Deer/Hog Hunter Pro – My First 300 Blackout AR Build

Background – The 300 Blackout

About a year ago, as I was shopping for a .308 AR platform. One of my buddies over at Pilot Mountain Arms mentioned to me that I should look into the 300 Blackout. Being an AR-15 fan (though at that time not a big AR-15 variant fan), I was skeptical. Like a good Gun and Gear Guy, I started doing my research. A year later (plus or minus a couple of months), I decided to and built my first 300 BLK.

The 300 BLK is a variant AR-15 cartridge. Essentially, it consists of the same bullet as a .308 (actually 7.62) in a slightly modified 5.56 cartridge. This is, also known as the 7.62 x 35mm. It was originally designed by Advance Armament Corporation to achieve ballistics similar to the 7.62x39mm (round used in AK 47). One of the desired goals was to have a round that could go super and sub-sonic while maintaining consistent performance. The latter has been an issue though, particularly with sub-sonic rounds. It is an effective round out to about 300 yards. The 300 BLK is becoming a popular cartridge for hunting wild hogs and deer.

Goals – My First 300 Blk

Always have build goals, even if they are as simple as “I need a cheap hunting rifle”.  The initial goals of this build were to:

  • Build my first 300 BLK.
  • Build a “model” gun for other gun builds. This means it should have some upgrades, but not be completely upgraded (intelligent trade-offs).
  • Try out some baseline manufacturers and vendors for other gun builds. These vendors included: Wilson Combat (barrel), EOTech (optic), Hiperfire (trigger) and a few others.
  • Produce a mid-weight gun. Not too heavy for a long day of hunting, but not totally trading upgrades for every spare ounce.
  • Have a solid deer/hog hunting gun for my use.

As I alluded to above, I always go into a gun build with goals. With the extensive “choices” available during any gun build, the absence of goals typically ends in:

  1. “Franken-guns”
  2. costing a lot more than it should
  3. wasted parts

Similar to the old carpentry saying, “measure twice, cut once”, having goals and doing your component research will lead to fewer mistakes.

Build Manifest For My 300 Blk Hunter

After some online parts hunting and research, I decided the build would be based on:

  • Upper/Lower – Aero Precision. I like Aero Precision uppers and lowers. They are no frills, but are very consistent and solid.  They are, also, at a good price point. I had an AP black lower, so I purchased an FDE (flat dessert earth) upper.
  • Barrel – Wilson Combat 16″ fluted stainless steel match grade barrel. This was one of the new vendors I wanted to try out. I had heard mixed things about Wilson’s barrels, but some people I trusted recommended them.
  • Foreguard – Troy Industries Alpha Rail. I decided on a 13″ FDE Alpha Rail. I had put a similar rail on another gun and I liked it. The size fits my hand well and they are light and strong . I tend to shy away from tubes that require specialized barrel nuts and the Troy Alpha tube doe.s not have this requirement.
  • Gas Block – Syrac Adjustable. I got the Syrac adjustable gas block. They were another vendor I wanted to try out. With the sensitivity of the 300 BLK round, I thought it was a good investment. I do not always put adjustables on my builds.
  • Muzzle Brake – Kahntrol HexMod. While at one of my local gun shops, I saw the Kahntrol HexMod brake and liked it. I was excited about the rumors I had heard about how well it minimizes muzzle movement.
  • Grip – Ergo Suregrip FDE. I love the size and feel of this grip. For a long day of hunting, you do not feel like a gator has been gnawing on your hand – many make mine feel this way.
  • Butt Stock – Magpul MOE FDE. I went simple and light with this. This is a hunting gun I do not plan on spending long periods of time with it cranked up on my shoulder taking long-range shots .  So, simple and light is a good choice.
  • Trigger/Firing System – Hiperfire 24e. There are a lot of choices in good triggers out there, and a lot of “religions” around them. I did not want a drop-in, though I still enjoy “building” them.  I did not want to take the time to work-up a stock trigger. Again, this is not a “long-range gun” or a “comp gun”, so I did not need a 2 stage complex trigger. I did want a very consistent and crisp trigger to allow me to take those “snap” shots.
  • Lower Build – There were several “parts” I wanted to try out on the lower build. In general, I wanted to go with more prominent releases and catches to allow for gloved manipulation of the gun. I wanted to go with an Ambi Safety.  Unfortunately, the “gods of ordering” were against me as no vendor had any when I went to order one. So, in the end I put on an enhanced bolt catch and an oversized magazine release.
  • Upper Build – When I bought the barrel from Wilson Combat, I found a great deal on one of their lightweight BCGs. I, also, grabbed a BMG Gunfighter charging handle. I used a standard brand name buffer spring and got an H2 Buffer. I picked up a standard buffer as well. Some of my reading indicated the combination of a heavier buffer (like an H2) might make it harder to tune the adjustable gas block.
  • Pins/Misc – I decided to spend the $40 extra dollars for the KNS takedown and pivot pins. Going forward, it may be a stock decision, but as you will read later, I have some reservations.
  • Optic – EOTech HHS2 with 3X Magnifier. After a lot of soul-searching and talking with gun guys, I decided on this optic. This was another vendor I wanted to try out. More so, the 300 BLK round is one that seems to be 300 yds or less a round – this is a perfect match for this type of optic. Since I was building it for both deer and hog work, the quick target acquisition and snap shooting capabilities of this configuration made sense.

This was not a cheap build. Altogether, the parts on this gun came in at $1500 (plus/minus a $100).  With the optic, this makes this gun a $2500 gun (the EOTech combo was $990).

The 300 Blackout Build

The one thing about non-standard (not 5.56 or .223) AR-15 builds is keeping track of “what’s what”. Each one has its own “unique-isms” of parts,  You have to remember to obtain “the right one” and assemble them correctly. In the case of the 300 BLK, one has to remember that it is a .30 caliber bullet in a standard size 5.56 cartridge.

This means that the little hole in the end of the barrel is .30 caliber in size.  If for some reason you decide to put a 5.56 size muzzle brake on it, well good luc

300 Blk, 300 Blackout, AR-15, MSR, Hunting

All the parts before the build laid out.

k. Also, this means that the diameter of the barrel where the gas port is located is larger. These are the major “what’s whats”, but there are a few other nuances. Here are the variances I have found:

  • You need to get a .30 caliber (or 7.62) muzzle brake. This means the threads are 5/8×24 TPI. DO NOT get a 5.56 brake! If you do, it will not fit (threads are 1/2 x 28).  Should you force it on (which has been tried), the larger bullet will not fit in the 5.56 hole and will shred or break (and potentially do other bad ju-ju to your gun).
  • Unless you have a unique barrel, the gas block size is normally .936 (not .750 as a 5.56).
  • Do not waste your time looking for a barrel set-up for a mid-length gas system. At one time, a few existed, but I do not think they do anymore. The 300 BLK burns up powder quickly and gets that very heavy bullet moving – a carbine length system works fine.

Other than those few things, the 300 BLK out-build is pretty standard.

300 Blk, 300 Blackout, AR-15, MSR, Hunting

Finished Upper

The build went pretty smoothly.  Nothing unusual happened, other than the take-down pin was overly tight. Later, I attempted to resolve the tight take-down pin issue and (to date) I am still having some issues. Originally, I thought the Cerakote job on the lower had left some excess in the lower hole. I attempted to clean the hole out and polished the pin down a bit. Neither worked.  I am in the process of contacting KNS about the scenario and will post the results later.

I found that the oversized magazine release I used “sticks” sometimes. I believe it is due to a bit of front-to-back walk that the oversized release configuration allows over the more recessed standard release. I am still working on resolving the issue before “punting” and just installing the standard release. If I find a good solution, I will write up my finding and post it on here.

In the end, I added a spare SureFire light on it and a flip-up BUIS. All in all, the gun weighed in (with optics) at 8 lbs 9 ozs. Not too bad for an upgraded gun, with a heavier than normal match barrel. I was not totally sure about how the gun would look with the mixed color upper and lower. But, in the end, I really liked the black lower/flat dessert earth lower/upper combination. I may do more guns like that.

300 Blk, 300 Blackout, AR-15, MSR, Hunting

Completed gun – sans optics

300 Blk, 300 Blackout, AR-15, MSR, Hunting

Completed gun with EOTech HHS2 & 3x Mag

300 Blk, 300 Blackout, AR-15, MSR

Front view of gun with optics


Lessons Learned

  • DO NOT waste your money (or the weight) on a match barrel. The “skinny” of it is the standard 300BLK  bullets you can find are greater than 1 MOA at 100 yds. This is largely due to pure physics. Look for a more detailed article on this topic later.
  • I have a love/hate relationship with KNS pins. The love part – it reduces a LOT of the tedium of the springs (et. al.) that have to go into the take-down and pivot pin assemblies. The hate part – the small detent in the release pin to be removed is difficult to operate. It is a push-me/pull-me scenario, and for guys with sausage fingers like me – not so easy!
  • Not completely sure/sold on the oversized releases. As indicated above, the magazine release still has some front-to-back play that is still causing issues. I find that the bolt catch release initially had some tendencies for coming unscrewed and the release pad kept falling off. Definitely use “blue” Loctite to secure those pieces in place.
  • The HipeFire trigger installation and online “how to’s” leaves out some steps that I found had to be followed in order to be installed correctly. A future article on will go into detail with these steps.

Final Likes/Dislikes

  • Like – HiperFire trigger. After figuring out some missing steps, I really liked the ease of the installation and quality of this trigger.
  • Dislike – Heavy match grade barrel. Like I mentioned above, I think it is overkill for the ballistics. The team over at Pilot Mountain Arms are compiling some great information on this topic and I hope to interview them here on I think the highest quality, lowest weight barrel for the money is a better choice. This is nothing against Wilson Combat – this barrel was a great barrel.
  • Like – Mixed mode colors on the upper/lower.
  • Dislike – Oversized releases and catches. For the money, I am not sold on them. It is a lot of work and I still have not seen an equivalent return on those dollars in shooting. I think the Ambi Safety would have been a good add-on.  I am finding that the oversized bolt catch release and magazine release was not a great decision. The oversized bolt catch release actually changes the position of the release (places it higher on the upper).  With this, I find I have to adjust my movements when using it.
  • Like – Ergo grip. Plain and simple – this is the best money spent every time!
  • Dislike – BUIS. These were a gift and I threw them on there. Ultimately, I may take them off. I find (as configured) they are redundant and not effective for a hunting gun. If I were going to put on back-up sights, I would probably put on 45 degree offsets.
  • Like – Magpul MOE adjustable stock. This stock is simple, light and it works!
  • Unsure – Adjustable gas block. I have not tuned the gun yet, so I am interested in how an adjustable will work with the 300 BLK round.
  • Unsure – EOTech HHS2 & 3X Mag. I have not yet sighted-in the gun.  In my initial “playing” with the gun, I find the sight “feels” like it provides a small/tight field of vision, and the illumination seems to be overwhelming. The 3X magnification seems sub-par. It could be my older eyes, but those are my initial “feelings”.  Also, I am finding the side buttons on the optic to be difficult to manipulate when I am un-gloved. So, if I am gloved I think it will be very difficult.

In the future, look for more posts on specific components used and lessons learned with this gun.  Also, look for bench tests and field tests (once hunting season is here). Coming soon are similar posts on my .223 Wylde Varmint Special and an 6.8 SPC deer/hog alternative.

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