Why different diameter bullets for the same caliber round?

[ptgarcia]

I was at the local gun store the other day, just cruising the aisles when I came upon the reloading components. I don't currently load my own rounds at this time but I do plan to in the future so I looked at what they had. The first thing I noticed was they had boxes of bullets marked .38 Spl/.357 Mag (148 gr. I think) but they offered different diameters. The difference was only 0.001" but I figure it must be significant for a company to produce both sizes.

So my question is, how do you know which one to use?

In my case I have both a M627 chambered in .357 and a new model Bodyguard 38, which is a .38 Spl +P gun, that I would be reloading for.

Someone please enlighten me!

 

[scattershot]

The bore size for the .38 Special and the .357 mag are the same, at .357. Cast bullets are generally loaded .001 over bore diameter as a rule, while jacketed bullets are bore diameter.

In the .45 Colt, the older rounds were loaded at .454 diameter, and the .45 ACP was .452. This has generally been standardized at .452, fo both calibers.

Whole books could be written on bore size. For example, the 38/40 round is actually .401, and the 44/40 takes a .427 bullet. Go figure.

Anyway, as a general rule, one to two thousandths over nominal bore size for cast, and actual bore diameter for jacketed.

 

[OKFC05]

My model 14 loves the .358 cast lead bullets, but accuracy drops off with the .357 lead. Somebody must need the .357 lead, but not I.

 

[elm_creek_smith]

Bore diameters vary within the same caliber since the cutters that form the rifling wear and since bullets and hot propellant gas can wear the bore as well. There are different diameters in the same caliber because different guns will shoot different diameter bullets...differently.

ECS

 

[zeke]

Bore sizes differ, bullet diameters can differ from what they are labeled and what they are measured at. Older S&W 38's seem to like the lead bullets at a measured .358, as an example.

Alot of 45 acp jacketed range from .450 - .451, despite what they may be labeled at. Differing lots of same bullets can also vary in dia, as well of special runs of bullets supplied to specific cartridge manufacturers.

It sometimes pays to slug your bore, and meaure your diameters.

 

[rwsmith]

Swaged lead bullets......

Swaged (softer) lead bullets that you get from Speer, Hornady and the others are also .001" oversize. They are easily sized to the barrel diameter in the forcing cone of the barrel. Jacketed bullets are harder to size down in the forcing cone so they are closer to actual bore diameter.

An interesting operation is to 'slug' your barrel (tap a lead bullet through it) and measure the slug to determine your actual bore diameter. People that cast bullets often cast them slightly oversized and run them through a sizing die to get the best diameter bullet for their barrel.

 

[Bluecoat76]

Just try .22lr as they have the same problem. I blamed a k22 for hard to extract empties out of one and s&w said it was dirty.(It wasn't) many years ago. Now 20 years later I find out that each different mfg. fits a little differently in the cylinder chambers. One culprit was Aguila brand. It chambered snugly and had to almost be hammered out. You have to try cartridges of different mfg. and decide on one that fits and extract easiest. The Aguila fits and shoots great in my rifle. That could be part of your problem with .38, although I've never seen it.

Good luck

 

[ArchAngelCD]

Quite normal. For the 38/357 jacketed bullets are usually .357" and lead bullets are usually .358". In the 45 Auto jacketed are .451" and lead usually .452" and so on...

 

[Nevada Ed]

Just for giggles..............
In the Navy, the Iowa Class 16" gun shoots a 72" long projectile that weighs around 2,240 pounds and has a 660 pound powder charge behind it for a range of 20 miles.

Just a little bigger than a .357 dia. bullet................

 

[Skipw]

Just for giggles..............
In the Navy, the Iowa Class 16" gun shoots a 72" long projectile that weighs around 2,240 pounds and has a 660 pound powder charge behind it for a range of 20 miles.

Just a little bigger than a .357 dia. bullet................

Do you know where I can get a sizing die for this one?

 

[Pointshoot]

660 lbs of powder for one shot - Come on Navy! Share just one shot's worth with us needy handloaders !

 

[iouri]

Just for giggles..............
In the Navy, the Iowa Class 16" gun shoots a 72" long projectile that weighs around 2,240 pounds and has a 660 pound powder charge behind it for a range of 20 miles.

Just a little bigger than a .357 dia. bullet................

Well, can it shoot +P CTG ?

 

[amazingflapjack]

cylinder throat sizes, and barrel sizes vary.

 

[mikld]

Also, caliber nomenclature can be confusing. A 38 caliber barrel isn't .380" (it's .357"+). A 44 Special/Magnum isn't .440" (it's .429"+). A .32 S&W isn't .320" (it's 312"+). A lot of the cartridge names are from way back when other facts came into play. There was no standard on how to name cartridges and manufacturers used different methods; some went with bore or groove diameter, some with chamber dimensions, some with powder charges, some with bullet diameters, etc. Can be confusing...