It seems a lot of people go from carbines to SBRs and never look back.  I've been leaning towards that dark side, peering into that abyss.  However, I only have money for one AR, and though my 14.5" BCM is great (lightweight, reliable, smooooth, etc.), I've always really wanted to get an SBR...I haven't shot one, but have held many, and love the feel.  I'm looking at the BCM 11.5" uppers (though I know the 12.5" are likely a better ballistic-sweet-spot).

I'd probably have to spend at least $750 with the change-over ($200 tax stamp, losing $300-$350 on my 14.5" ELW-F middy w/ BCG upper, Trust Engraving, buying another BCG, muzzle device, etc.), so I'd like to know that it would be a good bit lighter and handier--that the 3" of length and weight, and the ability to change muzzle devices, is worth $$$ just because I like them better.  I'm not worried about long-range effectiveness, because I never shoot past 100Y except like at 200Y once a year or so (though 11.5" guns can surely give someone a bad day at 500Y/600Y).  A suppressor is a long term (1-2yr) goal.

What I AM worried about (can anyone address these concerns):

1)  Are SBRs harder on eroding the gas port?  If so, the BFH might last longer there...if not, I'd just save the money and get an ELW.  

2)  Will the SBR have a lot more recoil than a 14.5" middy?  I'm a BIG guy, but unlike all those who say the 5.56 has NO recoil, I REALLY like how smooth and soft my gun is--the dot doesn't move off a 4" target at 100Y when I pull the trigger.  I barely feel any recoil, and I wanna keep it that way if possible.  I'd keep my A5 buffer, get a decent hybrid comp (something fairly effective--I don't care about noise), and perhaps one of the enhanced BCGs (like Lantac's) IF that would help bleed off extra gas/recoil.  

My 11.5 in Sig m400 pistol wears a PWS FSC556. It's a flat shooter, even with a regular CAR buffer. I don't think recoil will be an issue

I went from a 14.5 middy to a 10.5 5.56 and 10.3 300blk back to a 14.5 middy.

What made you go back to the 14.5 middy?

Do not sell your existing carbine you like. Instead of losing money on a firearm you enjoy, be patient and build a second AR over time. You will be waiting on the stamp approval anyway.
1. Buy stripped lower you like. Lowers are cheap now.
2. Have lower engraved with required info.
3. Send off your Form 1.
4. As your finances permit, acquire parts for the build.
5. Complete build as a pistol.
6. Receive your approved Form 1.
7. Install the stock on your new SBR.
8. Enjoy the fruits of your patience and effort.

if you live near Tampa, I can recommend a place for laser engraving... an additional $200 to $225 for a trust if you did not already include it

SBRs are a disease. And there is no cure. When I hold my BCM 14.5 middy it just feels like a Kentucky musket compared to the others.

I have a BCM middy, and a BCM 11.5.....I would never sell one for the other...NEVER

save your pennies and get your upper,

save some more and SBR your current lower,

save some more and by another BCM complete lower

I wouldn't sell a good carbine just to get a SBR, and I sure as hell wouldn't want my one and only AR to be a registered SBR that comes with all the BS legal requirements that go along with it, like having to get a permission slip from Big Brother to cross state lines with it, having to add someone to my trust before they can use it, etc.  

If you're short on money, do it piecemeal.  Start with a $50 stripped lower and $200 for the tax stamp while you wait on your e-filed Form 1.  While that is pending (it will be a few months), start accumulating the other parts.

Do you mean borrow  without you in visual sight?

Yes

This...^.  

I built a 14.5" mid-length and love it but also wanted a SBR in 300BO.  Never considered selling anything.  Just add another rifle to your collection.  If money is an issue which it was for me, just acquire parts when you can.  Pretty soon you will have it all together.  

My SBR is set up as a pistol right now because I have not had the 200.00 to spare on the Stamp yet but its coming.

I felt the same way when I finished my 14.5" compared to my 18" SPR and again when I built my 10.3" SBR.  Big differences in weight.

I would not sell any of them not to mention you will take a bath selling them.

Thanks for the ideas/thoughts and recommendations.

The main problem is I don't really feel like I can justify owning two guns that serve the same basic function (I do have backup AR parts).  We make enough, but not enough for me to justify being a gun collector--I ONLY have guns I actually USE:  a daytime/shorts carry pistol (G43), a pants and nighttime carry gun and main pistol (G19), a 22LR pistol for plinking suppressed, and an AR for any scenario where it's better than the other guns (a class once every year or so, a rare 2-gun shoot, hunting, SHTF, HD-if-I-have-time-to-get-it-vs-the-G19, etc.).

But instead of spending a total of $1200 on a full SBR build over time, I could "save" $500 and put that towards bills, a Disney-trip for the kids, and all of life's other expenses.  If I had TWO ARs, I'm pretty sure I'd have to sell one the first time we had a few financial emergencies hit at once (a clutch going out and a root canal or something).  Sadly, such situations tend to hit once or twice a year.

Keep the 14.5 as an investment and sell it for the total cost of the SBR + stamp + $1000.00 during the next gun panic. This post may appear to be a bit tongue in cheek but I guarantee it'll work if you just exercise some patience.

THIS. I have played around with a 10.5 sbr. Fun, light, good handling characteristics. But I wouldn't sell my 16 to buy an 10.5. I am going to save my money and slowly build one. Probably going to build an 11.5 pistol with a shockwave brace.

 

Do what I did.  SBR the lower you currently have.  Then pick up a 11.5" upper from PSA next sale.  They just had 11.5" complete upper $279.

Op
SBR your current lower.
While you wait, accumulate parts for a second upper.
Stamp comes back, you have a second upper.
Keep both uppers until funds permit you to buy another lower.
You can build an second upper for less than $500, if $500 is to much money for you to part with I suggest you do not get into the NFA game until funds permit.

I had a BCM 11.5'' upper for a few weeks (acquired it on a trade) and actually ended up selling it to get a 16'' upper. I did drop off a form 1 on it to my CLEO (no trust for me) and may still SBR the lower but I don't think I want a 5.56 SBR. I find them extremely loud and annoying and would have to suppress it. 1

I own multiple 14.5 middy's and a couple of 11.5's and this is the route I would take as well.

--
Yeah, I'll likely try this.  
That said, what is wrong with my notion that I don't really NEED 2 fairly similar ARs, since I'm not a huge AR shooter?  Besides the fact that it's arfcom, and "buy both" is ALWAYS the right answer!!  
I just don't see why everyone is opposed to my selling one (other than losing money--which does suck:  I've lost some just trying out different glock barrels for personal research purposes, and I've lost a good bit buying and selling AR optics figuring out I like red-dots best).  

NOTE:  I assume I SBR the current lower BEFORE buying an upper?  Though perhaps you said buy the upper first because I'd need the SERIAL NUMBER (though I don't think they have one) or exact length BEFORE filing the forms with my trust.  BUT THEN I'd have an illegal upper in the house (unless I also bought a temporary pistol lower).  
I'm getting an MRO in the upcoming sales (Cyber Monday or whatever), but will then file my current trust and form 1 (4?) or whatever electronically soon after.  Once it gets approved, I'll have someone local engrave it (I can't remember the name of the trust--here's hoping it's short...though it'll be a tiny font).  

Reliability
Concussion unsuppressed
No benefit to an SBR aside from looks
Running a lighter can of mini size instead of a heavier fullsize gave similar feel of weight  and suppression with 200fps  velocity for "free".
Cleaner
More rail space for better leverage on the gun
Less recoil for faster follow up shots

Reallt, I liked nothing about my sbrs except the stares a sexy MK18 with a can gets you, and those got annoying fast. I hate "what did that cost" and "do you have a license.?" Type drivel.

I think you're missing the point.  If you had said you wanted to sell an 18" or 16" for the pinned 14.5" or vice versa, then more power to you.  Your case is different because you are talking about exchanging your ONLY AR15 for an NFA item that comes with all the NFA requirements and BS.  I have a few SBRs, including an 11.5 556, but none of them will be my ONLY rifle / AR15.  

Plus, you have to ask yourself if all that extra cost is worth the reward.  Basically you'll be losing 3 inches of barrel, but gaining a lot of restrictions and at a large up-front cost.  In the title you use the word "upgrade", but I don't see it like that.  IMO the 14.5 you currently have wins out.  The 11.5 is just a toy/investment that will spend most of its time locked up.  

Plus, for the price you laid out, you could probably have or be close to a whole second SBR'd gun built on PSA parts (10.5" / 12" upper), and actually gain something rather than take a loss.  Keep in mind with the second rifle you can swap parts between both as long as you need to (bolt carrier group, charging handle, sights...).

This, or at least keep the 14.5 upper, so you can just swap uppers after you sbr your existing lower.

Yeah... I hate that shit too! I like to fly under the radar as well as I find attention, even good attention usually turns to bad attention for me. Case in point: I bought a nice vehicle recently, brand new (my first new car ever as I always purchased slightly/gently used.) It came with large rims and low profile tires. I notice people rolling windows down at stop lights to look at them, even ask me if they are stock. I ask myself, "How long before some idiot wants to steal them?" Maybe a little paranoid but it doesn't sit well with my below the radar lifestyle. I love the SUV however; my first twin turbo!

Same here! When I look at a 16" barrel now, it looks like an old Brown Bess to me!

Summed it up nicely: