So, now that the SBR is going to be legal in my state, I was thinking of undergoing a project with my recently purchased Six8 rifle. I'm thinking of swapping out my 16'' LWRC barrel for a Bison Armory 1:7 twist 11.5'' barrel, thus allowing me to shoot both supersonic and the 170-200 grain subsonic loads. I'm wanting to retain the piston system though and this is where things get a bit more custom.

I'm not sure if the gas block on the LWRC barrel will be an easy swap to the Bison Armory barrel and even if it is, will the piston have enough gas to cycle the piston, if using a subsonic round? It will have a suppressor attached to it constantly, either my AAC SDN6 or a Surefire Legacy 7.62, which I'm sure will help the cycling action on the subsonic round. I've already sent an email to both LWRC and Bison Armory about this setup and neither has responded to it in a few weeks now.

What says the hive mind, is this possible or am I going to be heading down a painful custom road? I've taken several pictures of measurements of parts, with the help of my friend, that I can post if people think it will help.

I'm sure there will most likely be issues with the porting and maybe other fitting issues as well. Also to my knowledge LWRC uses a special process in installing their gas blocks like heating it or either the barrel and then doing a hard press fit with a hydraulic press, or something else along the lines.

It's more complicated than just swapping out barrel lengths. The gas hole sizes will be different and have to be exact.

Plus there's some special tool for the barrel/upper interface. It's not something they will sell you.

Bare with me for asking the dumb obvious question. Couldn't you just buy a 10.5 or whatever it is complete lwrc upper?

Well, two reasons for why I'm not looking to do that.

1. I already have a LWRC Six8 in 16'' configuration. Reason I didn't get the shorter to start was my state didn't allow SBR but now we do.

2. I am looking to use the Bison Armory barrel for subsonic and supersonic round use.

I am well aware that it wouldn't be a simple plug and play swap but I figure where there is a will, there is a way. I've already taken numerous measurements on the width of the barrel and the gas journal. As far as if the gas hole isn't large enough on the bison barrel, I can always have it widened professionally. Getting the gas block off may pose to be a bit annoying but I'm sure there has to be a way to remove it.

This situation has come up a few times on another forum and general consensus is that it would be quite difficult, not impossible though.  Have you thought about talking to the guys at Modern Outfitter?  If there is anyone who can assist and definitely point you in the right direction, it is them.

Nope, hadn't thought about talking to them yet but will most definitely giving them a call. I have a bit of time till I am able to do it anyway though, as I cannot file my stamp until June. I was planning on having them do a cerakote job on my rifle as well, maybe can have them do 2 birds with one stone here.

Thanks for the suggestion!

Why not contact LWRC and ask them to do a barrel swap?  Think they use to do this, cause I was interested in getting one of my legacy M6s SBR'd and they quoted me a price.

Sent them an email a bit ago and they have yet to contact me back.

I would rather have two uppers.  One 6.8 for supersonic and one .300 for subsonic.        
 

I'm not interested in 300BLK, hence the reason I started this thread. I'm interested in having 1 carbine that does fantastic super performance and good sub, the BSP barrel can do that.

Are you talking about. DI build?

Nope, talking about finding a method to attach the gas block from my piston setup to the bison armory 11.5 inch barrel and moving LWRCs short stroke piston over onto it. Ben Triplett has actually exchanged some emails with me recently, he feels it should work but I'm still going to be in for a challenge on removing the block and barrel nut. Where there is a will, there is a way though.

I don't have any of the extra piston parts laying around yet, or the new barrel even. My law just recently changed for this and I cannot even file my stamp till June. I was avoiding buying the barrel, as I didn't want an "intent to construct" to somehow bite me in the ass.

As far as length goes, my Six8A2 looks to be carbine length and not mid length but I am unfamiliar with the gas block that LWRC uses. Guess it is possible for the port hole to be further forward and the gas comes back at an angle, which would boggle my mind. All of this is in theory craft stages, nothing has been done to work on this idea. In June, the only thing that will happen is submitting for a tax stamp, so I have a bit of time to work things out.

Some pictures of my gas system.

The barrel I am looking at is .75 at the journal of the gas port and then steps down to .70 after the block.

I'm willing to give a bit of trial and error and I understand that I am introducing possible headaches, until everything is tuned. I figure that is just part of the fun of going into the custom world.

Sounds like I will be shipping the rifle to you guys though, for both installation of barrel and a cerakote job, after my tax stamp clears.

Thanks again for the information, greatly appreciate it.