I’ve got a Centurion MK12 18" barrel and Ops Inc brake setup going on my SPR build.

Should I go ahead and put a Superlative AGB on it, or run it with a regular low pro gas block?

I’ll hopefully get an AEM5 or OCM5 suppressor eventually, but it’s not in the budget after this barrel and build anytime soon.

Does this barrel benefit from an AGB? The price is more, but a drop in the ocean for the overall build.

I have that barrel with the tabbed Centurion gas block, it is gassed very well. No issues cycling with or without AEM5. Brass ejects 3-4 o’clock with IMI 77gr

ETA: I’m running a Vltor A5 buffer system at H2 weight and Springco Green rifle spring, IIRC.

Gas blocks are easy enough to swap out.

Since it sounds like the can is a decent ways off, I’d just hold off on the AGB til you get the can and test it out with a standard gas block, then swap if absolutely necessary.  

FWIW, Centurion gasses their barrels very well.  So long as your can isn’t extremely high backpressure, I’d venture a guess it’ll be fine with maybe some buffer weight adjustments.

Sounds good. So I'm in dreamland about some necessity to "dial it in" to have it function ideally? I guess it makes sense from a practical point of view. If anything needed adjusted to work, Monty would have done it at the barrel's gas port.

It’s a bit more complicated than that.  A barrel manufacturer can’t make a single barrel that’ll work perfectly with every can.  Every can creates a different amount of backpressure, so what may be ideal for one won’t be for another.  I can’t comment on the OCM5 or AEM5 as I’ve never owned one.  It’s very possible (even likely) one may have more backpressure than the other, since they’re made by different manufacturers, with what I’d have to assume are different baffle stacks.

What I’m saying is that Centurion doesn’t hog out their gas ports to run weak, cheap ammo.  They build their barrels with appropriately sized gas ports that should offer reliable function both suppressed and unsuppressed with many suppressors.  If whatever can you get ends up having a lot of backpressure, it may be preferable (or needed) to cut off gas further.  That said, with a reasonably sized gas port, that’ll be less likely.  It being a RLGS on an 18” barrel helps matters even further as rifle length port pressures are much lower and more forgiving.

Just my $0.02.

In my opinion, you will not need an AGB for this setup.

I just provided anecdotal evidence from a sample of one. Like stated above, a rifle length has system has much lower port pressure than mid length and carbine, which makes it far less likely to need gas restriction.

I only have two rifles (one, really) that have actually needed an adjustable gas block:

The one that really needed it is a PA-10 .308 with a 16” mid-length gas barrel… when adding a Rugged Razor suppressor, the rifle cycles too fast to effectively eject the spent case. It cycled fine without the suppressor. Tuning with buffer weight and AGB gave me an operating envelope that could accommodate both modes.

The other gun has is a 10.5” 5.56. It works fine with or without a can, but I added an AGB just to tune it down a bit when suppressed.

Thanks guys. This is one reason I decided to get a good barrel and keep the front end identical to a MK12. As far as I know, the only difference in the OCM5 and the AEM5 is that the OCM is physically lighter and "modern construction" but essentially a clone.

I just built up the barrel with my low pro GB and got everything secured. If I get the can and think the AGB is needed, I'll take off the brake and add one. No big deal

https://blackrivertactical.com/WP/BRT-EZTUNE-Gas-Tube-Configurable-Rifle-p334967178

Just my opinion,  but, better option than AGB.


ETA link:

https://www.ar15.com/forums/AR-15/AGB-needed-for-SPR-MK12-ish-build-/118-788038/?page=1&anc=8687190#i8687190

I use a brt gas tube like the one listed above.  It works great.  I have mine to set to 100% suppressed use.  Not sure now much benefit you would get if you used one that was set up to run both suppressed and unsuppressed.

I have their tabbed gas block and it ejects at practically 5 o'clock, but I also use a Huxwrx flow through can. But even with the standard can, I'd bet you don't need an adjustable gas block.

I'm also running an A5 RE, Sprinco Green spring, and A5H2 buffer.

https://vimeo.com/1019204638

I’ve got a standard 7075 buffer tube on its way. I have a variety of buffers.

Should I build it up with a A5 buffer setup?

No. I run an A5 on my go to gun. I think it feels a little smoother. Is it worth it if you already have the std parts? No. Just roll on with what you're doing

Agree. I'd never drop the coin to convert, and lately I even question the extra money A5 costs over what can be had in carbine when building from scratch.

Not required, doubtful it will have any effect on performance. I started with a Mod0 configuration, then reconfigured to ModH.

Since ModH is really just an early version of what is now a pretty standard configuration (16” middy), I felt it got away from the DMR role, so I made a “Mod-G” with the 18” Centurion setup, replaced the PRI fore end with a URGI MK16 and A5 buffer system to see what a “modernized” Mk12 would be considering the suppressor and barrel as the heart of the system.

Thanks guys. This is my first high end build looking for accuracy, while maintaining a certain amount of durability and reliability. That's why I chose the MK12 barrel... since I'm still putting it all together, I can go straight into overthinking. "Buy once, cry once" and "Do it right the first time" may be good ways to think about this, but there are so many options and quality choices that we all end up building similar guns, but why do they all need to be the same?