So I currently have a 11.5" BCM upper and I’ve been curious about the 10.3" mk18 upper for a while but I’m still not sure of its worth spending more money for essentially a inch less of barrel. Any suggestions or opinions is appreciated.
You’ve got to have one. There’s nothing like a 10.5" (or 10.3")
Here’ my house gun.
Buy it, if you don’t like you can always sell it.
I can’t see there being a noticeable difference between the two and I can’t give any personal comparison as I don’t have an 11.5" gun. That being said, my 10.3" Mk18 is by far my favorite of my AR’s. Even suppressed it comes in under the OAL of my 16" rifle.
10.3 makes sense if you want a clone, otherwise 11.5 has been shown to be less problematic.
That’s one of things I want to avoid. I like the setup I have right now that’s why I’m unsure if I should start all over for a inch of less.
Make sure you order a adjustable gas block if getting a DD Mk18 upper. You will thank me later. I also have a +1 for 11.5’s over the 10.3/5.
I have an adjustable gas block on a DD 10.3 and still shoot my 11.5, also with AGB, more. There really isn’t any more reason needed to get a MK18 upper other than because you want one.
+1
I have actually never had a single issue with my 10.3" upper. No malfunctions whatsoever except when adjusting the Syrac gas block and took a little too much gas out of the system. The 10.3" DD barrel is over-gassed and was a bit harsh when runnign a standard gas block, but it functioned 100% with many different types of ammo of various quality and pressures. With my personal experience, I can’t see how an 11.5" barrel is any more reliable. I’ve stated before on the forums that having the over-gassed DD barrel combined with an adjustable gas block is actually a plus because it opens up the ability to run ammo of lower than optimal pressures in the event you had to (Wolf, Tula, and PMC come to mind).
I haven’t tried a adj GB yet, but I have a 10.3 DD setup with a blue spring co, and H2 buffer, 5 coil springco extractor spring and oring over the extractor…it runs like a champ.
Never had any issues.
If you want, hit me up via pm and you can shoot my 10.5". It’s not a mk18 as it has a NSR instead of a RIS II, plus an additional 0.2", but it’s fairly close.
I’m in Vegas. You just provide ammo. But not Wartak.
What about a 12.5?
And my buddy wants a mk18, I went 11.5 with A5 and was just thinking that both should be reliable but they go about it differently, is this correct?
Taken from a conversation with the CEO of BCM on this thread: https://www.m4carbine.net/showthread.php?147202-Why-doesn-t-BCM-make-a-10-5-quot-upper
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.
LMT 10.5 upper with a M4 RAS is the way to go. Runs out of the box, more than I could say for the upper I received from DD…
Agreed, and they retain resale value almost indefinitely because it’s such a known solid setup.
For somebody truly in doubt, the BCM 11.5" upper with the MK18RIS-II is still a truly excellent upper to build from, with all the feature set most people want from a Mk18. Similarly, an 11.5" with the 10.75" URX (3.1 or upcoming 4); or the truly sublime KMR handguard 11.5" KMR setup are all really solid starting points. To get an Mk18 without at least evaluating each of those options is a setup for winding up having one of each just out of buyer’s remorse.
I personally run a modified Mk18 setup myself (10.4" barrel with URX3 8.0" handguard that accommodates an OPS 14th can - running a Rosch SLM-2E w/ VTAC L4-Mini and LDI DBAL-I2 in front of an Aimpoint T1; sitting on my needlessly gorgeous Noveske Gen2 Chainsaw SBR lower - G&R LPK, GSSA, VLTOR A5, Magpul MIAD/ACS), so consider that a qualifier on my nearly universal recommendation to others to get an 11.5" setup. My upper originated as a communication error with ADCO, but if I run my M4S can on it, it’s a carbine that fits into a tennis racket case in ready-to-fire setup (assembled, loaded magazine in, suppressor mounted), which is seriously a cool setup… but functionally that kit does very little that a well sorted 11.5" setup with a more up to date QD suppressor couldn’t do.
The OAL gain is small, going to 10.5", you’ll only be able to really notice any difference is that the mass of a can moves a full inch farther away with an 11.5" deal, which becomes relevant after you’ve larded the upper up with weaponlight, control accessories, sights, and maybe IR laser/illuminator capability on top of running dangling a ~1lb can and muzzle device at the end… but that’s predicated on the assumption that you’ll be using it as a double stamp setup. If it’s not a double stamp, then 11.5" all day every day.
For the OP, you’ve already got a really phenomenal setup - if that isn’t doing all the things you want, then start really evaluating what about isn’t the exact flavor of unicorn you want - might be as simple as a different handguard or muzzle device, or even going to a smaller optic - because from where I’m sitting that setup is pretty sorted.
Each of my DD MK18 uppers have been 100% out of the box. I don’t see a lot of complaints about them despite what the LMT fans are claiming.
I have ~1K rnds through my factory built DD MK18. It has been flawless, albeit a bit over gassed. For most people wanting an SBR, IMO, 11.5 is the better choice. I’m dealing with extreme CQB issues so that 1" does make a difference for me (I also just like semi-authentic military weaponry).
Ok I will, don’t do it. Buy another one. There problem solved.
Thank you for your detailed explanation. My 11.5 won’t be suppressed anytime soon so that part doesn’t really play a part. I’ve heard mixed statements how some people say that an extra inch won’t matter where some say it does. I like the setup I have and I prefer the fsb. I guess my curiosity with the DD mk18 is the fact that I don’t own it lol. I have had a ris ii rail in the past and I prefer the shape of the omega I have right now better. I just wanted to see opinions out there on the 10.3. Even then some of what people are saying on here is that it does run good and that it doesn’t. I still have a lot of thinking to do. It’s hard going and dumping 1k on an upper just to not end up liking it or having problems with it. I appreciate you helping though.
I had zero reliability issues with my dd 10.3 with the adjustable gas block wide open. The reason that I installed an AGB to begin with was because I expected it to have a gas port on the large side, and I knew that I would be running 5.56 ammo through it. Initially, recoil was very sharp to the point of being rough. Adjusting the gas block smoothed it out immensely. My friend wanted that gas block to fail so he could laugh, but it was I who had the last laugh. But, still, I enjoy shooting the 11.5 more.