Barrel Profile Discussion

alamo5000 · Monday at 9:25 PM

I have a 6ARC with a 24" barrel on it. It's an AR platform.

It does shoot fine. No real problems with it, but I have been thinking about changing it up some. Basically put, I have been thinking about maybe going to a 20" or something like that. By the time you add a suppressor the OAL is pretty long. I got that barrel near the introduction of the 6ARC so I was kind of flying blind picking out what I thought I wanted.

My wallet starts to get scared when I start pondering 'options' but here it goes again. My general question is about the benefits of maybe getting a fatter profile or some variation of that. The gas block on the rifle right now is .750, but I am not opposed to going up to.875 if needed.

I am just getting started but on something like this I try to be more thoughtful vs just winging it and hoping for the best.

I am talking about ARs, but the questions in my head are a lot more generic as it pertains to the pros and cons of contours on actual shooting.

If you have any ideas, thoughts, or relevant comments please help me learn something.

Old Man with Gun · Monday at 9:42 PM

Thin barrels POI can wander as they heat and cool. But once you have a reasonable barrel thickness, you are just adding weight.

Most of what bull barrels get you is a heavier rifle that helps to mask bad habits. So they are easier to shoot well, but not more precise or accurate.

Bulls are good if you want to keep the weight of a longer barrel and not make it too long or front heavy.

If you are trying to shoot tiny groups it may be helpful. But with an AR, it is hard to do much better than 3/4 MOA consistently.

A 26" is good if you want max velocity, but if you want to walk around with it 18-20 makes more sense.

How you will use it directs profile.

Rider47 · Tuesday at 7:00 AM

I have found my decades of benchrest bolt action shooting and rifle building are applicable to AR/semi builds. It is simple: short and fat for precision. I have 4 AR-15's, three in .223Wylde and one 224Valkrie. Two are 16" one 18" and the Valkyrie is 20" merely because that is the shortest Kreiger would provide on a pre-chamber. All are .900" at the muzzle. (NONE are threaded!) My 16" and 18" AR-15's win 200 yard precision matches (with handloads). Short and fat.
PS I could not disagree more with the prior poster when they state:
"Most of what bull barrels get you is a heavier rifle that helps to mask bad habits. So they are easier to shoot well, but not more precise or accurate."
and
"with an AR, it is hard to do much better than 3/4 MOA consistently"

My experience has been that with a high quality true match grade SS hand lapped barrel (FAT and SHORT) and tuned handloads, consistent 5-shot 100 yard groups <3/4 MOA are quite attainable.

Old Man with Gun · Tuesday at 7:17 AM

I didn't say sub 3/4 was not obtainable, I said it was hard to do much better consistently. The AR platform will not compete against a good bolt gun was my point. Just saying the platform has limitations.

I'm glad that short and fat works for you, but there are plenty of competitors using mid weight longer barrels shooting just as well.

Shoots 700's · Tuesday at 8:24 AM

Whats you budget and what is the rifle used for?

chop the barrel you have if you want? Get another a tiny bit thicker, not sure it'll get you much.

TonyAngel · Tuesday at 12:40 PM

When I'm considering barrel profile, I first start out considering the thickest heaviest contour I can get in a 16" barrel. I then consider how far I need it to shoot and how much umph it needs to have when it gets there, to determine my needed velocity range and barrel length. Once I know how long it needs to be, I then consider how much I'm going to be carrying it around. If I'm going to be carrying it around, I like a total package of around a 10lb or less carry weight. Thicker, heavier and shorter is better, but you have to give a little to get what you need.

Rider47 · 2025-01-08T06:51:42-0500

"The AR platform will not compete against a good bolt gun was my point. Just saying the platform has limitations."
I did not see bolt vs. semi as an issue for the OP.

5 shot group at 200 yards with the AR-15 with a 16" barrel in the second image in my Post#3 above.
Short and Fat!

Old Man with Gun · 2025-01-08T09:10:02-0500

You seem to be obsessed that your way is the only way. The OP is shooting a 6 ARC suppressed rifle and didn't say what he wants to use it for. But a short fat barrel has many limitations.

a 16" 6 ARC makes no sense, you need barrel length to get velocity and there are reasons people shooting for distance seek velocity. Even if not shooting for distance velocity bucks wind. He already says he shoots suppressed.

Posting an unverified cherry-picked target on the internet means nothing. There is no evidence if you look across a wide selection of people winning a wide variety of contests that shorter unthreaded barrels are more accurate. Why doesn't short and fat dominate in F-Class, Palma, Service Rifle, small bore, silhouette, PRS, USPSA, IDPA, High Power Rifle or even 3-gun events?

This is from Camp Perry Nationals.

Rider47 · 2025-01-08T10:55:33-0500

"You seem to be obsessed that your way is the only way."
Once again, I disagree.
Short and Fat is when the only consideration is inherent precision.
Longer barrels for increased velocity to reduce windage for LD shooting, long barrels for increased sight radius for iron sights and longer barrels for improved rifle balance are just three applications. And thinner/short barrels for the above and for weight reduction and maneuverability for close up tactical weapons.
What is missing from this list: "F-Class, Palma, Service Rifle, small bore, silhouette, PRS, USPSA, IDPA, High Power Rifle"
is BENCHREST. Where inherent precision is paramount. (BTW I shoot competitive NRA silhouette, Tactical BR PRS, Benchrest (formerly 100/200/300, now only 600yard) and F-Class (600 and 1000yard).

Where we agree? Posting "an unverified cherry-picked target on the internet means nothing". True and Guilty!
This group was a surprise shot while doing initial load development on my new build. Ask me to do it on demand? Not F-ing likely!
But this rifle (16"/.900"/AR-15) is an awesome shooter, as are my other short/fat AR's.
(BTW - the last two 200 yard competitions I won also included bolt guns in the smallbore class, and on the last competition I actually only tied for 1st place as I foolishly invited a shooting buddy and lent him one of my AR's and handloads!)

As for threaded vs. unthreaded, once again, applications for each, but if you have removed metal from the muzzle of a barrel, you know what this does to the bore diameter . . .

The OP does not mention his application, but he is starting out with a 6ARC, so it seems inherent precision is at least on his radar (good choice!) and he specifically asks about the potential effect of going to a SHORTER/FATTER barrel in an AR platform. For whatever his reasons are. IMHO he will gain precision, not lose it, going from a 24" .750" to a 18" to 20" .875" or .900" barrel, if he goes with a quality barrel.

alamo5000 · 2025-01-08T12:08:46-0500

Shoots 700's said:
Whats you budget and what is the rifle used for?

chop the barrel you have if you want? Get another a tiny bit thicker, not sure it'll get you much.

I don't have a budget but I still want to be practical. If I need to save up to get what I want I would rather do that and have a rifle I really like.

I was going back and forth for a long time about getting a large frame AR to extend my range. Then 6 ARC appeared so I was all over it. With that I have interchangeable parts, powder, primers, without having to tool up and get parts and tools for something totally different. It's like manna from heaven as far as low hanging fruit is concerned.

Of course I want accuracy. The more the better. I built it to have a 1000+ yard capability for farther targets. Realistic use is for shooting steel within several hundred yards because that's what I have at home. That said it is also a 'Holy shit, they are looting' gun.

24" just seems a little bit longer than I need for that rifle. With the suppressor it's right at 50" OAL. If I ever did take it hunting it would be a little much length wise. I'm thinking about 20" is good for what I am expecting from that rifle.

moosemeat · 2025-01-08T12:44:52-0500

Old Man with Gun said:
You seem to be obsessed that your way is the only way. The OP is shooting a 6 ARC suppressed rifle and didn't say what he wants to use it for. But a short fat barrel has many limitations.

a 16" 6 ARC makes no sense, you need barrel length to get velocity and there are reasons people shooting for distance seek velocity. Even if not shooting for distance velocity bucks wind. He already says he shoots suppressed.

Posting an unverified cherry-picked target on the internet means nothing. There is no evidence if you look across a wide selection of people winning a wide variety of contests that shorter unthreaded barrels are more accurate. Why doesn't short and fat dominate in F-Class, Palma, Service Rifle, small bore, silhouette, PRS, USPSA, IDPA, High Power Rifle or even 3-gun events?

This is from Camp Perry Nationals.

View attachment 8586597
This is from Precision AR

The reason short and fat doesn't dominate is rules and velocity needs. F-class, palma, service rifle and silhouette all either have weight rules, appearance rules or need the velocity.

Old Man with Gun · 2025-01-08T13:40:04-0500

alamo5000 said:
I don't have a budget but I still want to be practical. If I need to save up to get what I want I would rather do that and have a rifle I really like.

I was going back and forth for a long time about getting a large frame AR to extend my range. Then 6 ARC appeared so I was all over it. With that I have interchangeable parts, powder, primers, without having to tool up and get parts and tools for something totally different. It's like manna from heaven as far as low hanging fruit is concerned.

Of course I want accuracy. The more the better. I built it to have a 1000+ yard capability for farther targets. Realistic use is for shooting steel within several hundred yards because that's what I have at home. That said it is also a 'Holy shit, they are looting' gun.

24" just seems a little bit longer than I need for that rifle. With the suppressor it's right at 50" OAL. If I ever did take it hunting it would be a little much length wise. I'm thinking about 20" is good for what I am expecting from that rifle.

I have a 18" 6.5 Grendel that I use for that and it does well. I built mine before the 6 ARC was out, but 18 to 20" I think is the sweet spot.

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