6x6.8 Barrel Length

[patriot]

Hello everyone, this is my first post here, but I've been lurking for a while now. I'm looking to build a 6x6.8 and want others opinions on the cartridge. My ambitions with the rifle include long range deer hunting, light varmint work and the occasional F-Class match. I would like to keep the rifle fairly light, keeping in mind I will be shooting a match every once in a while. I would like to keep my barrel length between 18" and 22". This leads me to my first question: What velocities can I expect of an 18" barrel using 87gr and 95gr bullets? What twist rate should I be using with these bullets? What gas system length would be optimum with those barrel lengths using a rifle buffer? Do I need an adjustable gas block for reliable function? Which bullets are recommended on deer sized game at 500yds and less? Thanks in advance for the advice, I can't wait to place my order.

[Deleted]

Sept 28, 2015 19:40:39 GMT -8 patriot said:

Hello everyone, this is my first post here, but I've been lurking for a while now. I'm looking to build a 6x6.8 and want others opinions on the cartridge. My ambitions with the rifle include long range deer hunting, light varmint work and the occasional F-Class match. I would like to keep the rifle fairly light, keeping in mind I will be shooting a match every once in a while. I would like to keep my barrel length between 18" and 22". This leads me to my first question: What velocities can I expect of an 18" barrel using 87gr and 95gr bullets? What twist rate should I be using with these bullets? What gas system length would be optimum with those barrel lengths using a rifle buffer? Do I need an adjustable gas block for reliable function? Which bullets are recommended on deer sized game at 500yds and less? Thanks in advance for the advice, I can't wait to place my order.

I'm not sure you want to go with a 6x6.8 for what your asking it to do. The 243 LBC is a better platform for the job you are intending it to do.
The 6.8 case is to long to shoot the 90 grains and up bullets. You will have to seat the bullet deep in the case just to make it fit a 2.300 magazine. The Grendel case is short and with a bigger diameter. This translates to more usable case capacity.

I guess what I'm trying to say is to shoot 87 grain bullets and lighter go with the 6x6.8 If you want to shoot the 90 grain bullets and up go with the 243 LBC.

For twist rates it will depend on the cartridge. The 243 LBC with the 95 grain target bullets is perfect with the 1 in 8 twist. The 6x6.8 is at it's best with the 1 in 9 twist, when using 87 grain bullets and lighter.

The velocity figures as well as barrel length really are the same question. You want to use this upper to shoot 500 yards, but you want to handicap it with a short barrel? Shooting that far with a short barrel will cost you 150 FPS plus, with an 18" barrel compared to a 22" barrel. With a 22" barrel shooting a 95 grain VLD or a Sierra 95 grain Match King you should be able to see 2950 FPS with the right load, from the LBC. The 87 Vmax will run a little over 3000 FPS from the 6x6.8

I always run a rifle length gas system on anything 20" and longer. If the barrel is 18" and shorter I use a mid-length gas system. This gives me total reliability. Stay clear of the 18" rifle gas unless you want to tinker, to get it to run. I also recommend using an adjustable gas block. There is no reason to over gas an upper when you have this option.

[patriot]

Sept 29, 2015 5:29:27 GMT -8 @rjohnson said:

Sept 28, 2015 19:40:39 GMT -8 patriot said:

Hello everyone, this is my first post here, but I've been lurking for a while now. I'm looking to build a 6x6.8 and want others opinions on the cartridge. My ambitions with the rifle include long range deer hunting, light varmint work and the occasional F-Class match. I would like to keep the rifle fairly light, keeping in mind I will be shooting a match every once in a while. I would like to keep my barrel length between 18" and 22". This leads me to my first question: What velocities can I expect of an 18" barrel using 87gr and 95gr bullets? What twist rate should I be using with these bullets? What gas system length would be optimum with those barrel lengths using a rifle buffer? Do I need an adjustable gas block for reliable function? Which bullets are recommended on deer sized game at 500yds and less? Thanks in advance for the advice, I can't wait to place my order.

I'm not sure you want to go with a 6x6.8 for what your asking it to do. The 243 LBC is a better platform for the job you are intending it to do.
The 6.8 case is to long to shoot the 90 grains and up bullets. You will have to seat the bullet deep in the case just to make it fit a 2.300 magazine. The Grendel case is short and with a bigger diameter. This translates to more usable case capacity.

I guess what I'm trying to say is to shoot 87 grain bullets and lighter go with the 6x6.8 If you want to shoot the 90 grain bullets and up go with the 243 LBC.

For twist rates it will depend on the cartridge. The 243 LBC with the 95 grain target bullets is perfect with the 1 in 8 twist. The 6x6.8 is at it's best with the 1 in 9 twist, when using 87 grain bullets and lighter.

The velocity figures as well as barrel length really are the same question. You want to use this upper to shoot 500 yards, but you want to handicap it with a short barrel? Shooting that far with a short barrel will cost you 150 FPS plus, with an 18" barrel compared to a 22" barrel. With a 22" barrel shooting a 95 grain VLD or a Sierra 95 grain Match King you should be able to see 2950 FPS with the right load, from the LBC. The 87 Vmax will run a little over 3000 FPS from the 6x6.8

I always run a rifle length gas system on anything 20" and longer. If the barrel is 18" and shorter I use a mid-length gas system. This gives me total reliability. Stay clear of the 18" rifle gas unless you want to tinker, to get it to run. I also recommend using an adjustable gas block. There is no reason to over gas an upper when you have this option.

Thanks for the quick response! If i have to run 90gr and less, im totally fine with that. I have a 243 bolt gun set up for the heavy bullets anyway. The reason i want a shorter barrel is for the weight savings. Ill be packing this thing around on foot a lot and would like to keep it fairly light, while maintaining enough barrel thickness to shoot it without it getting too hot in an F class or long range precision match. What kind of velocities could i expect using 75gr bullets or 87gr bullets in a 20" pipe? The reason i want to run the 6x6.8 is the availabilty and price of components. They seem to be inherently cheaper for this cartridge than the 243lbc and brass life seems to be better. Ive also read that the 243lbc can be finicky on feeding and i havent read anything like that about the 6x6.8. My main goal is the ability to kill a whitetail doe DRT at 500 with this cartridge if i do my part. Thanks in advance.

[Deleted]

Sept 29, 2015 13:44:42 GMT -8 patriot said:

Sept 29, 2015 5:29:27 GMT -8 @rjohnson said:

I'm not sure you want to go with a 6x6.8 for what your asking it to do. The 243 LBC is a better platform for the job you are intending it to do.
The 6.8 case is to long to shoot the 90 grains and up bullets. You will have to seat the bullet deep in the case just to make it fit a 2.300 magazine. The Grendel case is short and with a bigger diameter. This translates to more usable case capacity.

I guess what I'm trying to say is to shoot 87 grain bullets and lighter go with the 6x6.8 If you want to shoot the 90 grain bullets and up go with the 243 LBC.

For twist rates it will depend on the cartridge. The 243 LBC with the 95 grain target bullets is perfect with the 1 in 8 twist. The 6x6.8 is at it's best with the 1 in 9 twist, when using 87 grain bullets and lighter.

The velocity figures as well as barrel length really are the same question. You want to use this upper to shoot 500 yards, but you want to handicap it with a short barrel? Shooting that far with a short barrel will cost you 150 FPS plus, with an 18" barrel compared to a 22" barrel. With a 22" barrel shooting a 95 grain VLD or a Sierra 95 grain Match King you should be able to see 2950 FPS with the right load, from the LBC. The 87 Vmax will run a little over 3000 FPS from the 6x6.8

I always run a rifle length gas system on anything 20" and longer. If the barrel is 18" and shorter I use a mid-length gas system. This gives me total reliability. Stay clear of the 18" rifle gas unless you want to tinker, to get it to run. I also recommend using an adjustable gas block. There is no reason to over gas an upper when you have this option.

Thanks for the quick response! If i have to run 90gr and less, im totally fine with that. I have a 243 bolt gun set up for the heavy bullets anyway. The reason i want a shorter barrel is for the weight savings. Ill be packing this thing around on foot a lot and would like to keep it fairly light, while maintaining enough barrel thickness to shoot it without it getting too hot in an F class or long range precision match. What kind of velocities could i expect using 75gr bullets or 87gr bullets in a 20" pipe? The reason i want to run the 6x6.8 is the availabilty and price of components. They seem to be inherently cheaper for this cartridge than the 243lbc and brass life seems to be better. Ive also read that the 243lbc can be finicky on feeding and i havent read anything like that about the 6x6.8. My main goal is the ability to kill a whitetail doe DRT at 500 with this cartridge if i do my part. Thanks in advance.

I would go with a standard weight 20" barrel, rifle gas system with a target crown. You should be able to get around 3200 FPS with a 75 grain and 3100 with an 87 grain Vmax.

There are a few other little things that aren't quite right with your statements.
If your going to use the latest run of 6.8 brass its case life is not as long as the old SSA brass. If you figure in the cost of the brass and compare it to the Lapua 6.5 Grendel amortize it over the life of the brass it is actually cheaper to shoot the LBC.

I would argue that the 243 LBC is finicky to feed. It is in fact no more of a problem to feed than the 6.8 case. I can count the number of jams I've had on one hand. If assembled correctly it runs just like any 5.56 or 6x6.8

One other thing you should consider is, brass is the most important component in a cartridge. The ranges you intend to shoot will require your brass to be as close to perfect as possible. You will have to sort brass as well as match prep your 6.8 to get what your looking for. With the attrition rate at close to 2 to 1 the cost of your cheap 6.8 brass just doubled.

I'm not trying to put the 6.8 case down in any way. I have at least one of every caliber variant that Black Hole makes. But I do believe in using the right tool for the job, and at 500 yards the 243 LBC is a better tool.