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AR-15 Barrel Length

I built an AR-15 from LaRue components a few years ago. I took delivery of the upper and had a local gunsmith install a SureFire muzzle brake adapter to accommodate my new SureFire sound suppressor. I recently decided to change out the old muzzle brake for a new SureFire flash suppressor adapter. When I removed the muzzle brake I discovered that the threads had experienced galling - almost certainly because the gunsmith failed to properly Rocksett the device. The galling wrecked the threads, and then there was the high probability that the excessive torque needed to overcome the seized threads compromised the barrel. I decided to replace the barrel. And while this did not appear to be a warranty issue, I decided to stay with LaRue, so I contacted them and asked how much it would cost to replace the barrel. I'm glad I called them because they said they would replace it for free! :o $26 in shipping costs later (including $1,200 in shipping insurance), the upper is on its way to Leander, Texas.

Anyway, I called LaRue after I sent the package on its way via UPS and asked them to watch for delivery. I also asked them if I could replace the existing 16-inch barrel with a longer barrel. They said, sure, no problem.

What length barrel do you recommend? 18 or a 20-inchs...or just stay with the existing 16-inch barrel length? I don't compete in shooting events, and I'm not a big shooter, so I'm thinking an 18-inch barrel will capture most of the increased velocity from a longer barrel length, and significantly reduce muzzle flash when I am not using the sound suppressor. However, I'm wondering if I should go with the 20-inch barrel. I'd appreciate your thoughts.

Hal
 
18" works good for me. it is a good balance for length, especially since you are shooting a suppressor--by the way, i wish my state (Iowa) was free like yours!
 
Two things to look at carefully before you decide.

First and most important, check to see whether your gas port is positioned for a carbine, intermediate, or rifle-length barrel. Going longer will work, but you will likely experience fewer failures of cartridges, ejection, etc. when the gas system is properly tuned to your rifle.

Second, the velocity gains may be more modest than one might think. Here are some velocities calculated based on a handload that yields a muzzle velocity of 3259 t/sec from a 24-inch barrel:
  • 16" -- 3027 ft/sec
  • 18" -- 3098 ft/sc (+ 71 ft/sec)
  • 20" -- 3159 ft/sec (+ additional 61 ft/sec)
I can't speak to to the muzzle flash and noise, but the changes of impact over normal shooting distances will be rather small.

Bottom line, the system seems to have worked well for you with the existing barrel. So absent making a change "just because" then there doesn't seem to be a lot of advantage to changing.

By the way "just because I want to try it" is one of the reasons we have such a wide set of options to choose from! So, if you want to do it, go for it!
 
Purchased a DPMS 24 in 1/8 SS upper for my Stag lower had it at the Pa shootout last year no problem hitting the steel plate at 200 yards.
 
I have a 16" DPMS barreled upper that has no problem shooting sub moa at 300yds. Barrel length has little to do with accuracy out to 300yds, your accuracy come from barrel quality and shooting a well tuned load.

RJ
 
I'm using a SureFire FA556AR (http://www.surefire.com/fa556ar-m4fa-suppressor.html), which comes back over the barrel. As a result, it "only" adds 3.75-inches to LOA, although even that small amount of additional length added to a 20-inch barrel would seem to make it rather unwieldy. (However, to keep things in context, the venerable Kentucky Rifle had an average barrel length of around 40 inches. http://www.revolutionarywararchives.org/longrifle.html. But I understand that was a couple of months before NightForce opened their doors for business.)

LaRue said they would replace the existing damaged barrel with an 18-inch barrel as I requested, but they apologized that they are currently working on a large contract order for rifles with 18-inch barrels, so they may not have any extras in inventory for awhile. In that case I asked them to just go ahead and replace it with a 16-inch barrel - the same length as the damaged barrel. What it came down to was whether I should opt for a 16 or a 20-inch as a 2nd choice. It appears that the 16-inch would easily outshoot my abilities to affect the point of impact. And given the small gain in velocity when going from 16 to 20 inches, that seems like the best choice for me.

Thanks much for the responses.

Hal
 

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