6gt or 6creed

[Durdy1]

I have custom built defiance classic action with a 308 proof carbon 16.5 inch.I don’t shoot it enough. I am looking into 6mm and came up with the GT or the creed. This will be used for a dual purpose of precision/long range planking and also hunting white tail, mule deer, and may be an elk. I would like to keep a shorter 18 inch barrel. I like the speed of the Creedmoor however I do not want to be changing out barrels every 12 to 1500 rounds. I’m leaning towards a GT for the barrel life. I have thought about going to the 6 ARC, however if I just re-barrel my defiance action I could get into the six GT or Creedmoor without having to buy a new action for the arc. I have a s6 ARC 18 inch gas gun right now which is getting about 2560 ft./s out of 105 hybrids. Thanks for you insight.

 

[nm.otter]

GT is a very efficient cartridge and uses SRP. Limited factory ammo, though.

 

[TaperPin]

A 243 is good for 2500 to 3000 rounds.

 

[Rock’N Tacos]

A 243 is good for 2500 to 3500 rounds.

Would a 6CM be much worse?

 

[Marbles]

I recently went through the same question and settled on a 6 Creedmoor as I'm certain I can get the velocity I want from the creed without running hot.

While I reload, and rarely shoot factory ammo, the creed has better brass availability and better factory ammo availability.

Better availability of load data as well.

The 6 GT is less overbore and will burn less powder to get the same velocity. So, if it will do what you want, then you will get better barrel life from it. Plus even using the Gay Tiger brass, the 6 GT is less gay than anything with the Creedmoor name.

 

[TaperPin]

Would a 6CM be much worse?

Depends on what powder it’s loaded with and rate of fire. Everyone seems to try and make it something it’s not and use the hottest burning powders to max velocities and shoot it rapid fire like they are in a video game, so it doesn’t surprise me to read many replace competition barrels at the 2,000 round mark for best accuracy. Guys who are more careful with barrel heat, load lower temp powders like 4350, and keep pressures in a normal range are probably getting the same life as the 243 since the capacities are so similar. If someone is a reloader with a custom barrel there’s no advantage to the creedmoor and plenty of them that don’t feed reliably or get clickers from the straighter case.

I did edit my original post to say 2500 to 3000 rounds. 3500 is only doable if you start with an accurate barrel and don’t mind groups getting large, or midway through it’s life a few threads are cut off the barrel to set back a little and a little off the muzzle. Barrel wear and accuracy is on a continuum and even at 3000 rounds neither will have peak accuracy.

 

[nm.otter]

getting the same life as the 243 since the capacities are so similar.

FWIW, 6mm Creedmoor actually has 6% less case capacity than .243 Winchester.

 

[bpitcher]

How many barrels have you burned out? Not that it isn't a legitimate concern for some, but the vast majority of hunters will never shoot out a barrel (even if they should).

I went with the 6CM for the short barrel performance, component and factory ammo availability.

 

[Durdy1]

I have not burned out a barrel yet especially in 223 form as I have four different ones to shoot. But I can see myself getting into this 6mm a lot more and enjoying it. I enjoy shooting my six arc but wish I had just a little bit more performance. I will hand load all of my own.

 

[nm.otter]

I enjoy shooting my six arc but wish I had just a little bit more performance.

6mm GT is that:


Ratio column is case capacity in cubic inches divided by the square of the bore diameter in inches. It's a dimensionless number which can also be derived from ml and mm.

6mm GT ratio matches that of 6.5mm Creedmoor
6mm Creedmoor ratio lies between (and very close to) those of .270 Winchester and .280 AI.

 

[RyanT26]

If you can afford the ammo to actually shoot out a barrel, you should be good buying a second barrel.

 

[khuber84]

I have not burned out a barrel yet especially in 223 form as I have four different ones to shoot. But I can see myself getting into this 6mm a lot more and enjoying it. I enjoy shooting my six arc but wish I had just a little bit more performance. I will hand load all of my own.

6arc is like 33gr
6br,bra, brx, dasher are 38-41gr in that order
6gt is 44
6x47 is 49
6xc is 50
6Creed is 52

6 dasher loaded hot will do what a medium/lower psi 6gt will do, plus the gt feeds easier in my experience and general heresay. I had zero issues getting a 6br and 6bra to feed reliably either tho.

If a short-ish barrel is your plan, pick a case with decent capacity to start, so you're not running the ragged edge to get the mv you desire.

 

[TaperPin]

FWIW, 6mm Creedmoor actually has 7% less case capacity than .243 Winchester.

I haven’t checked for myself, but what Nosler publishes shows 6 creed with 49.1 gr of water and 243 as 50 gr. That .9 gr is 1.8%

If you add in the extra stick out to the bullet in the creed, which is freeing up combustion/powder space, the effective difference is even less.

The SAAMI pressure for the creed is 62k psi and 60k for the 243 so factory and reloading data sticks to those when developing maximum loads, but the brass has the same pressure capacity in either, so it’s one of the ways Hornady has pulled the wool over people’s eyes to make the creed look better than it is.

 

[nm.otter]

I haven’t checked for myself, but what Nosler publishes shows 6 creed with 49.1 gr of water and 243 as 50 gr. That .9 gr is 1.8%

Those capacity figures are calculated from case geometry, and do not include the neck.

 

[khuber84]

Lapua 6cm srp brass is 51.8gr water to slightest bubble atop neck.

 

[Coleredding00]

I settled on 20” 6gt. But i also have the brass and dies already, and plan to share ammo with my match rifle.

The realistic difference is about 100 fps with the same length barrel. If your max effective range isn’t far enough for expansion velocity to be an issue, i see no downsides to 6gt.

 

[dsotm]

6GT if you reload

 

[TaperPin]

Those capacity figures are calculated from case geometry, and do not include the neck.

Ok. I don’t think any of it really matters other than on paper.

The 6mm craze has sold a lot of rifles by marketing them as the latest greatest, but I have yet to find any use for most of them other than guys have something new to talk about. I do have a number of 6br barrels for varmints because they can hold up better to high volume shooting, but for 99.99% of the shooting public the 243 is all they need. To be honest, a couple of the br barrels will eventually get rechambered to either 243 or 6-06.

 

[wind gypsy]

I haven’t checked for myself, but what Nosler publishes shows 6 creed with 49.1 gr of water and 243 as 50 gr. That .9 gr is 1.8%

If you add in the extra stick out to the bullet in the creed, which is freeing up combustion/powder space, the effective difference is even less.

The SAAMI pressure for the creed is 62k psi and 60k for the 243 so factory and reloading data sticks to those when developing maximum loads, but the brass has the same pressure capacity in either, so it’s one of the ways Hornady has pulled the wool over people’s eyes to make the creed look better than it is.

Nosler's capacity in their load data is "useable capacity" based upon a certain bullet seated to a certain depth so not always a great representation. In this case, the difference between the two cartridges with the #'s you listed is probably pretty representative.

This hornady "pulling the wool over" because they designed a cartridge with a 62k SAAMI max pressure is silly though. Did winchester "pull the wool over peoples eyes" 100 years ago because the 270 win had a 65k PSI max pressure?

In the case of basically all of the creedmoors, hornady was dragged to them by enthusiasts who were wildcatting them as alternatives to existing 260, 243, etc already.

 

[pathnz]

I went GT and have no regrets. 18 inch, 105-108-109 @ 2750-2800 with book loads of varget/h4350. Have shot deer to 630+ metres, very mild. Maybe 1400-1500 rounds on the barrel now, most of them in 10rd strings and still shooting the same as new