Understanding the 6.5x 284 Norma Caliber

[Rich B]

So here it is, this is my first post anywhere. I am just starting to research into the sport of long range target shooting. Leaning towards F-Class Open competition in the future. I have been researching the different types of rounds used in these types of competitions and I like the way the 6.5x 284 Norma is performing. What I dont get is the name of the round. Why is it called 6.5x 284 if it is really a 6.7x .264. Did the manufacturer just round down the 6.7 to 6.5? That would make sense to me but whats up with the 284? I am also looking at starting this sport with the Savage 12 Benchrest rifle so any opinions on this would be appreciated as well. I have done a ton of reading on many aspects of long range shooting and my vocabulary is growing fast but I am still a newbie so please try and keep that in mind when replying to this thread. Thanks

 

[cbannor]

It is simply a 284 winchester case necked down to a 6.5mm bullet.

 

[Browninglover1]

It supposedly has to do with the nomenclature of how calibers are named. In he US we name our cartridges based off diameter of the bullet but in Europe they name the cartridge based off the diameter of the bore before riflings are added. Hence a .264 inch bullet has a 6.5mm (.256) bore.

 

[Michael Eichele]

As stated, the '284 Winchester' is necked down to hold a 6.5mm bullet and is called the 6.5x284. Kind of like the 30-378 WBY. 378 WBY case necked to 30 caliber.

If you're considering an f class rifle, more and more guys are moving away from the 6.5x284 due to barrel life. Many have moved to the 260 Remington which offers only a minor amount more windage than the 6.5x284 but offers more trigger time with added barrel life. Many are also finding the original 284 win is a better alternative as well. A slight advantage in the wind with better barrel life. A bit more recoil but everything is a trade off.

Personally I'm using a 29" 308, 11.25x 5R running 190 VLDs at 2750. About the same wind as the 260 rem with a lot better barrel life. Many say that barrels are like tires. When they wear out, replace them which is true to a point but its hard to see your 'hummer' barrel deteriorate so fast. Some barrels are real gems. It's a shame to ruin them with barrel burner cartridges. Tires don't have personalities like barrels do.

 

[Browninglover1]

As stated, the '284 Winchester' is necked down to hold a 6.5mm bullet and is called the 6.5x284. Kind of like the 30-378 WBY. 378 WBY case necked to 30 caliber.

I think his hang up is with the 6.5mm part. A 6.5mm bullet is really not 6.5mm it's 6.7mm. The minor diameter of the barrel is actually what is 6.5mm. I have no idea why someone chose to name calibers this way because if you throw calipers on a 6mm, 6.5mm, or 7mm bullet they definitely don't measure like they should.

 

[Michael Eichele]

That's right. The land to land measurement is .256" which is 6.5mm, bore diameter is .264" which is 6.7mm. .300" versus .308". .300 is 7.62mm.

I think we agree just in different words. We get hung up on 'slang' terms versus reality. Such as we often refer to 'calibers' when we mean cartridges comparing say the 30-06 against the 300 win. Both are the same caliber but different cartridges yet we still say the 300 win is a bigger caliber.

 

[Mikecr]

What you're calling land measure = bore
What you're calling bore = groove