To summarize - I had a DD 14.5 pinned upper with a TA31F ACOG. This past winter I decided to SBR both my AR lowers. When my stamps came back, I sold the pinned DD upper.

I currently have a 10.5" DSG upper with a Geissele MK4 rail, and Troy BUIS. I also have an AAC 300 BO 9" with a seekins 10" MCSR. The 300  upper is fun, but not really a 'go to' emergency type rifle.

Im looking to understand my best options for finishing these two SBR Lowers.  

For the 10.5 I am thinking of rebarreling it to 11.5 using a Faxon 11.5 Big Gunner, and putting a micro dot on it. I am reading 10.5 is a poor choice? The Geissele rail is the 9.5 MK4 version, and seems like it wouild work well with an 11.5. I could sell the 10.5 Seekins barrel as it's new.

I would like to build a 'primary' carbine around my TA31F ACOG. I love this optic and am confident with it. I dont really have a desire for a 16" rifle now that I have a couple registered lowers.

Should I ditch the whole 10.5/11.5 concept and build a 12.5 for my acog only? Or would it be better to run the ACOG on a 14.5 and set up the shorter barrel as 10.5 /11/5 for a micro?

I want a 'go to' rifle that I can run my pending F1 suppressor (6.5") on, and run from 25yd to 300, with the ability to be successful at 500 in a pinch. (ACOG)  Im not so much looking for a PDW, as I have that in other guns, which are purpose built PDWs.  Im worried that a 12.5 inch rifle will not work well with my acog and be too bulky with a suppressor. I realize I cant have one rifle to do everything, but I feel like I am not doing this right with 10.5 and 14.5. Looking for advice for those who have more technical experience with what the best setups are. I dont want to waste $ on stuff I will regret.

1. The 10.5 isn't a bad choice. It is a compromise of velocity for maneuverability. It will still have good performance up close with proper ammo selection, and you can still hit targets at a decent range.

2. There is no rule that a 10.3/10.5/11.5 must have a red dot on it. You could use your Acog on your 10.5 if you wanted. I planning on moving my TA-33 to my 11.5 soon.

Why not use an acog on the 10.5"?  Look at the mk18 thread, if it wasn't effective socom units wouldn't be using it.  

I have taken big hogs with a 10.5" barreled AR pistol, and thousands of dead terrorists approve  of that length (10.3").

Buy ammo and go shooting man.
I doubt seriously the acog holdovers are going to work perfect for anything but what that model was designed for.

That said you can shoot at 500 with a 10.5"  we do it regularly.

so the 10.5 / 11.5 is OK with the ACOG, and I should just ditch the idea of a 12.5 or 14.5 all together?

ETA - let me ask this - if I do say, an 11.5 (Im not fond of the barrel I have) what am I giving up in terms of velocity / ability vs a 14.5 at 300 yards ?

You will obviously loose some velocity with the shorter barrel.  How much depends on the round of course.



A 10.5-11.5" barrel shooting common ammo like m193 and m855 type loads should still be above 2500 fps or so at the muzzle, and can still provide effective hits on target out to 300yds, of course, with the lower muzzle velocity, your hold-over to reach that range will be greater than with a longer barrel.  As such, the subtentions on your scope's reticle will correspond to different ranges that it would with the 14.5" barrel



 

IIRC, the BDC in the TA31F is set up for M855 out of a 14.5" barrel. You cab still use the BDC for other ammo/barrel combinations, but you will need to memorize the relation of the BDC to impacts.

As a go to rifle from 0-300 yd you will be just fine with a 10.5/11.5. There are some really great rounds like the barnes TSX that will perform well at those distances. Although 500 is stretching it for 5.56 with a short barrel.  Keep in mind that a 10.5" can be just as accurate as a 16". The only difference will be the 16" will get some extra velocity to keep it more stable, longer.

As for an acog....I don't see an issue with using it. I have really started to shy away from reflex sights on my rifles. I prefer some type of magnification and find that a 4x prism optic works really well out to 300 yards...while a red dot starts to suffer at 100+. I'm not saying you can't make good hits, but I like the extra magnification for target ID and scanning

Ive become very comfortable with my acog


So if the faxon 11.5 barrel (I dont like the barrel I have - I want to rebuild the upper with higher quality parts as it will be my prime carbine) is a middy gas, don't people say 11.5 middy gas barrels arent combat reliable? Specifically BCM has mentioned that here:


http://www.ar15.com/forums/t_2_138/174764__Q__Why_BCM_chose_the_11_5andamp_quot__SBR_over_the_10_5andamp_quot__.html

There are no 11.5 middy gas barrels. The mid length gas system is too short. 12.5" is the shortest you practically can go on a middy.


And the 11.5 and 10.3/5 inch barrels are very reliable and are in use all over the world with domestic and foreign armed forces. Colt CQBR and Commando come to mind.




Just build what you want man, don't over analyze it. Maybe this will help:







 

The faxon is mid? Or am I confused?

Just when I think I know what I am leaning toward wanting

Why would you not go 300 blackout? It's the perfect sbr round. 0-300 yrds with 8-10" of barrel all day long. Cost of ammo is really only talking point for negativity but Ozark puts out some quality ammo in the .39-.42 c/rd that is very accurate. I have used roughly 1500+ rounds from them with absolutely NO issues. Toss a can on that thing and it can't be beat for a carbine.

Already have a 300 BO. This is a different animal. I want a 556, go to SBR I can trust my life to when ammo might be an issue for the 300BO, or I simply dont want to use it. Besides the 300 is a budget build. While cost is a concern to me here, I'd like the best value for my money while being a deployable weapon

nathan please dont take this wrong - its a question not a 'shot' - but, how does using a (or needing ) an adjustable gas block make a combat reliable arm, on a weapon system that isnt really designed to use one? Wouldnt something that runs on a standard gas block be the better choice?

Also - where does the gas opening lie on the 11.5? I will be running a 9.5 Geissele rail, would that cover the gas block on the 11.5 faxon? It seems like my gas block would be exposed by .5 inches or so? Im not sure of thasts a good or bad thing.

Well, I stand corrected, off to go learn something new.

 

Innovative Arms W.A.R upper & a quality 10.5" - 11.5" barrel with pinned gas block will be my SHTF sbr build.

You've already got the Geissele rail and ACOG, so use them.  I sure as hell would if I had them.

I ran a TA31 on both a 10.5 and 12.5 to see which had a closer correspondence to the BDC.

The 12.5 did better but at the end of the day it was hard to hit the small steel swingers at 300 & 500.

Moved to a MRAD 1-4x and being able to dial MILS is superior IMO.

For point shooting at a human sized target the acog will be gtg - I just wanted a little more precision. Strelok will show you the hash mark point if you have the ballistics for your load and barrels.  Example the 400 strata line actually equals 374 yards and so forth.

If you're not taking it into combat, don't worry about combat reliability. Those barrels get worn out, and over time the gas posts open up from use and start to affect the recoil characteristics of the rifle. But that's after several thousand dollars worth of ammo, so you can just buy a new barrel by then. If you truly want combat reliability you are left with 10.3" carbine, 14.5" carbine, and 20" rifle. Those are the combat proven barrel configs in the US military. I think there are s few 16" carbines in use, but not many, and Colt Canada also makes the C8 in 16" carbine for some countries.

Past 300? Rarely. But it would be fun and nice to be able to hit at that range.

Im awful tempted to go with a 11.5 BCM and sell this stuff I have. I like the geissele 9.5 rail though. I'm also not 100 % sold on BCM. Im sure they run great but thats almost DD money,. and I trusted my life to my DD - but it was useless to me with a pinned FH - I got wehat I paid for it so I am starting anew.

I spent the money on the ACOG for a reason, and I need a good SBR upper to match. Will I run suppressed all the time? No. Can I tune a rifle? Yes. (I have a 300 BO and develop loads for it, and tune it with a seekins adjustable and the right loads) Do I need the thing to run on any ammo I might have to put thru it? What good is a go to rifle if you can't?

No I wont be deploying with the rifle. But god forbid something bad happens for an extended amount of time, and I need a rifle that runs on any 5.56 I throw down it. I need this build to be it. I might not have access to 'my ammo'

The lower is milspec, and will have a Magpul CTR, and Geissele G2S. (unless I put my MBT in it)


I really like the idea of the 11.5 length. Im not opposed to 12.5, but the inch might be nice with the can.

I have a problem with the price of those BCM barrels. It seems like the fall-off of price vs return is past on those, given the results with the faxons. But the mid gas system and need for an adjustable gas block seems to possibly be counterproductive for what I am trying to build? I don't know. Then again maybe I am overthinking the gas block. It might make the rifle a pleasant shooter, and setting it with the crappiest , weakest ammo you have might ensure reliability. Also my gas block would partialy be exposed because my SMR is 9.5".

The faxon is under $150. The BCM is double that price. I find it highly unlikely that the BCM would out perform the Faxon at the 2:1 ratio of price.  Then again, if I have to buy a 100.00 SLR adjustable gas block to run the faxon, what am I saving?

I appreciate everyone's opinion  - this has been a very informative discussion for sure so far.

Another option for a lower priced barrel is Ballistic Advantage.  Lots of really good reviews on their barrels.  I'm patiently waiting for the11.5" Modern Series to come back in stock.  They also have a 12.5" if you're leaning that direction.  The reason why I'm waiting for them to get the 11.5" in stock vs ordering from one of the vendors that carries them is you can get a pinned low profile gas block for an extra $40 when ordered direct from them.

Lots of companies offer good 11.5" barrels, why limit yourself to those two brands?

Stag, Ballistic Advantage, VooDoo, Spikes, Green Mountain, Colt, DD, PSA, Del-Ton, just to name a few.


I think you need to narrow down what you want instead of trying to condense what's available.


If you like 11.5", set a features and price goal and then make a selection.


Sometimes I will do a search in the Equipment Exchange here, for instance "11.5" and see what pops up. Lots of good deals to be had.

Ive thought about BA, but faxon seems to get better reviews, and mnore of them, when thinking of affordable barrels.

Their 'if you arent happy' is also better than a '3 shot at moa under x conditions' guarantee.

I have a BA (Aero) on my M5E1. I havent got to shoot it yet. I have heard anecdotes, but not seen much in terms of paper proof.

I have not ruled out BA at all either. Nor FN / PSA etc.

Not a fan of Spikes, or delton and Stag. BA is on the list - kind of - Colt tests have been good lately on the 14.5. DD I trust, but Id probably just buy an upper whole from them again if I went DD again.

Im not really limiting myself. not at all.

The biggest question is what are you going to use the rifle for.  Seems to me you are looking to build what I call a Urban Combat Rifle.  Something that works up to 300 yards effectively.  I know that the DD 10.3 was made and I am sure that some Special Operations group had some requirement that the barrel and supressor had to be a short as possible without limiting combat effectiveness out to a certain range.  BCM has their own opinion that 11.5 is the best running barrel for a SBR.

As far as the adjustable gas block goes there are 2 trains of thought ... 1...great for fine tuning a weapon system...2....Just another part to fail.  As far as why the military doesn't use a adjustable gas block is keeping training to a kiss principle.  It has to be trainable to a person who has never touched a weapon before so the less movable/adjustable parts the better.  Also the military is firing lot ammo ... it should be pretty consistent.  By having a adjustable gas block you can fire all types of ammo from really strong to really weak loaded stuff.    Some people will chime in and say Mr. Stoner didn't design it with a adjustable gas block so it doesn't need it.  I believe the forward assist wasn't in his design but was a after thought from the military.


For some family issues I have put on the back burner 3 builds... they are all SBR's 2 are 10.5 in 5.56 and one is a 8 inch 300 blackout.  I have all the parts for the builds and someone has the barrels for me.  I don't want to have a constructive intent issue.  In the future for my last build I want to make a pdw 7.5 that will for sure get a adjustable block on it.

I don't picture what I want as an urban carbine. Something more all around. Its also not a pdw. I have 9s or even the 300 for that.

I picture it being more of an intermediate carbine of ideal length that I can suppress without being too bulky and long.

My old 14.5 pinned dd for that bill nicely, save the suppression aspect. I also felt that it was heavier than it needed to be. The govt profile seemed like it wasn't a good fit for me.

The rail did work great when I used my gg&g ultralight bipod.

I'm in the process of building a 12.5" upper, for a good all around gun. I think you should give a length like that some thought.
Right now my all around setup is a 10.3" for up close along with another 16" scoped upper.

Ta31 Acog, LaRue mount on a 10.5 Noveske barreled SBR.

This thread is timely.  

I'm trying to put together a solid "woods/outdoors" SBR.  Something that is bombproof with a magnified optic and a suppressor attached most of the time (AAC Mini-4).  The terrain in my area can go from dense woods to wide open fields very quickly.  I'd like something that can do it all in that environment.

I've got a pinned 14.5 Block II-ish carbine (RIS II FSP) with a TA31 RCO on it but it's a long heavy bitch with the suppressor mounted.

I've also got a 12.5 MicroMOA barrel with Govnah, SLR MLOK rail, and Law Tactical folder I'm working on. I planned to use a 1-4 or 1-6 on it, maybe even something up to 8 or 10 power. It could possibly fill the "woods" role but I'm not sure the durability of everything when compared to something with a fixed FSB, ACOG, and pic rail.  There's something to be said for the simplicity of a fixed FSB and an ACOG when it comes to durability.

For some reason the BCM Kino (12.5) really has caught my attention for this outside general purpose SBR.  I think a Kino with a TA33G-H, Centurion C4 midlength cutout rail, 51T Blackout flash hider, and a Mini-4 would do everything I want.  It would be the same length suppressed as my Block II-ish carbine unsuppressed.  It would also be very durable.  

Only downside to the Kino is that it would be relatively heavy compared to say, a 10.5 or 11.5 with a carbine cutout rail and the same optic.  That's where I can't decide if the extra weight and barrel length is really going to do much for me over a 10 or 11.5.  Plus side is that it would suppress better and also be less blasty unsuppressed compared to the shorter barrels.  




TLDR:  I'm in just about the same boat as OP.

A Kino might be the ticket for me, maybe for OP too?
 

Honestly you guys think too much. Lol.

Get what you want. Be happy.

You realize you wil also pay the price in weight of a lopro gasblock along with the fsb.
I get the want for a longer sight radius if ur running a red dot and practice irons a lot.

But speaking as someone who scoped a dissy once....... That weight becomes virtually useless.

Yeah.  Seems like most low pro gas blocks are around 2 ounces give or take so it's not a huge penalty but it's there and they do add up.

It's one of those things where looks and the possibility of unlikely scenarios are trumping rationality .  Those Kino's with a cutout rail look awesome and if for whatever reason the optic goes down the longer sight radius is there.  I'm pretty dead set on a fixed front sight post and have long arms so I'll get some use out of that extra real estate. Plus they look awesome, did I say that already?

I really think the extra length with the suppressor is more obnoxious than the added weight.  It'll still be lighter than the 14.5 with RIS II.  Plus, I've carried heavier carbines before.  I don't think 2 ounces will kill me.






Yeah, that's kinda why I think I'm just gonna stick with the Kino idea even though I could go lighter.  I just really want a Kino and sometimes you just have to go with what makes you happy.

Oh, and sorry to hijack your thread OP.  Seemed like we were looking for something with similar capabilities so I figured I'd jump in the discussion.

God thats badass. I have a UBR on my Aero M5E1.

Isnt that heavy for an SBR?

I think I am going to go faxon 11.5 with an adjustable SLR gas block. In fact I was going to order it tonight, but the place I am ordering from is out of stock on set screw .625 SLR blocks, and only has clamp on types.

You arent hijacking man. I strongly considerd a 12.5 myself. But I really do think I want to try 11.5. Im about to build a HK33 SBR in 12.3 anyway. besiides, 12.5 is awful close to 14.5 and I think an 11.5 will balance better for me.