Help me decide between 16" or 18" barrel

[heem_infinite]

I can't make up my mind if I want to do a SPR type 18" with a DD Lite 14.0 or a 16" with the DD Lite 12.0. It will primarily be used for range fun but I might carry it on duty every once in a while. My 10.5 SBR is with me now. If I do the 16" I might be inclined to take it on duty more often. I don't plan on shooting past 300 yards with it. What would be the advantage if any in going with the 18"? I know there was a post about this a while ago but I can't find it.

[USMC03]

I wrote the following in another thread several months ago:



Just some food for thought:


Barrel length has nothing to do with accuracy. Depending on ammo, etc. the difference between a 16" barrel and a 20" barrel is only around 100 feet per second.

Velocity with 3 different barrel lengths using 5.56 M193 55 grain ball

14.5" barrel - 3064 feet per second
16" barrel - 3132 feet per second
20" barrel - 3259 feet per second

With this ammo, chrome lined barrels, the velocity gained from a 16" barrel to a 20" barrel is 127 feet per second......for each inch of extra barrel you are gaining 31.75 feet per second in velocity. The velocity gain isn't as great as many may have thought.


18"
-You can use a rifle length gas system on a 18" barrel (slightly smoother than a mid-length gas system). Some companies use an intermediate gas system (between a mid and rifle length gas system on 18" barrels)

-Slight velocity gain (approximately 50 - 75 feet per second - depending on barrel, ammo, etc.) at the cost of added length and added weight (on most stainless barrels a 18" barrel will weigh 6 to 8 ounces more than the exact same 16" barrel)


16"
-Shorter, lighter, more compact, thus making it a little easier to shoot from unconventional shooting positions.

-Most will use the mid-length

-Slight loss in velocity



I used a White Oak Armament 18" SPR barrel on a competition gun several years ago. Great barrel, but it was on the heavy side (for my preferences, based on my body size and shooting style) and went back to a 16" barrel: https://www.m4carbine.net/showthread.php?t=718&highlight=White

Some good info on 1/7" vs. 1/8" twist rates can be found here: https://www.m4carbine.net/showthread.php?t=29302




Weight comparisions:

http://www.03designgroup.com/photo/ar15-upper-receiver-weight-comparisons/icon-ar15-upper-receiver-weight.jpg
03designgroup | AR15 Upper Receiver Weight Comparisons http://demigodllc.com/icon/extwh3.png (http://www.03designgroup.com/technotes/ar15-upper-receiver-weight-comparisons)

[heem_infinite]

That was the thread i was looking for. Going by the weight comparison link the 18" weighs about 9 ounces more. Since I wouldn't be carrying it much I'd rather have it to get more range if possible. How much will the 2 inches effect the range? The place I shoot at has a 600 yard range that I may want to try every now and then. Now I just need to find some more money. thanks

[hikeeba]

Just an observation based on USMC03 velocity data:

Flight time of the M193 from a 16" barrel to a target at 600 yds = ~1.72 seconds
Flight time of the M193 from a 18" barrel (3132 fps + 62.5 fps for the additional 2") to a target at 600 yds = ~1.69 seconds.

Difference in projectile flight time between 16" and 18" barrels = 0.03 seconds.


I am no expert on this topic, but I will guess that range won't be much different between an 18" and a 16" barrel. Point of aim and terminal ballistics may vary slightly at the stated 600 yards.


I have spent the last several months pondering an upper build. First I thought I wanted a 20". That idea quickly morphed into building an 18" SPR something-or-other. I was stalled there for quite awhile, until I came across a couple of USMC03's posts relating to the topic. Since I'm only a hobbyist, and it will be a small miracle if my guns ever see targets beyond 300 yards, I finally decided on a good, heavier profile, 16", 1:7, Wylde chambered barrel. That is my example. heem_infinite, your duty application may dictate something completely different.


If I haven't mentioned it anywhere before, I'd like to say thanks to USMC03. Your informative posts and matter-of-fact demeanor in which your info is presented is what originally prompted me to join the M4Carbine community. I like it here. I look forward to learning more, and contributing when I can.

[USMC03]

Thanks for the kind words, Brother