Trying to understand barrel life between different calibers

[ocp]

Hi Everyone, new to the forum, hope this is in the right spot.

I was talking with a friend of mine the other day about the differences between 6.5x55 and 6.5x284. The thing we were talking about was barrel life between the two. Let's assume the same bullet/velocity which from what I've read 140 grn at 2950 fps should be reasonable. So the same bullet/velocity out of two different calibers. How does the barrel life compare?

The 284 is generally considered to be a "burner" while the swede has a pretty good reputation for good barrel life. I don't have first hand experience with either of these calibers and I'm trying to decide between them for my first bolt action 6.5. If the swede still has better barrel life, how and why? What are all the factors contributing to that?

Thanks for your help

 

[Terry]

To obtain the same velocity you need similar energy. In your example barrel ware should be similar. The reason the reputation differs on these two is that the 6.5-284 is usually loaded hot, and the Swede is loaded much milder.

 

[ocp]

Alright that makes sense to me. So, all things being equal there, why would you pick one caliber over another? Obviously everyone has a different opinion about these calibers, but what would be your argument to pick one caliber of the other?

 

[Terry]

The Swede is made for 2,700 with 140's.

 

[Toolbreaker]

Alright that makes sense to me. So, all things being equal there, why would you pick one caliber over another? Obviously everyone has a different opinion about these calibers, but what would be your argument to pick one caliber of the other?

The Swede's body taper is greater, and the shoulder angles are less than that of the 6.5x284, so brass growth may need tending to more often on the Swede (given equal pressures). Magazine feeding may be easier with the Swede for the same reason, though. The Swede does have a longer case neck, but only slightly at +.043". Both offer great brass to work with from Lapua, Norma, ect. Although you didn't state a barrel length, if you're wanting to lean on 3000 fps, I think I'd opt for the 6.5x284 though. It has slightly more case capacity, so pressures can be run lower for the same velocities.

As far as barrel life, I think Terry got it. I'd doubt you could differentiate between the two if running at the same velocities.

 

[ocp]

Thanks for the replies, that helps out a bunch in trying to understand this.

 

[Marksman63]

http://www.accurateshooter.com/technical-articles/excel-formula-predicts-useful-barrel-life/

 

[keith.herrington@aol.com]

Two factors not discussed thus far: powder quantity and how hot the powder burns. When Ackley first started looking at his larger capacity "Improved" cases he and others discovered that the barrel life was shorter, they believed due to more powder being burned, but also to get the best performance they were pushed to their design capacity. Since the 284 has about the same capacity as a 30'06, somewhat more than the 6.5X55 case is designed to hold, popular loads often have much more powder than did a comparable 6.5X55.

Second, the temp at which various powders burn is an important factor. Varget has a rep for shorter barrel life due to the higher temperature at which it burns.

Keith

 

[357Mag]

OCP -

Howdy!

" Expansion Ratio " is a method of comparing various chamberings. This is a comparison of total "volumne " of the gun ( chamber + bore ). Those cases that are headed towards the " over-bore "
capacity end of the spectrum, are those that have lower & lower Expansion Ratio numbers.

For a given calibre and barrel length, the way to change Expansion Ratio is - change chamber volumne.

For a given calibre and chamber volumne, the way to change Expansion Ratio is - change barrel length.

To match a notional 6.5 X 55 rifle's Expansion Ratio when intending to shoot a 6.5 X .284 rifle; it could be done by going w/ a longer barrel length on the latter rifle.


With regards,
357Mag