I’ve got a MK18 SBR that I want to suppress, but I am kind of displeased with the weight of the firearm as it’s configured already. I am strongly considering selling the MK18 rail and putting on an Apex forend with an AAC Ranger3 thread on can. I want to set it up so that the can goes beneath the last inch or so of the rail, giving it a sort of MP5SD look. My only concern is that the can may get the forend too hot to handle. Does anyone have any experience with this?
This is what I’m going for:
Short answer is Yes, running a rifle can under a handguard sucks. It looks cool in pictures, but sucks in practice.
That said, if you use gloves and the can only inserts an inch or so, and you don’t shoot much, you might be fine.
Agreed with above.
What I particularly like is when someone does it to a QD can like the AACs or Surefires that need the latch to be pressed. As if sticking something into the hole in the rail is acceptable.
And I wouldn’t run a thread on can for a semi-auto so, nope, I would never do this for a variety of reasons, only one being heat.
All I’m really concerned about is heat. I know a bunch of people say that they don’t like it for this reason or that, that’s really irrelevant. When you say it “sucks” do you mean it gets too hot, or that you just don’t like it?
Centerfire rifle silencers get fast hot. Faster on a short barrel.
Of course, but will that heat transfer significantly to the rail even if the can is free floated? I need answers about this specific setup. I’ve seen quite a few people do similar stuff with the KX3s and no one seemed to have any complaints.
Did it once, won’t do it again.
SO WAS IT HOT?
Rofl, Jesus fuck people.
Really fucking hot.
Mine isn’t even “under” the rail, just extremely close and the rail gets way too hot to hold and even makes my gloves smolder. I can only imagine that a suppressor actually under the rail would cause amazing heat transfer to the rail, and you could easily have a rail that reaches several hundred degrees. I even had to remove a Gear Sector hand stop because the aluminium hand stop became way to hot to touch even with gloves.
Mine, with a tiny gap between the front of the rail and the can will get the rail so hot that the Magpul XTM rail panels will start to smoke.
It will make your rail too hot to use, I don’t recommend it for more than very casual use.
Alright, I appreciate the input. Guess it’s back to the drawing board.
Edit: Also, I’ve never run a can close to the rail. My MK18 with the M4-2000 would be about as close as yours is, so I guess I should expect it to get unreasonably hot?
I have a similar set-up for a 300BLK 10.5" barrel with a JP 15" rail and an AAC 762-SD. What about running some heat wrap on the suppressor to help absorb the heat?
S/F
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Looks like Daniel Defense is introducing a factory 16" suppressed 1-stamp gun.
http://www.flickr.com/photos/zero7one-photo/8385140057/
Not really. You have to think about radiation. There’s not much surface area of the can facing backwards, the heat is primarily radiating 360 degrees away from the bore/hole/whatever it’s called on a suppressor. Whereas when the rail gets in the way of that radiant heat it collects it.
I’ve shot extremely hot suppressors that were very close to the end of the rail and didn’t have any issues other than burning my leg when I let it hang on the sling.
So it gets hot, right? 
I plan on doing this for a 9MM AR SBR build, but it’s a novelty range toy, and being a pistol caliber should get as hot as quickly.
But still, I expect it to get hot and it’ll be a direct thread, so no QD issues.
There’s no such thing as “QD issues”. Thread on cans tend to unscrew themselves when they get hot. I’ve personally witnessed this at the range.
I thought they can also “weld” solid and require heat and torque to remove?
Pretty sure that has more to do with carbon build up than heat itself. I have 2 g5 mounts and they’ve each acted differently. One on my sbr came loose a few times, the other was a hard mother to get off. I didn’t use rock set for either.
My 9mm thread-on is constantly slipping off as it heats up.
Bottom line I would never use a thread-on rifle can on an AR unless I used some means of locking up the threads. It’s not as if you can grab it to tighten or check for tightness.
9mm won’t get too hot as fast, it should be fine if you don’t run it hard.
It’s easy to add an O-ring to 1/2" pistol threads if they have a thread relief cut. 1mm O-ring, 10mm ID.