on my winchester 180 grain 300WSM are pretty flattened, with a bit of firing pin crater, for factory loads. At the same signs on handloads, I would back off a bit. this in a new CZ3 MRC barreled action. It was hot (95F), but not THAT HOT. are the winchester factory primers just whimpy soft?
I have a chrony, but did not use it.
thanks for input.

Sounds about right in my 300WSM...though I've only about 15 factory loads (compared to the 500 or so reloads) through it.

It is a 65000 PSI cartridge, BTW. That's plenty hot!

I seem to recall they had some problems with the ammo when it was first issued. I'd call them and ask about the lot number.

three different loads, three different lots. I think I have just not shot high pressure cartriges before. The old breakaction and 280 loads were no where near 65,000 PSI.

It does appear that all three factory ammos show similar primers, so presume it is not ammo, it is just hot weather and high pressure vvs soft winchester primers.

thanks

Jamie

If you can find the thread... I asked the exact same question about 2 years ago. FLAT factory primers. (black & blue shoulder!) Completelty normal was the consensus (pic's were included)







The silver primer was a handload and not flattened

Every factory cartridge I have run through my .270 does that. I wouldnt worry about it unless I started gettin stiff bolt lift.

quote:

I have a chrony, but did not use it.

Put it thru a chrono and see what you get.
to get the advertised velocity they advertise the primers will look like a warm hand load.

"Flattened" primer appearance is most often caused by slightly excessive headspace.

In the case of the .300 WSM, well, there may be other causes also. In order to achieve velocities similar to those from larger cases the WSM's simply HAVE to be loaded to higher pressures (the "efficient short-fat" case myth notwithstanding). As is customary with many new chamberings, the ammunition companies are fairly confident that the rifles so chambered are all new and of strong design. Give it a few years and the ammo companies will quietly drop pressures (and velocities) back to about what they load everything else.

quote:

the primers will look like a warm hand load

65 Grains of H4350 behind a 180 Nosler BT (my pet whitetail load) or Sierra MK (my pet paper killing load) give me primers about like that (and averaging 2955 fps) on partial FL sized (slight crush fit) reloads. I have split one case mouth, on the 9th reload of that piece of brass. Mine is a factory M70 chamber, FWIW.

Check the datum line on an unfired case and then on a fired case. If the shoulder has moved considerably foreward, then the slightly flat primers are from the case moving forward under firing pin impact and upon ignition they slam the case back against the boltface and the already slighty backed out primer, and slam it back into the pocket while slightly flattening it. How did you size the reload? NK size? PFL size? If so, the shoulder probably headspaced it correctly.

If that is not it, then I would say you got a nice tight chamber and along with a high pressure cartridge, you are simply running close to max. And, if that is the case, and it likes the load, I'd stick with it. BUT, a bit slower might find a great harmonic too.

I don't believe Win. primers are especially soft. What I believe is that those "ss" magnums are loaded to very high pressures in order to get the velocities they must have to use for advertising hype! I'd be willing to bet that in a few years, those MV's will be revised downward, just as happened with the original .44 Magnum load - it started out at 1570 FPS for a 240 grain bullet back in 1956.....

My experience with factory loads was the same.

Flat primers and questionable accuracy from what should be a fairly accurate rifle pushed me over the edge to the reloading side.

This is a dirty cold bore shot(DCBS) to follow-ups test I did yesterday. Upper left target is the DCBS. Other shots within 60 sec. of DCBS. Discount #5.(Had to play)

DCBS TO Follow_ups

If you are shooting a 300WSM the load is:

Norma brass

GM210M primers

64gr H4831

168 gr. Nosler Cust. Comp.

YMMV

Slightly off-topic, but I've found in recent years that nearly every factory loading I've purchased and fired (especially the premium loads) show flattened primers after firing. Like Russ said, I won't worry about it unless I experience other pressure-related problems.