Why do some calibers use small and some use large primers?

[mpolans]

Why? Seems like a lot of money and effort could be saved if manufacturers switched all or most calibers to small pistol primers.

[latech15]

I don't know the technical answer, but I would assume that with 45, it is to ensure powder detonation. If you have ever reloaded 45, there is some powder that will hardly make a dent in that big void when loaded to major power factors. I guess that the large pistol primers are more easily capable of setting off powder even if it is all at the other end of that big case. That being said, occasionally I run across a Fiocchi brass in 45 with a small pistol primer pocket instead of large.

[JeffWard]

Because small primers would look silly in such a large case....

LOL.

Seriously, most of the calibers we use today were designed about 100 years ago, when primer/powder technology was much lower. Since then, it's tradition and commonality. A modern small pistol SIZED primer could ignite any round on the market today, but changing over all calibers of brass to one primer size would obsolete half the brass in production/existence. The major ammo manufacturers put out such a HUGE volume, millions of rounds, that standardization is irrelevant.

JW

[mpolans]

I wish small pistol .45acp was a lot more common...it'd make reloading a lot easier.

[sargenv]

It seems to be common in my neck of the woods... I picked up 250 ish pieces of once fired at the range.. 150 of it is small pistol primed 45..

[Corey]

I wish small pistol .45acp was a lot more common...it'd make reloading a lot easier.

I wish small pistol .45acp never existed...

[GrumpyOne]

I wish small pistol .45acp was a lot more common...it'd make reloading a lot easier.

I wish small pistol .45acp never existed...

It's like digging through a box of 40 brass and finding the occasional 10mm....Now, why oh why, did they think the 10mm needed a large primer when the 40 has a small primer?

[wide45]

...It's like digging through a box of 40 brass and finding the occasional 10mm....Now, why oh why, did they think the 10mm needed a large primer when the 40 has a small primer?

.40 did not exist when 10mm was designed. The 10mm was intended for large framed guns, which would naturally use large primers.

Later when the .40 was developed, gunrags reported the small primer was used because size large primers would be more prone to catch the ejector of the 9mm sized guns the cartridge was designed for.

I have a .45 that needs large primers as the firing pin strikes well off center.

[lugnut]

I wish small pistol .45acp was a lot more common...it'd make reloading a lot easier.

I wish small pistol .45acp never existed...

Went to the range the other day with a friend. Both of use were shooting .45. I was using my reloads with Starline brass.... he used a Federal value pack. Man was I pissed to see his cases had small pistol primers!!! Once he saw that he didn't want the brass and I had to find my brass from the piles. Then when I got home I double checked and YES- I found two of his with small pistol primers... bastid!

[IMC87]

It seems to be common in my neck of the woods... I picked up 250 ish pieces of once fired at the range.. 150 of it is small pistol primed 45..

Winchester 'winclean'. They use small pistol primers for these rounds. Looks kinda weird

Edited May 11, 2011 by IMC87