HCS Mk18 Mod1

I am about to venture into my first NFA weapon.

Wanting a 10.5" 5.56 to start. Likely going with an AAC suppressor.

I recently bought a RECCE from Kevin at HCS. He is a phenomenal guy and built me a phenomenal carbine.

So, while I know little about, nor ever really been interested in a Mk18, I see no reason not to go this route. Besides, if I did anything else it would likely be a LaRue or Noveske, and I cant find one of those uppers in stock.

So, I am looking for thoughts on the HCS Mk18 mod1. Kevin would happily change the specs if I wanted. I wonder if the LMT barrel is the best route. Or any other changed I should consider.

Pics would be great too.

The LMT uppers are excellent. If you would want to save a little cash, the BCM 11.5" uppers are widely known to be excellent as well and that extra inch isn’t much.

Just a thought, but if you’re set on an as-short-as-possible set up, the AIM price for a DD mk18 upper cannot be beat.

I bought an LMT 10.5" and it has been an excellent carbine, running through thousands of rounds without any issues, and has proven to be very accurate.

That said, amd5007 is right, BCM and DD also make very nice short barreled uppers.

I really like the weapons that High Caliber Sales makes, it would be really cool to order a Mk12, Recce and Mk18 from them and have the US SOCOM trifecta.

My 10.5" LMT with DD 10" Lite rail

Cameron

Cameron

That is a great idea. And as much as I enjoy dealing with Kevin, and the quality I have seen so far, I may do that.

I already have his RECCE on an SR15 lower. And will likely be ordering the Mk18 Mod1 soon. Only problem is that the Mk12mod0 doesnt appeal to me very much. And to me it would seem like duplication. The RECCE does all the MK12 does in a smaller, lighter package.

A couple years ago I had a really nice, correct PRI Mk12 but sold it pretty quickly.

Looking forward to the Mk18 though, just working out details with Kevin.

Here is the Mk12 Mod0 I had. I never got around to putting the OpsInc 12th on it, although my buddy, to whom I sold it has the correct can mounted on it, it shoots great. Just wasnt for me.


And here is the badass RECCE from Kevin. I havent been able to get past 300 yards yet, but every single group at 300 has been way under MOA. 5 shot groups, when shooting off a bipod and bench, have averaged about 2" at 300. With some at 1.5" So I am optimistic once I go to 600. Hopefully today. Also, I have not loaded any ammo for it. All rounds have been Mk262 or the Black Hills equivalent.

Your first NFA is going to be a 10.5" suppressed??? Just letting you know now, you’re likely to be disappointed. A lot of people are with very short suppressed ARs.

That setup is never going to be particularly “smooth” or even remotely quiet / hearing safe. If you’ve neve shot a suppressed AR, I would do so before commiting to your plans here… Or at the very least I would suggest a 308 can vs a dedicated 223.

That just seems to be a recurring theme I’ve been noticing.

How do you figure that? My first NFA item was an LMT 10.5" that runs 100% both unsuppressed and suppressed. I have yet to have a problem with it all.

It runs smoothly and is drastically quiter than without a can. In fact the 10.5" with an A2 is quieter than my 14.5" with a comp.

I think a 10.5" with a can is a great choice for a first NFA item.

That mirrors my experience. I have a 16" Recce type and bought an 18" BCM SPR, I too sold the SPR as it was just too close in performance to the Recce.

Sold the BCM SPR and kept the DD Recce

Now my two favourite carbines are my 16" Recce and 10.5" Mk18.

Cameron

LOL, assume much?

I have fired quite a few suppressed weapons. From 50 bmg and 338LM bolt guns at LR, to 7.5", 10.5" and 12.5" shorty AR’s.

Hell, that is what helped me decide on the 10.5". And the suppressor I am leaning toward is the AAC 7.62sd-n. Reason being, I want to be able to use it on multiple hosts. The 10.5" I intend to get next, as well as my 16" RECCE and the 300BLK SBR upper I want next.

If I had the funds and patience, I would buy a dedicated can for each host, but I dont. So I am leaning toward the AAC 7.62 for everything.

At any rate, not sure what issues you have had with 10.5’s, but of all the SBR’s I have shot, I like my buddys’ 10.5" Noveske the best. Since I am hoping that the SBR I get first will have a shorter OAL with the can on it than my M4’s are MINUS the can.

I want compact, light, reliable and quiet. That is my intention, and that is why I want the 10.5". You may have issues, but the ones I have shot have been both pleasant and accurate.

Now, back on topic. The one concern I have with the HCS Mk18 is the lack of a switchblock. I had talked myself into not worrying about it, but the more I talk with buddies who shoot suppressed short barreled guns, the more I think I want one.

I sent Kevin an email and I am going to try and determine my options. I am not sure if he has an option for a switchblock, but I think I want one. Any opinions on this guys?

Cameron, those are some badass looking weapons, and it looks like you and I are on the same path.

I absolutely love the way both your RECCE and (especially) the MK18 look.

That is exactly like I want mine to look. I have one concern (other than the lack of a switchblock, as far as I know) and that is the UBR stock. Probably a tie for me between the LMT Sopmod and the Magpul UBR stocks as my all time favorite.

I am concerned the UBR may be a little heavy for this project because I want light as possible. Do you need the UBR for balance on the Mk18 or do you just like the UBR? (Who wouldnt, they are beautiful but built like tanks)

Also, I assume you do not have a switchblock? How is that working out for you shooting suppressed? A lot of blowback?

While the Magpul UBR is not the lightest stock available I find it balances my SBR well. The LMT has quite a heavy barrel profile, couple that with a longer rail and especially a can, I find that the UBR balances things quite nicely, but stocks are personal preference…

My LMT does not have a switch block and there is more gas coming back when suppressed, but not something that has caused me to even go so far as to install a gas busting charging handle. I might get on for the new BCM Gunfighter charging handles that are designed to block gas.

Cameron

Sounds reasonable. I am likely going to roll with what I have to start, and if I need to balance with something heavier, I will.

I want … quiet. … I want the 10.5".

Ok boss. Well good luck because that has not been my experience with 10" ARs.

Fwiw, I see 11.5" as so far superior to 10.5" that I’ll offer you that as a recommendation, but I know the Mk18 is 10 so that’s probably what you’re going to go with. Enjoy it!

Which 11.5" and can are you running?

Are you familiar with the concept of relativity?

Yes, I want quiet, and I want short, leaning toward 10.5. Having shot both 10.5and 12", both with the same can. Not much difference.

Both were quiet,but relative to a suppressed long barrel rimfire they were loud as hell. Relatively. So I expect quiet
and short. Relax man. This is supposed to be fun.

ETA- and I appreciate your recommendation on the 11.5. I am considering options and have a long wait to figure it all out. That is why I am asking questions. Having read the dwell time comments, I can see the importance an extra inch, or even 2,of barrel can make. All options open.

12.5" with a Ranger2

I have an SR7 on order, but AAC can’t seem to get their shit together enough to ship them! I would have gone with a 11.5" but I’m already planning a 9" 300blk, so it seemed to make sense to me to have small, medium, and large sizes, the 12.5" being a nice medium. To that point, I had a 13.7" midlength… Can not recommend that either.

For dwell time, internal pressures and wear, terminal ballistics, etc I think 11.5-12.5" is the shortest I’d go in an AR. Any shorter and I think 300blk or 6.8 make more sense.

I did some highspeed full auto testing for a small mfg a couple weeks back… I was not impressed by any 10.5" there compared to my 12.5". Maybe they were different, but it really seems 10.5" is noticeably more violent than 12.5". The round is designed for a 20" barrel, I’m more than happy to comprise if all it means is 2" oal and an insignificant extra amount of weight.

I know I have said it before in the thread, that my 10.5" runs without issue. I think the compromise is that for a shorter package you will have more blast, more noise, less velocity and a requirement for more gas. That is just the reality. Is the 11.5" less of a compromise, yes but them the 12.5 is even more so and for that matter the 14.5" makes a lot of sense, and then if you are going 14.5" you may as well get the 16"…

If we keep trying to mitigate the compromises than we would probably end up with a 20" with rifle length gas system.

The reality is that a correctly made 10.5" will be 100% reliable, but will certainly wear faster and create more noise/gas/blast etc. It’s my opinion that the benefits of the short 10.5" length out way the costs.

Cameron

Why don’t you tell us more about your SBR’s? I have a feeling there is more to the story. Not one of my SBR’s nor the ones I have built for others has yet to have a malfunction.

This includes thousands of rounds suppressed and unsuppressed through my own, multiple magazine types and various types of ammo.

Oh? That’s so amazing it’s unbelievable.

Well believe it. My 11.5" SBR with can just over 2100 rounds in 3 days during the Magupl Dynamics Carbine II Course= ZERO issues.

All the previous shooting with it= ZERO issues.

12.5" SBR Magpul Dynamics Carbine Course= ZERO issues.

I don’t use shitty parts, I understand how the system works and I have tailored my weapons to run. I also don’t use clown shoes ammunition.

The other SBR’s that I have put together for various personnel have yet to have any issues.

Why don’t you elaborate more on your particular SBR’s? Make, model, etc…

I too have had zero issues over many thousands of round


s with my properly lubed and maintained LMT 10.5".

I apologize I do not have an exact round count immediately at hand.

I just don’t get it. If I use widget X and have a problem, I don’t immediately assume that everybody that uses widget X also has the same problem. People tend to use weird emotion based reasoning when it comes to firearms…

Here is an SBR and it’s the “horrifyingly unreliable on the internet” 10.5" barrel to boot, after shooting approx 3,000-4,000 rounds without being cleaned. I shot a mixture of surplus M855, commercial Federal .223, and Hornady steel cased ammo, and took a 3 day class with Magpul Dynamics.

Amazingly it has never had a failure of any kind to feed, fire or eject. It still has never had a failure that was not attributable to bad ammo or bad magazines.

The reality is that an established firearm like the AR15, Mk18, 1911 etc all work perfectly well when they have been built correctly.

Cameron