6.5mm question

[ctam]

Hi all,

Apologies if this topic has been covered before. I would like to try the high BC 6.5mm pills in my Blaser. My choices of barrels are:

6.5x55 Swede at 22 inches
6.5-284 at 25 inches

I am shooting to 600, and want to minimize wind-drift.

However, I am worried about the short barrel life of the 6.5-284.

My question is: if I load the 6.5-284 to a moderate load (eg 140gr at 2650), wouldn't the throat wear be LESS than if I got the 6.5x55? It will use less powder, have lower pressures, and a longer barrel.

Thanks for your input.

 

[josephberry]

Re: 6.5mm question

I would go with the 6.5 284 and do exactly that. (load light) It gives the option of being able to really crank it up if need be.

 

[raptor99]

Re: 6.5mm question

I have shot the barrels out of two 6.5x284s but loved them. I also am on my 4th 260 barrel and finally last year went to a 6.5x55.

I really like the 6.5x55 for several reasons. First they are very accurate and you can load them up to near 6.5x284 velocities or you can down load them to 2600fps and get 4000+ rounds out of one. The case is big enough to use slow burning powders so you can get increased barrel life with less heat and pressure. They have enough umph to push the 139s easly where the 260s are maxed out trying to push the heavier bullets.

I now shoot the 123s in my 260s and the 139s in my 6.5x55 so I have the best of both worlds. Both guns are deadly with the above bullets and both are fairly mild loads. I have a load for the 6.5x55 that will shoot to within .5 moa of what my 6.5x284 data was but I know shooting that load will burn the barrel out just as fast in the 6.5x55 as it did in the 6.5x284s. You can't have it both ways.

 

[ctam]

Re: 6.5mm question

How long is the "sweet spot" in terms of barrel length for 6.5x55 ?

 

[polish handgunner]

Re: 6.5mm question

I would go for the 6.5 x 55. You'll get more bangs for your $$$.

 

[Greg Langelius *]

Re: 6.5mm question

When evaluating cartridges and seeking items of comparison that might have a bearing on throat life, I look at the neck lengths. The longer they are, the more I like them.

You can download any cartridge, but you can't change the neck length.

Sweet spots and barrel lengths?

I think the greater the case capacity the more length it can use to advantage. I think that running bullets beyond a certain velocity (IMHO around 2900fps) has drawbacks, possibly related to copper fouling and bullet deformation. I think that barrel length can be used to generate velocities at lower temps and pressures, leading to extended throat life.

I run a .260 at 28", launching 142SMK's at about 2800fps, which some might consider a conservative velocity. I hope so. It's fast enough, it's accurate, and it's not turning the throat area into an all-out blast furnace. I think the Swede was originally barreled at around 29-30" and that the 6.5-284 competes very well at 30".

Greg

 

[ctam]

Re: 6.5mm question

Thanks Greg. Why is the neck length related to throat wear?

 

[Greg Langelius *]

Re: 6.5mm question

It's kinda engineering, but basically, when the powder kernels turn the corner from the shoulder into the neck, it's kinda like a sandblaster stream. it takes a few diameters to straighten out and flow less erosively.

Maybe more importantly, combustion is taking place and the temperatures get concentrated at the choke points. It is the extreme temperature cycles that checker the throat and cause its failure.

Part of the path is the case neck, the rest of it is the bore throat. The case neck is replaceable, the throat isn't; so the more of that path you can occupy with case neck, the better.

Greg

 

[ctam]

Re: 6.5mm question

Makes sense! How long is a short, or long, neck?

 

[skeetlee]

Re: 6.5mm question

260AI Thats what i want!! Lee

 

[hhowe]

Re: 6.5mm question

I have a 6.5 with a .294 neck. I have more than 3000 rounds through it. I took it to the range just to shoot it at 100 yards, shot a 4 shot group measuring .19" I have been told that the 6.5's are barrel burners, but haven't seen it yet.

 

[NY700]

Re: 6.5mm question

With groups like that who cares!what caliber? How many fps are you shoorting at. A light load will extend life. What barrel are you shooting. Keep shooting till your groups are shot then cut a couple inches off and rethroat it and keep on going.

 

[Greg Langelius *]

Re: 6.5mm question

How long is long? Short?

Sounds like an H2IK issue (H2IK = Hell If I Know). Longer is longer than shorter, I guess...

Greg

 

[bohem]

Re: 6.5mm question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">How long is long? Short?

Sounds like an H2IK issue (H2IK = Hell If I Know). Longer is longer than shorter, I guess...

Greg </div></div>

Generally "Long" seems to be referenced as at least 1.5 calibers in length. Short is 1 caliber or less.

The neck length on the 30-06 is "long" and so is the 6BR or 6Rem, but look at the neck length on the 243 Win, that's short.

To add to Greg's discussion on neck length, look at the relative barrel lives of the 6Rem vs. the 243 Win. The 6Rem *should* be a barrel torching monster if just powder capacity is considered, the life should be akin to a 6.5-284 but it's really more like a well treated 223.

 

[Hummer]

Re: 6.5mm question

Greg is right which is why I developed several cartridges. First is a 300 Confederate Sharpshooter. It is a 300 Savage reamer run in further and then neck formed with a 30.06 chamber reamer and you fireform 308 cases.
The other design is a 306 Confederate Sabre. 303 Brit case blown out to 30.06 shoulder,neck and throat. Made by taking a 30.06 reamer and having it reduced to .454 on the base. Gives three more grains capacity and now headspaces on shoulder instead of neck. Increases case life of 303 cases as well.