After seeing pictures of the 605, I know it will be my next build. However, I am wanting to do it a little differently. I want it in 300 blackout. I saw a picture of a 605 with a can on it knew that’s what I wanted to do. I’ve figured out that I am going to need to run a pistol length gas system and use the front sight base to hold the hand guards on. I also have a flash hider that is long enough and compatible with my Reece 7 to meet the 16” pin and weld requirement. What I need help is with two things:

1) Barrel: to use the front sight base, I need to find a barrel. Seeing as how 99.9% of the 300 blackout barrel market is geared towards lo pro gas blocks, this is gonna be a tough one to find. There is also the issue of the barrel extension lining up with the A1 slick side upper. Any suggestions?

2) Buffer weight: my experience with 300 blackout is limited to the 8” pdw I have, and the rifles/pistols I have shot for test firing. I haven’t heard or seen a person use a full length stock and rifle buffer system on a 300 blackout. Is this something that anybody here has had experience with?

This one is built on a government profile carbine barrel. There is a low pro gas block under the handguards at the carbine position and the FSB is pinned on. It required a small bead to be welded on to make the barrel diameter correct for it.
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I kept the 16" barrel length so I did not have to SBR it or pin the flash hider as my can is a thread on.
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As for the buffer, I just use a standard rifle buffer with mine but it is .223 but I also have a Mk 18 Mod 0 clone that is a 10.5" with a pistol length gas system in 300 blackout that I also use a standard carbine buffer in. The 300 seems to be pretty buffer insensitive.
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Very nice sir. I have found with supers and subs from 16 down to 6" barrels the 300 isn't buffer sensitive either with a carbine system. I'm honestly not to sure what a rifle buffer weighs in at, so thats why I was asking. I'm pretty sure I have found the barrel I want to use. How hard is it to drill the holes for the taper pins? I have access to good tools to do the job, just never have done it before. Since it is just going to be used told the hand guards in place, are taper pins necessary?

I farmed it out as to make sure you get it right requires a jig and considering that's going to determine your sights I didn't want to mess it up.

Taper pins aren't necessary in that like you said it's really just holding the front hand guard cap. But I liked the idea as I wanted to make sure my front sight was rock solid and considering the front sling loop is there too...

Send it off to John Thomas and he will get you all squared away and back in the mail probably in a few days for a reasonable price and then you know it's right.

Agreed, JT will hook you up. He helped me with my barrel. A pic attached for inspiration

Very nice! Forgive my ignorance, but who is JT?

John Thomas

http://www.retroarmsworks.com

Ah gotcha. Yea i’ll Be in contact with him for sure then.