45 acp brass primer size

[wayne h]

Just started reloading for the 45 acp, using range pick up brass. I have noticed that speer, some federal and blazer brass has a smaller primer pocket from remington and some other federal head stamps. What is this all about? Thanks Wayne H.

[I'll Make Mine]

There are two different pocket sizes in .45 ACP brass. Some is Large Pistol, some is Small Pistol. Don't know as it makes a big difference, other than that you'll want to keep them separate -- if you're like me, you really don't need the sudden wake-up you'd get from trying to seat a large primer in a small pocket (you'd likely set it off if you try).

[ole 5 hole group]

In my opinion, it must be cost savings for the manufactures because if it had anything to do with performance, it would have been done several decades before now.

The small primer pocket doesn't seem to degrade accuracy, so I would think within the next couple of years, we might see all commerical 45 ACP with small primer pockets. It's a real PITA using a progressive when a small pocket shows up.

[I'll Make Mine]

The small primer pocket doesn't seem to degrade accuracy, so I would think within the next couple of years, we might see all commerical 45 ACP with small primer pockets.

To turn this on its head, if it were cost related, we'd have seen it decades ago; I first read about small vs. large primers in .45 ACP in the 1970s (as I recall, WWII military cases used small primers, but post-War civilian market ones went large -- except those that didn't).

It costs the same to make either kind of brass, and the difference in primer cost (at the manufacturer level) can't be more than fifty cents, retail, on a box of ammunition (might be as little as a tenth that). I think it's more of a cost saving in terms of what tooling a manufacturer has already set up where they make the brass.

BTW, you could make almost as much of a case for large pockets being a cost saving, since that would allow swaging the pockets on the same equipment that does the large rifle pockets on .30-06, .308, .270, and all those other rifle cases that have the same head dimensions -- avoiding the capital cost of setting up to do the .45 pockets on a different machine after initial brass drawing.

[ReloaderFred]

This subject has been discussed many, many times, here and on other forums. Here is an explanation I made in one of the threads on THR:

The demand for non-toxic priming has been long in coming, and has resulted in a lot of pressure on the ammunition companies to produce primers that don't contain lead. The long used standard priming compound has been lead styphnate, which has worked very well for a long time. It has a long shelf life, is stable and reliable, but releases vaporized lead into the air when detonated. Primers do detonate, since the priming compound is an actual explosive.

Numerous compounds were tried, and the one that was settled on is Diazodinitrophenol, aka DDNP for short. It's nearly as stable as lead styphnate, but has a much higher brisance. That's speed, or velocity, for those not familiar with explosives. The higher brisance results in more pressure, faster. This pushes the primer back out of the primer pocket much faster than lead styphnate priming does. When a primer detonates, it backs out of the primer pocket and the pressure from the burning gases of the gunpowder drive the case back against the bolt face, which reseats the primer into the pocket.

The DDNP primed cases showed extreme flattening of primers from this effect. This was caused by the fact that the primer was backed out longer than with the previous priming compound and flattened the primer cup by the time the case caught up with it. This can cause problems with some types of firearms, rendering them inoperable.

The first attempt to slow the DDNP primers down was crimping the primers in place. This was a marginal fix and didn't always work. The next attempt was enlarging the flash hole to relieve some of the pressure, which worked better. They found that combining crimping and enlarged flash holes pretty much cured the previous problems.

Along the way, they also found, or rediscovered, that the .45 acp case doesn't require a large primer to set off the small volume of powder in the case. There have been .45 acp cases primed with small pistol primers for many years, and quite successfully. The earliest one I have in my collection is headstamped 1957, but I've heard of much earlier examples, and I read one account that when John Moses Browning invented the .45 acp, he originally used a small pistol primer, but the Army insisted on large primers, so that was how he made them. I haven't verified this story, but it sounds plausible.

That brings us to the current era, where several companies are now making .45 acp brass with small primer pockets. I've seen Speer, Federal, Blazer and at least one other brand, but I don't remember which one it was, so I won't hazard a guess and possibly make a mistake.

I've been loading both large and small primed .45 acp brass exactly the same for several years now. With the same data, except for the primer size, they hit the paper in the same place. Forum member The Bushmaster found that the same powder charge produced an average of about 35 fps less with the small pistol primers vs. large pistol primers with the same bullet.

Small pistol primers are nothing new, except in the U.S. Over the years I've seen many examples of small pistol primed .45 acp cases, but they were all of European production, and mostly Berdan primed.

There is no conspiracy by the ammunition companies against reloaders by changing primer sizes. The large primer has never been necessary in the .45 acp, and quite a few people who shoot mostly bullseye are reporting better accuracy at the 50 yard line with the small pistol primed brass. There is no cost savings to the manufacturer, since the small primer pocket means there's more brass in the base of the case, which adds up over many millions of rounds. The costs to make primers is basically the same for large and small, hence the same price for both from most companies.

Hope this helps.

Fred
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[Eutectic]

To turn this on its head, if it were cost related, we'd have seen it decades ago; I first read about small vs. large primers in .45 ACP in the 1970s (as I recall, WWII military cases used small primers, but post-War civilian market ones went large -- except those that didn't).



WW2 U.S. military .45 cases had mostly large pistol primers, but some did use a special Frankfurt Arsenal designed pistol primer that was actually .204" diameter. This primer was neither large (.210" dia.) or small (.175" dia.)
Small primers in the .45 Auto came along in the "Non-Tox" craze...

Eutectic

[ReloaderFred]

"Small primers in the .45 Auto came along in the "Non-Tox" craze...

Eutectic"

Not so. Like I stated, I've got one in my collection headstamped 1957, and I've had them in my possession that were even earlier than that, but didn't keep them. In some areas of Europe, small pistol primed .45 acp was the norm.

I'm neither endorsing the change, nor condemning it, just stating the facts and reasons for it.

Hope this helps.

Fred

[Eutectic]

Not so. Like I stated, I've got one in my collection headstamped 1957
Fred

"WW2 U.S. military .45 cases" is how my post started. If your 1957 round has a true small pistol primer of .175" diameter and is United States manufactured I would sure like to see a picture of it.

Eutectic

[44man]

My friend bought a S&W in .45 ACP. We got very poor accuracy. I was sitting at my bench and said "the LP primer is too much."
Since I do not shoot the cartridge I did not know that SP cases were out there. I made shims so I could load SP primers and that cut groups a huge amount. He found a pile of brass and it has proven more accurate in his 1911 too.
I built his 1911 and it will do 1/2" at 30 yards so an improvement is something to see.

[ReloaderFred]

"If your 1957 round has a true small pistol primer of .175" diameter and is United States manufactured I would sure like to see a picture of it.

Eutectic "

I should have been clearer in my post. The example of a small pistol primed .45 acp case from 1957 that I have is NOT of U.S. manufacture, nor were any of the other early examples I've had over the years since I started reloading in 1963. All the examples I've seen were of European origen, but they do prove that small pistol primers have worked in the .45 acp for many years prior to the U.S. manufacturers using them.

Hope this helps.

Fred