I'll throw in my .02. Most of what is in here I agree with the exception of barrel life. I do not claim to be any expert but I can tell you these statements as fact as I do shoot some PRS events.. I was too under the presumption of better barrel life with a 6.5mm flavor over the 6mm but that seems in large part to be a myth. I am currently on my second .260 Rem barrel. My first one started to go south at about 1700 rounds. I pulled it at about 2300. The gun was still accurate but the speed had dropped 100 fps which was causing me to need a lot more elevation at the longer ranges. All of this was with mild load of 42.0gr of H4350 and new the barrel was pushing a 139 Scenar at 2780fps. Mild by all standards, and with my second barrel I am running 42.3 grains and running 2820 fps. Other team members have had similar experience with the .260 with barrels starting to go south at about 1700 rounds so this is not a one off case. That is with both Kreiger and Bartlein's.
As far as the 6mm a competitor just had a podium finish with IIRC 2800 rounds on a 6CM. And most of the GAP guys are getting about 2700 rounds on a barrel so really the barrel life argument seems to be mute and arguably backwards.
IMO this is the break down between the 2 bullet choices. 6.5 you have a little more recoil but you have a bigger splash on the target or the berm to spot your shots but at the expense of more recoil which could cause you to move off target if you have poor recoil management. It has more drop than the 6mm but if you are shooting at a KD target then who cares as long as you know what to dial. The only time the "flatter" 6mm will help is on UKD targets which MIGHT compromise 2 targets of the entire course of fire at the matches I have been to. Most matches just have 1 target and several have not had any. The 6.5mm at 1K have about 10% greater wind deflection than the 6mm.
The 6mm, it is faster, much flatter at distance and has about a 10% better wind deflection at 1K yards. The barrel life is the same or better when compared to the .260's that I have seen. The recoil is slightly less but you give up that larger impact signature of the larger 6.5mm bullets which can at times cause a spotter to not give you a hit call if it burns the edge or if you hit reactive targets near the hinge may cause them to not fall. I also heard a lot of guys saying how they had to keep chasing the load all the time in the 6mm where in a 6.5 you could find the load and shoot that until the barrel burned out. Well with the hybrids in the 6mm that seems to be a thing of the past. A very competitive shooter running a 6CM told me he finds the load then loads up 2K of them and runs the heck out of it with 105 Berger hybrids. I have shot one of the 3 guns he has in this caliber and shot about a 4" group at 840 yards with it so I'd say it works well enough for this game.
6.5mm Calibers
260: Best case capacity of all the rounds which in theory should give the best MV. Great Lapua Brass available and you can make brass from .308, 7mm-08, .243 if times get tuff.
6.5CM: The obvious choice IMO if you do not reload as the 140 AMAX loaded ammo from Hornady is reasonably priced when you can find it and even though it has slightly less case capacity many times you can get better MV than you will from a .260. A team guy swapped from .260 to 6.5CM and his MV's went up. The drawback is only having one source of head stamped brass.
6.5x47L: The slowest of the 3 but again great brass available from Lapua. It has a small primer which in turn stays very tight. I have heard of guys getting a ridiculous amount of reloads out of them due to the small primer pocket staying tight. Like 25+ but you will usually lose it by then at tactical matches. You will be slightly handicapped due to speed but not by much and certainly one to entertain.
6mm
.243Win: The old faithful of the 6mm's but running the heavy for caliber projectiles and running them in AI mags you can run out of room and have to seat the bullet deeper in the case which eats up the case capacity and in turn velocity.
6mm Creedmoor: A great round that has the horsepower to get to the PRS speed limit of 3150fps. Some guys are running about 3080 in a good accuracy node but it is close to the limit. Also some matches state 3100 fps as the limit so you are good no matter where you go. The down side is that GA is the only source I know of for head stamped brass. They had a big shipment come in but it is almost all gone and they are not expecting more until Q2 2014 and who knows when they will actually get it.
6XC: A round that has exceptional accuracy with slightly less horsepower than the above. You can not get to the speed limit but this caliber has produced some great accuracy in the bench rest ranks. The down side to it as well is that brass can be hard to find but I think there are more than one source producing it. I am going off of memory and may be wrong so don’t hold me to it but I think Norma and Nosler make it.
In summary either a 6mm or 6.5mm will serve you well. If you go 6.5mm and don’t reload I think the 6.5CM is the winner. If you do then I chose .260. For a 6mm I would and actually am going 6CM on my next build. You can get the bullets up to the speed limit but just make sure you get some brass NOW. The 2 major concerns I had heard about the 6mm's was the barrel life was about 1200 rounds. Well that doesn't seem to be the case at all. And the second was that you had to constantly change your load by chasing the lands. Well with the hybrids this does not seem to be the case either.
I agree that the .308 is just handicapping yourself but trying to pick apart the 6mm vs 6.5mm is in large part spinning wheels. At the end of the day it is the nut behind the bolt. Make a choice and go with it, I promise if you like the game you are going to try another flavor down the road no matter what you choose. But with any of the above choices you will not be handicapped by caliber.
And whatever you do, do not make it a Barbie barrel 18" - 20" rifle. 24" is the shortest I would go. There are too many guys on here jerking off about how fast my short barrel rifle can go. Well I tell you what podna it would have been faster with more barrel length PERIOD! The short barrels have there place, especially for a dedicated suppressed weapon, but a short barrel is not advantageous in this game. 26" is pretty common.
