I forgot, she has my address. Unless you burned it and even then I might not be safe.
You can't go wrong with a Colt (true Colt, not a Colt Competition) regardless of the model. If you're happy with the 6721, it won't hurt to have a "backup."
Or...
You might consider getting some spare parts for your existing rifle as well. Spare BCG, action spring, charging handle, spare barrel (you can always get a gunsmith to fit it later) and a lower parts kit. Probably run you a couple of hundred bucks or so for spare "stuff."
OR!!!!!!!
There's always getting a spare upper with all kinds of bells and whistles you might want and toss your original upper into "backup" mode. Generally cheaper than a complete rifle (depending on what you get) but you can tailor it to what you would desire. I can make some recommendations depending on what you might like and NO! You aren't allowed to be bland and blah with the "yeah, mine's okay" nonsense. And it's cheaper, so the Mrs. Unit will be slightly happier. Not as happy, but maybe under the price of the hitman she sends to Oklahoma.
You're killing me here...let me work my way through your response.
First off, "Mrs. GW"...Diana, as you know...really doesn't care. She indulges my penchant for guns, ammo, flashlights, and Yuengling. In return, I never ask her how much she spends at Belk's. Detente', of the domestic variety. So we can kid about it, and should, but she really doesn't care. OTOH, she does come from Pittsburgh stock, and I've met some of her extended family with Italian last names who own concrete businesses up there, so...yeah, I burned your address. I owe you that.
My line of thinking is that if any type of AR ban comes to pass, it would be a good idea to have redundancy for anything that might fail on my rifle. Best answer: another my rifle. So we're at another 6721. Anything on "this" rifle can transfer to "that" rifle. Best, simplest solution.
That's where I am. One rifle, with one purpose (okay, maybe two). So what's the best way to protect that interest long-term? Honestly, I don't know, so I asked. I think just buying another 6721, and laying it up in a bag full of dessicant is probably the simplest solution. But I want your opinion. I'm never going to ascend to your level of gun building. I just want a rifle that I can win a fight with, and with the way the wind is blowing now, a level of redundancy. Another one of the same rifle seems...to me...like the best solution. The 6721 comes with a chrome-lined barrel and a full-auto BCG, so it's a solid gun.
Don't go buy a "Grand Vol Fathead" just yet, but you know how much I value your advice. And your wit. But if I told you $800 plus shipping for the 6721, is there a better way?
Oh...if a guy called "Fat Jimmy" shows up to check your phone lines, shoot him.

lol: