BCM: 14.5" Standard Carbine Gas Upper or 16" BFH Midlength Upper?

[CajunCourier]

I just finished assembling a new lower (LMT). I'm going to just buy a complete upper rather than building one. I've narrowed it down to a BCM 14.5" pinned and welded standard button cut barrel with carbine length gas (they don't make a carbine gas 14.5 in BFH), or a BCM 16" Mid with a CHF barrel. Which one would work better with .223 lower pressure ammo in cold or otherwise harsh conditions?

Which would you pick as a general purpose carbine, and why?

[Clint]

A 14.5 Midlength is a better configuration than the two listed.

[CajunCourier]

A 14.5 Midlength is a better configuration than the two listed.

Don't those have a history of needing full power 5.56 to be run consistently? What's better about it?

[Wake27]

Don't those have a history of needing full power 5.56 to be run consistently? What's better about it?

Those answers have already been answered 7 million times on this site.

[Clint]

14.5 MID is an Optimal gas system configuration.

Here is a nice article about some of the testing that was done recently to prove it.

https://www.m4carbine.net/showthread...-VS-MID-LENGTH

Don't those have a history of needing full power 5.56 to be run consistently? What's better about it?

[1168]

Its been very well covered on this site, but given an appropriately sized gas port, 14.5” mids cycle .223 just fine. Most barrels available seem to be ported with .223 in mind, even if they say 5.56 on the side. As Clint pointed out, midlength gas is optimal for 14.5” barrels. The carbine length gas system was originally spec’d for reasons that have nothing to do with reliability or durability.

[CajunCourier]

Got it. Well this certainly complicates my choices even more.

[RHINOWSO]

You are measuring with a micrometer here, either of the 3 uppers will work fine.

I have a 16" Mid BCM ELW and it is great.
I have a 14.5" Mid Noveske and it is great.
I have 16" Carbine Colt and it is great.

The more important question is do you ever see the need to change out of the muzzle device? While not impossible on a 14.5 pinned, it can be more difficult.

[1168]

Got it. Well this certainly complicates my choices even more.

To better understand your goals:
Is there a reason you are married to .223? Or perhaps there’s a particular load you have in mind?
Are you in Louisiana? How cold are we talking about?

[CajunCourier]

To better understand your goals:
Is there a reason you are married to .223? Or perhaps there’s a particular load you have in mind?
Are you in Louisiana? How cold are we talking about?

1. I'd say I'm pretty married to .223/5.56 in this rifle. I do plan on a .300 blk pistol w/ brace as my next AR, but for this one I want to be able to use my horde of PMC Bronze .223 for practice.

2. I am in Louisiana, but I frequently work up north during the winters. There are some carbine classes I'm planning on attending while I'm up there this year. If it's anything like last year, it's going to get pretty damn cold while I'm there (North Dakota and Minnesota), so I want it to be able to run reliably in those conditions.