Why winchester choose 338" bullets?

I would like to know why winchester decided to load its 338 winchester magnum ( I think the first 338 caliber commercial cartridge)with 338" bullets when 333" bullets were already available.
Is there a so big difference between the 2 bullet diameters performances?

I read that also the british 33 BSA ( developed in 1921) was loaded with 338" bullets.
It is very similar to the 338 winchester magnum,only shorter and much less powerful.
Could be the 338 winchester magnum considered an improved version of the 33 BSA,developed preserving the original bullet diameter?

Pivi - I have never designed a bullet. Since in my lifetime, even as a child, we already had calibers that would do anything a firearms EVER needs to do, I never developed any interest in that type of experimentation when I really got into shooting and then reloading. Was never a “wildcatter.”

However, if I wanted to design a bullet or a new cartridge, I would ask myself several questions.

What do I want the cartridge to do?
About what bullet weight should it be to achieve what I want to achieve?
What velocity does it have to go to achive these goals?
What case capacity do I need to achieve the “power” I am looking for?
What properties must the bullet have to achieve proper accuracy?

There are lots of other questions, but you get my point, I am sure.

The answer to these questions of themselves might well determine bullet diameter, shape and length.

It is probably not an accident that the calibers of firearms are often in what seem to reasonable and even people with a fair firearms knowledge, to be strange, like .277, .338, .458 (why not just .45 or .46?) etc.

There are so many variables in gun and ammunition design that it truly is a science - one that has been worked to death in my opinion, but then, every inventor wants to build the better mousetrap, I suppose.

I agree

According to me winchester studied a lot before choosing that particular bullet diameter ( the same thing when they developed the 270 winchester,with its “strange” .277 bullets).I know that very slight variations in bullet shape,weight and diameter as well may increase dramatically a lot of parameters such as “balistic coefficient” or the sectional density.
That’s why,for example,the cheytac cartridge was developed for 408" bullets instead of the commonly available 416" ones.Or why 41" cal rifle bullets are usually of 416" diameter instead of 411" ,standard for pistols.
Rifle and pistol cartridges are used for different purposes,obviously

Do you know what are the differences between 338" and 333" bullets according their sectional density or balistic coefficient?


Don’t forget that most bullets are groove size. Therefore the 338 is actually a true 33 bore whereas the 333 is a 325 bore.

I suppose there is a natural tendancy to keep everything in nice even numbers, at least here in the U.S.A. which is why most of our calibers are so. 25, 27, 30, 33, 34, 35, 45, etc

When the 338 was first being developed by W there were no readily available 333 diameter bullets here. The 333 and 334 cartridges all used bullets obtained from overseas.

Sectional density and ballistic coefficient depend on the size, weight, and shape of a bullet. You cannot say that a 338 bullet has a higher SD or BC simply because of its diameter. The 40 bore was probably chosen for the CheyTac because they were able to get the high BC they wanted at the desired bullet weight, and therefore velocity. There is no reason they could not have gotten the same or higher BC with a 41 bore had they wanted.


Pivi: Winchester had already made a rifle firing .338 diameter bullets years before its .338 Magnum. This earlier effort was the .33 Winchester, for the 1886 Winchester. If the folks at New Haven were contemplating a new .33 after World War Two I’d guess that .338 would naturally come to mind for the bullet diameter. JG

wasn’t the 33 winchester loaded with .333" bullets?
The only cartridge I was able to find loaded with .338" bullets and developed before the advent of the 338 winchester is the 33 BSA

John & Ray,
I understand,I think.It is about different starting points.
I tough that you have to choose the bullet diameter needed to reach some parameters such as BC and SD first and then see if that bullet is correct for some purposes about power or accuracy, for example.You say that first of all you have to decide what purposes are you looking for and then develope a bullet whose BC,SD and diameter ( shape,structure etc) accomplish your needs in the best way

So,probably,for the 338 winchester magnum the best compromise was a bullet with that diameter,that BC,that SD etc.


The 33 Winchester used .338 bullets. But it was discontinued in the 1930s in favor of the new 348 Winchester and its much better rifle.

And don’t forget that important criteria, maybe the most important one, MONEY. If a factory is looking to introduce a new cartridge the boys in marketing first have to decide if it will sell. They don’t care about BC, SD MV or any other numbers. The 338 Winchester could be sold as a powerful hunting cartridge, capable of taking any North American game, without the recoil of the 458 Winchester but with more energy than the big 30 calibers. An American 375 H&H if you will. They were convinced that they could sell that to American hunters and so it was born.


Pivi: No, the .33 Winchester employed .338 diameter jacketed flat-nosed bullets in its standard factory loading, now long discontinued. JG

Ray and Gill,thanks for your replies.
I have to correct my data about the 33 winchester.
I have only a 33 winchester case sample :),so I wasn’t able to check the bullet diameter on a loaded sample and my COTW reports .333" bullet diameter in the dimensional data tables


A very good reason to use new .338 diameter bullets was to avoid all the old .333 ones. The .338 Winchester was new belted magnum cartridge designed for Alaska and large game.
If I remember correctly the older .333 game bullets gave variable results on game animals and were not designed to expand properly at a higher velocity of the .338 . They would probably expand too much and not give sufficient penatration .


Very Interesting Glenn.
So the reloaders couldn’t use bullets that would have performed bad on large game or at very high velocities.
It was a way to “specialize” the cartridge

I read on an old article on an italian gun magazine that Weatherby had some problems loading his high velocity cartridges with bullets designed for 30-06-class ammunition

.338 Winchester Magnum prototype with no head stamp.