Q about bullet dia. versus "caliber"

[Wannashootit]

Forgive the new reloader question...
When I began reloading for our .223's I learned that I needed .224 bullets...

I'm going to be reloading for my son's new Sav. .308 he's getting this weekend - and far as I can tell the bullets are .308...

Also picked up a couple of M91/30 Mosins to play with, and the Prvi Partisan has .311 bullets, but I'm told it varies and to slug the barrels. Confusing stuff...

So, HOW is the optimal bullet diameter determined, and why does my .223 take .224 bullets, while the new .308 will take .308 bullets?

 

[Victor N TN]

Re: Q about bullet dia. versus "caliber"

Buy a Lyman's Centerfire Handloading Manual. It lists all the needed data for each caliber. It also has a lot of beginner information.

One of the first things I tell new loaders to do is buy this book and read all the NON data specific chapters. Then read the safety chapter again. Do that and you'll be miles ahead of the pack.

 

[ChrisGarrett]

Re: Q about bullet dia. versus "caliber"

I'm no Mosin expert, but I think the Finns got theirs in .308" caliber and everybody else (Russians) used a .311" bullet. You can always slug the barrel to know for sure, but that's how I understand it.

You will find some die sets, especially 7.62x39, with both sized expander balls, because AKs can be all over the map.

You can obviously shoot .308" bullets out of a .311" bore, with varying degrees of accuracy, but you probably don't want to fire too many .311" bullets through a .308" bore.

Chris

 

[cmh2007]

Re: Q about bullet dia. versus "caliber"

well, you can shoot a .308 out of a .311 barrel. a friend of mine has a PSL in 7.62x54r. he slugged it at .310, so we decided to try some .308dia bullets out of it. seemed to work very well. velocities were just a shade under what the book stated we should have been getting. so we aint going to complain.

 

[pjparker]

Re: Q about bullet dia. versus "caliber"

There have been volumes written about cartrige case nomenclature, and the bottom line is that there is no ONE system of identifying what you've got.

The bore size on barrel manufacture is the initial hole drilled thru the blank. .300" for a .30 cal, for example. Then the grooves have to be cut, and for the example .30 cal, they are .004" deep, so it takes a .308 bullet to fill out the resulting grooved hole (.004" x 2).

What manufacturers choose to call their creations is another matter entirely. Both the .300 H&H mag and the .308 Win take the same .308" diameter bullet. The Brits seem to favor the bore size, and we want to know the bullet size - go figure.

Add to that, variations within one caliber from poor or varying quality control from wartime production make this a very interesting and sometimes frustrating hobby.

Read everything you can get your hands on and you will still be confused. You have just joined the club!!!!

Paul

Google Cartrige case nomenclature for enough info to fry your brain.

 

[Fuzzball]

Re: Q about bullet dia. versus "caliber"

"and why does my .223 take .224 bullets, while the new .308 will take .308 bullets?'

There are significant differences in marketing nomeclature and the bore/groove size. The .22 Savage Hi-Power, .218 Bee, .219 Zipper, .220 Swift, .221 Fireball, .222, .223 Rem. (and the identical 5.56MM), .224 Weatherby Magnum, .225 Winchester all take the same .224" bullets. Marketers chose monikers that sound distinctive or impressive, not technically precise.

Most people call the cartridge itself a "caliber", including the lables on factory ammo.

 

[DirtyDave]

Re: Q about bullet dia. versus "caliber"

I have not slugged my Mosin's bore, but I load .310 and .308 dia bullets for it, and it shoots them well. If your Mosin will shoot .308's well, it opens up your bullet selection quite a bit. Not a huge selection in .310 - .312 dia bullets.

PS: .357 Mag and .38 special will blow your mind.....

 

[kombayotch]

Re: Q about bullet dia. versus "caliber"

Realize that groove diameter is not the be-all-end-all as some make it out to be. It can affect accuracy and will affect pressure, but choosing a bullet diameter isn't always as straight forward as matching bullet diameter to grove diameter, depending on how the rifling is made.

I have a two groove barrel on a 303 British Lee Enfield I recently picked up, and have slugged it. The land diameter is 0.303", the groove diameter is 0.316". The grooves measure 0.098" wide. It's hard to see those features on my slug in a photo, so here is what it looks like drawn out in CAD:

This gives a cross-sectional bore area of 0.0734 inch^2. The default cross sectional-bore area in Quickload for a .308 barrel is 0.0736 inch^2. So, my Enfield barrel is actually tighter than the "typical" 308 barrel Quickload uses as a model. Will it shoot 308 bullets well? I don't know yet, but it's quite apparent that they won't be floating around in the bore. Cross-sectional area of a .308 bullet is 0.0745 inch^2, so it's still getting swaged to the shape of the bore, and then some. Bullets of 0.312" diameter have been shot through this gun without any issues. It's a common bullet diameter for this caliber.

In the end, you need to test different bullet diameters to find out what works best. For safety reasons, stick to a bullet diameter that is the same or smaller than the common bullet diameter used the cartridge, or only bullets that have load data listed for them in your manual.