1st 300BLK build - Need opinions

Hey shooter's.

So I now think I have enough 556 AR's. I was recently watching John Lovell's 556 vs 300BLK YT video and it got me thinking that I should at least build a 300BLK upper to add to the safe, cause at any point I could pop it on a lower. The main use case for this upper would be home defense and a truck/woods gun. In both cases I dont really see myself taking more than 1-5 shots but I would want all the benefits that BLK offers over 556.

The main three questions I have about the build that I would want guidance on:

1 Barrel length: I'm looking at tubes from Aero precision. I'm not sure if I should go 8" or 10".

2 Rail: Should I go with a 1.3" inner diameter rail that stops at the muzzle device, or go with a 1.75" ID rail that will shroud over the can?

3 Can: Should I get a dedicated K can? or is my Vox S (in jail) a better can for the job?


The configuration I'm kinda thinking right now looks like:

8" Barrel
9-10" rail 1.75 ID
Vox K

I'm just worried that with that short of a barrel and can I won't get the suppression I might want? I dont need massive suppression, but if I am cooking off 1 - 5 rounds indoors at night I want "best case scenario". Thats the whole reason I am going BLK over 556 is because 556 suppress poorly from short barrels.

Well do you plan on super sonic or subsonic loads??

With subsonic suppression should be fine.

My 8.5" suppresses well with supersonics, with a Omega.
Don't know anything about VOX.

Sent from my SM-G991U1 using Tapatalk

8" barrel. The strength (and basic reason for design) of the 300BLK is that it has decent downrange energy out of a short barrel (unlike 5.56).

Do NOT put the handguard over your suppressor. This looks cool and seems like a good idea, but the handguards will get too hot to handle quickly.

Up to you on the can. I went full sized on the 300BLK because I wanted it as quiet as possible, and the shorter barrel gave me more room for a bigger can while still keeping the overall package compact (again - the whole basic design reason for 300BLK in the first place).

I put a K can on my 5.56 and it's perfect there. Just depends on your wants.

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Originally Posted by Matt in TN

8" barrel. The strength (and basic reason for design) of the 300BLK is that it has decent downrange energy out of a short barrel (unlike 5.56).

Do NOT put the handguard over your suppressor. This looks cool and seems like a good idea, but the handguards will get too hot to handle quickly.

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Must one just get used to the short reach or are there ways to compensate?

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Originally Posted by Disciple

Must one just get used to the short reach or are there ways to compensate?

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Depends on what accessories you have/want. A sling stud, light, or fingerstop all can help you remember. Or you can keep grabbing your hot suppressor by mistake - that's a pretty effective reminder too. ;-)

Here's a fingerstop I use on one. It's just enough without getting in the way for other stuff. Makes a good barricade stop too: https://www.smokecomposites.com/parts-and-accessories

For ammo I will probably reload for it and brew some 110-125gr supers. I want to shoot supers because from same barrel length there is nothing in 556 that comes close to the terminal performance and all shots should be under 50 yards.

About the rail being past the can... will it still get hot if the can and rail have some spacing? I get if they are damn near touching there could be a thermal bridging affect, but if I can see good daylight think it will still be an issue? If so, then I will probably go with a 10" barrel and short can just because I want at least a 9.5" rail cause I'm still a taller guy even if I want a shorty gun.

Quote:

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Originally Posted by Disciple

Must one just get used to the short reach or are there ways to compensate?

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I use a vert grip on a gun that short and run the stock an extra click or two out, which of course eats into the length savings that such a short barrel offers. Even in .300 BLK, I might choose a 11.5” barrel over a 8”.

Would it be practical to mount the VFG on a cantilever rail section, placing it below the suppressor, or would that burn your hand?

Quote:

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Originally Posted by Disciple

Would it be practical to mount the VFG on a cantilever rail section, placing it below the suppressor, or would that burn your hand?

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Its probably possible. I don’t think I would try it. For the rail and barrel lengths OP suggested, the grip would probably end up slightly behind the can, so that he can still activate his light. Maybe some kinda wrap ahead of that.

I think the best solution would be a little more barrel, or a little shorter rail. In that order.

I have a 9" barrel with an 8" rail and use a VFG. The VFG is definitely a lot further back than where I run it on a 16", but I honestly dont even notice when switching between the two. I thought it would take getting used to, but even with a full size suppressor there isnt any of the "overswing" that you can get on longer guns when you grip too close to the magwell.

That lack of "overswing" got me thinking so I just measured and the front of my VFG is ~11" back from the muzzle on both the 9" (suppressed) and 16" (unsuppressed) guns. Didnt plan it that way, but its how it worked out. Thought it was interesting. Maybe thats the sweet spot for balance for me, I dunno.


1. Barrel- Between 8" or 10", I would go with 10". I wouldn't really want anything shorter than 9". Or like 1168 said, 11.5" is tempting, and then you have 10" rails you can play with.

2. Rail- Stop at the muzzle device

3. I shoot supers with a 300 SPS (outside) and if you're only taking a couple shots, ear pro is close to optional, and I'm pretty anal about hearing protection. My buddy just ordered a 7.62 mini that I'm interested in comparing to the SPS, but that'll be a while.

As a reference, the 9" with 300 SPS has a 2" shorter OAL than a 16".