Why 18"?

[irons_shooter]

I never understood why people like 18" AR's for competition. What does it gain you? If you are going for weight, then a 16" fits the bill very well. If for accuracy, the 20" is the way to go. If you are looking for lightweight accuracy, a 16" will shoot just as good as an 18" any day of the week. I use a 20" for irons only to get the longer sight radius. I used a 16" with an eotech before and it is more than accurate for 3-gun.

Please help me out on this one. The only legitimate reason I can think of is if you want a rifle length gas system without the extra 2" of barrel. I have recently seen people spend the better part of $500 more for a gun with an 18" barrel on it over a 16".. Just curious...

ETA, this is a rant from another discussion I just had with someone on another forum who told me I must know nothing about rifles if I don't shoot an 18"...

 

[pyplynr]

I believe your correct. If it is iron sights the the longer sight radius of the 20 would be better but if it has optics then the only difference is velocity and the drop of the bullet. But whether it's 24" or 16" the accuracy is no different. Plus the shorter bbl will be lighter and easier to maneuver. Unless your shooting long distance I don't think you would ever see any difference. I don't really know about the rifle length vs any other system but what I know is about length in bolt action barrels.

 

[Chambers]

Please help me out on this one. The only legitimate reason I can think of is if you want a rifle length gas system without the extra 2" of barrel. I have recently seen people spend the better part of $500 more for a gun with an 18" barrel on it over a 16".. Just curious...

ETA, this is a rant from another discussion I just had with someone on another forum who told me I must know nothing about rifles if I don't shoot an 18"...

I like rifle length gas.

I agree with you, though. I would never pay that much extra for an 18" barrel. That's ridiculous. My gun has an 18" stainless DPMS barrel with rifle length gas and was $160 with a low profile gas block. The only drawback is that it is a heavy profile, so I'm buying an identical one to have turned down since I need the rifle in the meantime.

Beyond all else, a lot of the guys on the interwebz like to feel good about their purchase, and that they gained something from spending 200% more than they need to.

 

[Glocktogo]

A 20" is not inherently more accurate than a 16". Practically with irons, yes, but you could just mount the front sight at the end of the barrel and accomplish that. Nothing says the front sight has to be where the gas block is. Also, many AR's these days have forends that extend well beyond the gas block. With an optics gun, all that really matters is weight and balance. The AR weight preference has swung wildly over the years. Early AR's were extremely light even with 20" barrels. Then everyone wanted a shorter rifle. Right after that, everyone wanted a heavy barrel. Pretty soon, everyone was marketing 16" .920" barreled AR's, which were ridiculous. Then everyone wanted to hang the kitchen sink off them. They quickly realized that if they had a 9# 16" AR, it got REALLY heavy when you started festooning it with lights and VFG's and pontoon outriggers. Not long after that, people realized they needed a lighter rifle, then smaller and fewer widgets. The SBR craze hit next, which usually remained fairly portable. However, it was quickly realized that they suffered from one serious flaw. Beyond 100 yards, their ability to put a man down was seriously compromised. Heavy bullets ensued to extend the fragmentation range. And so on and so forth....

Right now we're starting to really get back to a more effective AR setup. A true to spec SP1 with a slow twist barrel and 55gr bullets is still one of the most effective killers inside 100 yards, but it doesn't do everything well. Inside 100 yards, a 14.5" AR with RDS, BUIS and a small weapons light, loaded with something like TAP T2 or Superformance is just about perfect. If you need more range, a 16-18" light to medium profile barrel and a low power variable will do everything you need, but the 18" will have better effective range without being as unwieldy as a full stocked 20"

Most of the guys choosing an 18" gun are doing it because of the parameters of the game they're playing. An 18" will knock over distant steel with a marginal hit better than a 16". That allows them to avoid penalizing extra shots and transition to the next target quicker. The 18" is still compact enough to negotiate close, tight courses without too much extra movement. As Chambers stated, the more you can expand the gas and recoil systems, the smoother the gun will run. Shorter guns by nature have more violent actions.

If I had to choose one single platform today, I'd still go with a 16" setup. Since I don't have that restriction, I have an 11.5", 16" and 18". Each fills it's intended role very well.

 

[Wormydog1724]

I LOVE my 16" WOA stainless barrel. It has the midlength gas system and the BattleComp. I have a CTR stock and a TR24 G accupoint with a 13" Troy TRX extreme rail.

I sacrificed weight in the barrel and optic but made up for it in the handguard and stock. The BattleComp takes away most if not all of the muzzle flip/rise/jump and the midlength gas also helps with the crazy .223 recoil!

I am 100% satisfied with my rifle setup. I take off the accupoint and put a 1.5 power ACOG on top and drop in a .22lr conversion kit for steel challenge and plinking.

Anyways, I didn't buy in to the people who said I needed an 18" or 20" barrel for 3 gun.

 

[Spiff]

18" is the most common point of diminishing returns for muzzle velocity. I assume that's one of the reasons the military went with it on the SPRs.

I've also seen that some of the upper 3 gunners run 17" rifle gas barrels. Whatever. I don't think it matters that much.

 

[Wormydog1724]

Austin...

3 gun January 16th... You there?

 

[technetium-99m]

I got a good deal on an 18" Sabre barrel.

When it needs replaced I'll screw on a 0.750 20" rifle length gas barrel.

 

[Spiff]

Planning on it bro.

 

[irons_shooter]

A 20" is not inherently more accurate than a 16". Practically with irons, yes, but you could just mount the front sight at the end of the barrel and accomplish that. Nothing says the front sight has to be where the gas block is. Also, many AR's these days have forends that extend well beyond the gas block.


Most of the guys choosing an 18" gun are doing it because of the parameters of the game they're playing. An 18" will knock over distant steel with a marginal hit better than a 16". That allows them to avoid penalizing extra shots and transition to the next target quicker. The 18" is still compact enough to negotiate close, tight courses without too much extra movement. As Chambers stated, the more you can expand the gas and recoil systems, the smoother the gun will run. Shorter guns by nature have more violent actions.

Really? You are going to tell me that a 55 grain nosler ballistic tip with 25 grains of AA2460 going 3165 in an 18" barrel compared to that same round going 3120 in a 16" is going to have that much of a difference on a LaRue at 400 yards? (yes I have chrono'd out of both with my long range load)
I have known an Iron sighted rifle or two so I know why we choose 20" barrels. I have also shot a 3-gun match or two so I am also familiar with weight distribution as well as balancing an AR platformed rifle, but that was good reading for someone not as familiar. Most of the folks that have responded have answered the question with the response I figured and that is rifle length gas without the extra length of the 20".

 

[Glocktogo]

Really? You are going to tell me that a 55 grain nosler ballistic tip with 25 grains of AA2460 going 3165 in an 18" barrel compared to that same round going 3120 in a 16" is going to have that much of a difference on a LaRue at 400 yards? (yes I have chrono'd out of both with my long range load)
I have known an Iron sighted rifle or two so I know why we choose 20" barrels. I have also shot a 3-gun match or two so I am also familiar with weight distribution as well as balancing an AR platformed rifle, but that was good reading for someone not as familiar. Most of the folks that have responded have answered the question with the response I figured and that is rifle length gas without the extra length of the 20".

Which is also what I mentioned and what first came to mind.

I was simply adding some additional comments. It's difficult to gauge the experience level of someone on the internet. Your 18" might see a bigger velocity gain if you switch powders to one that has a more optimal burn rate for a longer barrel. I certainly wouldn't use the same powder in my 11.5" that I'd use in my 18. Granted, with only two extra inches it isn't a huge gain, but it's a gain nonetheless!

 

[jtischauser]

I like rifle length gas.

This is exactly why I went 18".

Beyond all else, a lot of the guys on the interwebz like to feel good about their purchase, and that they gained something from spending 200% more than they need to.

Thanks for thinking of me Mike. I am a firm believer in buying crap just because it cost more. Everybody knows that because something is expensive it is always better.

I would really like to try a 16" or 17" mid or intermediate length gas rifle with all the lightend internals and adjustable gas block. I am still trying to find that perfect weight. I want my rifle to be heavy enough so that it does not bounce all over from recoil but is as light as can be.

The barrel length means nothing to me in terms of accuracy or velocity. 50 fps more or less velocity on the center of your target means nothing. My job is to deliver the accuracy of the rifle if the barrel is from a quality manufacturer in conjunction with match ammo.

 

[tacticalj]

Mostly because I picked up a Sabre setup for about $500 less then they sell for new with less then 200rds through it! I was opting for a 24" for the 6.5G, but this deal came up and I had to buy it. I don't know why people do that, I guess they figure it's the best of both worlds.