View Full Version : Whats the advantage of an 18" barrel over a 14.5" Barrel?
Averageman
04-13-18, 18:22
I have an older "Frankengun" with a 14.5 in. BCM upper. The lower has a Geissele trigger that sits in a Spikes lower. I've owned this over a decade, closer to 15 years and have around 2500 or more rounds through it. It was my first AR and to date I've had only one hiccup with it and that was due to a dirty chamber. I currently use an AimPoint PRO with it.
I've been thinking of buying another upper for it and putting a 3X9X30 Optic on the other upper and setting both aside to gift to my Son when he graduates.
I have to ask because I'm curious as to the the answers I would get from the brainbank here, other than as a platform for a more powerful , what would be the advantage?
I ask because I'm seeing a good deal on 18 inch uppers right now from Aero Precision.
Thanks
A/M
Increased effective range (terminal ballistics-wise) due to the longer barrel. Can't think of much else, not that it isn't a laudable goal. I'd say if that tripped your trigger then go 16" and call it a day.
ExplorinInTheWoods
04-13-18, 20:26
So if you're going to put a 3-9 or any other higher magnification scope then the 18inch is the way to go. You gain or lose 30-50 fps for every inch of barrel with 223. You'll have a higher muzzle velocity so less drop at distance and usually 18 inch guns are rifle length so less recoil than a carbine or mid length. I have a noveske 18inch on my 3 gun rifle and love it. 18 is good for 3 gun or good for a coyote gun you'll carry around.
BrigandTwoFour
04-13-18, 20:37
Advantages:
- Higher starting velocity
-- Less holdover/dial required for any given distance
-- More flexible point blank zeros
-- Increased fragmentation range
- Rifle length gas
-- Smoother recoil impulse
- Longer sight radius if using fixed irons
Disadvantages
- Increased weight, particularly at the front of the weapon
- 18" rifle gas, while mostly figured out, can be touchy with gas port size
- Increased length when dealing with tighter spaces
longshot2000
04-15-18, 08:57
- 18" rifle gas, while mostly figured out, can be touchy with gas port size
This is very true, and not widely known. There are only a few barrels that handle 18" very well, and also, only a few that handle 14.5" and shorter very well. A Carbine gas system with a 14.5" Colt barrel works like a charm. A mid-length gas system with 16" is almost foolproof for most barrels. 10" rifle length the same. 18" and 10.3" are very, very tricky. Douglas does the best with 18" and Colt and LMT with the 10.3" to 12.5". Douglas figured out the 18" on the Mk12 barrel, and the barrel smiths I work with agree. Even more expensive barrel makers have extreme erosion at the gas port on 18" barrels.
That said, I am a fan of the long barrel for longer distances and accuracy. I am also a fan of the 14.5" M4 carbines. Just remember what each is designed for. Technical people will argue that accuracy is not a function of barrel length, and that is technically true over a short distance. The issue is not just velocity gets you out further, but for the 5.56 bullet, it is at what distance does the bullet cross the sound barrier, i.e., become transsonic. The faster it starts, the further out that place of turbulence is hit. The longer the barrel, the faster it start
So what's the range of optimal gp size for the 18"? Also, is it safe to say that a 14.5/16" is more of a "combat" length barrel?
I’ve been told barrel steel plays a role with gas port erosion on an 18” rifle gas barrel. Frank at CLE will not use Krieger or Bartlein for 18” rg. He knows more than I do but KAC uses Krieger for their lpr’s. I “think” crane spec is .0995 for the gas port, I could be wrong. I have one with a .0993 (measured with pin gauges) that functions fine in Ga winters.
ETA: I’ve spoken with Frank over the phone to get the info about the barrel steels. If you’re placing an order he will take the time to explain.
Averageman
04-15-18, 12:08
After reading all of his and contemplating what I'm getting in to a bit more, I will do one of two things.
Look for a 20 in barrel BCM upper, I have one and it rocks along all day long, or skip the whole thing and give him the carbine and twenty five mags and 1K of some 55 grain stuff I have in the closet.
Either way, it should be better than going in to a 18 in barrel I have no experience with.
longshot2000
04-18-18, 17:58
I’ve been told barrel steel plays a role with gas port erosion on an 18” rifle gas barrel. Frank at CLE will not use Krieger or Bartlein for 18” rg. He knows more than I do but KAC uses Krieger for their lpr’s. I “think” crane spec is .0995 for the gas port, I could be wrong. I have one with a .0993 (measured with pin gauges) that functions fine in Ga winters.
ETA: I’ve spoken with Frank over the phone to get the info about the barrel steels. If you’re placing an order he will take the time to explain.
Exactly. I was reading your post, thinking I wrote it. Yes, Frank is the expert, and the source of my comment on the Douglas barrels in 18"
All is a an acceptable plan, but look what into BCM uppers. They small price crease is worth every penny. Your son will thank you endlessly.
PB
vicious_cb
04-18-18, 21:37
Realistically there's nothing you can hit with a 18" barrel that you can't hit with a 14.5" or 16" barrel. But that 18" will hurt you if you trying to get in and out of cars with the thing.
Averageman
04-18-18, 21:46
Realistically there's nothing you can hit with a 18" barrel that you can't hit with a 14.5" or 16" barrel. But that 18" will hurt you if you trying to get in and out of cars with the thing.
That wasn't really the point though was it?
I was looking for another upper as host to an optic besides the red dot currently on the dedicated upper I have on it now.
Being that my Son is 22 and going to college as he works a full time job, he doesn't have the scratch for a single AR. Giving him that one, plus an upper with a good 3x9x40 scope on it would enhance that, having a longer barrel would add to the potential of increased velocity with better ammunition.
Saying a 14.5 barrel will do everything an 18 inch barrel will (and clearly there is a loss of velocity,) simply isn't true or practical when it comes to the addition of a variable power optic. So one lower + two uppers is a logical solution in this case.
I've decided to go with a BCM 20 inch upper as I have a BCM rifle now that hosts one and essentially the problem is solved.
Thanks Though.
Using "one lower, two uppers" as a guideline, I suggest looking into building the lower as a pistol utilizing the new SB Tactical SBA3 adjustable brace and the BCM A5 style RE, A5H2 buffer and Sprinco green spring.
Then, build one upper as an 18/20 inch and the second lower as an 11.5 inch. My 20 inch Battlecomp equipped upper on an A5 lower has amazingly flat recoil. My 11.5 inch upper on the same lower is also smooth and soft.
Just ran some quick numbers through a calculator comparing M262 out of a 14.5 and 18 inch barrel at sea level:
14.5:
MV 2590 FPS
transonic 800-850 yards
drop at 600 yards 5.42 Mils
18
MV 2780
transonic 900-950 yards
drop at 600 yards 4.54 Mils
So an 18 inch barrel gives you about an extra 100 yards of supersonic flight and shoots roughly a mil flatter out to 600 yards.
Averageman
04-19-18, 17:50
"Back in the Day"...
I dunno, I was curious about 18 inch barrels because the was an interesting price on them at the time, that deal came about the same time I asked the question. It has since left the building like Elvis and Chuck Berry.
Eighteen inch barrels intrigued me as I have no experience with them. After reading some of the cautionary advice here concerning how they can be finicky, I'm not feeling the love.
Honestly I was always pretty adapt at picking out where my rounds were flying, even past the three hundred yard mark with irons on my A2, "back in the day."
I'm feeling a bit guilty that my Son, who isn't much of a shooter, doesn't share the love and doesn't own a firearm at this time. So, it's going to be a BCM 20" upper and the lower and the 14.5 rifle as a gift.
"Back in the Day"...
I dunno, I was curious about 18 inch barrels because the was an interesting price on them at the time, that deal came about the same time I asked the question. It has since left the building like Elvis and Chuck Berry.
Eighteen inch barrels intrigued me as I have no experience with them. After reading some of the cautionary advice here concerning how they can be finicky, I'm not feeling the love.
Honestly I was always pretty adapt at picking out where my rounds were flying, even past the three hundred yard mark with irons on my A2, "back in the day."
I'm feeling a bit guilty that my Son, who isn't much of a shooter, doesn't share the love and doesn't own a firearm at this time. So, it's going to be a BCM 20" upper and the lower and the 14.5 rifle as a gift.
Having used a M16A4 and a SDM-R overseas Im a bit partial to a 20inch rifle. I have shots on man sized targets out to 1000 yards with that SDM-R and M262. Not the easiest shooting Ive ever done but I had a full case of M262 to myself, so I had a lot of ammo to practice with. 600 and in with that rifle was actually fairly easy on man sized targets. I was limited to an ACOG so smaller targets were hard just for the fact I couldn't see it as well.
I have a PSA upper built with an FN chf cl barrel in 223 Wylde. I have not shot it much, but it shoots well. I don’t know if those barrels are susceptible to the erosion issues. I really like it — shoots Hornaday 75 steel match pretty good.
Sent from my iPhone using Tapatalk
edited to remove info that was just gonna clutter since OP already solved the issue.
Edited.....since OP got what he needed, figure I'll remove the info as not to clutter
Edited.....since OP got what he needed, figure I'll remove the info as not to clutter
The Big T comes out of retirement, long time no hear Big Fella.
PB
"Back in the Day"...
Eighteen inch barrels intrigued me as I have no experience with them. After reading some of the cautionary advice here concerning how they can be finicky, I'm not feeling the love.
I spent some time obsessing over gas system length and decided on the Noveske 18" intermediate as a 'compromise', or perhaps better tuned to that length than rifle. It functioned flawlessly this winter on 5.56 pressure ammo. Picked up with fitted bolt and pinned gas block for just under $400 (Midway clearance). Once you become symptomatic with BRD you'll build one anyway, resistance is futile...
Edited.....since OP got what he needed, figure I'll remove the info as not to clutter
I wish you would stop deleting the information from your posts.
Great info. I’ve got a 18” I haven’t fired yet because I haven’t purchased any glass for it.
I wish you would stop deleting the information from your posts.
We need to start quoting him.
Trident, your posts are not “clutter”. Most of us appreciate the info.
Trident, your posts are not “clutter”. Most of us appreciate the info.
Fact.
In the world of 14.5 versus 18, the obvious issue is length, then comes velocity and maneuverability (obviously based on the length difference). After that we can start looking at dwell times, recoil impulses, the variables in barrels for intended purposes (SS vs a myraid of others) and on and on.
The larger issue is the question of what the intended use is, and is almost always one of the first things posted in a thread. Another way to phrase the question would be to ask the OP what they intend to use as an optic (any OP, not just this one). If a user plans to mount a fixed 10x scope, or (something I wish I could publicly comment on but can't quite yet), the answer would appear to be based on a longer barrel. Not just because of a pickup in velocity, but because there is no practical way to be clearing buildings. Can a 14.5 be a dedicated precision rig? Absolutely yes it can, and it can do it admirably well if the user understands its limitations.
Below are a 14.5" and 18" setup with the same optic shown on each. For someone shooting at a KD range of 100 yards (200 or other in close ranges), and a lack of ability or intent to shoot farther, it will do everything its larger sibling will, and just as nicely. Lets not forget that those who live in the woods are not targeting the same way as those who live in the wide open desert flat land.
Lastly, quality of the barrel is so important it can't be understated. In this case, the barrels shown are an 18" MK12 barrel barrel from Monty at Centurion Arms, and a 14.5" barrel that Johnny gave me years backs. Both are fantastic and stand out above what I would consider a "typical" good barrel.
Figure the use, then figure the optic, then worry about barrel.
https://68.media.tumblr.com/f15da1142311690c8a0a27c9513e1237/tumblr_p7e69zQXER1rrcg2fo1_1280.jpg
https://68.media.tumblr.com/eeaccbd2ebf3a05c270b3204c826eb06/tumblr_p7k3ljRRlc1rrcg2fo1_1280.jpg
HelloLarry
04-26-18, 15:20
A longer barrel generally makes for a heavier gun.
A heavier gun is easier to shoot well. Heavier guns are less sensitive to holding forces and trigger technique.
I've been thinking of buying another upper for it and putting a 3X9X30 Optic on the other upper and setting both aside to gift to my Son when he graduates.
I have to ask because I'm curious as to the the answers I would get from the brainbank here, other than as a platform for a more powerful , what would be the advantage?
I ask because I'm seeing a good deal on 18 inch uppers right now from Aero Precision.
Thanks
A/M
IMHO, unless you simply MUST have a pencil barrel why don't you just buy A Windham Weaponry 16" Dissipator upper barrel assembly and call it even?
You'll get the right size carbine length barrel and the flat top upper receiver and you'll get the longer rifle-length sight distance that continuously proves to be the best length for accuracy with a 1-7" twist that will spin all popular ammo weights with no problems. Personally I think this will be your best all-around choice for a shorter barrel as opposed to the longer barrels.
I generally choose 16" as I like to have the ability to change muzzle devices (I keep threatening to get a suppressor) I never do change so 14.5" should work for me. I do have one Noveske complete upper with a 18" barrel. I have a Leopold VX-R 1.5 x 5 x 33 (30 MM tube) Firedot Scope on the rifle it came with a JP ? muzzle brake on it. I don't guess I shoot it any better than my 16" Armalite upper, the 18" Noveske with the scope is heavier and more unwieldy
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