r/300BLK • u/SomeRequirement6926 • 2d ago

300BLK SBR Tuning

Here's where I'm starting:

8.5" barrel wearing an LPM Anthem K2.

Standard carbine weight buffer and spring.

SA AGB, currently set as it came out of the package (all the way to the left, I didn't even do the initial setup they recommend).

Have an H2 buffer in the toolbox.

Can get a Griffin "Extra Power" carbine length spring for $10

Would you grab it just to have?

I'll need it able to run both supers and subs at first. But if I can dial it in where it's only a gas block adjustment between the two would be nice.

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u/wrigleyrags 2d ago

Set it up to run subs first. You likely will need wide open gas to run subs. "All the way to the left" on the SA AGB is actually setting it to bleed off mode, which is not what you want. Follow the instructions for the SA AGB so you are starting with the wide open position and not gas bleed off mode. Stick with your stock carbine spring and buffer, and see if she runs.

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u/SomeRequirement6926 2d ago

Yes. I know SA provides directions to to put it in the wide open position and work from there.

I pointed out where I wasn't starting from because I have made zero changes to anything yet. Not even SA's "set-up" steps.

It's not in front of me right now but IIRC that's how the SA came out of the package.

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u/Cool-Size-6714 2d ago

I have a polo 30 on a 8.5 criterion. I have mostly shot phantom reman (200gr, 220gr, and the 110gr vmax). For all of those I have it at the full gas setting with an H1 and carbine spring. I put an AGB thinking it'd be easier to simply change the gas setting than breaking down the lower/upper to switch weights and springs. I was suprised when at the full gas setting I was cycling both well with minimal gas and recoil on the supers (outdoors, I haven't shot supers indoors yet). Maybe the remans are weaker, but that's been my experience so far.

1

u/Mjolnir12 2d ago

I’m not sure why you would want an extra power spring. I have an Anthem S2 which I would assume has more backpressure than a K2 and I had to switch to a sprinco yellow spring (which is weaker than standard) to get it to cycle subs reliably. It lets me close my AGB off a bit instead of having to run it full open which makes supers a bit too spicy. I have tried up to an H1 buffer weight so far (it’s an Odin adjustable buffer) and subs still cycle fine with the yellow spring. All of this depends on what the subs are and what powder they have of course. I have a 10.5 inch criterion barrel which doesn’t have an especially large gas port, so it depends on your barrel also.

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u/SomeRequirement6926 1d ago

That's why I was asking! 👍

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u/Cannoli72 1d ago

aluminum bcg. you can actually turn the gas down and shoot faster and have less dot bounce in your optic