View Full Version : Barrel heat in Mk18 profile barrels
Question for the more experienced members or anyone who used a Mk18.
The barrel listed on DD’s website is 1.15 # (18.4 oz). This is very light. How did it hold up under sustained use, particularly when paired with the suppressor?
It doesn’t seem like a problem, as I haven’t heard about it.
I’ve got a nice 11.5” barrel that is 23.5 oz. It’s on my “generally chasing ounces” carbine, which when suppressed is heavier than I would prefer, particularly considering I will eventually add a laser/illuminator to the end of the handguard. I’m considering changing the barrel out to an 11.5 or 11.3 that is a little lighter.
The 5.5 oz isn’t that big of a deal, as it is better balanced than the 10.3. Before anyone comments on weight, I have a persistent left shoulder problem that when supinated in an aggressive hand-over-bore extended grip is perfectly fine, but I cannot slide my hand back into heel-to-magwell supinated grip as I used to do when using an AR for a while. Explanation offered due to the typically negligible weight difference that I wouldn’t have concerned myself with previously. The shoulder thing reared it’s ugly head again after a number of years being fine.
AFAIK, the MK18 barrel is a pure gov profile so the only reason it may seem light is because it’s short. I haven’t shot mine in significant enough strings to know for sure, but I’ve definitely never noticed any issues, to include during the minimal time it had a KAC can hanging off of it.
Also should be important of note, SOF’s MK18 barrels are the same profile. Between clone needs and actual SOF, shit tons of rounds have gone through those barrels and while the M4 was upgraded to a Socom profile, the MK18 never was so I assume it has to be good enough.
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DD uses an aggressive taper from .675" to .575", which seems pretty thin, but also seems to work just fine.
Our 10.5" PRO barrel for example uses a much more gentle taper and comes in at 19.0 oz.
There is definitely the possibility to shave 3-5oz from your current setup.
DD uses an aggressive taper from .675" to .575", which seems pretty thin, but also seems to work just fine.
Our 10.5" PRO barrel for example uses a much more gentle taper and comes in at 19.0 oz.
There is definitely the possibility to shave 3-5oz from your current setup.
Is that not a normal gov profile? I don’t remember ever seeing actual measurements.
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Is heat really a problem in semi-auto with a well made barrel?
https://www.m4carbine.net/showthread.php?186379-Argument-for-pencil-barrels
https://www.youtube.com/watch?v=QTovPt4weIs
FWIW, My 10.3" Colt upper has a Socom profile barrel and a .070 gas port just like the FN and Colt 10.3" Socom barrels in this thread. It runs like a champ, suppressed and unsuppressed, and handles the heat very well. I barely notice the extra weight and my RIS II rail still fits perfectly over it.
https://www.m4carbine.net/showthread.php?170268-USGI-10-3-quot-URG-upper-build
https://www.m4carbine.net/attachment.php?attachmentid=49249&d=1513448615
https://www.m4carbine.net/attachment.php?attachmentid=49248&d=1513448560
Is heat really a problem in semi-auto with a well made barrel?
Depends on how many rounds you want to shoot at one sitting, and how fast you shoot them.
10 rounds per minute, will get the barrel 6" forward of the breech to about 625 degrees F.
https://i.imgur.com/xPy7Sh5.png
20 rounds per minute, will get the barrel 6" forward of the breech to about 875 degrees F.
https://i.imgur.com/hIF8qrH.png
60 rounds per minute, will get the barrel 6" forward of the breech to about 1,200 degrees F.
https://i.imgur.com/DPNaSjT.png
And, this location will be the hottest location for any "government" profile type barrel, ie, one that tapers from 0.70" to 0.60" just before the front sight buttress.
Saved for future reference. Thanks!
Question for the more experienced members or anyone who used a Mk18.
The barrel listed on DD’s website is 1.15 # (18.4 oz). This is very light. How did it hold up under sustained use, particularly when paired with the suppressor?
It doesn’t seem like a problem, as I haven’t heard about it.
I’ve got a nice 11.5” barrel that is 23.5 oz. It’s on my “generally chasing ounces” carbine, which when suppressed is heavier than I would prefer, particularly considering I will eventually add a laser/illuminator to the end of the handguard. I’m considering changing the barrel out to an 11.5 or 11.3 that is a little lighter.
The 5.5 oz isn’t that big of a deal, as it is better balanced than the 10.3. Before anyone comments on weight, I have a persistent left shoulder problem that when supinated in an aggressive hand-over-bore extended grip is perfectly fine, but I cannot slide my hand back into heel-to-magwell supinated grip as I used to do when using an AR for a while. Explanation offered due to the typically negligible weight difference that I wouldn’t have concerned myself with previously. The shoulder thing reared it’s ugly head again after a number of years being fine.
Had a MK18 upper that would choke running full auto suppressed - turns out DD had oversized the gas port to accommodate "cheaper" ammo*. They replaced the barrel with one that had properly sized gas port and it runs like a champ. Once that was swapped out it had no issue dumping mags and the heat was not an issue - the rails did have Ergo panels - until we hit three mag dumps back-to-back and that got the can hot enough to get the grass to burn. The rail was uncomfortable at that point (to say the least) and heat was felt even through gloves.
The owner of the upper has really abused the shit out of it on his registered lower.
66434
For a semi suppressed it is honestly a non-issue.
* - edit to add: IIRC this was an issue on the commercial uppers. I do not know if DD still runs a larger than spec gas port on commercial uppers now. I ws told LEO and .mil barrels always have in-spec ports. Also, this information is over 6 years old so take it with a grain of salt.
Question for the more experienced members or anyone who used a Mk18.
The barrel listed on DD’s website is 1.15 # (18.4 oz). This is very light. How did it hold up under sustained use, particularly when paired with the suppressor?
It doesn’t seem like a problem, as I haven’t heard about it.
I’ve got a nice 11.5” barrel that is 23.5 oz. It’s on my “generally chasing ounces” carbine, which when suppressed is heavier than I would prefer, particularly considering I will eventually add a laser/illuminator to the end of the handguard. I’m considering changing the barrel out to an 11.5 or 11.3 that is a little lighter.
The 5.5 oz isn’t that big of a deal, as it is better balanced than the 10.3. Before anyone comments on weight, I have a persistent left shoulder problem that when supinated in an aggressive hand-over-bore extended grip is perfectly fine, but I cannot slide my hand back into heel-to-magwell supinated grip as I used to do when using an AR for a while. Explanation offered due to the typically negligible weight difference that I wouldn’t have concerned myself with previously. The shoulder thing reared it’s ugly head again after a number of years being fine.
With your situation, 5.5 ozs on a barrel is a big deal. If a lightening your AR helps your shot better, saves you pain or reduces fatigue, go for it. A lighter barrel will get hot with fewer rounds, but you can easily manage the heat. The barrel and suppressor can be cooled with water or a wet rag. It won’t hurt anything. (Be careful when using a wet rag. You have to keep the rag wet so you don’t burn yourself.)
The "government" profile varies quite a bit between various makers.
The original M16 barrel is .670 -> .600, but that is a fairly light barrel with the .625 gas block journal.
Colt continued this with many barrels, including those with the .750 gas block journal.
Most other makers start with .670 but taper to a different small dimension, usually between .660 and .600.
Is that not a normal gov profile? I don’t remember ever seeing actual measurements.
I can tell you that it doesn't take much for a MK18 Mod1 to heat up pretty badly. Gloves are pretty much a necessity.
In the linked video below, the shooting drills shown, when all added up, were enough to make the handguard very uncomfortable to hold.
https://youtu.be/2sRkIC6sST0
Sparky5019
09-19-21, 13:54
Question for the more experienced members or anyone who used a Mk18.
The barrel listed on DD’s website is 1.15 # (18.4 oz). This is very light. How did it hold up under sustained use, particularly when paired with the suppressor?
It doesn’t seem like a problem, as I haven’t heard about it.
I’ve got a nice 11.5” barrel that is 23.5 oz. It’s on my “generally chasing ounces” carbine, which when suppressed is heavier than I would prefer, particularly considering I will eventually add a laser/illuminator to the end of the handguard. I’m considering changing the barrel out to an 11.5 or 11.3 that is a little lighter.
The 5.5 oz isn’t that big of a deal, as it is better balanced than the 10.3. Before anyone comments on weight, I have a persistent left shoulder problem that when supinated in an aggressive hand-over-bore extended grip is perfectly fine, but I cannot slide my hand back into heel-to-magwell supinated grip as I used to do when using an AR for a while. Explanation offered due to the typically negligible weight difference that I wouldn’t have concerned myself with previously. The shoulder thing reared it’s ugly head again after a number of years being fine.
I have an older (2014ish) DD MK18 barrel that has seen 1000s of rounds of suppressed full auto and a 1000 or so unsuppressed FA. Surefire SOCOM RC suppressor. No major issues with heat over time. Accuracy is fine though it’s trending down over time as expected but still very acceptable. Any specific questions pm me.
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