Looking to see what everyone's preference is regarding barrel length between the two.  I am specifically looking at an SR15.  Just trying to decide which barrel to go with.  Already have a MK18 10.3 inch.  Just trying to add more diversity to the cache.  Thanks in advance.

Personally, I find it hard to pay for a tax stamp for a 14.5 inch barrel. I would just put a permanently attached muzzle device on it and be done, and never worry about a 5320.20.

When I first got interested in SBRs, I didn't know where to start.  I read some things about recommended minimum barrel lengths for silencers and was taking that into account.  After some research I decided that Colt might know more about the whole SBR thing than I did so I figured that the specs for the Colt Commando would be my starting point, and the 11.5 inch barrel seemed like a good compromise.  Now I have SBRs from 7 inches to 11.5 inches.  Funny, the gun I have always wanted to build was a retro GI profile M4 but never have because of the 14.5 inch barrel.  Most of my non-sbr ar type guns are mid-length guns and shoot great with the 16 inch barrel and mid-length gas system.

I read a couple articles over the last 6 months about muzzle velocity and accuracy.  At the distance most of us will shoot a 5.56 gun, the barrel length (14.5 v 11.5) does not seem to have a measurable difference in accuracy.

You will be giving up, generally, about 100 fps per inch if that matters.  If you go shorter than 10 inches then velocity tends to decrease on a steeper slop.

So if it was me, I would go with the 11.5 inch barrel unless I was going to create a semi automatic sniper system (M110) type gun with a big glass optic.

http://www.sadefensejournal.com/wp/?p=1093

if you already have a mk 18 i would look at the 14.5" , with the 14.5" you get the longer gas system.

the longer gas system and appropriately sized gas port help make the kac's smooth shooters.

I was going to say the same thing.

I went through the same dilemma last month, I ended up with the 11.5

i was really sold on the 14.5 but felt it was a waste of an sbr lower.

i want to get one still though, but will go pin and weld route.

cant go wrong on either , my 11.5 is smooooooth.

I have 10.5", 11.5" and 14.5" 5.56mm short uppers (not KAC) for use on three SBR lowers and the 11.5" is a sweet spot, especially when you have a suppressor adding back length and weight.

If I didn't live in MD I would pin and weld the 14.5", using a QD suppressor mount/flash hider, but since 2013 only heavy barrel ARs are permitted here in MD, except for NFA firearms, so pinning and welding a flash hider would make that upper legal with only the one lower I owned prior to 2013.

There just isn't enough difference between a 16" and a 14.5" to go out of the way to buy a whole SBR, pay the stamp and wait.

On the other hand, you could get the 11.5" SBR and add a 14.5" upper later.

If you can find a 14.5 Mod 1 dimpled upper I would go that route. One of the finest uppers ever made.

If I were buying a factory KAC SBR I would definitely get the 11.5 CQB. I currently own a KAC mod 2 14.5 carbine but I decided to have it pinned and welded for convenience. I do have two 10.3 Mk 18 variants as well as a Colt Commando 11.5 and 14.5 M4 SBRs. The current mod 2 11.5 KAC CQB would be the only other SBR I would consider purchasing. A friend of mine owns one and we shoot it regularly both suppressed and unsuppressed and it is so smooth and a lot less gassy than the SBRs that I currently have. The KAC mod 1 are the most aesthetically pleasing but the KAC mod 2 is superior in performance due to their new style gas system.

I have a 10.3", a couple 11.5", and a KAC in 14.5". I prefer the 10.3" over my 11.5".

To me the perfect combo is a 10.3"(red dot) and a 14.5"(ACOG). I don't use my 11.5" anymore after having the 10.3". I wish KAC made a 10.x" upper. My 14.5" KAC is SBR'd and totally worth it to me. I bought the upper and lower separate and ran the lower with a brace until the stamp cleared.

To say the 11.5" vs the 14.5" is almost nothing is not true. The 14.5" is way softer shooting, quieter suppressed, darker in the night, and cleaner shooting.

I have a 16” KAC that I originally wanted to cut down to 14.5”, but it’s way more accurate than I expected.

Maybe I can talk the wife into letting me acquire a 14.5”

I went CQB 11.5 but I already have a 13.7 and 14.5, but as others stated whatever fits your current herd, would probably be best for you. Though, you really can’t go wrong either way

Both?

I wen't 11.5" since I already had a BCM 14.5".

Attached File

I currently have an 11.5" with a can on and its great.

also have a 16" mod 2 upper with a can on it and its a little bit long but shoots super smooth compared to the 11.5. Standing offhand follow up shots at 300 yards is easy peasy.

Get the 14.5 now and pin and weld a MAMs or something.  If you already have an SBRed KAC lower, hold it in reserve for a later date.

I own both... I recommend getting the 11.5. I only ever shoot the 11.5 anymore.

I went 11.5".  I had plenty of experience with 14.5" in the Army and being forced into a 16" in the civilian world was not much of a change so I wanted something drastically more handy.

The kicker is the suppressor---I would rather have the shorter gun with the fullsize can for the same OAL vs the longer gun with the smaller can.

Stamps should be back on both the Mod2 11.5" and 556QDC any day now based on the posts here as I bought both in Mid October.

I may get a 14.5" in the future though.  Probably after a 9.5" SR-30 since I already have a 762QDC for my SR-25s.

I have both and I prefer my 11.5's to my 14.5



This is the correct answer.

This guy has it figured out. Also, thanks for the help the other day. I ended up getting the QDC based upon your help.

That's how I'd do it getting both---11.5" with QDC and 14.5" with CQB/QDC.

Why not get the 11.5” and SBR the lower? Then you can buy the 14.5” upper and swap them around at your discretion.

Got the call today, my stamps for my QDC and SR-15 CQB both came in today.

Awesome combo and glad I went that way.

lucky!

i got my 11.5" sr15 but im still waiting on my cans stamp to arrive at my ffl, ATF said its approved, just have to wait for usps to do their thing.

The 556QDC/CQB suppressor looks right at home on the 14.5







Happy to help, my friend!

Congrats, y'all! I look forward to seeing photos.

Eotech EXPS3-0 and Surefire M600DF should be here tomorrow for it:

Now I got it all set up.

annnnnd sploosh.
was just researching doing an 11.5" upper and what handguard to do. Came across this thread and now I think I'm set. Want to put a sico asr  flash hider on it for use with an Omega. Want to get the can as close as possible.

double tap

not going to get an omega much closer than a URX4 10.0" on a 10.5" barrel. The rail overlaps the asr mount by about .25". See photo below.

On the 11.5" and 10.75 URX it will have a larger gap unless you direct thread.

Attached File


ETA: yeah, here is an 11.5" barrel with a 10.75" URX4 and an ASR-mounted Omega. Larger gap. Still not that bad.

Attached File

wow great find with pictures. I'm definitely wanting an 11.5" barrel setup, which means if I want the way the top picture looks I'd need an 11" handguard. Otherwise, the bottom picture is still pretty good.

your setups btw or no?

all mine.

Attached File

very nice stuff brother.  I'm still thinking 11.5", and leaning towards the URX IV 10.75. But maybe, a BA Hanson 11.3" barrel would produce the same gap you've got on your 10.5" barrel setup.

I'm sure you won't really notice a difference. The only reason the gap on the 10.5 is so short is because the rail is 10.0" instead of 9.75". I didn't care either way, I just wanted to use a URX on a 10.5" and it just happened to be very close.

The 11.5"+ 10.75" rail is a great combo.

Attached File