Brake or no brake on 10.5" 6mm arc?

[Luumor Jonson]

I'm planning on putting together a 6mm arc with a barrel between 10 and 12". I've never fired anything with that short of a barrel and don't know what to expect. Would a muzzle brake make it more pleasant or increase concussion? Unfortunately, suppression is not an option, and I may have to pin and weld, so I have to make up my mind before I can try it. This is mainly a "just because" project. Plinking and hunting if velocities will allow. I imagine doing a fair amount of prone shooting with it.

Does anyone have any wisdom to share?

 

[TonyAngel]

If you're gonna pin and weld, just get a longer barrel. Getting a 10" to 16" isn't easy. With the added weight, you're better off with more barrel.

As for the brake, the concussion will be ungodly. It won't be fun.

 

[SBRSarge]

With the short barrel, a brake will be brutal even with the mild 6mm ARC. My 13” barks pretty loud without a can or Blast Shield.

If you can do an SBR but not a suppressor, get a SIlencerCo Blast Shield, or something comparable. It’ll help. Hell, even with a 16” barrel, it’ll help with noise and concussion.

 

[LRRPF52]

My 12” Grendel isn’t bad unsuppressed, but I only shoot it suppressed.

6mm ARC will have higher muzzle exit pressure due to significantly-less bore volume.

Higher muzzle exit pressure = louder dB.

 

[Rob01]

As Tony said just get a 16" barrel and put a brake on it or a KAK flash can. No reason to get a 10" or 12" and then extend them to 16". You get all the length and none of the velocity.

 

[kl3309]

BRAKE!
If you've got to be miserable shooting a blasty short barrel, so does everyone else on the firing line.

 

[TimK]

Oofa. That's going to suck for you and everyone around you. I built an 11.5" in .223. Tried to get a zero on a rainy day at the indoor range. Quit after 2 rounds.

 

[LRRPF52]

If you do go with a brake, see if this one will bring you to 16”...

 

[TonyTheTiger]

If you do go with a brake, see if this one will bring you to 16”...

The JP tank brake is not actually nearly as big/long as it looks.

 

[TonyTheTiger]

I would absolutely put a brake on it, but I'm probably in the minority and I've never shot at a bench before, so no one to be mad at me about the concussion.

 

[roostercogburn98]

I would absolutely put a brake on it, but I'm probably in the minority and I've never shot at a bench before, so no one to be mad at me about the concussion.

I’ve started to brake most of my new builds, or as I upgrade they get a brake. A nice simple two port has become my favorite

 

[TonyTheTiger]

I’ve started to brake most of my new builds, or as I upgrade they get a brake. A nice simple two port has become my favorite

Yeah I keep it simple on the shorties. Anything with aggressively angled baffles could potentially be very unpleasant for the shooter.

 

[Bakwa]

If you end up going with a ~10" barrel, please report on what gas system, buffer system, and bolt you plan on running.
I want to do a 10.5" Grendel something bad, but I'm afraid to commit if it won't be reliable, or if it is too harsh on the bolt.

 

[Bigjake83]

If you end up going with a ~10" barrel, please report on what gas system, buffer system, and bolt you plan on running.
I want to do a 10.5" Grendel something bad, but I'm afraid to commit if it won't be reliable, or if it is too harsh on the bolt.

Craddock and I were talking the other day and he had mentioned that he was spinning up 11.5" 6ARC barrels with Carbine+1 for some federal boys with great success.

 

[Bakwa]

Craddock and I were talking the other day and he had mentioned that he was spinning up 11.5" 6ARC barrels with Carbine+1 for some federal boys with great success.

Oohhh...
Makes me want to make some phone calls.

 

[LRRPF52]

The JP tank brake is not actually nearly as big/long as it looks.

I was trying to make a funny, but I failed. The JP Tank brakes are crazy loud. Would be brutal on a 10.5” 6mm ARC. Exit pressure is way up there.

 

[LRRPF52]

Craddock and I were talking the other day and he had mentioned that he was spinning up 11.5" 6ARC barrels with Carbine+1 for some federal boys with great success.

That makes more sense than CLGS because 6mm will have a lot higher gas port pressure at the shorter location.

I would push it out as far as possible, and either configure it suppressed 100% of the time, or have RifleSpeed or Bootleg adjustable gas.

 

[unclemoak]

Short 6arc is definitely cool, but I don’t know this I’d want to shoot this 12” gun without the can.

 

[TonyTheTiger]

Short 6arc is definitely cool, but I don’t know this I’d want to shoot this 12” gun without the can.

View attachment 8533436

What's the red piece under the handguard?

 

[mark5pt56]

What's the red piece under the handguard?

Looks like an ARCA rail?

 

[TonyTheTiger]

Looks like an ARCA rail?

I suppose it does when I zoom in a bit.

 

[MarshallDodge]

I have a 11.5 5.56 BCM upper that I bought second hand. The previous owner put a Griffin blast shield on it, and which works as intended. Really takes the edge off.

 

[Bakwa]

What's the red piece under the handguard?

It's ARCA.

 

[Midpack]

It's ARCA.

Manufacturer?

 

[Bakwa]

Manufacturer?

D Wilson

 

[LRRPF52]

Short 6arc is definitely cool, but I don’t know this I’d want to shoot this 12” gun without the can.

View attachment 8533436

Who did your barrel work and what bolt are you using? That’s a sick set-up.

 

[unclemoak]

Who did your barrel work and what bolt are you using? That’s a sick set-up.

I made my own barrel.

I forget what kind of bolt this one has. It's either one from Classified Defense or JP.

 

[LRRPF52]

I made my own barrel.

I forget what kind of bolt this one has. It's either one from Classified Defense or JP.

Got any pics of the barrel uninstalled? Looks to be dimpled nicely.

Very slick. These higher performance cartridges really bring the AR-15 into where it should have been from the start.

I love 5.56, but it doesn’t cut the mustard as the distance increases.

 

[unclemoak]

Got any pics of the barrel uninstalled? Looks to be dimpled nicely.

Very slick. These higher performance cartridges really bring the AR-15 into where it should have been from the start.

I love 5.56, but it doesn’t cut the mustard as the distance increases.