10.5" barrels and gas ports
Currently in the process of sorting an SBR build and had some questions on the available 10.5" 5.56 barrels out. From what I've been able to find, .070 to .071" is the correct port size for this config.
Question is - is anyone making mil-spec chrome lined barrels (with an fsp) to this spec? Rifle will mainly if not exclusively be shooting 5.56 pressure ammo.
No luck on finding the Colt or LMT barrels anywhere and I've heard mixed results on DD and Noveske barrels (regarding port size). Any opinions on cutting a 6920 or BCM 16" socom barrel to 10.5 and opening up the port?
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10.5" barrels and gas ports
Quote:
Originally Posted by
usmcvet
I'm a FSP lover too! Only one of my uppers doesn't have one.
I have two LMT 10.5" that have run very well for me. I have no idea what size the gas port is.
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The LMT was my other option, as a turnkey upper. There’s a few on gunbroker right now. I figured with the 16” Colt I get to shoot it as is while the stamp processes. Makes the wait go by..
10.5" barrels and gas ports
Quote:
Originally Posted by
marco.g
The LMT was my other option, as a turnkey upper. There’s a few on gunbroker right now. I figured with the 16” Colt I get to shoot it as is while the stamp processes. Makes the wait go by..
ADCO didn't great job cutting an AR bbl down for me. I'd use them again. You'll be with out your gun for a while. Extra uppers are great to have. Why 10.5? My next several uppers have been BCM 11.5" I've had no issues with the LMT 10.5" guns but I read Paul's post on why he chooses 11.5" for fighting guns. I think it's a sticky here on M4C. I'd link it but haven't compl figured Taptalk out! I'll look for it.
Found one thread:
https://www.m4carbine.net/showthread...0-5-quot-upper
"Why doesn't BCM make a 10.5" upper?
ETA -
Q: Why BCM chose the 11.5" SBR over the 10.5"
I get this question a lot. It is a good one. When we spec our program we can build anything we would like, so we sat down and looked at the pros and cons.
First Statement: I know a good 10.5" SBR can run very well. I personally own a semi MK18 type and it runs great. No problems.
A: Dwell time.
Dwell time is the time that your gas operated weapon maintains pressure to continue the cycling of the weapon. It primarily exsists from the time the bullet passes the gas port in the barrel to the time the bullet exits the muzzle. When you pull the trigger and fire the weapon the movement of the bolt carrier group unlocks the bolt, extracts, and ejects the spent casing. Then it cocks the weapon, feeds, chambers the next round, and then locks again. One of the thing that can make SBRs finicky is the dwell time (or lack of).
The 11.5" carbine is approximately 4% longer weapon than its' 10.5" counterpart, but this extra inch gives the barrel a 40% increase in length for dwell time. IMHO, this is an excellent trade off. This additional dwell time (all other things being equal) will allow the carbine to be more forgiving to different ammo types, extremes in air temperature, weak or worn extractor springs, worn extractors, buffer weights, etc.
Last Statement: For those folks who have a 10.5" that works very well, I would reply; me too. (see first statement)
If I had to "go to war" with a AR15 Carbine, I would grab the BCM 11.5".
The BCM 11.5" Runs Like a Dream.
Hope this info helps,
Paul"
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10.5" barrels and gas ports
Quote:
Originally Posted by
marco.g
Markm,
You guys ever shoot that upper with a can? How’s it handle the pressure?
I ran a SF SOCOM 5.56 and 300 on the 10.5" LMT. Semi and FA. It ran like a sewing machine! The 300 is mine and the 5.56 was the PD's. The 300 was fun FA too on my Franken upper. A Noveske BBL, BCM upper and BACK rail. https://uploads.tapatalk-cdn.com/201...eae8df7b1b.jpghttps://uploads.tapatalk-cdn.com/201...8cd8e35929.jpg
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10.5" barrels and gas ports
Quote:
Originally Posted by
jpaul
Sounds like the OP has everything worked out. In case anyone else is interested, Specialized Armament usually has (in their words) Colt MK18 barrel assemblies available. SAW definitely isn’t the cheapest place around, but if you need it now, they’re in stock.
No, what it says is:
“Colt Defense 10.3 inch SOCOM MK18 barrel assy with all SA Reliability Package mods.
1/7 twist, chrome-lined bore and chamber.”
They also won’t disclose what these SA mods are, or the gas port size. I’m not wasting my money on a company that won’t be up front with modifications they do to a barrel or a gas port size that come from another company, assuming that they aren’t lying about it being a true colt MK18 barrel and not just a cut down.
They can take their barrels and kick rocks IMO.
It’s also interesting that they are the only company that seems to be able to source these and always have them in stock, while other retailers haven’t had them in years.