I have not. I just know my 10.3" is horrible. I will re-evaluate the 12.5 and my options, given this. I thought that the 12.5" would be closer to the 10.3" than to the 14.5", honestly.
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After looking at rail-space, etc. I don't know if the 9" rail is going to give me the room I want with the K16i, to run the SR switch how I want, etc.
Here is a 10.5" barrel and a 14.5" gun with a Z6i mounted on it for reference (the K16i's Swarovski twin)
http://i575.photobucket.com/albums/s...87775A2043.jpg
The bottom gun is setup almost identical to what I have in mind, actually.
I'd go with the Middy.
My BCM 14.5 mid with H buffer and standard carbine spring has been 100%, even with Tula (however this was after several thousand of M193 and that old Hornady 55gr "training" ammo). Start changing with the recipe in terms of buffer and spring weights, and you'll get problems.
If you're not going to run the FSP, and you're going to attach a lot of stuff, might as well just go with a 13" rail.
As far as velocity:
http://sadefensejournal.com/wp/wp-co...02/barrel6.jpg
That's with M855.
Since you already have a 10.5 I'd just get the 14.5. Better tools for the job. Remember, there is no "one to do it all". Everything has advantages and limitations.
Kindof where I am headed with the thing.
BCM...those barrels don't come from Daniel Defense, do they? Also, from what I understand, BCM's gas-ports are more tuned for 5.56 while Daniel Defense's are a bit more open, yes? I wonder if this carries over to their 14.5's.
I heard/read that BCMs are hammer forged by FN. i cannot confirm this.
I dont know what port size they run on their 14.5 middy but I remember asking Joe Marler what port size theirs had and IIRC, he said ".078 for better reliability", i assume across a wider range of ammunition. This was some years ago when 14.5 middy's were all the rage and I dont know if they still run the same size or how big or little a diff that is/was to BCM's at the time.
That chart just verifies what I've been saying - you only gain 100fps between a 12.5" and 14.5". You've already got an NFA lower. Why not pin a muzzle device on a 14.5" and throw it on a Title I lower and put the 12.5" on the SBR?
Again, no dog in this fight. Just trying to save you tons of money, money that I wish I had saved.
Part of the difference for configurations I run is that the 1.93-2.01" height scope mounts frees up room under the optic for a DBAL, which makes the shorter setups more attractive. Since you've mentioned length and wanting to find the goldilocks setup, to be completely honest I've even been messing with the idea of running a 13.7" barrel as an SBR setup (with URX3 10.75"), but the honest answer is that it doesn't make a ton of sense.
The 14.5" is fairly easily justified for a TitleII lower owner wanting a do-all recce, but the 12.5" can still do a lot in that regard too, it's more of a case where the difference between a shorter than 3' long gun and longer than 3' long gun is unusually huge, especially when some of the densest handling part is dangling off the muzzle (in an inch and a half wide cylinder), so tucking that even even am measly 2" can really do a lot.
As far as handguard, if you're already happy running the Troy's, the KMR will fill that role just as well, being extremely light, with the BCM mini-VFG and some key-mod panels, you'll be more than adequately isolated thermally if you have a bunch of plastic around there - iirc the KAC cover is probably the best candidate for that. I've always felt that lighter longer guns handle like shorter ones, so little stuff like running a 3V Scout and KMR rail can make it an easier rifle to run - same idea with the offset KAC sights - that means you can run a much lighter (if you like that height over bore, the API super-light might be the best option) fixed scope mount without losing and effectiveness.
Don't get Gunz started on the source of the BCM barrels, but right now you can source really high quality barrels from plenty of sources, including BCM/DD/Centurion/Noveske, in both 12.5" and 14.5" flavors, so if the 14.5" covers that area you want for compromise performance, go with that and drive on.
The only reason we're looking at you a bit funny on wanting a Recce type SBR upper is that you've already got a 14.5" unit (I'm assuming a lighter barrel), so how different do you want the recce one to be (or rather, how similar do you want this one to be). The same argument, if your existing 14.5" is a lighter rifle, why not set this one up to run exclusively as a high performance suppressed only setup (and run a brake on it) then set up your other 14.5" as the training/practice/unsupressed focused rifle, configure them identically, and take advantage of the fact that you have two very similar awesome optics. I've got the ghetto version of this for my go-to rifle pair (a 16" Recce with heavy barrel and 1-6x optic, then a 16" Lightweight with TR24RT or AP T-1 that is the training analog for both the recce and my dual stamp SBR in those two configurations).