Have I got this right on bore diameters?

U

Unlicensed Dremel

Moderator
.22 short, long, and long rifle, AND 5.45 x 39mm, are all .221-.222 (but is it one or the other of those two, officially?)

.22 magnum, however, along with many many other centerfire chamberings, from .22 hornet to .220 swift, are all .224.


Also, are the .577 Tyrannosaur and other ".577s" actually .585?
 
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.22Short, Long and Long Rifle are spec'd at 0.222 groove, 0.217 bore.

.22Mag is spec'ed at 0.224 groove, 0.219 bore.

Almost all of the various "22 caliber" center-fires are .224 groove and 0.219 bore. There are exceptions, the .22 Hornet is .222/.217

The 5.45x39 is spec'ed by CIP at 5.60/5.40 (0.220/0.212) (I think)
 
Bore means groove to me, not lands (and I believe, technically, too). Therefore bore and bullet diameter = same (I think).

OK, so I was right - but it's .222, not .221 for .22lr.... 5.45x39 is also .222, not .221? (not that it matters a great deal...)

.22 Hornet is .222/.217
Click to expand...

What? Really? Hmmmmm. You sure? Any other exceptions?
 
The "bore" diameter is called that because it is the size of the hole drilled ("bored") in the barrel blank. The grooves are then cut (not "bored") in the "bored" barrel, so obviously the groove diameter is larger than the bore diameter.

Bullets are groove diameter; the pressure created by the gas from burning powder forces the bullet through the barrel and the lands cut into the bullet, causing it to turn on its axis.

Sorry, Unlicensed, you can use any terms you want, but if you are discussing the subject with others, it is necessary to use the accepted terms to avoid confusion.

Jim
 
Must not be totally necessary, about 90% of internet posts misuse the term "bore diameter". And often by people who will be darn quick to tell you the difference between "clip" and "magazine."

As to why you shouldn't pay too much attention to cartridge designations:
.218 Bee, .219 Zipper, .220 Swift, .221 Fireball, .222 Remington, .223 Remington, .224 Weatherby, and .225 Winchester ALL shoot .224" bullets.
But .22 Jet and .22 Savage High Power don't.

And why does a .22 Hornet barrel spec look so much like a .22 LR?
Maybe because the first .22 Hornet was built on a 1922 Springfield .22 LR, rechambered and with the firing pin relocated to centerfire. Ammo was the .22 WCF necked down from .228" to .223" and firing .22 Velo Dog bullets run through a spitzer bullet swage backwards to turn a FMJ into a JSP.
 
And some cartridges are designated by bore diameter and others by groove/bullet diameter. Probably the best known pairing is the .30-'06 (and other .30 calibers), which is called by the bore diameter (30/100ths of an inch) and .308 Winchester (and other .308's) which is called by the groove/bullet diameter. But no matter how they are called, both use the same .308" diameter bullets. Of course, simply dividing the difference by two will show that the groove depth is .004".

Jim
 
From SAAMI's glossary:

BORE DIAMETER
1. Rifled barrels: the minor interior diameter of a barrel which is the diameter of a circle formed by the tops of the lands.
2. Shotguns or muskets, the interior dimension of the barrel forward of the chamber but before any restrictive choke or expanded muzzle.

GROOVE DIAMETER
The major diameter in a barrel which is the diameter of a circle circumscribed by the bottom of the grooves in a rifled barrel.

Check out SAAMI's web site on info and specs to compare cartridge names with their bullet diameters against their barrel's bore and groove diameters. Very interesting.
 
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I believe only some of the older .22 Hornets actually used the old .22 rimfire barrel dimensions. Almost all the recently manufactured .22 Hornets shoot .224 bullets.
If you have a .22 Hornet that is not one of those early Springfields, it's likely a .224.
 
I have read that early factory Hornets were .223".

But, as you say, most production rifles are surely .224" and recent production is 14 twist, too; at least at Ruger.
 
I've read that too. One of the bullet makers had two '22' bullets .One was .223 " and all the others were .224"
 
mete said:
I've read that too. One of the bullet makers had two '22' bullets .One was .223 " and all the others were .224"
Click to expand...

Hornady makes .222, .223 and .224 bullets. Sierra makes .223
and .224. I'm sure there's smaller outfits that makes all 3 sizes too but most of the big names don't anymore.
 
Pre WWII .22 Hornet barrels were usually .223". Many post war rifles kept that bore diameter, but this changed over time, and now the .22 Hornet is usually found with a .224 bore.

The .22 Rem Jet (used in the S&W revolver) fires .222" bullets. (possibly to let S&W use the rimfire rifled barrel)

.22 Savage High Power used .228" bullets.

All current US .22 centerfires use .224" bullets. I'm not sure about the 5.45x39mm.
 
And .001" (one thousandth of an inch) really doesn't make much difference either way. Typical barrel specs vary +/- .0005", and bullet diameters can also vary. IMHO, not a big deal. For accuracy, a cross wind or the bedding of the barrel would worry me more than whether the groove diameter of a .308 barrel is .3078" or .3082".

Jim
 
Yes, if you look at the SAAMI specs, you will be horrified at the tolerances considered safe and workable. Most name brand barrels and bullets will beat those easily.
Frex, a .22 Hornet has a nominal groove diameter of .222". It does not have a diameter tolerance, just a minimum open bore/groove cross sectional area. The bullet spec is .2245" even in that tight bore, but with a +0 -.003" tolerance. So anything from .2215" to .2245" would pass.
 
And that could be written as .223" +/- .0015". So how, I wonder, does that jibe with complaints from folks who measured their .223 rifle barrel internal diameters with a yardstick and are sure the too-small .222943" groove diameter is the reason the gun won't shoot?

Jim
 
But it wouldn't be SAAMI spec any more.
As best I can tell, they show cartridge dimensions as a maximum with only a minus tolerance; and chamber dimensions as a minimum with only a plus tolerance. This makes it clear that a minimum chamber must accept a maximum cartridge.
 
Brian Pfleuger said:
Bore doesn't mean groove and neither technically means lands because there are no "lands" in the SAAMI spec.
Click to expand...
Technically true, but only semantically.

SAAMI doesn't give standards for land dimensions or even use the term in their specifications.
They do, however, specify:
Bore diameter.
Groove diameter.
Number of grooves.
Width of grooves.
And minimum bore and groove area.

All of those factors influence number of lands, width of lands, height of lands, and surface area of lands. ...Since analyzing things with the lands as your focus, is sort of like looking at a negative image of SAAMI standards.

It's just a different perspective on the same concept.
 
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