Wanting to build a sbr upper for one of my registered lowers and was wondering if possible to build one with a mid length gas system. It would be a 223 caliber most likely will be using spikes tactical products since they are a few miles up the road. I can outsource the barrel if needed.

Possible?  Sure, why not?  

14.5" midlengths are all the rage right now, and without a pinned muzzle device, an SBR upper.

That being said, your question is backwards.  You should be matching the gas system to the desired barrel length, not the barrel length to the gas system.  However, if you just want to do it to do it, there have been folks who have run 12.5" midlengths and even 11.5" midlengths.  

~Augee

I would want to  do a 10-12" barrel

11.5 inch barrel, midlength gas . . . (carbine length probably would have made more sense, but I got a good deal on a barrel . . . ) . . . runs fine, btw.

Being interested in wanting to build a SBR, here is a barrel length study that will provide some insight that I believe should help in making a decision on best barrel length for a SBR. At the time of the study they used M855 ammo, but stated in the study that there are ammos that are addressing the reduction in bullet velocity with a shorter barrel.

From the study;
"Equally illuminating in this study was the correlation between velocity and barrel length (see Graph 2).  To generate a lethal wound channel, the M855 projectile must have a velocity of at least 2,500 ft/sec on impact with the target.  Below that critical velocity, the M855 bullet simply drills a 1/4 inch hole in the target, which too frequently is not lethal unless it passes through a vital structure.  Some of this limitation is being addressed with newer projectiles not available to the authors at the time of the study.  In the longer barrels, the maximum velocity of 2,979 ft/sec was in the 20-inch barrel with a velocity of approximately 2,700 ft/sec in the 14.5-inch barrel.  The critical velocity of 2,500 ft/sec was in a barrel between 9 and 10 inches in length, which further shows the folly of considering a 7-inch barrel for this cartridge."

"....with shorter barrels, tuning of the gas port for weapon cycling becomes far more critical.  Adding a suppressor, which does slightly increase bore pressure, will result in more erratic and forceful cycling of the weapon leading to earlier weapon failure.  It is necessary to remember that the 5.56×45 NATO cartridge was designed specifically for a 20-inch barrel on a gas operated weapon with 7 inches of dwell time after the gas port.  The 14.5-inch M4 barrel retains the 7 inch dwell length after the gas port."

Source: Barrel Length Studies in 5.56mm NATO Weapons http://sadefensejournal.com/wp/?p=1093

Kino

Kino is a carbine gas system with a mid length fsb.

I think the info you seek is in this thread!
http://www.ar15.com/forums/t_6_51/392684_midlength_12_5.html

Mine has been flawless with q3131a and federal m193 with the can on or off.
12.75 inch barrel mid length gas.

Dwell time is less important than gas port size.  I run a 14.5" mid, 10" carbine, 16" rifle among other configurations.  Total volume of gas entering the bolt/piston is what matters.