Oval vs Flat Primers

I was looking at the WINCHESTER LITTLE BIG HORN CENTENNIAL 1876-1976 44-40 AMMO and it brought some questions (I am a 44-40 freak). I noticed all of the boxes I could find on the net were coded LE which would be May 1976....of course right? Well, I also noticed a few that had flat primers rather than the "oval". So far the only days of production I can find are the 19th, 23rd and 25th. I also noticed that the hand-loading components "White Box" with the red W were produced from 1974 to 1977. Any idea if this was the transition from one primer design to the other? Prior to the mid 1970's, Winchester primers were "oval" rather than "flat" as they are today.

Also, about Pre-WWII, Winchester flip-flopped several times between oval and flat primers. The following was found in Vol.I of Dan Shuey's "W.R.A.Co. Headstamped Cartridges and Their Variations":
"When smokeless powder cartridges evolved in the mid 1890's, the No.'s 1 and 1 1/2 were adapted with a different formula. They were also marked with a form of "W" to denote for smokeless loadings. All of these primers used an oval-shaped cup until around 1900 when it was thought that a flat or pan-shaped cup would give better and more positive ignition. According to (George) Watrous, this thought and trial process was repeated several times for a number of years with the results being the same. After a period of use, the shape of the primer cup was always returned to the original oval shape because the results with the flat shape were unsatisfactory."

Thanks for that sir. I started loading in the mid 60s, and never encountered the oval, or domed primers, though my first press, bought used, a CH, was set up o seat the oval primers. I used it with the flat primers. With no problems.

I remember the oval primers, 1960's early 70's, my first reloading press, a blue Pacific 'C' press, came with two primer rods, one for flat, one for oval. Winchester and CCI were the two brands available in my area so I switched back and forth. Component selection was very limited compared to today, no Internet, but Herter's, others and the US Mail brought primers, powder, guns to your door.

The popular idea of judging excessive pressure by looking for flat primers was based on the old style dome topped primers. Seems a lot of people didn't get the message so the legend lives on ... but it's nearly worthless trying to guess excessive pressure based on the flatness of already flat top primers.

Most of today's scarry and truly flattened/square corner primers are the result of excessive headspace, not over pressure.

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Originally Posted by 1hole

The popular idea of judging excessive pressure by looking for flat primers was based on the old style dome topped primers. Seems a lot of people didn't get the message so the legend lives on ... but it's nearly worthless trying to guess excessive pressure based on the flatness of already flat top primers.

Most of today's scarry and truly flattened/square corner primers are the result of excessive headspace, not over pressure.

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Sorry 1hole, you failed to understand the topic. This topic has nothing to do with looking for pressure signs. Try reading the topic again.

Don't be sorry, I'm not. Perhaps you should read my post again.

My point is that there was more than one reason the change from domed to flat primers was moderately significant to reloaders, it wasn't just cosmetic. If you're disinterested in learning that, so be it; I can live with it with total comfort. :)

One hole may have missed the topic but you missed the correct description lol... domed primers is the correct term, not OVAL lol... try fitting anything oval into a primer pocket bub.

most oval were older and some [could be } corrosive , but they tend to be soft for the old hand guns
as you may see all now are flat, and take a good hard hit to fire
many of the oval did not have an {anvil } and had one in the case, called a balloon case that had it built in case
they could miss fire or delay fire if used in reg case NOT GOOD

My Lyman Spartan press from the late 60s also came with rounded and flat primer seating punches.

Thanks Guys,

As I stated in my OP, I am aware of the brief history and of the testings between Oval and Flat primers...I was trying to "keep it simple".

My question was for the transition dates from one to the other (at least by Winchester). I was kind of thinking since many of you guys have been handloading since the year 1492 and were friends with Christopher Columbus...., you may remember the change ;-)

So just a quick recap.

Was 1976 the transition period between Winchester's Oval primers to the new Flat primers?

I have somewhat, since the OP, narrowed the dates to about April 1976 to August 1976.....I was only 10 at the time and I never really thought about it till recently.

You are right about reloading since 1492, though I mostly had access to CCI primers in those days, never Winchester. The white box/red W primers I have now are all flat.

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Originally Posted by Pressman

You are right about reloading since 1492, though I mostly had access to CCI primers in those days, never Winchester. The white box/red W primers I have now are all flat.

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LOL, thanks!! I am getting to where I mostly use CCI 300's now. I kind of like them better than Winchester.

Attachment 264593

1976 is close i have some herters that dates to about then are oval has a 2 prong anvil most likely made by federal

I started loading in 1970, but all my primers were-and have been- the flat type, though my Pacific press had primer cups for flat and rounded. (Until today I had never heard them referred to as "oval".) I do remember being admonished to make sure I had the correct stem for the primer type I was using in loading materials.
Back before WW II, Remington and Peters cartridges were flat and Winchester and Western Cartridges were rounded, "Convex," at least according to Phil Sharpe. But when I started reloading Only CCI and Remington were available in my area. I later bought Winchester primers, cerca 1975, but they were flat then.

So exactly when did Winchester switch over? Danged If I know. Gun Digest makes no mention of it in the 1975 Edition, and I don't have any of the late 70's issues anymore. Nothing is said in the 1980 issue. Certainly my 1984 Dillon 450 had only the one primer seat, so they apparently felt sure I was not going to load round-top primers. I don't remember any fan fare about it in the firearms press of the day. Either Winchester felt it was no big deal, or they didn't want to admit they were following someone else's lead.

The only thing that mattered (for us) between oval and flat primers was that oval tops would visibly flatten a bit as chamber pressure rose. It wasn't a "scientific" pressure test but it was something and something was better than nothing but flat primers started flat and they ended flat. Still, the old stories of "flattened primers" and high pressure continues to wander around as reloading "wisdom".

Most of the truly "flat" primers we see are the result of excessive headspace which allows the already flat primers to back out a few thou when fired. Then the case body stretches and the head moves back; that way, even normal pressure loads can form some very flat primers!

When did the change to flat top caps occur? Best I can remember it was in the late 60s but it wasn't an instantanious thing, it took a few years for every maker to change.

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Originally Posted by 1hole

The only thing that mattered (for us) between oval and flat primers was that oval tops would visibly flatten a bit as chamber pressure rose. It wasn't a "scientific" pressure test but it was something and something was better than nothing but flat primers started flat and they ended flat. Still, the old stories of "flattened primers" and high pressure continues to wander around as reloading "wisdom".

Most of the truly "flat" primers we see are the result of excessive headspace which allows the already flat primers to back out a few thou when fired. Then the case body stretches and the head moves back; that way, even normal pressure loads can form some very flat primers!

When did the change to flat top caps occur? Best I can remember it was in the late 60s but it wasn't an instantanious thing, it took a few years for every maker to change.

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You may have missed the point of the topic or I missed the point of your reply.

Winchester kept messing with flat primes over the years before finally switching from oval primes to flat primers by 1976 on their production ammunition for the 44-40. That is an absolute fact.

"Flattened primers" from over pressure is a whole different subject.

Attachment 279874