Disclaimer: When I wrote my post above I had a few shots of J.D…That being said my reading comprehension is not the best when I’ve been hanging out with Jack Daniels 
Thus there are a few things that I missed in BB493’s post.
Just a few options you may want to consider:
My Department doesn’t allow Patrol Officers (non-SWAT) to use SBR’s or suppressors (SWAT members can use either or both).
That being said, if your Department is progressive enough to allow SBR’s or supressors, that’s awesome.
I see very little application for a SBR in patrol. And please don’t take that statement the wrong way, I don’t want to turn this into a SWAT vs. Patrol thread. A majority of my work in SWAT is CQB missions and for the last 7 1/2 years I’ve used either a 16" barrel or a 14.5" barrel with a perminately attached muzzle devise (16" overall length) for SWAT, and see no REAL need to go with a SBR. I’m 5’06" and have had no major issues in confined spaces with a 16" barreled carbine.
In patrol a majority of the time you will depoly the carbine will be for permiter work (barricaded gunman, bank robbery, etc), felony take downs, etc. A majority of the time you will be out in the open. There are times where you will get to clear a house, school, warehouse, etc (burglary in progress, alarm, open door, etc). In this application I feel that a 16" barrel (when I refer to a 16" barrel I’m refering to a barrel that is 16" or a 14.5" barrel with a muzzle devise that brings the barrel out to 16" overall length) is a better choice.
A few of the down sides to a suppressor:
-Weight: A suppressor can drastically effect the weight and balance of a gun. I have carbines that have balance very well and feel good in the hands, but once a suppressor is added the gun becomes very muzzle heavy, feels unbalanced and cumbersome.
-Heat: Under sustained fire (tactical carbine class, department qualification, etc) a suppressor becomes very hot, extreemly fast. I have read somewhere (either in a manual or on a supressor manufacturer’s website) that for every shot you shoot through a supressor it raises the tempture of the suppressor. So just shooting a mag of 28 rounds raises the temp of the suppressor 210 degrees (and that’s not counting the ambient tempture outside). If the temp outside is 90 degrees and you shoot a 28 round mag though the suppressor it will be approximately 300 degrees. The barrel, forend, upper, lower, and even the buffer tube can be effected by the heat to differing degrees.
-Carbon Build Up: Shooting a suppressor on an AR platform makes the gun extreemly dirty in a very short period of time.
-Noise: In enclosed areas (smaller rooms, hall ways, etc) a suppressor can be suprisingly loud. Not as loud as a non-suppressed gun, but it’s still loud.
-Point of Impact Shift: With most suppressors you are going to experience some degree of point of impact shift. There are many factors involved (ie. suppressor make and model, length of barrel, countour of barrel, etc)
You stated that the main reason you wanted to go with a SBR and a suppressor was to: “My main goal is to get a rifle I can use for close quarters without blowing out my eardrums. I figured with the short barrel and suppressor, that puts it right around the same length I’m already at. I’m not sure I really want anthing with an overal length longer than 16” with the suppressor."
In a law enforcement setting chances are slim to none that the other Officers around you and the bad guy will be using suppressors. But chances are high that if an Officer Involved Shooting occurs that you won’t be the only person shooting. Thus you still want to wear hearing protection.
This may not be the coolest answer, but it may be one of the most cost effective and practical answers:
Have you considered just getting a pair of Peltor Comm-Tacs and put them in your rifle bag?
You could don a pair of Com-Tacs faster than you could put a Q.D. suppressor on a barrel and they will provide hearing protection from your gun, fellow officer’s guns, and the suspects gun. This is something that a suppressor can’t do.
I have had officers fire their carbines with there muzzle 12" or so from the right or left side of my head (think of going down the hall way in your standard house, it’s not practical or possible for 2 grown men to walk shoulder to shoulder down a hall way). There are several instances that I can think of when a team mate may have to be a step or two behind me, off to my left or right, when he brings his rifle up to fire. This puts his muzzle even with the side of my head. Situations like this is where a pair of Peltor’s pay for themselves.
A good set of hearing protection and a pair of eye protection in your rifle bag can go a long way. But that’s a thread in and of it’s self that belongs in the gear section.
I have been wearing Com-Tacs under my helmet on SWAT calls for the last 3 years and have been next to other team members when they have dischared their guns (both pistol and rifles), use of distraction devises, etc. Another advantage of the Com-Tacs is that they amplify the noise around you (ie. people talking, breaking branches, ruffling of leaves, hearing people in the attic when no one else could, etc).
-A LMT upper is $485 and the LMT bolt carrier group is $130
-Tax Stamp for the SBR is $200
-Tax Stamp for the Suppressor is $200
-Suppressor $500 to $1200
Total = approximately $1,515 to $2,215
A few options that may make bugitary constraints a little easier:
-*Instead of getting a complete upper, why not just purchase a new barrel ($250 ro $350 range vs. almost $500 for a new upper)
-*Skip the SBR route and if you don’t like your current barrel, rebarrel the gun with a 16" or 14.5" (with perm. muzzle devise) and purchase a suppressor. This would save you the price of a new upper and the price of the tax stamp on the SBR.
If you are going with a suppressor on a 16" or 14.5" barrel I would suggest something along the lines of a Colt 14.5" M4 SOCOM barrel (heavier profile than the standard M4 Govt countour. Like the ones pictured here: http://www.ar15.com/forums/topic.html?b=7&f=22&t=284588
I recently put the Colt 14.5" M4 SOCOM barrels on all 3 of my Colt LE6920’s. This made a big difference on the point of impact shift on my G5 suppressor. I copied this from another thread I wrote in reference to the M4 SOCOM barrel + suppressor:
There is only 4 oz of difference between the Govt profile barrel and the M4 SOCOM barrel (you can tell a slight difference in weight). A pic of the M4 SOCOM barrel can be seen here:
www.ar15.com/forums/topic.html?b=7&f=22&t=284588
The reason I went with the Colt M4 SOCOM barrel (heavier profile) is due to point of impact change when using a suppressor. The shorter and stiffer the barrel is, the less point of impact change you will experience once the suppressor is installed on the barrel.
When using a suppressor, you will experience a point of impact change. All of my guns are sighted in at point of aim / point of impact at 50 yards. Here is what I expereince using the M4-96D and the G5 suppressor using both 16" M4 profile barrel and the heavier Colt 14.5" SOCOM barrel:
When I was using the M4-96D in conjunction with the Colt 16" M4 profile barrel, my point of impact was low and to the right (between 4 and 5 o’clock) and approximately 4" low at 50 yards.
After the M4-96D was converted to the G5, the G5’s point of impact shifted to approximately 3" low at 6 o’clock using the same barrel at the same distance (host guns were 2 Colt LE6920’s).
After switching to the Colt 14.5" M4 SOCOM barrel with the Gem-Tech G5, the groups are only approximately 1/2" between 5 and 6 o’clock at 50 yards.
BTW, the Gem-Tech Bi-Loc flash suppressor when perminately attached to a 14.5" barrel makes the barrel’s overall length just over 16".
-*Stick with your current 16" barrel and get a Surefire suppressor. www.impactguns.com has the Surefire suppressor for $1,045 + the $200 tax stamp. This would save you the cost of a SBR tax stamp and the cost of a new barrel or upper. The advantage of the Surefire is that it’s a back over the barrel design, is fairly light, has very little point of impact shift, and only extends 3.75" past the end of the muzzle (because approximately half of the suppressor goes back over the barrel)
-*Scrap both the SBR and suppressor projects and set up your current carbine the way you want it and have enough money for a 2nd carbine.
Just my opinion: For a Patrol carbine I would invest in a pair of Peltor Com-Tacs that I would keep in my rifle bag and scrap the SBR and the suppressor idea and use the funds to set my current carbine up exactly the way I wanted and if I had enough money left over I would purchase a 2nd carbine to use as a back up (incase my primary went down during training, was at the gunsmith, etc).
If you look at the big picture, a good set of electronic hearing protection cost as much as a tax stamp and the benifits of good hearing protection for a Patrol or SWAT Officer FAR outweight the benifits of a suppressor or a SBR (and that’s not to say that suppressors and SBR are not desireable tools in a LEO setting, it’s just you get so much more “bang” for your buck with a good set of electronic hearing protection).
But there are so many options out there that you really can’t go wrong. You just need to find out what works best for you and get the best gear you can afford.
That being said, my answer is not the only answer and opinions vary based on personal preference, mission statement, and personal experience.
Good luck
Take care and stay safe,
