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Expecting a baby........300 BLK


dpete
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Definitely not a human baby, I'm way to old for that nonsense.  A micro 300 BLK pistol build.  5" barrel w/micro gas, 4" handguard, KAK round pistol buffer tube that will get either a foam pad to start, or my original Sig brace later.  Sights will be the Burris Fastfire III I already have with Magpul flip ups front and rear.  Everything in between will be standard AR15 fare.  All the parts are inbound right now.  The big question mark right now is muzzle device.  A standard birdcage flash hider is what I'm starting with, but I might get a flash hider I can thread my suppressor on to.  This thing should come in somewhere around 22" total length and hopefully will turn into a fun little blaster and truck gun.  I'll see how it does with the 110gr Varmageddon loads I have for my other BLK or I can always make up some special loads for it.   An almost life size picture of what the upper will look like.

ar15-upper-assembly-5-inch-300-aac-black

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Posted (edited)
2 hours ago, Rsquared said:

I do love me some SBR length equipment. This should be a fun little guy. Looks good too.

You've got the official R2 seal of approval my good man.

Thanks! I also have a SBR lower I can slap this little bugger on for those super short rifle moments. I might have to break down and camo another AR so this one matches the others I have.

Edited by dpete
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@98Z5V  Its going to be a bit unique because of using the KAK Sig brace buffer tube.  I held it up to one of my other rifles with a standard 7" ID tube and the KAK is 2" longer!  I thought WTF, never gave it a second thought when it was installed before and it worked just fine.  Tonight I pulled out a tape measure and found out what is up.  The tube is 9" end to end exterior length, and 7" interior length.  The thing has a 2" long aluminum plug in the back of it.   WTF solved.  Being as long armed as I am I might just add a bit to it before sliding the foam pad on.  Lord knows I've got enough solid aluminum at the back for a screw to grab on to and hold my homegrown extension in place.

1512600237_03212220021.thumb.jpg.1b6ed26e1e1a658c3d0d44658ad802a7.jpg

 

1652912338_03212220031.thumb.jpg.bb0adec33e34c574ce0eaee4f3d24fc2.jpg

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1 hour ago, 98Z5V said:

I have one of those on my 300BLK pistol that goes in the tennis racket case...   :thumbup::laffs:  You should have just asked...   Prevent some mental anguish there...  :lmao:

It seems to me that when I discovered the differences in the tubes you were busy out at the SDTF up to who knows what kind of shooting and other shenanigans.  A bit busy in other words.  :banana:

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Looks like a fun gun! Big poop eatin' smile on my face the second I saw the upper. For sure you'll have plenty of gas to run it. Please keep us in the loop.

Yeah, I'd do the can thing. I think you'll want it with that short barrel. I don't think that short birdcage will do squat.

Have you considered a folding buffer tube adapter? It will slightly lengthen the buffer and make for a very small handgun when folded. IMO that gun just cries out for one. A folding firearm that short when folded would be absolutely wild!

Just curious, do you have a chrono' to check velocity? Inquiring minds want to know the data.

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2 hours ago, BrianK said:

Looks like a fun gun! Big poop eatin' smile on my face the second I saw the upper. For sure you'll have plenty of gas to run it. Please keep us in the loop.

Yeah, I'd do the can thing. I think you'll want it with that short barrel. I don't think that short birdcage will do squat.

Have you considered a folding buffer tube adapter? It will slightly lengthen the buffer and make for a very small handgun when folded. IMO that gun just cries out for one. A folding firearm that short when folded would be absolutely wild!

Just curious, do you have a chrono' to check velocity? Inquiring minds want to know the data.

An option to the birdcage or can is a flashcan to direct all the blast forward.  The can I have is a Form 1 that I built with quieting a 308 AR in mind.  Its 10+ inches long.  It works great on my 8" barrel BLK with subs but it goes against the short concept adding that much length to this little thing.

I've looked at the Law folders.  Very nice and very pricey.  One review I saw stated that it adds about 10.5 oz to the overall weight.  Not something I'de like to do.  It would be slick to have the folding option but for practical purposes it might save 30 seconds over grabbing the upper and lower from the case and popping the pivot and takedown pins in.  I have a laptop case that has been laying around for several years that I'm going to try to use.

Yes I've got a chrono and several flavors of 300BLK reloads to put to the test. 

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All the upper parts showed up yesterday and I'll be putting it together today as soon as I return from getting the BCG from my local gun pusher.  With the birdcage flash hider, and KAK pistol tube this thing is going to be 23" long.    @98Z5V  The gas port is only 3" from the front flat face (front of pic rail) of the upper, and measures .109" in a .75" journal.  With the back of the bullet travelling under two inches from inside the case to going past the gas port I'm thinking an adjustable gas block wouldn't be the worst idea.  Your thoughts?  There is going to be a lot of gas going down the gas tube hitting the BCG unless its tuned down.

Mocked up for visualizing.  Nothing tightened down.

1874190372_03262209541.thumb.jpg.94062ab04a4499bff1ba2ce875d790b0.jpg

 

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An adjustable block certainly won't hurt, on that setup.  That's not alot of barrel length, a super-short dwell time, and the port is 'Uge.    Might be interesting to run it once or twice wide open and see what happens.

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Posted (edited)

@98Z5V   I've got an adjustable block incoming hopefully this week.  Just in time for the lower and the rest of the parts to get here.  I'de be tempted to put the block and gas tube I have on the upper and mount it on my SBR lower just to give it a test but at 17* outside I'm going to pass on that idea.

Edited by dpete
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On 3/27/2022 at 10:00 AM, dpete said:

@98Z5V   I've got an adjustable block incoming hopefully this week.  Just in time for the lower and the rest of the parts to get here.  I'de be tempted to put the block and gas tube I have on the upper and mount it on my SBR lower just to give it a test but at 17* outside I'm going to pass on that idea.

I'd be curious if it runs like that, with s standard gas block.  I've had a few barrels shock me with their gas ports in the past - that KAK 12.5" midlength gas barrel shocked me, for sure.  The Wilson .338 Fed barrel shocked me, too.

Oh, by the way brother - we hit the mid 90's over this weekend.  It's too early for that shiit, I'll tell ya.  :bat:

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Parts have arrived and she is put together...mostly.  I'm still waiting on the adjustable gas block that USPS says is supposed to be here tomorrow.  I'm thinking more likely Saturday or Monday considering where tracking says it is right now.  If I get anxious over the weekend I may put the standard gas block on it just to see how it runs unrestricted.  

23" of pint size blaster 300 BLK

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First outing is a success!   The adjustable gas block arrived this morning and I had it installed shortly after.  @98Z5V It ran like a top with the gas block wide open.  First shot with 1 round in the mag had bolt hold open on empty.  Next mag with 3 rounds all fired and ejected perfectly.  Then I commenced shutting down the gas.  First two clicks, had BHO.  4 more still had BHO.  4 more still had BHO.  I kept shutting down the gas until finally I had no bolt movement, I assume gas was shut off completely.  Two clicks open and BHO again.  Ejection was right at 4 o'clock with empty cases landing about 3-4 feet out.  I'm guessing that I have it two clicks above fully shut off and have perfect function.  This is with a 3.0 oz carbine buffer and standard spring.  Shooting subs with the gas set for supers had no BHO, and I didn't play with it to determine how far it needed to go to get there.   The recoil is a smooth push, not a sharp punch like I expected, although I did use my original Sig brace for testing purposes.  It was a cloudy day and the birdcage flash hider did its job, there was no noticeable muzzle flash when observed from 20 ft to the side.  Shooting it you don't really realize how close the muzzle is to your face compared to a 16" carbine.  Next up is some accuracy tests at 25 and 50 yards.

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4 hours ago, Rsquared said:

Yeah, I think that we all have. Let's take a flash back to 2017 in the fall.....at the SDTF.

Kate.....the MK18.....at 

 

4 hours ago, Rsquared said:

Yeah, I think that we all have. Let's take a flash back to 2017 in the fall.....at the SDTF.

Kate.....the MK18.....at night.

 

Kate owned the dark. Let there be  light!

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