6 Creedmoor vs .243 AI

Ive been doing some research, and isn't a 6 creedmoor really just a 243 AI? I mean slight differences in catridge base to neck measurements im sure but to me, they are practically the same round. As far as Im concerned, making a 6 Creedmoor is a marketing gimmick designed to catch a larger fan base than calling it 243 would do.

-243=6mm.

-.243 and 6 Creedmoor parent case is .308 if you make your own.

Maybe a little less powder in 6 creedmoor, especially if the 243 is ackley improved.


Main reason I ask is I wouldn't mind having just one more barrel for my savage action before I wait a while and go to a custom magnum action for a 338 LM or something in that category. Would love to start doing a little competitive shooting and I dont want to burn my 7mm SS barrel I have coming out, but I dont want to deal with the 308 barrel either when trying to touch 1000 yards +

http://www.6mmar.com/Super_LR.html

Parent case for 6 Creedmoor is 6.5 Creedmoor (obviously), whose parent case is .30 TC, not .308 Win. http://www.rifleshootermag.com/ammo/...6-5-creedmoor/

I seem to recall reading (on the GAPrecision site?) that people are getting 2500-3000 rounds from 6mm Creedmoor barrels, while 800-1500 or so seems to be the expected life of a 243 AI barrel.

The Creedmoor case is a bit shorter than 243 - you can load heavier bullets seated longer with the Creedmoor case and still fit in a 308 magazine.

Gotta go with those above. Creedmore is hornady's baby and brass is pretty readily available. I have shot a lot of .243, but you don't see many .243 uppers being built because of the longer case. 6cm is gaining steam as a great mag fed, repeater compatible short action cartridge. That means it can accept the long bullets and still fit in a stander short action, along with feed well out of a magazine. I looked into 6.5 cm pretty hard, but just couldn't bring myself to jump on a case where Hornady is the leading producer of brass. I do not know much about forming brass from .308 or .243, but it seems pretty labor intensive with the long neck and sharp shoulder. It's not a simple size and trim.

AI is also typically a 40* shoulder, correct? The Creed is a 30* shoulder, which should mag feed a little more reliably.

All points made above are good. The primary purpose of the 6 Creed was again for mag length restrictions. The 6mm battle is the same as the 6.5 battle between the 260, Creedmoor, and Lapua variants. They all do about the same, but the cases with the 30* shoulder have a few advantages.

The 243ai will get about 200fps more than the others due to increased case capacity, but the 40* shoulder is known to not feed as reliably.

As for barrel life most guys are swapping barrels at 1500rds in any of these variants for serious competition as they are seeing the lands wear done a few thousanths every 100rds through the barrel.

I shoot the plain old 243 with 105 AMAXs vice the 105Hybrid. With 41.3grs of H4350 I'm driving them to 3025fps and haven't adjusted my load in any way in 800rds. The Bergers seem to be a bit more jump sensitive.

Might think about the 6mmXC as well. Same basic thing as the 6 Creed but able to be pushed a bit harder. The one I put together for a buddy of mine was literally the easiest cartridge to load for. every load we tried printed half inch or less five shot groups at 100 yards. I think we ended up at 41 grains of H4350 and pushing the 105 Hybrids right around the 3150 mark out of a 26" barrel.

Nothing wrong with a standard .243. Started shooting one in matches in 2005 and had no problem fitting them in AICS mags with 115s. I still have a .243 in the safe and shoot the Hornady 105 BTHP and loaded .020" off the lands they are only 2.810" OAL. Get them at 3080fps with 42.6grns of H4350.

My main match rifle is a 6.5 Creedmoor so I have plenty of brass to make 6mm Creedmoor so my next 6mm barrel will be a 6mm Creedmoor as I have a lot of friends who shoot it and really like it. It will allow you to get a slightly shorter OAL and good velocities with 105+ weight bullets.

Either 6mm is a good choice for long range shooting when paired with a proper twisted barrel for the bullets used.

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Originally Posted by LoneWolf

As for barrel life most guys are swapping barrels at 1500rds in any of these variants for serious competition as they are seeing the lands wear done a few thousanths every 100rds through the barrel.

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Most barrels have lands of approximately. 004 to .005 tall, I doubt it is the lands being wore down but the throat being eroded. This is why you can set back a barrel 1.5" and rechamber it.

Great info. Thank you.

For the record, reason I was thinking 308 is a parent case is because you can make 6.5 creedmoor from it. Doesn't mean its parent case though. Takes a lot of annealing to bump that shoulder back so far.

I would also need to consider if it will work in an AR10. I plan on building one maybe next year late summer or winter. Ive been looking at 6.5 creedmoor but Ive heard 6mm has no recoil and extremely accurate. So if I have one chambered in my bolt gun, I might as well save pennies and use the same caliber for the AR so everything is already there for reloading.

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Originally Posted by lrshooting

Great info. Thank you.

For the record, reason I was thinking 308 is a parent case is because you can make 6.5 creedmoor from it. Doesn't mean its parent case though. Takes a lot of annealing to bump that shoulder back so far.

I would also need to consider if it will work in an AR10. I plan on building one maybe next year late summer or winter. Ive been looking at 6.5 creedmoor but Ive heard 6mm has no recoil and extremely accurate. So if I have one chambered in my bolt gun, I might as well save pennies and use the same caliber for the AR so everything is already there for reloading.

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They say the parent case is the 30 T/C but the 30 T/C parent case is 22-250. You can neck up the 22-250 case to 6.5 and load a low end powder charge to pop the shoulder forward. The case will be about .010 short from standard length but if you look in the Hornady manual it comes out to the "trim to" length in the book.

Or you can just buy 6.5 or 6mm Creedmoor brass and make your life easier ;) Forming Creedmoor brass from .308 is a major pain in the ass.

Lrshooting, the 6.5 Creedmoor is also very accurate but there will be less recoil with the 6mm just because it's a lighter bullet than the 140s in the 6.5. With a brake neither are heavy recoiling rifles. Pick the one you want and go with it.

What Lone Wolf said. +1

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you can just buy 6.5 or 6mm Creedmoor brass and make your life easier ;) Forming Creedmoor brass from .308 is a major pain in the ass.

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The 308 to 6.5 or 6mm Creedmoor makes no sense at all. Have built three Creedmoor's and never had a problem with the Hornady brass.

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Originally Posted by Josh

Most barrels have lands of approximately. 004 to .005 tall, I doubt it is the lands being wore down but the throat being eroded. This is why you can set back a barrel 1.5" and rechamber it.

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I did mean throat erosion. Thanks for the correction. If brass is your concern then you can always build a 6x47 Lapua. This would be my choice if I started a 6mm build from scratch, but I haven't had any issues with that Hornady 243 brass either....

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Originally Posted by LoneWolf

I did mean throat erosion. Thanks for the correction. If brass is your concern then you can always build a 6x47 Lapua. This would be my choice if I started a 6mm build from scratch, but I haven't had any issues with that Hornady 243 brass either....

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I have always been interested in the 6x47, isn't it the 222 Remington Magnum necked up?

Different 6x47. I'm referring to the Lapua variant 6-6.5x47 Lapua.