6mm and .243 Bullet Comparison?

[TnTom]

Disregarding the chamber, case config etc. what is the difference in a bullet that would be loaded in a 6mm and one that was loaded in a .243. None right?

 

[Derek M.]

Disregarding the chamber, case config etc. what is the difference in a bullet that would be loaded in a 6mm and one that was loaded in a .243. None right?

Right. In fact, I think it is a shame that the 6mm Remington didn't take off like the 243 Winchester did. The 6mm Remington is a really great caliber and if you really want a wizbang 22, take a 6mm Rem and convert it to the 22-6mm.

 

[boomtube]

They are the same.

The 6mm and .244 Rem are also the same cartridge. Only "difference" is in the rifles, and the only difference there is the barrel twist; former is 1:12, latter is 1:9.

 

[TnTom]

I may not be asking this correctly which will be obvious

When a bullet is designated in metric like 6mm,6.5mm,6.8mm why do they not convert into the English equivalent?

If a rifle is chambered for a 6mm does the bore have the same diameter lands and grooves as a rifle chambered in .243 win? If that's the case is a 6mm not really a 6mm?

 

[roninflag]

a 7mm-08 ,a .280 rem, a .284 win and a 7mm rem mag all shoot .284 caliber bullets. a 264 win mag and a 6.5-284 fire .264 caliber bullets. a 6mm br , a 6ppc , a .243 win, and a 6mm rem all shoot .243 caliber projectiles.

 

[boomtube]

"When a bullet is designated in metric like 6mm,6.5mm,6.8mm why do they not convert into the English equivalent? "

When asking us why "they" do much of anything you're asking the wrong people.

 

[TnTom]

a 7mm-08 ,a .280 rem, a .284 win and a 7mm rem mag all shoot .284 caliber bullets. a 264 win mag and a 6.5-284 fire .264 caliber bullets. a 6mm br , a 6ppc , a .243 win, and a 6mm rem all shoot .243 caliber projectiles.

So really there is no dimensional difference in the bore. A .280rem bore is cut the same as a .284win bore? The only difference being the designation and the reference is relative to the case configuration only? Same as a 6mm and .243win would be reflecting a difference in the case?

 

[roninflag]

Tn - right. if you order a .284 from krieger you could use it for a .280, 284 win , 7mm short, 7 mm rum ect. the reamers to cut the chamber are different. the barrel's and land and groove diameter is the same

 

[Derek M.]

If you have several rifles:

a 243, a 6mm Remington, a 6BR, a 6x284, etc. etc., it doesn't matter. They are all the same bore diameter. And if you load bullets for any of them, the box will say"6mm/243"

Just like 7mm is to 284 and 277 is to 6.8 and so on.

 

[Kevin Thomas]

TnTom,

The problem here is one of cartridge designation, and yeah, it's largely "our" (American's) screwup. The Europeans have a very specific method of cartridge designation; bore diameter and case length (in millimeters), with an added "R" for a rimmed cartridge. 6.5x55, 7x57, 7.62x54R. If I'm describing a 7x57 and a 7x57R, you understand exactly what the differences are between the two, based on the European system. Here in the US we never really settled on a standard method of cartridge designation. We've used caliber, charge weight and bullet weight, as in .45/70/405, shortened that (sometimes) to caliber and charge, i.e. 45/70, or .30-30. We've used designations that had nothing to do with either, as in 38/40, and we've used year of adoption, such as .30-'03 and .30-'06. When we get into strictly commercial cartridges or those standardized by wildcatters, anything goes, and it usually has more to do with marketing or sales appeal. Jim Carmichael likes to name his cartridges after cats; the 6.5 Bobcat, the 260 Panther and the 22 CHeetah being well known examples. Bottom line is, there's no real standardization here, and that leads to a lot of confusion. But hey, it DOES give our cartridges a lot more style and flair!

There's a few exceptions to these basic guidelines, but they're relatively few and far between. Most of those exceptions are truly bastardized rarities, and have never been adapted to sporting use.

The following are some of the more common bores that you'll find in both European and Imperial measurments. Some, like the .257" and the .375" aren't really used much with meteric designations, while others aren't normally seen listed in Imperial units, like the .366". Basic list goes like this;

5.5mm = .224"
6mm = .243"
6.5mm = .264"
6.8mm = .277"
7mm = .284"
7.62mm = .308"
8mm = .323"
8.6mm = .338"
9mm = .355"
9.3mm = .366"

Hope this helps!

 

[TnTom]

Well that clears it up perfectly and thanks to ALL for taking the time clearing up both questions so well.