18" vs. 20" 5.56

jLorenzo

jLorenzo

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Feb 20, 2017
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#1
What are your opinions? I used to want my SPR to be decent at semi close range but in real life I only ever shoot it off the bipod or tripod. I will be target shooting, some local matches and very occasional varminting. I have a 18" now but the accuracy is not there and its going to be replaced. I like how it handles and feels although it is a A2 profile. I will be shooting 75s and 77s mostly but also would like to plink with xm193 and use something like the 50gr Federal HP (surprisingly shoots a touch over a minute in my current 1:7) for varmints/predators.
I'm leaning towards 20" to add a little bit to its supersonic range.
 
#6
I mean I was a little surprised I just figured a 1:7 wouldnt like a factory 50gr the best out of a ton of different factory loads. only thing that shot better was Norma match 77gr. All the other heavies were unimpressive including Black Hills, Hornady and FGMM. Its a crap barrel to be honest.
308pirate said:
Why are you surprised by that?

99% of what you read on the internet about twist rates is complete bullshit.

As far as the length difference (2") it matters only regarding handiness.
Click to expand...
 
#8
There's no guarantee that a barrel is going to like a particular kind of ammo, regardless of how much the barrel cost, how much the ammo cost, or what bullet it's slinging. You stand better odds with certain manufacturers of getting a barrel that will shoot well across a wide variety of ammunition types but even then things happen. I had a 16" WOA barrel a couple of years ago that was super picky, it didn't like anything except Hornardy Frontier 55gr HP. I ended up sending it back to Brownells and they sent me another one, which has shot well with a couple different kinds of heavies and reasonably well with ball ammo, so all's well that ends well.
 
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#9
jLorenzo said:
I mean I was a little surprised I just figured a 1:7 wouldnt like a factory 50gr the best out of a ton of different factory loads. only thing that shot better was Norma match 77gr. All the other heavies were unimpressive including Black Hills, Hornady and FGMM. Its a crap barrel to be honest.
Click to expand...
Twist rate has virtually nothing to do with accuracy once the bullet is stabilized enough.

Excessive twist maybe matters at ELR ranges. Otherwise once you have enough with a margin you're done.

Twist rate, nitriding, tolerances, 4140 vs 4150, etc, are just some of the few nuggets of bullshit to come out of arfcom..................

BTW, do you still have that Howa 1500?
 
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#10
At 600 yards you may need a little more adjustment for wind. The 18 shoots well enough at 600, you may only get 725 to 750 yards before transonic instead of 750 to 800 yards. Some shooters report less velocity loss than others.
 
#11
Shooting inside of 600 yards I can't tell any difference between my 22" and 20". Or the 20" to 18". Same with 18"/16", 16"/15"/14.5"/14", 14.5" to 13.7" etc.
Point being that the ballistic advantage of the 30-60 fps you get from 2" of barrel isn't apparent inside of normal 223 ranges.
Now if I shoot my 16" against the 22", or the 13.7" against the 18" it becomes obvious that the longer barrel is better, but not by as much as you would think.
 
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#13
Strykervet said:
Really?
Click to expand...
In response to my post? Yes really. I've got 5.56 barrels from 10.5" to 22" in .5"-2" increments and they all like the same 77gr load well enough to do apples to apples comparisons between them.
I've saved a few buddies a lot of money by lining them all up together at 500 yards and asking if the 2" longer barrel they want so bad makes any difference.
 
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#14
jLorenzo said:
What are your opinions? I used to want my SPR to be decent at semi close range but in real life I only ever shoot it off the bipod or tripod. I will be target shooting, some local matches and very occasional varminting. I have a 18" now but the accuracy is not there and its going to be replaced. I like how it handles and feels although it is a A2 profile. I will be shooting 75s and 77s mostly but also would like to plink with xm193 and use something like the 50gr Federal HP (surprisingly shoots a touch over a minute in my current 1:7) for varmints/predators.
I'm leaning towards 20" to add a little bit to its supersonic range.
Click to expand...

There are a lot of different variables here, so I'll break down a few of them to eliminate some generalities:

  • Semi-close range - What does that mean to you?
  • Accuracy not being there - Let's unpack this:
    • Ammunition - What kind of ammunition are you shooting? (weight, manufacturer)
    • Optics - What is your current setup?
    • Barrel - Let's unpack this too:
      • What manufacturer made the barrel?
      • How many rounds through it?
      • Is your barrel nut properly torqued?
These are all important factors in diagnosing the issue without focusing on the shooter's proficiency (because everyone here shoots .5MOA 5x5s all day long, clearly :LOL:)

gunsnjeeps said:
At 600 yards you may need a little more adjustment for wind. The 18 shoots well enough at 600, you may only get 725 to 750 yards before transonic instead of 750 to 800 yards. Some shooters report less velocity loss than others.
Click to expand...

An 18" barrel will get you out to 800 no problem if you know what you're doing with 77gr SMKs and a decent optic. You would be surprised what 55gr XM193 is capable of in terms of performance out past 300 yards too...

Honestly I find that an 18" barrel is the upper limit of what I like on a practical AR, and a 20" barrel with a 1:7" twist really doesn't offer any advantage enough for me to consider it, given both options.
 
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#16
308pirate said:
Twist rate has virtually nothing to do with accuracy once the bullet is stabilized enough.

Excessive twist maybe matters at ELR ranges. Otherwise once you have enough with a margin you're done.

Twist rate, nitriding, tolerances, 4140 vs 4150, etc, are just some of the few nuggets of bullshit to come out of arfcom

BTW, do you still have that Howa 1500?
Click to expand...
I am aware it just surprised me that American Eagle 50gr varmint load was one of the best shooters. I am very happy it does shoot because I have a good amount of it I am saving for yotes and prairie dogs. I do still have the Howa.
 
#17
Leftie said:
There are a lot of different variables here, so I'll break down a few of them to eliminate some generalities:

  • Semi-close range - What does that mean to you?
  • Accuracy not being there - Let's unpack this:
    • Ammunition - What kind of ammunition are you shooting? (weight, manufacturer)
    • Optics - What is your current setup?
    • Barrel - Let's unpack this too:
      • What manufacturer made the barrel?
      • How many rounds through it?
      • Is your barrel nut properly torqued?
These are all important factors in diagnosing the issue without focusing on the shooter's proficiency (because everyone here shoots .5MOA 5x5s all day long, clearly :LOL:)



An 18" barrel will get you out to 800 no problem if you know what you're doing with 77gr SMKs and a decent optic. You would be surprised what 55gr XM193 is capable of in terms of performance out past 300 yards too...

Honestly I find that an 18" barrel is the upper limit of what I like on a practical AR, and a 20" barrel with a 1:7" twist really doesn't offer any advantage enough for me to consider it, given both options.
Click to expand...
Semi close range would to me be 150y and in, shooting the optic at min mag and possibly off hand. I have found that really I dont need this gun to do that and even if I did I would be able to work with it.
As far as the accuracy goes I have tried a ton of factory stuff and handloads. 75s, 77s both Berger and Sierra, many flavors of 55 and 69gr loads. Basically everything that was even remotely available before the panic. The only stuff that shot anything close to what I want was surprisingly American Eagle 50gr HP and Norma Match 77gr. I went through a ridiculous amount of handloads trying to get this thing to shoot.
I am not the best shooter but when I have a consistent system working I can do pretty well.
The barrel is a factory PSA 18" 1:7 A2 profile that I got on a complete upper that was on sale. I was being overly optimistic in thinking I could dial something in that would shoot. If I was just using it for minute of man stuff it would be fine but I want to get a little more precise with it than that.
I am close to buying a barely used WOA 18" SPR barrel soon.
Scope is a cheap BSA 6x24x44 FFP with a mil hash reticle for now. I just dont dial with it because the tracking is not reliable but the glass is actually ok.
 
#18
jLorenzo said:
What are your opinions? I used to want my SPR to be decent at semi close range but in real life I only ever shoot it off the bipod or tripod. I will be target shooting, some local matches and very occasional varminting. I have a 18" now but the accuracy is not there and its going to be replaced. I like how it handles and feels although it is a A2 profile. I will be shooting 75s and 77s mostly but also would like to plink with xm193 and use something like the 50gr Federal HP (surprisingly shoots a touch over a minute in my current 1:7) for varmints/predators.
I'm leaning towards 20" to add a little bit to its supersonic range.
Click to expand...
Criterion CORE 18" with rifle length gas is a solid choice. I'm officially endorsing this barrel with BH 77TMK/SMK 😉

TP...
 
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#19
How far out are you trying to push a .223? I dont know about you, but my local matches can go out to about 500yds. If i wanted to shoot a match with further distance id have to go pretty far. That being said i think youd be fine with an 18". Ive got a JP upper with their 18 .223 wylde and it shoots better than i can. If i need to go farther than the .223 is comfortable im shooting a different caliber anyways.
 
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#22
jLorenzo said:
Semi close range would to me be 150y and in, shooting the optic at min mag and possibly off hand. I have found that really I dont need this gun to do that and even if I did I would be able to work with it.
As far as the accuracy goes I have tried a ton of factory stuff and handloads. 75s, 77s both Berger and Sierra, many flavors of 55 and 69gr loads. Basically everything that was even remotely available before the panic. The only stuff that shot anything close to what I want was surprisingly American Eagle 50gr HP and Norma Match 77gr. I went through a ridiculous amount of handloads trying to get this thing to shoot.
I am not the best shooter but when I have a consistent system working I can do pretty well.
The barrel is a factory PSA 18" 1:7 A2 profile that I got on a complete upper that was on sale. I was being overly optimistic in thinking I could dial something in that would shoot. If I was just using it for minute of man stuff it would be fine but I want to get a little more precise with it than that.
I am close to buying a barely used WOA 18" SPR barrel soon.
Scope is a cheap BSA 6x24x44 FFP with a mil hash reticle for now. I just dont dial with it because the tracking is not reliable but the glass is actually ok.
Click to expand...

This is all helpful - if you're shooting at 150 yards and closer, I hesitate to ask, why even bother with an 18" barrel? Unless you want the velocity for some reason, I would really just go shorter, likely to 16" or a 14.5" pinned option. The 16" at 150 yards and in will be nearly functionally identical to an 18" without the extra length, and they will both be supersonic. A 16" barrel with a mid-length gas system is a pretty solid setup and has a proven track-record.

Regarding the scope: Have you verified that the reticle is actually MRAD as opposed to a BDC hash for a specific caliber? (not that it will really matter at 150 yards, but it's a good thing to know when you are much closer or much further away from a target). It's good that you know that it doesn't track reliably. I would also check and verify that your scope mount is properly seated/torqued etc. I remember a long time ago a friend of mine telling me that his rifle didn't shoot well at all, only to discover that his scope mount was so poorly attached that it was wobbling... The rifle shot better than well after solving that issue.

I'm not going to comment on the handloads, as I am by no means anywhere near proficient in handloading, but if you're shooting Norma Match and you aren't receiving good results at 150 yards, I would take the rifle to 25 yards, build an extremely solid firing position, and shoot a couple groups with the same point of aim to see if there is a hardware variable (the gun, ammunition, optic) or if it is a software variable (the shooter). I would then use the same setup to bring the rifle out to 50 yards, then 100. The goal isn't to zero the rifle, per se, but rather to see if the barrel, optic, and ammunition combination is consistently providing your desired results by controlling and eliminating as many variables as you can. During this test, it's really important that you use all of the same type ammunition during each course of fire

If PSA's QC let a barrel through that isn't holding up to spec, I would reach out and contact them first before spending more money...

In summary:

Check optic and mount/rings for correct installation
Check optic reticle for consistency/accuracy
Shoot controlled groups at increasing distances to check if your issue is indeed the barrel.

Hope this helps.
 
#23
I went with a 20" barrel and have shot out to 800 where it is still supersonic and had decent luck. If you aren't pushing that yardage, go shorter. Mine is a heavy barrel rock river upper and it isn't much fun to shoot offhand. I am still contemplating cutting off 2 inches and threading it 5/8-24 so I don't have to use an adapter with my 30cal can.

To me, the rifle length gas system especially with some tuning thru either buffer weight or adjustable gas block or both can make an AR-15 loose all its snap and be really easy to spot traces. If you can get a rifle length gas system with an 18" barrel, I would go that way.
 
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#24
10-shot group of Sierra 55 grain BlitzKings fired at a distance of 100 yards from an 18" Noveske barrel.


noveske_spr_barrel_10_shot_group_02_JPG--1828207.jpg



noveske_spr_with_bipod_and_scope_11-1439-1828208.jpg






10-shot group of Sierra 55 grain BlitzKings fired at a distance of 100 yards from a 20" Noveske barrel.


group_01_measured_resized-1828202.jpg




noveske_20_inch_barrel_ar15__outside_01_-1828203.jpg







Velocity comparison from the same Noveske barrels.



noveske_18_inch_vs_20_muzzle_velocity_00-1828212.jpg




....
 
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#25
Leftie said:
This is all helpful - if you're shooting at 150 yards and closer, I hesitate to ask, why even bother with an 18" barrel? Unless you want the velocity for some reason, I would really just go shorter, likely to 16" or a 14.5" pinned option. The 16" at 150 yards and in will be nearly functionally identical to an 18" without the extra length, and they will both be supersonic. A 16" barrel with a mid-length gas system is a pretty solid setup and has a proven track-record.

Regarding the scope: Have you verified that the reticle is actually MRAD as opposed to a BDC hash for a specific caliber? (not that it will really matter at 150 yards, but it's a good thing to know when you are much closer or much further away from a target). It's good that you know that it doesn't track reliably. I would also check and verify that your scope mount is properly seated/torqued etc. I remember a long time ago a friend of mine telling me that his rifle didn't shoot well at all, only to discover that his scope mount was so poorly attached that it was wobbling... The rifle shot better than well after solving that issue.

I'm not going to comment on the handloads, as I am by no means anywhere near proficient in handloading, but if you're shooting Norma Match and you aren't receiving good results at 150 yards, I would take the rifle to 25 yards, build an extremely solid firing position, and shoot a couple groups with the same point of aim to see if there is a hardware variable (the gun, ammunition, optic) or if it is a software variable (the shooter). I would then use the same setup to bring the rifle out to 50 yards, then 100. The goal isn't to zero the rifle, per se, but rather to see if the barrel, optic, and ammunition combination is consistently providing your desired results by controlling and eliminating as many variables as you can. During this test, it's really important that you use all of the same type ammunition during each course of fire

If PSA's QC let a barrel through that isn't holding up to spec, I would reach out and contact them first before spending more money...

In summary:

Check optic and mount/rings for correct installation
Check optic reticle for consistency/accuracy
Shoot controlled groups at increasing distances to check if your issue is indeed the barrel.

Hope this helps.
Click to expand...
I did check the mount it did come lose one time but the issue was immediately apparent this was not my main issue, I said I WAS getting good results with the Norma match and AE 50gr stuff. Ive shot many, many, many groups with all different kinds of ammo those two were the only ones that shot right at a minute consistently.
As far as 150 and in stuff, I meant I wanted a gun that could do that IN ADDITION to normal long range work that an SPR is typically used for.
Having a 16" and 10.5" really negates the need for my 18" gun to be used at those distances besides supported group shooting at 100y.
I can shoot clover leafs with some of my other bolt guns, after spending as much time and money on ammo/loading and seeing videos like this

that mirror my exact (and I mean EXACTLY) experience I can safely say it is the barrel.
That being said its plenty accurate for its original design as soldiers rifle. I want a precision gun though and will be buying a WOA as long as the seller comes through.
 
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#26
jLorenzo said:
I mean I was a little surprised I just figured a 1:7 wouldnt like a factory 50gr the best out of a ton of different factory loads.
Click to expand...


Contrary to what the Internet Commandos say, quality light-weight bullets can produce excellent precision at shorter distances when fired from semi-automatic AR-15s with faster twist barrels. The groups pictured below were fired from one of my Krieger barreled AR-15s using 50 grain Sierra BlitzKings.


50 blitzkings 5 shot group at 100yards.jpg




50 grain blitzkings 10 shot group at 100 yards 001 copy - Copy.jpg




....
 
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#27
Molon said:
Contrary to what the Internet Commandos say, quality light-weight bullets can produce excellent precision at shorter distances when fired from semi-automatic AR-15s with faster twist barrels. The groups pictured below were fired from one of my Krieger barreled AR-15s using 50 grain Sierra BlitzKings.


View attachment 7560917



View attachment 7560918



....
Click to expand...
I had no doubt that lighter bullets can be extremely accurate. I suppose the fact that it was very hard to get a bolt gun with a twist faster than 1:9 for many years made me skeptical as to how well lighter bullets would do in a 1:7. It seems the industry has just been behind in this respect. I am definitly glad I gave the 50 grainers a shot. I dont see the point in getting a .223 with anything other than a 1:8 or 1:7 unless your doing something weird like only shooting 40gr varmint bullets at max speed.
 
#28
I’ve had great success with both light and heavy loads out of my 1:7 twist 16” Wilson Combat barrel.

I picked up some blue box Black Hills 40gr V-max rounds and got the best 100yd five-shot groups of my life.

Groups at 100 yds with the 40gr V-max consistently beat out the Black Hills MK 262. But at 200 yds, the MK 262 consistently beats the 40 gr V-max groups. Is this common?

I think the barrel & ammo quality have as much to do with group size as the twist, as long as there is enough twist to stabilize the bullet.

Other than extreme cases like uber-light weight, lightly constructed bullets that come apart from too many RPMs, I don’t think fast twist can hurt. And, I believe some bullets’ design factors in speed of rotation along with impact speed to assure expansion.
 
#29
Slower twist .224" barrels allow you to drive light varmint bullets to speeds that might destroy them (from too much rotational velocity) in faster twist barrels.

This does, in general, extend the max point blank range for some varmint cartridges and reduces the need to dial or hold over as much on targets that might not be available for very long.

Every tool has a purpose.
 
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#30
Honestly, at this point what ever is available that suits your needs at this time. There is not going to be a significant difference in practical use between the 18 or 20.

While I really like the 12.5 to 14.5 length in AR's I have a 20 inch A4 that is a blast to shoot. if you are not getting into or out of vehicles a ton, the extra length is not going to really impact you that much
 
#31
The quality of the barrel will be far more important for your uses than the length. The WOA you have your sights set on is going to be a significant upgrade over your PSA barrel. My 18" SPR is kind of the sweet spot for me between long range and handiness,, and it's what I take coyote hunting most often these days. I would probably be fine with my 14.5" or even 11.5" for most of the opportunities I've had, but the 18" gives me more confidence in variable conditions.
 
#32
jLorenzo said:
I am aware it just surprised me that American Eagle 50gr varmint load was one of the best shooters. I am very happy it does shoot because I have a good amount of it I am saving for yotes and prairie dogs. I do still have the Howa.
Click to expand...
That American Eagle tipped Varmint shoots awesome in a lot of guns. It’s a crime they discontinued it.
 
#33
A heavy 18” is my personal preference. I just shot a match down here by Houston a couple weeks ago with it in low altitude and humid heat and I was able to hit the 60% IPSC silhouette at 1,000 a couple times. I was running my mod 1 KAC LPR with the heavy Krieger barrel on it….
move never found any real Benafits to going longer than 18” on an AR platform, the marine corps made me carry a 20 around for long enough
 
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#34
I throw this out here also,

m193 does some wicked things out of a 20” 1:12 twist barrel like like original m16a1

that’s where all the 223 myths come from about it being like a grenade going off and bullets coming out at crazy places. Slow twist fast speeds make that fmj yaw like crazy when it hits.

for 77gn ammo a 7-8 twist 18” is the ticket.
 
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#35
Having shot the 18" for awhile now, I will be going 20" next time. Most of my shooting is super casual and I like to stretch the 77/75s as far as I can. No negatives going to a 20" for me personally. I have a solid load with RL15 getting just over 2700 with 75s and decent brass life. Lines right up with classic 308 dope, 1 mil = 300y, 2 mil = 400y, etc.
 
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#36
I have a 18” SPR I build a couple of years ago. I’m using a LaRue Stealth barrel. It shoots 69 and 77 gr SMKs well enough, without checking my records I believe it’s around .6 MOA. I was following YouTuber “Johnny’s reloading bench“ and started experimenting with other bullets. The 55 gr V-Max did surprisingly great. Way cheaper then SMKs.
IMG_2697.jpeg
 
#37
I feel like whoever starts a thread discussing 18" vs 20" barrels for accuracy and then half a page down divulges that he's shooting a PSA/ BA/ Faxon barrel should have his account automatically migrated to ARFCOM, or even worse... Reddit.
 
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#39
Rimfire Jesus said:
I feel like whoever starts a thread discussing 18" vs 20" barrels for accuracy and then half a page down divulges that he's shooting a PSA/ BA/ Faxon barrel should have his account automatically migrated to ARFCOM, or even worse... Reddit.
Click to expand...
Daggumm, where's the downvote button? You can't insult reddit, reeeeeeeeeee

But seriously, budget barrels shoot budget groups. This thread is asking how to make a lean hamburger taste like brisket.
 
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#40
rothgyr said:
Daggumm, where's the downvote button? You can't insult reddit, reeeeeeeeeee

But seriously, budget barrels shoot budget groups. This thread is asking how to make a lean hamburger taste like brisket.
Click to expand...

Reddit gun communities are by far the worst offending people. So much terrible advice on there. It's a hive of guys who build guns for the purpose of Instagram likes.

OP: As others have stated, you'll likely not notice a difference between 18" and 20" given you're using quality ammunition. Personally I like the 20" simply because the extra 2" for a little more "giddy up" doesn't bother me since I'm not hauling it through the woods or anything.

I had a 20" WOA SPR 1/7 which held .6 MOA all day with good 77gr SMK. Rifle length gas on a 20" with a suppressor is extremely smooth and pleasant to shoot as well.
 
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