With those numbers, what's your opinion on the "sweet spot" for velo-barrel length/can combo?

Green2Maroon said:

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The 13.7 might be the best velocity for the barrel length. Not losing much to the 16.

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I would personally lean more towards the 12.5", only about a 6% loss in velocity but a fairly noticeable difference in length of barrel versus the 13.7"

I believe SOCOM adopted 11.5" a couple/few years ago.

TikkaShooter said:

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With those numbers, what's your opinion on the "sweet spot" for velo-barrel length/can combo?

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Im clearly the wrong person to answer that since I'm indecisive and own all 4.

A 13.7 or 13.9 p&w to 16" because our laws are dumb would be a great "if I only had one" rifle. Put an A5 buffer system, an eotech and magnifier on a unity riser combo and you have a good that can do everything moderately well.

That being said, I used that 13.7+a blue training can in a cqb class and its amazing how a SBR+a can still feel like a musket when moving around in a structure.

10.3 is brutal even with a can. A better 5.56 can would help a little, but not much.

11.5 is a sweet spot on short as possible while not beating the hell out of parts or your ears, IMO. Theres a reason the can is still on the 11.5" gun.

Any of them can work. Just have to choose which tradeoffs you can live with. The ft lbs energy difference between my 12" Grendel and 12.5" 5.56 were certainly interesting. 123gr Grendel load had twice the energy at double the distance. Need to see how good a 77gr 5.56 load would do, but it spanked the heck out of bulk blasting 5.56 ammo.

Interesting numbers. I havnt run xm193 from mine but good to know.

As far as 77smk, I consistently get 2550 roughly from my 16" and 2280 from my 11.5"

These are handloads, using 25 grains of varget or 21.8 of h322. Accuracy is equal and POI with both charges. I've been able to push them to just over 2600 in my 16" but accuracy wasn't there and pressure was getting dicey.

Very good data


I'm still partial to 20"

The more I have seen posts/articles about 5.56 performance and how it was designed to work, the more I lean to building a 13+ in. upper to keep fragmentation on the table.

Damn nice!

CactusThomas said:

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Very good data


I'm still partial to 20"

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Until you out a can on it and carry it around.

The cons of cans far outweigh the pros on ARs for me. I only shoot 223/5.56. It would be different if I was into 300 blk or similar. But to each their own.

CactusThomas said:

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The cons of cans far outweigh the pros on ARs for me. I only shoot 223/5.56. It would be different if I was into 300 blk or similar. But to each their own.

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Depends on use/purpose. When not at the range most AR shots are headed at a hog or coyote out of the truck or mule with minimal notice. Passengers are thankful for the suppressor.

SBR'd 5.56 is a noisy Fer. I like my wife liking me.

TSJ said:

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The more I have seen posts/articles about 5.56 performance and how it was designed to work, the more I lean to building a 13+ in. upper to keep fragmentation on the table.

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Yep, intent of the round was originally small, very fast projectiles from a 20" barrel. I still like 20" ARs but I know very few people who own one anymore. Heck, even bulk stuff out of a 20" barrel is zippy enough to vibe check cheap steel plates, etc.

If you're going to shoot a shorty at anything other than paper or steel, highly recommend better ammo than xm193.

Eta: that being said ive rung steel past 500 with 193 from a 14.5" barrel plenty so its not like its incapable.

Was planning a whole post on the fallacies around zeroing ARs at some point, just havent gotten around to it yet.

Too many projects, too little time.

HumbleAg04 said:

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Depends on use/purpose. When not at the range most AR shots are headed at a hog or coyote out of the truck or mule with minimal notice. Passengers are thankful for the suppressor.

SBR'd 5.56 is a noisy Fer. I like my wife liking me.

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Sums up why most of us own so many. Always easy to think of another purpose a new gun fits "just right"

CactusThomas said:

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The cons of cans far outweigh the pros on ARs for me. I only shoot 223/5.56. It would be different if I was into 300 blk or similar. But to each their own.

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Completely disagree with this. A can makes a massive differenc on an AR, love being able to shoot mine with minimal ear pro and it doesnt hurt. The occasional shot without it doesnt make my ears ring, much less ring for 2+ days.

I also likethe way the can makes it barel heavy, it is easier to stabilize for me. Plus...can. can is always better.

BenderRodriguez said:

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HumbleAg04 said:

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Depends on use/purpose. When not at the range most AR shots are headed at a hog or coyote out of the truck or mule with minimal notice. Passengers are thankful for the suppressor.

SBR'd 5.56 is a noisy Fer. I like my wife liking me.

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Sums up why most of us own so many. Always easy to think of another purpose a new gun fits "just right"

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Correct. Currently on 4 but have a JP LMOS BCG extra so I mean... why not a 5th?

Good ole Vigilance Elite, they have a Youtube video that I have posted on here before that explains this very well. This is what I do for my 5.56 ARs

And someone said SOCOM went with 11.5", that is because most of their engagements were inside of 100 yards with some out to 300. After that the 5.56 is not very effective and they need a new weapon system

LOL understatement, especially with AR style weapons, include elevation to the equation...gotta do some more training. For those in Texas we are spoiled with fairly flat shots, we have some steep elevation changes on our property and it made for a good laugh.

CactusThomas said:

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The cons of cans far outweigh the pros on ARs for me. I only shoot 223/5.56. It would be different if I was into 300 blk or similar. But to each their own.

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wut? Interested to hear what these massive cons are

BenderRodriguez said:

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Was function checking a few guns with a new suppressor, decided to use the magnetospeed3 to verify some velocity numbers as well. Thought they might be of use if anyone is debating what barrel length to pursue on an SBR/AR pistol build.

All guns were fired with the same ammo (XM193 55gr 5.56), same day, same conditions, same can. Could have shot them all on a single lower to eliminate as many variables as possible but the goal was function checking, not running a precise science experiment.

Anyway, hope they're useful for someone.

16": 3056 fps
13.7": 3001 fps
12.5": 2868 fps
11.5": 2797 fps
10.3" 2725 fps

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HA! I'd plugged in 3000 fps in strelok for my solgw 13.7 as a guess before my new chrono comes in.

Was the m193 the winchester white box stuff? Curious because different manufacturers have reported some very significantly different fps numbers for m193 (but rarely know if that is because they are testing w/ different barrel lengths bc for some damn reason they don't feel it's important to tell us)

tk111 said:

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CactusThomas said:

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The cons of cans far outweigh the pros on ARs for me. I only shoot 223/5.56. It would be different if I was into 300 blk or similar. But to each their own.

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wut? Interested to hear what these massive cons are

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Cons are pretty obvious - weight, length mostly.

And with 5.56/.223 you won't get a huge amount of noise reduction because for whatever reason that round is just loud AF.

That being said, on my 10.5" barrel with an 8" can, I have essentially a normal length rifle that is very tolerable shooting - with ear plugs it is awesome, even without plugs it isn't horrible IMO.

schmellba99 said:

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tk111 said:

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CactusThomas said:

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The cons of cans far outweigh the pros on ARs for me. I only shoot 223/5.56. It would be different if I was into 300 blk or similar. But to each their own.

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wut? Interested to hear what these massive cons are

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Cons are pretty obvious - weight, length mostly.

And with 5.56/.223 you won't get a huge amount of noise reduction because for whatever reason that round is just loud AF.

That being said, on my 10.5" barrel with an 8" can, I have essentially a normal length rifle that is very tolerable shooting - with ear plugs it is awesome, even without plugs it isn't horrible IMO.

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Agree with the weight/length if you're shooting anything over 16" but the sound and signature reduction have been huge in my experience. It makes a world of difference especially when shooting around other folks.

Not WWB, this is some of my IMI XM193 stash.

And yeah, dont trust box listed fps numbers.

Green2Maroon said:

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The 13.7 might be the best velocity for the barrel length. Not losing much to the 16.

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As I said in the other post, a 13.7" is a really great compromise size.

Like mine a lot.

I think it depends what you are using it for, 10.5 for close in work, 11.5 as something that can reach out a little further, 13.7 if you plan on shooting some distance, 16" if you want something to go out a little further, 20" if you hate life.