My poor scratched and scraped DPMS AP4 7.62x51 rifle has worn a lot of hats. It was the second AR format rifle I ever purchased a year or so after my heavy barreled DPMS 308B. First and foremost as a hunter and target shooter, I loved the utility of the 308 round. These DPMS AR 308's seemed the logical purchase for both sporting, target shooting, and hunting of any North American game.
Like so many other firearms, my original DPMS AP4 wandered into my arms after being a used gun deal that was an unbelievable $600... yeah I dare you to find that deal on any AR format 308 these days. In fact I saw a DPMS 308 Bolt Carrier Group alone that was selling for $700 alone. The downside was that after I beat this already used rifle it was in need of a new bolt.
I always enjoyed how light that DPMS AP4 rifle was comparatively to heavy bull barrel 308 ARs, however a recent ultra-light build beat it out and pushed this now heavier AP4 to the back of the safe. This rifle was in need of an update and this time I wanted to go to a heavy barrel to improve precision and long range hit capabilities. The choice was an 18" Black Hole Weaponry 308 Barrel, new bolt carrier group, with all new furniture, optic, and trigger to completely update the rifle. My old AP4 easily delivered 1"-1.5" groups at 100 yards, but of course my expectations were higher for this build which has clawed its way to a little over $3000.
ABOUT BLACK HOLE WEAPONRY
When you want huge accuracy improvements beyond a free-float handguard, the obvious upgrades are an improved trigger and target barrel, but it is the barrel which can net the biggest benefits. The problem is that upgrading from a standard mil-spec to a premium mil-spec hammer forged barrel these days will typically lighten your wallet upwards of $250 and in reality provide good durability improvement but marginal accuracy improvements. Upgrading further to match grade barrel will pull $350-$600 from your wallet. Fortunately for those that are looking for sub-MOA accuracy, Black Hole Weaponry has an affordable match grade polygonal rifled 308 barrel that starts around $320. Not heard of Black Hole Weaponry? They sell barrels direct to customers, however they are primarily an OEM barrel supplier for many AR brands you know that punch tiny little groups. I featured a lightweight .223 Black Hole Weaponry barrel in my ultralight Mega Arms monolithic upper build last year and was so impressed, I decided one of their 308 barrels would be just the ticket for the high precision intent of this build.
The Black Hole Weaponry barrels will fit and install perfectly in place of or as any other standard DPMS 308 format AR barrel and are available in all the standard contours and gas system lengths. If you want a certain weight, feel, barrel profile, fluting, or barrel finish on the stainless barrels in a carbine, mid, or rifle-length gas system, Black Hole Weaponry can accommodate almost any request within their regular list of options. You can even specify a threaded or a standard target crown. The result of all these options provides the AR15 or in this case me the DPMS 308 barrel buyer with a huge amount of options to customize the fit, feel, and finish desired. Including this barrel, I have two other barrels from Black Hole and they are all excellent tack drivers.
FIT, FEEL, & FINISH
Black Hole Weaponry wins the attention to detail barrel maker award. They only purchase certified US materials and keep the certificates on file, then record material lot numbers and track each piece of steel through the entire manufacturing process. After profiling and finishing, each barrel is marked near the extension with their name, the lot number, chambering, twist, and the inspectors stamp. They perform magnetic particle inspections (MPI) and other non-destructive testing to assure the integrity of each barrel and pull random samples for destructive testing. A hell of a lot of attention to detail on a $320 base configuration 308 barrel with polygonal rifling.
The barrel I choose was their standard bead blast 18” mid-length gas system. The barrel is polygonal rifled with a 308 match chamber, 11T twist, and a threaded muzzle. Flutes look cool and could have dropped some weight, however actually wanted a bit of extra weight and knew that the extended 15" Precision Reflex Delta Carbon Fiber forend I was planning on using would cover most of the barrel anyway, so the added cost of fluting was sort of pointless cost in my case.
Black Hole Weaponry 308 Barrel - The Black Hole Weaponry barrel features three-land polygonal rifling based on 416R stainless steel with a rifling shape is a series of arcs instead of square corners, as in the traditional style of Enfield rifling. This arc shaped rifling has long been held in very high regard for its accuracy, increased velocity, reduced gas cutting and ease of cleaning. From my experience with two other Black Hole barrels, polygonal rifling deliver outstanding accuracy and run significantly cleaner and require far less cleaning compared to other comparable cut rifled barrels which in the end has delivered accuracy which held during extended shooting.
The barrel features Black Hole’s own 308B match chamber with a 1x11 twist ready for a .936” gas block. Black Hole’s 308B chamber is similar in theory to the idea of the .223 Wylde chamber for .223 chambered rifles, but in this case to optimize .308 or .5.56 ammunition for accuracy. I used a Precision Reflex low profile gas block for the mid-length gas system. My old AP4 was a carbine length gas system packed a snappy punch, however this mid-length system noticeably smooths things out a bit.
PRI Quite Brake - Working down the barrel I tipped the ⅝”x24 threaded muzzle with a Precision Reflex 308 Quiet Brake to take just a bit more bite out of the 308 recoil and improve follow up shot recovery. As with any brake, they are far from quiet and in fact they are freaking loud as hell, however the PRI is a fair bit less annoying to other shooters, but do not expect any warm embraces.
PRI Delta Carbon Fiber Forend - PRI products are outstanding quality so in addition to the gas block and brake, I selected an extended black 15" Delta Carbon Fiber forend. Honestly, I am in love with this forend as it locks down onto the receiver like a bank vault. The forend is extremely stuff with zero wiggle all while being very light. This stability means a rock solid mount for the Atlas bipod.
The big advantage with the PRI Carbon Fiber forends is not the look of carbon fiber, but the weight, stiffness, durability, and heat dispersion capabilities. If your guns kicks out heat like this 308 will during consistent shooting, a carbon fiber forend from PRI will deliver a significantly cooler forend than aluminum.
DPMS Bolt Carrier Group - Stunningly the most difficult part of this build was obtaining a new bolt carrier group. In these insane times, to say I got lucky is an understatement on finding a brand new DPMS bolt carrier group direct from DPMS. I waited months for the backorder to fill however, it finally arrived all without getting raped on Gunbroker for the $700 bolt I saw online.
Generally a best practice when replacing a barrel is to also replace the bolt to allow a new bolt and barrel to wear and marry together. In this case I replaced the bolt and carrier group together. Most accuracy nuts believe that this will provide a tighter fit and increase accuracy. In my case the older bolt was pretty worn, so this was a must do replacement before shooting just one round.
Atlas Bipod & Mako Furniture - To add bipod stability, I choose an Atlas bipod simply because I believe it is the best bipod available anywhere for any amount of money. For furniture I stayed with my original Mako Group ergonomic grip and recoil reduction stock with removable cheek piece simply because I like them and they work. I noticed that Mako has a new rear monopod adapter for my Mako stock however they are backordered.
Geissele Hi-Speed National Match DMR Trigger - The tweaked stock trigger was definitely not up to matching the capabilities of the new Black Hole Weaponry barrel so I looked to my favorite AR trigger company. In this case I choose the very high end Geissele Hi-Speed National Match DMR (Designated Marksmanship Rifle). This trigger combines the 1st stage of a match trigger with a 2nd stage of a crisp service trigger to perfectly fit the hunting, target and precision tactical rifle build intent. This trigger is superb.
Other Extras - Another custom piece retained from my initial build was the Phase 5 Tactical Ambi-bolt release. Although I cropped the extension a bit after photos were complete to free up some space within the trigger guard, this is a godsend with the long stroke on the 308’s.
The Phase 5 Tactical bolt release also allows clearing the gun or handling malfunctions by pulling the bolt back with the left hand and trigger the catch with the right. For magazines, if you have any experience with the DPMS 308 platform, you know that without tweaking stock metal mags, a Magpul PMAG LR20 is the way to go to assure reliability.
Burris MTAC 6.5-20X Scope - Previously I had a 4.5-14X Tac30 on my old DPMS 308B build and it performed perfectly, however I did want a bit more power without raising the low end of the power too much. After seeing the 6.5-20 MTAC at the Shot Show, I knew it was the perfect compromise of high and lower power for this build.
The new Burris MTAC G2B Mildot reticle adds additional Mildot subtense, resettable zero and mil-based windage and elevation adjustment. Most importantly the MTAC is crystal clear and with a 30mm tube that sucks in light a bit more than a smaller 1” tube. Crystal clear repeatable click adjustment all at about half that of comparable optics.
FUNCTION & ACCURACY
As with any new custom build it takes a magazine or two to functionally break in the rifle. A lube job with Premium Synthetic Oil from Black Rain Ordnance helped functioning in the first couple magazines. I was lucky and only had two little feeding bobbles in the first two magazines before reliability settled down to what I have come to expect before the makeover of this old DPMS AP4.
I fired a couple boxes of Hornady Steel 308 match to settle things down and also find zero with the Burris. After that I worked through about 100 handloads to make sure my 100 yard zero held and then re-established a zero at 200, then finally 300 yards. With this rifle, my hope is to push beyond the 500-yard limit of my outdoor range and a 300-yard zero will allow that 500-yard contact without touching the elevation tuning.
A feature of the polygonal rifling is that you will find yourself cleaning the barrel significantly less to maintain accuracy. In fact, Black Hole Weaponry recommends to only clean the barrel with just a dry cleaning patch and to only use solvent if needed. Polygonal rifling has none of the crevices which increase fouling and decrease accuracy. After all my testing, I pulled two dry patches and an oiled patch through the barrel and it was clean.
Accuracy Groups - For accuracy testing, I reached into my stash of Hornady ammo and luckily I had a few boxes of Hornady’s 150 gr SST, 150 gr SST Superformance, 168 gr A-MAX Superformance Match and 178 GR BTHP Match. From my experience, Hornady ammo has delivered outstanding and these results continued that legacy.
My best 5-shot 100 yard group was with the Hornady 150gr SST .456” group which from perspective is outstanding for a semi-auto 308 firearm. As you would expect at longer distances in the 200+ ranges, heavier bullets start to gain an advantage. By the time I was reaching out to the 300 yard line the 168gr rounds were my favorite round with tighter groups.
Using my iStrelok ballistic iPhone app to dial in with a very light breeze, my personal best 300-yard group shot from prone from the Atlas bipod was with the 168gr A-Max Superformance Match which delivered a 2.17” group at 300 yards. What was surprising was that as long I did my part, I kept my other two groups under 2.25". I was thrilled with these initial groups, but most interesting to me was how the groups held together at those longer ranges and that the most accurate round at 100-yards was not the most accurate at 300-yards. To give you some perspective my old DPMS 308B best 300-yard group was just under 4" which is not bad at all, but not in the same class at this barrel.
I know shooting off sandbags or locking into a LeadSled would immediately minimize the human variable and decrease groups. Additionally with a bit more work on understanding how this rifle shoots long-term and a little reloading bench load tuning I have no doubt sub-2" 300-yard groups are possible off the Atlas bipod. At this point I have not pushed the rifle beyond the 300-yard range, however once I work through a few Sierra and Hornady reloads, you can bet I will see what this rifle can do out there near the 1/3 mile marker. Based on conversations with a few tremendous distance shooters, I believe this build could easily deliver accurate shots out at 1000 yards. At those distances I have a whole lot of work still to do on my side to reach out that far.
Average 5-shot 100-yard groups
Hornady 308 Win 150 gr SST
Best 5-shot 100-yard Group .456” - 5-Group Average .743”
Hornady 308 Win 150 gr SST Superformance
Best 5-shot 100-yard Group .593” - 5-Group Average .789”
Hornady 308 Win 168 gr A-MAX Superformance Match
Best 5-shot 100-yard Group .478” - 5-Group Average .692”
Hornady 308 WIN 178 GR BTHP Match
Best 5-shot 100-yard Group .494” - 5-Group Average .710”
The other major components of this rifle including the PRI handguard, Burris 6.5-20 MTAC, and the stunning Geissele National Match trigger will have dedicated review, so I will not go into those details here. I will note each and every one of these components performed stunningly. As I have proved to myself over and over again through upgrades, the barrel is the heart of accuracy and realistically just a barrel swap and a quality optic on my old AP4 could have delivered nearly the same results. Of course the super sweet Geissele trigger added to the accuracy abilities, and the PRI forend provided stability, and the rest of the upgrades just made the rifle feel, and handle better. The quality of each component absolutely contributed to the accuracy of the rifle.
I doubt you will here many other writers admit this, but to be totally honest this rifle's accuracy far exceeds my ability to shoot it. It can deliver .5" 100-yard groups all day long in my hands and in the hands of someone really good could probably deliver near single hole groups. The same goes for those longer distances where an I am delivering just over 2" groups. Perhaps later this year I will have an opportunity to put this in the hands of a military shooter who I know can wring out the accuracy of this barrel.
The other reason I went this far and perhaps a bit overboard on this build was timing. Hands down this was the most difficult build I have ever done; not because of assembly, but because of parts availability. Pricing is nuts on some of the parts in today’s market and if you can get in line, there is a huge waiting period. In the process, I actually sold my other DPMS 308B to help fund the cost of this build. Believe me when I say that I took a big deep breath to sell a working and very accurate DPMS 308B to fund hopefully getting parts for this build. To put this in perspective, I started this build in June of 2011 and just finished it up in February 2012... yes it has taken that long. A long back ordered DPMS bolt from DPMS arrived just in time to relieve my panic.
Along the way while I was waiting I “may have” upgraded far beyond my initial goal with a new forend, new optic and new trigger...and once you are half way in on cost, you convince yourself to go even further. I am thrilled with the initial results of the Black Rain Ordnance 308 barrel, however the next fun and hard part is putting in the time and work to take advantage of the capabilities of the amazing barrel and build with consistent shots way out there in the distance.
- Used DPMS AP4 - $600
- AP4 barrel sold - ($250) subtracted from total
- 18" Black Hole Weaponry 308 Stainless Bull Barrel - $320
- PRI Precision Reflex Industries - Carbon Fiber Delta Forend - $390
- PRI Precision Reflex Industries - Low Profile Gas Block - $59.50
- PRI Gatorgrip Quick Release Scope Mount - $190
- PRI Precision Reflex Industries - Quiet 308 Brake - $83
- Burris 6.5-20 MTAC scope - $680
- White Oak Mid-Length Gas Tube - $15
- Atlas bipod - $279.99
- The Mako Group - AG-43 Grip - $27
- The Mako Group - Buttstock - $120
- Geissele Hi-Speed National Match DMR Trigger - $279
- ---Total $3045
Black Hole Weaponry - http://www.blackholeweaponry.com
PRI - www.precisionreflex.com
The Mako Group - http://www.themakogroup.com
Geissele - http://geissele.com/
Burris Optics - http://www.burrisoptics.com/
DPMS - http://www.dpmsinc.com/
Hornady - http://www.hornady.com/