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


About a year ago as I was shopping for a .308 AR platform when 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 – but at that time not a big AR-15 variant fan – I was skeptical. Like a good Gun Guy I started doing my research. A year later (plus or minus) I decided to and built my first 300 BLK.

The 300 BLK is a variant AR-15 cartridge. It essentially consists of the same bullet as a .308 (actually 7.62) in a slightly modified 5.56 cartridge. 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 maintain consistent performance. The later has been an issue 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 even deer.


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

  • 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 tradeoffs).
  • 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 some 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, absence of goals typical 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 gun build mistakes.

Build Manifest

After some online parts hunting and research, I decided on a build based on:

  • Upper/Lower – Aero Precision. I like Aero Precision uppers and lowers. They are no frills, but very consistent and solid, while 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 also tend to shy away from tubes that require specialized barrel nuts, and the Troy Alpha tube doesn’t.
  • Gas Block – Syrac Adjustable. I got the Syrac adjustable gas block. Another vendor I wanted to try out. With the sensitivity of the 300 Blk round, I thought it was a good investment. I don’t 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 also 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 hunting, you don’t feel like a gator has been gnawing on your hand like many make mine feel.
  • Butt Stock – Magpul MOE FDE. I went simple and light with this. This is a hunting gun I don’t plan on spending long periods of time with it cranked up in my shoulder taking long range shots – so simple and light is a good choice.
  • Trigger/Firing System – Hiperfire 24e. Lots of choices in good triggers out there, and a lot of “religions” around them. I didn’t want a drop in (still enjoy “building” them), but didn’t 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 didn’t 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 also wanted to go with an ambi safety, unfortunately the “gods of ordering” were against me and no one had any when I went to order. So in the end I put 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 did get an H2 Buffer. Although I also picked up a standard buffer. Some reading indicated the combination of a heavier buffer (like and H2) might make it harder to tune the adjustable gas block.
  • Pins/Misc – I decided to spend the $40 extra dollars for KNS takedown and pivot pins. On the one hand going forward I think it may be a stock decision, but as you will read later, I have some reservations as well.
  • Optic – EOTech HHS2 with 3X Magnifier. After a lot of soul searching and talking with gun guys, I decided on this for the optic. This was another Vendor I wanted to try out. More so, the 300 BLK round is one that seems to be 300 yd or less round, which is a perfect match for this type of optic. Since I was building it for both deer and hog work, the quick target acquisition, 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) and with optic it makes this gun a $2500 gun (the EOTech combo was $990).

Pre build parts

All the parts before the build laid out.

The 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 on unique “isms” of parts that you have to remember to obtain “the right one” and assemble correctly. In the case of the 300 BLK, one has to remember that it is a .30 caliber bullet in a standard 5.56 cartridge size.

This means that that that little hole in the end of the barrel is .30 caliber size and if for some reason you decide to put a 5.56 size muzzle brake on it – well good luck. It also 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 as well. Here is what I have found that varies:

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

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

Finished upper

The build went pretty smoothly, nothing unusual happened other then the take-down pin was overly tight. I did later attempt to resolve the tight take-down pin issue and to date 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. I also polished the pin down a bit. Neither has worked.  I am in the process of contacting KNS about the scenario and will post the results later.

I also 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 trying to resolve the issue before “punting” and just installing the standard release. If I find a good solutions I will write up my finding and post it on here.

In the end I added a spare SureFire light on it and flip up BUIS. All in all the gun weighed in with optics at 8lbs 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.

Completed gun sans optics

Completed gun sans optics

Completed Gun with EOTech HHS2 & 3x Mag

Completed Gun with EOTech HHS2 & 3x Mag

Front view of gun with optics

Front view of gun with optics


Lessons Learned

  • Don’t 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 an more detailed article on this topic later.
  • I have a love/hate relationship with KNS pins. The love part is that 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 is the small detent used to release pin to remove it is difficult to operate. Its a push-me/pull-me scenario and 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 causing issues. I also find that the bolt catch release, initially had some tendencies toward coming unscrewed and the release pad falling off. Definitely “blue” Locktite any of those pieces in place.
  • The HipeFire trigger installation and online “how to’s” leave out some steps that I found had to be followed to get it to install correctly. A future article on will go into these steps in detail.

Final Likes/Dislikes

  • Like – HiperFire trigger. After figuring out some missing steps, I really liked the ease of installation and quality of the trigger I found in the HiperFire 24e trigger.
  • Dislike – Heavy match grade barrel. Like I mentioned above, I think its 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 probably a better choice. Nothing against Wilson Combat, the barrel was a great barrel.
  • Like – Mixed mode colors on the upper/lower.
  • Dislike – Oversized releases and catches. I think for the money I am not sold on them. Lots of work, and I still haven’t seen an equivalent return on those dollars in shooting. I think the ambi safety would have been a good add-on but the oversized bolt catch release and magazine release I am not finding such a great decision. The oversized bolt catch release actually changes the position of the release (places it higher on the upper) and I find I have to adjust my movements to use it.
  • Like – Ergo grip. Plain and simple, best money spent everytime!
  • Dislike – BUIS. They were a gift and I threw them on there. I may ultimately take them off. I find as configured (otherwise) they are redundant and not that effective for a hunting gun. If I were going to put on back up sights I would probably put 45 degree offsets.
  • Like – Magpul MOE Adj Stock. It’s simple and light and works.
  • Unsure – Adjustable Gas Block. I haven’t 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 sighted in the gun yet.  I do find in my initial “playing” with the gun the sight “feels” like it provides a small/tight field of vision, as well as the illumination seems to be overwhelming. The 3X magnification seems sub par. Could be my older eyes, but those are my initial “feelings”. I am also finding the side buttons on the optic difficult to manipulate ungloved. 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 in this gun, as well as 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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