.243 vs 6mmm barrel life??

[Homerange]

Because they do not offer it, and he is willing to pay for quality brass. If you have a source for 7x57 brass that is of adequate quality for your purpose, I see no reason for not using it.
http://www.lapua.com/en/reloading-components/cases.html

Thanks, that clears that up. Yep we have little problem getting 7x57 brass here in NZ whereas 6mm Rem is quite hard to get without waiting for months for special orders.
I might even have a scrounge in my range brass bin for 7x57 and have a play with some.

 

[onelastshot]

I've got a 6mm Remington as well as a 6mmAI. The 6mm Remington has a definite edge for reloaders, especially the 6mmAI. The barrel life of both the 243 and 6mm are very similar; the key in barrel life lends to choice in slower burning powders and shooting discipline; shooting at a slower rate, allowing the barrel to cool between shots is critical to overall barrel life.

 

[TAJ45]

I've got a 6mm Remington as well as a 6mmAI. The 6mm Remington has a definite edge for reloaders, especially the 6mmAI. The barrel life of both the 243 and 6mm are very similar; the key in barrel life lends to choice in slower burning powders and shooting discipline; shooting at a slower rate, allowing the barrel to cool between shots is critical to overall barrel life.

And if there is anything to the Turbulence Point/Throat Wear theory, the edge goes to the 6 REM that has sharper shoulder as well as longer neck.

 

[mikegaiz]

Everyone thinks that their gun, what ever it is, is the best. So just shoot it and the heck with everyone's opinion, we all have them. They are both barrel burners. Some of the new cases designs will give you the same performance and greater barrel life. Isn't science wonderful. So shoot what you have and plan for the future build. However to open another can of worms, if you want your 243, or 6mm to last longer? Shoot molly bullets and use ball powder like H380. This is the truth, I have a 243 with a Hart Barrel with over 6000 rounds through it and it will shoot under an inch at 100 yds. It has only shot molly bullets and H380 powder. It is worn but still shoots. And that is a fact, For what that is worth.

 

[Brians356]

Because they do not offer it, and he is willing to pay for quality brass. If you have a source for 7x57 brass that is of adequate quality for your purpose, I see no reason for not using it.
http://www.lapua.com/en/reloading-components/cases.html

I've read on this forum and elsewhere that the available Prvi Partisan 7x57mm brass is pretty good, and the price is certainly reasonable.

I played with forming 6mm Rem from both 257 Roberts and 7x57mm. From my notes, the neck wall thickness increased about .0008" from 257 Rob and about .0018" from 7x57mm. I agree there is a benefit derived from neck turning the parent case rather than the formed 6mm Rem.
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[Brians356]

Some of the new cases designs will give you the same performance and greater barrel life. Isn't science wonderful.

Got an example (in 6mm)? One you might have in mind is 243 WSSM, but it burns the same amount of powder in equalling the 6mm Rem. I would like to see reliable data from 6-Creedmoor, but I don't know of any just yet.

if you want your 243, or 6mm to last longer? Shoot molly bullets and use ball powder like H380.

Two overachieving spherical powders are CFE 223 and Superformance. However, do not try CFE in 6mm Rem, it is unstable for some reason, even though it works great in both 243 Win and 243 WSSM (which otherwise is the 6mm Rem's ballistic twin.)
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[Homerange]

I've read on this forum and elsewhere that the available Prvi Partisan 7x57mm brass is pretty good, and the price is certainly reasonable.

I played with forming 6mm Rem from both 257 Roberts and 7x57mm. From my notes, the neck wall thickness increased about .0008" from 257 Rob and about .0018" from 7x57mm. I agree there is a benefit derived from neck turning the parent case rather than the formed 6mm Rem.
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It might seem neither will be a problem if one is neck sizing only.

 

[Brians356]

It might seem neither will be a problem if one is neck sizing only.

No problem if FL sizing. That way forms the shoulder to neck transition good and proper.

For my part, I ran the 7x57mm through a 257 Roberts FL die first, then through the 6mm Rem FL die.
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[Brians356]

Off the top of my head, Dasher, 6x47 Lapua, 6 Creedmore, 6 grendel

Same top velocity as 6mm Rem, when loaded to equal pressure? Huh.
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[Brians356]

Not exactly same but close,the 6 XC is the closest, ...

Fair enough, but "close" isn't "the same performance". There still ain't no free lunch.

PS I've corrected an earlier post, I get 3800 fps (not 3500) for the 70-gr TNT using Superformance, from a 24-in barrel 6mm Rem. Yikes!
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[Brians356]

Will it hold under a under a minute at 300 to 600 yds?

Irrelevant. You should keep in mind, I only engaged you regarding your implication that newer, smaller cartridges provide the same performance, science being wonderful.
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[Brians356]

My last reply. What good is a gun/case that does not hit what you are aiming at?

Again, you insist on lurching to a new topic, hoping no one notices? I called you on the performance fallacy, you admitted "close" and got no cigar. Now you're trying to turn lemons into lemonade. Probably wise of you to retreat.
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[Brians356]

Quae in speculo resplendent vultus
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[ImBIllT]

Folks once claimed that neck length and shoulder angle impacted throat life in addition to powder charge. I haven't shot enough cartridges that were close in capacity but different in shape to have any personal experience, but I've heard multiple claims that the 6mm Remington did tend to have a longer barrel life than the .243 Win. I've also heard that unburned powder eroded throats as well. That would suggest that smaller powder charges of faster burning powder would increase throat life. Again, I can't confirm it. While there are certainly loads for large cartridges using fast burning powders and sacrificing 200-400fps, I've never seen much reason to use them. Anytime I had a barrel burner, it was because I wanted that extra velocity. Why push a 40gr bullet at 3500fps with a 22-250 when you could do it with less powder and more barrel life from a .222 or .223? Anyway, I've always heard that reduced loads could increase barrel life, but I never saw the point.

Not to mention, barrel life is relative. You can shoot 1" at 100yds with a fairly trashy barrel. There's a fair difference between barrel life of a bench gun, barrel life of an F-class gun, barrel life of an NRA high-power gun, and barrel life of a hunting gun. At longer the range, with a less supported the shooter, and a larger target, it becomes much more the Indian and much less the arrow.

 

[Webster]

And if there is anything to the Turbulence Point/Throat Wear theory, the edge goes to the 6 REM that has sharper shoulder as well as longer neck.

I don't think anyone ever proved the turbulence theory. It was made up without any facts to back it up. Nobody that creates an AI case worries about bore life, you just keep buying more barrels. I shot a 6mm Rem for about 30 years at GH. 3 barrels. About 7000 rounds down each barrel. Before 1000 shots the barrel surface looked like alligator hide. They still shot 1" groups. I sectioned every barrel I ever owned lengthwise at work and examined them. After about 7000 shots there was no rifling for about 6", so I had about 6" of free bore. Still good enough to kill GH to 300 yards or more.

 

[Homerange]

I don't think anyone ever proved the turbulence theory. It was made up without any facts to back it up. Nobody that creates an AI case worries about bore life, you just keep buying more barrels. I shot a 6mm Rem for about 30 years at GH. 3 barrels. About 7000 rounds down each barrel. Before 1000 shots the barrel surface looked like alligator hide. They still shot 1" groups. I sectioned every barrel I ever owned lengthwise at work and examined them. After about 7000 shots there was no rifling for about 6", so I had about 6" of free bore. Still good enough to kill GH to 300 yards or more.

Thanks for this.
Can I ask of the powder used and targeted velocities, guessing they were handloads.
30 yrs back is a bit of an ask I know and if you can't remember no worries.

 

[ImBIllT]

Webster-I have a Marlin model 322 in .222 Rem that won't spin a cleaning rod for close to half the barrel length. Last time I put it on paper it shot a five shot group about a half inch. I believe that a good barrel will outshoot a bad barrel well past the barrel's prime. Obviously neither of us is talking about serious benchrest accuracy, but it definitely points to just not being too worried about barrel life outside of competition. Would I build a 6mm Rem for competition? No. There are numerous cartridges whose disadvantages are negligible, when shooting at known distances with wind flags, that will far outlast it and do so at a lower cost. For purposes other than paper punching on the other hand, it should be a dandy little cartridge. If I had one, I would make good use of it.

 

[Brians356]

Webster-I have a Marlin model 322 in .222 Rem that won't spin a cleaning rod for close to half the barrel length.

That 322, if produced after 1955, has Microgroove Rifling, cut 0.001" deep in 22-cal barrels.
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[ImBIllT]

I know the thread is about barrel life, but another reason to choose one over the other is action length. A 6mm Rem is a little long for a Remington 700 SA, but it makes a wonderful re-barrel option for old Mauser actions. It usually feeds with little to no alteration, with a .308 length cartridge often causes feeding problems on the old Mausers unless you know how to alter them. The 8x57 is an excellent big game cartridge but with limited bullet options and the lack of a flat trajectory, the 7x57, 257 Roberts, and 6mm Remington are very attractive alternatives for those actions.

 

[ImBIllT]

That 322, if produced after 1955, has Microgroove Rifling, cut 0.001" deep in 22-cal barrels.
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That it does, but it spun the cleaning rod when I got it. It also won't stabilize a 60gr flat base despite its supposed 12 twist. I wish I could buy ten more. It's one of my favorite firearms. No doubt the heavy barreled Sako's would be just as lovely. The barrel thickness is just right...more than a sporter, less than a Rem 700 varmint taper.