Case size and barrel wear

[Tim N]

Hi All,
If I load a 6.5 284 to 260 velocities is there any reason the 284 would wear a barrel quicker than the 260?

[John Smith]

Hi Tim, given that logic cannot always be applied in a linear fashion , particularly in terms of heat and pressure, in about 900 rounds you should know and then I would love you to share the result

John

[AlanF]

Tim,

I would guess slightly more throat erosion in the bigger case because more powder would be required to get the same velocity, but all the same a big improvement on typical 6.5-284 barrel life, plus longer case life.

Alan

[DaveMc]

Short answer yes!
As Alan said - a lot more powder to give out same energy. That extra powder is transformed into waste (heat) energy and goes mostly into throat erosion.
I ran a few 6.5*284's and tried to get longer club barrel life out of them. 800-1200 rounds for me.

You will get better barrel life but not the same as a smaller case doing same velocity.

[Tim N]

Thanks for the info

[macguru]

The barrel life is clearly a function of case capacity vs throat surface area. If you have two 6mms , say, with similar throat areas and one is burning 30g of powder, and the other 45gr , then the smaller case will give you a longer barrel life, since barrels wear from the throat forwards. Slower powders will reduce this effect a little bit, but there is no way to get a 243 ackley to last like a 6br. (even though 50% more powder only gets you 15% more velocity !)

Of course, as calibre increases the area of the throat increases and wear decreases, so a 284 will outlast a 6.5/284....

[bruce moulds]

2217 (h1000) has been known to be a low calorific powder.
flame temp is one of the things that erodes throats, so keeping temps down helps.
low pressures reduce temp as well, hence 2217 could offer a double whammie benefit in this case.
the question is whether or not the extra powder offers extra shotblasting to the throat, thus negating the cooler burn.
this powder has offered quite reasonable barrel life in the 243 Ackley.
one problem with the 6.5/284, and the 284 is the short neck. the 260 shares this design fault.
keep safe,
bruce.

[Norm]

Bruce,

Can you explain how a long case neck helps extent barrel life. I have heard this often.

Would not a cartridge with a long neck just offer a cartridge with more space to fill with powder.

[johnk]

The theory is that the longer the neck, the more the abrading occurs there rather than in the throat, subject of course to the seating depth of the projectile. If you seat to the base of the neck, then you have the whole neck as an alternative throat; seat .030" & that's your neck length.

[bruce moulds]

hi norm,
what he said.
I acyually see it as a longer neck in conjunction with a shoulder angle that deflects burning powder and flame onto the neck internal rather than the leade/throat.
the 243 win is particularly bad in this respect as compared to the 280 Ackley.
it is reported that the 243 Ackley has better barrel life than the std 243. but I cannot prove this. I know a guy that shot a 243 Ackley for a hell of a lot of shots using 2217 powder, and this powder is used in a similar case for across the course stateside with the claim of good barrel life.
of course a bigger case capacity will always suffer lower barrel life. enter the 6.5/284. with its short neck.
as dave said, 900 to 1200 shots, and it might not even be worth rechambering. 12 barrels have told me this.
your 7/08 Ackley should give good barrel life.
that is why I prefer the suoer lr to the 260 imp. less powder, and a longer neck.
I suspect that boattails might deflect heat onto the bore surface, thus causing more erosion than flat base. can't prove this either, but the 107 sierra is believed by some to shorten barrel life. this could be other reasons, because across the course and long range br is where the story comes from, both of which involve rapid fire, also a cause of shortened barrel life.
higher pressure almost by definition involves more heat. this is where it might not be fair to compare the 6.5x47 and the 6br with large primer pocket brass. they can be and are loaded to higher pressure, because the cases can take it.
the br has been known to go through barrels above its size.
one of the many interesting subjects we consider and surmise upon.
keep safe,
bruce.

[SMITHTON]

Hi All, I have pondered on all 30 cal. cartridges and the 8x57js necked down to 30 cal. would suit me, knowing some of the shortcomings but, is there some reason I am crazy for considering it?


Darryl.

[Quick]

I think a lot has to do with choosing the correct powder for the cartridge. A fast powder in a large case will build up more pressure but will produce less volume of gases so you need pressure to help propel the projie, whereas a slow powder with a good case fill will usually produce less pressure and have greater volume of gases to propel the projie down the bore.

just my thinking on the subject. Choose the right powder for the case and you should get good barrel life and good accuracy. Also choosing an efficient cartridge to start with helps aswell too.

[johnk]

Just remember that you'll need to gear loading gear to suit, as well as that reamer. One of the reasons I opted for the 30-284 was that Wilson 6.5-284 necking dies were opened out enough to take the .30 neck & that they would do a seating die for $20 above retail for their off the shelf calibres.

[SMITHTON]

Thanks John, I will be going your way with 284x30.

Darryl.