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300 AAC Blackout Complete

mingaa

mingaa

Raconteur
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14.5" 1:8 barrel with pinned and welded birdcage to reach 16"
Magpul AFG & BUIS - 3 lb. Timney trigger, Primary Arms micro dot and a 40 round mag just for fun.

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Local guy did a nice job on the TIG weld! I drilled and fabricated the pin - went .100 into the barrel threads. The birdcage was some of the hardest steel i ever worked with! Maybe ity has to be because it is heavily machined - really surprised me and the drill press!

First time out it short cycled. I swapped lowers, BCG etc. Pretty sure it is just under-gassing. I opened the gas port from .079 to .094 - max is .120. First time out it was close - it ejected brass (landed at 4:30 location = low gas sign), reset the firing pin and trigger but didn't load next round or lock back. Hoping the 3/32" hole does it!

I'll be at the range shortly despite 17* and 6" of snow. I gotta know!!! :D
 
Nice, looking forward to seeing how it performs
 
4:30 isn't really bad.

I know that 3 is ideal, but it's possible that with a different charge or powder (or brand) that it'll be spot on. Then take into consideration supersonic or subsonic loads to find a happy medium for both.

Long as it's cycling and locking the bolt open, what more can you realistically expect?

Also, great job pinning the flash hider.
 
Thanks guys. I did find some 5744 powder ( as well as 296) locally and I have bullets from 110 to 178 gr. I'll be shooting super only for the time being. The gas system is pistol length - new to me. Today's tests didn't happen due to family business but I'm really anxious to sort out the capabilities of this setup ASAP!

I'll be out to zero the sights early in the week and hope things run smoothly and I can get started on the chrono looking for a major power factor load! *fingers crossed - 5744 and 175/178gr look like they will do it, on paper*

We are shooting IDPA in the morning despite 5-6" of snow and temps in the teens so I'm taking a break to enjoy that if enjoy is the right word!!

The trigger makes me grin. We'll see how it is in the heat of competition!

More early in the week!
 
That looks like a really great build. I confess the 300AAC round absolutely fascinates me to no end. I look forward to more pics and range report. And a video would be quite nice (thanks in advance.... :lol: ).
 
Nice build. I just read an article last night on the 300 ACC Blackout and will second an interest in reading how it will perform for you.
 
Guys if you guys want to get into more research, check out the originals:

300/221 and 300 whisper

The blackout is hardly anything more than a standardized whisper, which has been around since the 80's.

It only got a huge spike because of Cerberus' marketing department ;)

Olympic Arms has been selling an AR upper from an earlier variant of this cartridge (with rather dismal sales actually) since at least the 90's. Up until Cerberus got saami standardization, and a few companies started making factory loads for it, and before the gun magazine writers started pushing it with vigor, hardly anyone wanted anything to do with it.

But the truth is, the blackout with all intents and purposes has been around for a long time, but was considered more of a wildcat.
 
The enlarged gas port and slight gas tube realignment solved the short cycling. The gun ran through 30 rounds of medium loaded 150gr fmj and handled it like a champ. The cases are landing at about 4 o'clock but feel strong and right.

I'll start chrono ASAP and see what happens with different weight bullets and loads (110-180 in stock here) - I'm only looking at super sonic for now. I want to find a major power factor load and shoot it in 3 Gun. A 178 gr bullet and Alliant 5744 show it on paper. I'll put that round together ASAP! Woot!! There are a few more on the shelf - I may go back for more Monday!

Nitesite - I'll continue to document as I move ahead for sure!
 
sweet rifle.

I always thought the extractor claw variance dictated where the brass landed. All mine land at 4, from 55 gr hand loads to 77 grain 556 nato, and the deflector is always marked on the outer half of the deflector, the half closest to the receiver is always untouched

how is that sight ?

Is it pistol length because of the caliber ?
 
My guess is that the gas tube @ pistol length is "calibrated" so that when mingaa shoots his lower-powered subsonics there is enough gas port pressure up close to the BCG that it will still cycle the gun even when pressures are already dropping. I hear that the subsonics are really going to shine their best as far as cycling goes if they happen to be shot in a short-barrelled gun like a 10.5" that has a can on it plus a pistol-length gas tube for a little added (back) port pressure. If an AAC BO with supersonic rounds is fired in most guns that are tuned correctly the gun has sufficient gas pressure to cycle the action even with a carbine length gas system.

I could be totally wrong so please correct me because I need to learn more about the platform..... From what I have gleaned it can be a very delicate balance of buffer, gas tube length, bullet weight, bullet velocity, barrel length, suppressor (or not) and whether you regularly use dental floss and rinse.
 
Oli - you probably know more about brass extraction than I do. I've read a couple of articles about location on the clock and how to interpret it but I filed it away as sounding reasonable. My real life experience with that is minimal and the brass is landing darn close to where it was before I upped the gas flow.

I'll need more time with the sight but my initial impressions are great. I matched it with a fairly minimal UTG base that was offered through the PA - the next best absolute co-witness was going to put me at the sale price if a Vortex SPARC - the sight that I am really comparing it to. It matches perfectly with Magpul buis. The adjustments are a bit stiff - they may relax with use but the détents are crisp. It has 11 brightness settings and I was shooting on 3 and 4 on bright days! It feels very natural shooting both eyes open. The small size is probably helping me forget about the sight even being there. My current opinion - it is well above the $100 grade that I have invested in that, the base and shipping!

Of the barrels thst I looked at only 16" came with carbine length gas systems. Mid and rifle do not exist. Anything under 16" comes (my experience) as pistol length. The round burns quickly using less powder than a 223/5.56 round - the effective powders are a bit limited, not bad and I was able to put together 4 pounds with no trouble (more if I could afford it) - I see a bit of capitalism being exercised with the "IT" powders Accurate 1680 & 5744 ($30+) - but I've been able to buy them locally and bullets across the range have been available. 30 cal. has so many uses.
 
nitesite said:
My guess is that the gas tube @ pistol length is "calibrated" so that when mingaa shoots his lower-powered subsonics there is enough gas port pressure up close to the BCG that it will still cycle the gun even when pressures are already dropping. I hear that the subsonics are really going to shine their best as far as cycling goes if they happen to be shot in a short-barrelled gun like a 10.5" that has a can on it plus a pistol-length gas tube for a little added (back) port pressure. If an AAC BO with supersonic rounds is fired in most guns that are tuned correctly the gun has sufficient gas pressure to cycle the action even with a carbine length gas system.

I could be totally wrong so please correct me because I need to learn more about the platform..... From what I have gleaned it can be a very delicate balance of buffer, gas tube length, bullet weight, bullet velocity, barrel length, suppressor (or not) and whether you regularly use dental floss and rinse.
Click to expand...
Yep - that is pretty much what I have learned about the round and upper configurations as well. Iirc, one of the goals while developing the round was to gain military interest SO ideally uppers could be swapped on the fly (with standardized rounds) and they would work with AR lowers with no modifications to springs, buffers etc.

Enter Joe Q Public and his want to tinker and a wide variety of approaches are evolving.

My interest in the gun was largely to fire 30 caliber ammo in a modern, accurate, semi auto format. I rarely shoot beyond 100 yds. Even if I were to hunt with the gun MO landscape makes a 100-150 yd shot a 'long' shot. With the charge and bullet weight they drop like a rock farther than that.

I like the 1.5" I was able to cut back on the overall length and the slight weight/balance change. From what ive read there is no effect on accuracy and rounds do not benefit from added dwell time as much as other rounds. I'm looking to get a major power factor round developed ASAP but there is maybe one 3Gun match a year where I will be checked for that. At the club events that I shoot they will score me major just for shooting 30 caliber - a scoring plus if I can keep my times good. Now that the gun is running well I'll be looking at buffers and springs that may smooth it out just a bit. My rate of fire is never super fast - I depend more on accuracy for good scores.

I don't have any real interest in sub sonic rounds YET - maybe in time!!
 
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