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Looking to build a 300blk using a KAC URX 3.1 handguard. I need to get a barrel and wondering if the Noveske 8.5" barrel would work or if I should get an AAC 9" barrel to be safe. What I want is the muzzle device and or suppressor will be close to the rail as possible without too much barrel showing.
Do any of you have this set up or do you have a similar set up with a 8" handguard or either a 8.5" or 9" barrel? Muzzle device will be either a AAC or Surefire.
Thanks
I thought about something similar (12.5" barrel with a 12" rail).
But I'm pretty sure that won't work. Look at the Daniel Defense MK18. The rail is 9" with the barrel being 10.3". And that configuration results in the muzzle barely peaking out past the rail. Anything like a suppressor mounted on a MK18 usually barely clears the rail. So I think only leaving 1/2 of an inch of barrel beyond the rail length is a no-go.
Its hard finding a rail you like and then finding a barrel- especially below the 10.5" length. I know the KAC URX 3.1 10.75" handguard goes well with a 11.5" barrel- I've don't that, Noveske 13.7" rail goes well with any 14.5" barrel.Quote:
Originally Posted by Snipe315
In general, the barrel should be 1" longer than the hand guard.
Here is an 8.0" hand guard on a 9.0" barrel, leaving ~.325" of barrel exposed.
The minimum you need depends on the exact suppressor combo.
https://dqzrr9k4bjpzk.cloudfront.net...1000374719.jpg
That's the HG AAC used on their 9" uppers. Plenty of pictures of that setup out there to look at, and I wouldn't go shorter than that 9" barrel.
The 8.5" barrel is designed for a 7" (7.38" actual) HG and gives that 1" difference as Clint mentions above.
Where this gets complicated is:
-The length the HG is marketed as is not the actual measured length.
-The barrel and HG are not measured from the same point, so an 8" HG on a 9" barrel DOES NOT have 1" of barrel past the HG.
-A thread on silencer goes to the end of the threads but QD mounts vary in how far back they put the silencer on the barrel.
The rail on a MK18 is 9.55".Quote:
Originally Posted by Snipe315
I don’t have any URX3’s or any barrel shorter than 10.3, but I do have a few URX4’s (and other brands) and I have a barrel in just about every length between 10.3” and 20”.Quote:
Originally Posted by elephant
Even the 9” may be too short, but should work. The minimum length delta between barrel and handguard is 7/8” in handguard barrel combinations that I have measured. And manufacturers frequently round off, or otherwise misrepresent the length of barrels and handguards. I have a 12.5”barrel/11.5”handguard upper, in which both the barrel and handguard are .25 longer than the spec sheet, so they still work out nicely. DD rounds down on the RIS, see below. I would choose a barrel that is 1”-1.5” longer than the handguard. Leaning toward 1.5” longer if you are using a brake, or don’t want to deal with the possibility of having to do a return. Also, consider going 1.5” long for suppressors.
KAC is no different in rounding off handguard lengths.
14.5” URX4 - 14 3/4”
13” URX4 - 13 1/8”
10.75” URX4 - 10.75”
Consider the barrel lengths these get paired with on factory rifles.
The Mk18 rail is a bit longer than 9”. I don’t have one in front of me. The 12” RIS is 12 5/8”, and the shortest barrel that can be used is 13.5”, actual measurement. I would go 13.7”.Quote:
Originally Posted by Snipe315
Y’all’s 14” medium barrel is MF’ing perfect with a 13” URX4.Quote:
Originally Posted by Clint
Yup,
There's that magic 1" difference again.
Quote:
Originally Posted by 1168
an 8.5" might just clear or you may have to mill a bit off the front of the urx but not much
this is a 5.56 and not 300blk but should be comparable. here's a 9" barrel with an 8" urx 3 rail
https://i.postimg.cc/d1jKyxWs/IMG_1789.jpg
https://i.postimg.cc/J07Cc5gb/IMG_1792.jpg