Best route to a SBR

I am looking at building the following SBR configuration:
Rock River Arms upper and lower
9mm
10.5 barrel

Which registration route would be better and why?:

Option 1: Buy a complete RRA 9mm rifle, register it as a SBR, then cut down the barrel after the tax stamp goes through.

Option 2: Buy a RRA 9mm rifle lower, with stock already attached, register it for SBR, then buy the 10.5 pistol upper after the tax stamp goes through.

Option 3: Buy a complete RRA 9mm pistol, register it for SBR, then add a stock after the tax stamp goes through.

I really have no interest in shooting this gun before I get a stock on it so I am leaning most towards option 2 at this point. If you have an opinion on this matter please let me know. I am a little nervous about cutting and crowning a barrel so option 1 is my third choice right now.

Any help?

I would encourage bulding/shooting it in a legal config before sending your forms in. Think of it this way: by creating an SBR via a Form 1, you are essentially stuck with that thing for life (no one wants to buy a lower with someone else's name engraved on it on a Form 4 when they can Form 1 one themselves and have their own name on it). Bulding and shooting ensures everything works good: no out of spec holes (positionally or diameter wise), nothing wrong with the mag well/mag catch/bolt catch, make sure the receiver extension threads in and works properly, etc. Doing this rules out option 2.

So between option 1 and 3, which both let you shoot it before your stamp comes back, I vote for option 3. I went this route with my 9mm build, because its cheaper to convert from a pistol to a rifle. Hell, you can just use a regular buffer tube if you want to, as long as you dont have an extra stock immediately accessible to it (I bought a pistol buffer tube kit because I have a bunch of stocks laying around, and I wanted the foam cheek weld). 50$ from Phase 5 for the whole pistol tube kit. Barrel work from ADCO will be around $100 on top of the cost of the barrel. Yet buying a pistol length barrel in the first place costs the same as a 16" barrel.

Have you shot a 9mm AR Pistol before? It's really not bad, nowhere near as bad as a 5.56 pistol. It should be plenty of fun to shoot in the 6 months you wait for the SBR stamp.

All your options would work just fine. But i'd probably go with option 3. You can shoot it while you wait and it's easier to add a stock than to cut and thread a barrel.

Option #3 (AR pistol) lets you tinker and have it in great running condition by the time you're allowed to add a stock.

I went with option 3. I didn't buy a complete pistol, but I build a pistol for use while I wait for the SBR stamp to come back (pending about 4 months now). I bought a CMMG 9mm dedicated lower and pieced together the upper using parts mostly from the EE and a 5" barrel from ADCO. I sent the collection of parts to ADCO for assembly and had it back assembled in less than a week. I went with a RRA flat top upper, 5" 1/2 x 36 ADCO barrel, Colt BCG/CH assembly, and a Spike's BAR handguard/rail. I have a suppressor pending also, so I wanted a handguard I could easily fit the suppressor inside.

If you decide to go the shortening route, I'd suggest ADCO for that work, they are fast and do a great job. I had a Colt 9mm 6450 for a while, but once I got the pistol built I ended up selling it. The 16" 9mm just isn't that much fun. The pistol is more fun to shoot (and will be better as an SBR). On the other hand, a 16" 9mm AR just seems way too big for the performance it offers. YMMV.

Interesting ideas. I'm waiting out a stamp on a 6450, and it never occurred to me to go the pistol route. Cheaper indeed to add the buffer tube, and easily enough done yourself. Hadn't thought of it, and wanted the Colt in any case, but a really clever idea.
BTW, I'm dealing thru' a Class III dealer, and they simply want me to add an additional serial number to the one already on the gun. They assure me that they have done this before, many times, and have never had it questioned.
I agree that I'd not be crazy having a rifle with someone elses name on it, but the number deal answers that question.

As regards the effects of bobbing the barrel, I'm going with 10.5", and intend to chrono some standard loads before and after the amputation. I'm not expecting to lose any velocity.
Moon

I'd go the pistol route. You at least know it will run, and can tinker with it. I don't really enjoy my AR pistol that much, but I had it together for about 10 months before I got around to getting all my stuff together to submit the form 1. At the the rate the ATF is going i'll be lucky to have the stamp back this calendar year, but for the time being I do at least have a a fully working firearm I can use.

They still need to print their manufacturing info (Name/Location) on the receiver. And they don't have to give it a new serial number, but they can if they want to.

OK, lots of good feedback here so thanks everyone. However a new question has arisen as a result. It seems a lot of folks advise the pistol to ensure it works well before SBRing it, This may sound a little naive but are 9mm conversions that unreliable? I thought that due to their popularity that a couple of top notch companies like Colt and RRA would have them working as well as their 223 counterparts. My bro has a Colt 6450 that had some feed issues but I thought it was just a rare bad one in the bunch and he got it working great before long. Is this the exception or the rule?

9mm ARs tend to be magazine picky. You need to stick with quality mags in order for them to feed reliably. IMO, the Metalform magazines are the best, but I haven't had any issues out of my RRA magazine either, which is a modified Uzi mag. Other than that, they're pretty reliable. You don't have to worry about gas system issues like you might on a 5.56.

AR pistols are lame. Nothing more than a novelty. Get the RRA LAR-9 rifle, send in the form 1, and when it comes back send your barrel to adco and chop it to 4.5 inches. Turn around time is seriously like one and half weeks. It will run just fine. Ive got two of them SBR'd.

My Colt has run just fine from the get-go; only issues I've had were some JHPs loaded too long (by me); I've adjusted the OAL and solved the problem.
But I'm talking about an out-the-door rifle. Drop in mag blocks and other mods have a potential for causing trouble; it's just prudent to test hop what you've got.
Moon

Sometimes the "picky" part is the magazine block-to-magazine fit, but essentially, if you find a mag that works every time, buy a lot of that magazine.

My SBR started as a stripped lower that didn't even have an LPK in it until the paperwork was submitted. While I was waiting, I built everything except the upper, with the last part to arrive being the barrel (not by design, but it worked out that way).

As noted above, make sure whatever you have on hand can be assembled into a legal configuration (pistol lower if you have the short barrel in your possession, etc.) and you'll be set.

1. Why not just buy an SBR from Rock River ?
2. Purchase a different caliber rifle.......
and a 10.5 inch 9mm upper.....
send in Form 1 papers.......
Wait the 3 to 6 months for approval of Form 1
Now you have another upper for seperate build/spare.

I agree, Adco charges $65.00 to chop and thread. Not that much money, and you get to shoot a rifle with a stock on it. ADCO is also top notch. I bought my 5.5" barrel from them, and I've had no problems with everything lining up with the suppressor.

I say option 3

You can run it and work the bugs out if need be while you are waiting. I have been lucky with my RRA upper in that it has not given any problems with the cheaper C-products mags but if you have an issue it is usually the mag or mag block causing it.

If you consider the cost of getting it cut, crowned and re-threaded including shipping versus just changing the buffer tube and putting a stock on once your stamp comes back it will be a little bit cheaper to add the stock to a pistol. Some may say that a pistol is lame, I am not a big fan of them, but this is not your long-term goal so who cares how lame it may or may not be for 6 months!

To me the bigger thing is being able to change the buffer tube and put a stock on the day you get your stamp back because nothing is worse than getting your shiny new stamp back and then having to ship off your upper and wait.

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