View Full Version : 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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Andro Corp. I have one of their .070 port size 10.3" barrels. If i'm not mistaken they are made by Ballistic Advantage. I know you said you wanted a 10.5" (which they has as well), but I don't know what the gas port size is.
Here is the 10.3 http://androcorpind.com/556-nato-10-3-fsb-port-size-0-070/
Tigwelder1971
01-18-18, 14:50
"Question is - is anyone making mil-spec chrome lined barrels (with an fsp) to this spec?"
Colt. "This is a NEW (not a take off or cut down) Colt 10.3" 5.56 1/7 twist chrome lined barrel. HPT/MPI Testest with an M4 barrel extension and F marked FSB. Includes a barrel nut and handguard cap. Gas Port size is .070."
Finding them is the chore.
Any opinions on cutting a 6920 or BCM 16" socom barrel to 10.5 and opening up the port?
That is ABSOLUTELY the way to go if you don't mind paying to get the work done.
DD might be starting to make smaller ports... but I doubt they're small enough. I wouldn't take anything Noveske is making now.
Was thinking about buying something Noveske. Anything wrong with them, and what would you recommend in place?
I am personally thinking of something 16", but to keep the thread happy what would you say for a 10.5 inch?
Thanks for the replies, ended up going with a 6920. Going to run it as a 16” till the stamp comes in and then cut to 10.3”. Will probably send to ADCO for the work.
Threw on a KAC RAS and an Aimpoint I had. Digging it so far - need to get more rounds on it.
https://uploads.tapatalk-cdn.com/20180118/5c10029b05caa1825535f0b8620c1861.jpg
Was thinking about buying something Noveske. Anything wrong with them, and what would you recommend in place?
I am personally thinking of something 16", but to keep the thread happy what would you say for a 10.5 inch?
BCM is always a safe bet. There aren't any acceptable 10.5s out there that I know of. SCIONICS RGP 11.5 is nice at .071" That could be cut to 10.5 with NO port work, but it's kinda nuts to pay to have just 1" lopped off of a barrel.
OP gratz on your rifle. I am a fan of the RAS. ADCO does great work. Will he need a new buffer? I recall mk18's using a H2 or something the like.
I have BCM's and I am bored of them. 16" Noveske stainless even gets the no from markm?
I'd be using an H2. Noveske 10.5" have Linda Lovelace gas ports.
OP gratz on your rifle. I am a fan of the RAS. ADCO does great work. Will he need a new buffer? I recall mk18's using a H2 or something the like.
I have BCM's and I am bored of them. 16" Noveske stainless even gets the no from markm?
BCM is always a safe bet. There aren't any acceptable 10.5s out there that I know of. SCIONICS RGP 11.5 is nice at .071" That could be cut to 10.5 with NO port work, but it's kinda nuts to pay to have just 1" lopped off of a barrel.
Do you happen to know the size of Sionics' non-RGP 11.5" gas port? I noticed they sell 11.5" barrels with two different gas port sizes.
16" Noveske stainless even gets the no from markm?
When Noveske was making good stuff, they were over priced in my opinion. Now, their quality seems to have dropped, huge gas ports, etc. I wouldn't buy Noveske stuff at a deep discount.
Do you happen to know the size of Sionics' non-RGP 11.5" gas port? I noticed they sell 11.5" barrels with two different gas port sizes.
I don't. I only have the RGP. I could only guess that it's .004-.005" larger than the RGP.
DD Mk18 gas port are a confirmed .070" now, just FYI.
Whoops, sorry... missed the FSP thing.
DD Mk18 gas port are a confirmed .070" now, just FYI.
Whoops, sorry... missed the FSP thing.
God bless them. The should do an FSB run. I know us FSB hard heads are in the minority.
God bless them. The should do an FSB run. I know us FSB hard heads are in the minority.
Completely agree.
I may have missed it somewhere, but doesn’t LMT offer a Crane-spec’d Mk18 FSP bbl?
God bless them. The should do an FSB run. I know us FSB hard heads are in the minority.
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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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.
They've changed the port size over the years. Used to be that LMT made them to CRANE spec.
You can get a DD with a FSB...
https://danieldefense.com/10-3-5-56mm-carbine-1-7-government-profile.html
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..
Do you happen to know the size of Sionics' non-RGP 11.5" gas port? I noticed they sell 11.5" barrels with two different gas port sizes..076" is their standard 11.5" GP.
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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..
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.php?147202-Why-doesn-t-BCM-make-a-10-5-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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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.
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I remember those 11.5 writeups, not finding them now either. It was definitely in the back of my head while figuring this one out. Dwell time, bolt speed, parts breakage, muzzle velocity all point to the 11.5. But, I wanted the shortest 5.56 with a Fsp, which led to “I want a CQBR.”
I remember those 11.5 writeups, not finding them now either. It was definitely in the back of my head while figuring this one out. Dwell time, bolt speed, parts breakage, muzzle velocity all point to the 11.5. But, I wanted the shortest 5.56 with a Fsp, which led to “I want a CQBR.”
Sounds like a plan! Get what you want. Keep an eye out here on the EE and Gun Broker. Have you considered a Colt 10.3"? That's as short as I'd go.
Outbid stock here:. http://www.gandrtactical.com/Colt-103-CQB-556-Barrel_p_325.html
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Thanks for the heads up on that! Looks like arms unlimited had them out of stock as well. Let’s see if they’re available in the next 4 months. Prefer that to cutting up a perfectly good carbine.
Pappabear has a Colt 10.3 that runs like a champ. The port doesn't cycle/feel oversized at all.
Markm,
You guys ever shoot that upper with a can? How’s it handle the pressure?
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/20180120/65bb5ea516b253668feeb1eae8df7b1b.jpghttps://uploads.tapatalk-cdn.com/20180120/b043e4643fbe172564a3d38cd8e35929.jpg
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... Colt 10.3"? That's as short as I'd go.
http://www.gandrtactical.com/Colt-103-CQB-556-Barrel_p_325.html
Pappabear has a Colt 10.3 that runs like a champ. The port doesn't cycle/feel oversized at all.
That Colt 10.3 has a .070" gas port, which puts the gas drive right at the "5.56" level.
This is perfect when combined with quality parts and quality ammo.
This looks good too! http://sionicsweaponsystems.com/store2015/5/23-5-chrome-lined-w-low-profile-gas-block.html
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This looks good too! http://sionicsweaponsystems.com/store2015/5/23-5-chrome-lined-w-low-profile-gas-block.html
That was the one I was asking about the size of the gas port earlier. Too bad they don't offer the RGP model with the FSB.
I'd be willing to bet, if you contacted the shop it would be an option.
That was the one I was asking about the size of the gas port earlier. Too bad they don't offer the RGP model with the FSB.
That was the one I was asking about the size of the gas port earlier. Too bad they don't offer the RGP model with the FSB.
Call me crazy, but in the drop down for options I see "add FSB +$40" right there on the Web store for the 11.5 rgp barrel.
I called about a year ago and asked for an 11.5 with a .0590" gas port (so I could determine the best size for my setup.) I had it in a few weeks. So, I'm sure you can get an RGP with a FSB.
Call me crazy, but in the drop down for options I see "add FSB +$40" right there on the Web store for the 11.5 rgp barrel.
How did I miss that, thanks!
Good to know on the DD 10.3” barrel, and smaller gas port, I need one that is not as over gassed as my present one is. Now it seems much more violent then a friendsMK he just got from Daniel Defense, I did mine back in 2012 so I’m betting it’s a much larger gas port?
Markm,
You guys ever shoot that upper with a can? How’s it handle the pressure?
Sorry I missed this post. But Pappabear runs a can on everything. No issues.
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.
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.
https://uploads.tapatalk-cdn.com/20180612/6c1263c9f52fcf47be976cf705f50865.jpg
Just picked up from the smith today. Cut to 10.3” and gas port opened to .070.
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