18″ Tactical Sniper Rifle
Note: The images above are the SI DEFENSE UPPER RECEIVER mounted to a DPMS LR-308 LOWER RECEIVER and do not feature the SI DEFENSE LOWER RECEIVER that will close out this build project.
Below is a list of the hardware I selected for this build. When possible I will explain the reasons for my decisions as they apply to this project. Every attempt will be made to include images of the actual parts as well as how much I paid and links to where I obtained the parts from. Build 1 : The project will be based on the DPMS LR-308/KAC SR25 platform utilizing SI Defense Upper and Lower Receivers. SI Defense has a great reputation for quality weapons and parts. I have been wanting to do a project based on SI DEFENSE hardware for quite some time. I wish my budget allowed to use the Fail Zero hardware as well as an SI Defense 308 Bolt Carrier group. Maybe next time. If I didnt’t already have a DPMS barrel I would have purchased that from SI DEFENSE as well. I want this gun to have a manageable size and weight so that it can be fired comfortably from the shoulder as well as with a bipod or from the bench. The 18″ barrel should provide for minute of angle accuracy out to 200 yards and farther. Update: January 2, 2011 – Im waiting for the JP Handguard to arrive from the factory. There’s a possibilty that I will use a MA-TEN upper and lower instead of DPMS. I dont know maybe Ill use the MA-TEN for build #3. Update: January 12, 2011 – My JP Handguard has shipped! The MA-TEN is going to Precision Target 308 AR 18″. Note: I get a lot of emails about the DPMS SASS Gas Block and whether it will under the VTAC. As soon as I have the parts in hand I will publish my findings.
SI Defense makes some great stuff and I thought it was time to utilize them in a project.
I had originally selected a DPMS stripped upper for this project but DPMS has been playing around with picatinny rail heights and I dont want to support their behavior. So after a bit of thinking I decided on a rather unique upper receiver from SI Defense. Now some guys are going to cringe at the idea of a lack of forward assist but here’s the thing. These 308 rifles do not require a forward assist due to the amount of energy created by the .308 Winchester/7.62×51 cartridge. If your bolt doesnt lock closed something is wrong with the weapon or ammunition pure and simple. In fact the forward assist can get you in trouble by forcing the bolt to lock. Here’s SI Defenses info on the .308/7.62 Generation II Upper Receiver: SI Defense .308/7.62 Generation II Upper Receiver Re-distribute your light, laser and optic on your AR to the receiver for a better, balanced set-up on your rifle or pistol. If you do not want to use the rail, simply remove it and save the weight for a more streamlined look. Your can purchase your upper with or without a picatinny rail. The cost is only $10 more with the rail. The upper rail and mounting screws can be purchased separately for $18. The upper receiver is CNC machined from 7075 solid billet and anodized per Mil-A-8625. Upper features shell deflector and a removable picatinny side rail mount. There is no forward assist. The removable rail is machined from billet 7075 aluminum and has three 8-32 screws to mount it securely into place with a 3/32 allen wrench. Both the upper picatinny and the removable picatinny rail are built to MIL-STD-1913 specifications. The threaded holes in the upper receiver do not penetrate into the upper receiver bore, so you do not have to worry about any wear from protruding screws. The length of the picatinny rail is 5.025″ The picatinny rail is compatible with the HKG3 upper and the .223 upper. Upper is compatible with ©DPMS hardware and lower receivers. Upper is not compatible with ©Armalite lower receiver or parts or with the SI Defense HKG3 lower receiver.
FACS-308 LRPK-LTG $59.95 Fulton had it in stock without the trigger group. That was exactly what I wanted. Delivery was in about 3 days!!!
$182.99 The JP Enterprises Tactical 4lb fire control package come in at nearly $100 cheaper then the ATC SR Gold we used in build 2. That’s the first reason for going with this trigger. The second reason is to be able to compare the various triggers for the content of this site as well as to see if the lower cost units perform nearly as well or equal to the top of the line Jard, Geissele or ATC. JP has been making triggers for competition .308 AR’s for years. I have no reservations about this being an outstanding trigger for this .308AR build.
DPMS LR-308 SASS 308 Winchester Bull Barrel 1 in 10″ Twist 18″ Fluted Stainless Steel Black Teflon
DPMS LR-308 SASS 308 Winchester Bull Barrel 1 in 10″ Twist 18″ Fluted Stainless Steel Black Teflon 308-BL-SASS Not many options here at this time. DPMS barrels get pretty decent marks for accuracy and the price isn’t too bad either $229. Barrel length: I struggled with this aspect of the build for a while. I had originally wanted a 24″-26″ for the extra few hundred fps in bullet velocity, however after a little research I noticed many guys getting their long barrels shortened to 18″-20″. Upon investigation the weight and added length really make the gun strictly a bench rifle. That’s not what I want. There should not be any measurable accuracy differences between this 18″ heavy barrel and its longer siblings at the range 100-400 yards that I will be shooting. To comply with local laws I decided it was more practical to remove the threads from the barrel then to have a flash hider pinned, welded and the barrel refinished. To that I brought the barrel to my day job and removed the threads in the lathe. Once the threads were removed I cut an 11 degree target crown. Check out the results below.
308-BCA $210 I had originally planned on getting another Fulton Armory Bolt Carrier Group until I stumbled across the DPMS 308-BCA BCG for $210. Thats $100 less than the Fulton Armory. Cant ignore those economics. With the money I saved Im going to purchase the JP enterprises 308 ENHANCEDBOLT™ bolt. Complete bolt assembly is precision machined from an ultra-strong steel alloy to last up to 10 times longer than a standard carbon steel bolt, minimizing the risk of bolt failure during a critical engagement. SAE 9310 steel has a tough, ductile inner core highly resistant to stress fracturing, with a hard outer surface that resists galling and wear, to ensure a service life of up to 60,000 rounds. This is the same steel used in the transmission gears of Formula 1 race cars, so it’s ideal for high-impact, high-heat applications like sustained full-auto fire. Meticulously machined radiuses on all 90-degree corners on the locking lugs help distribute impact force evenly and further reduce risk of premature wear and cracking. Fully supported extractor face and precise extractor engagement further ensure smooth, reliable cycling.
The MECHARMOR TacOps-1 Generation 3 AMBIDEXTROUS CHARGING HANDLE is now going to be the standard on all my AR build whether AR-15 or 308AR. Visit MechArmor to purchase. I have created a page dedicated to the MECHARMOR TacOps-1 Generation 3 AMBIDEXTROUS CHARGING HANDLE handle here.
Troy Battle Sights (BUIS)
This was an easy decision. The Troy Battle Sights (Rear SSIG-FBS-R0BT-00, Front-SSIG-FBS-FMBT-00)are the best sights available for the AR15,M16,M4 rifle period. They are precisely machined of aluminum and stainless steel. All adjustment screws are recessed and cant accidentally be altered. They apertures are machined correctly to retain zero regardless of which aperture is being utilized (small aperture is correctly offset). The sights are on the correct plane to be co-witnessed with most optics. These sights are most likely the most expensive units available. If your life might depend on them one day they will be priceless.
MAG330 Im trying to determine if this stock meets CT state laws. I might have to get Magpul UBR and pin it. I wish Magpul would manufacture a fixed buttstock based on the form of the UBR in it’s extended position. I think it could replace A2 stocks worldwide. Im passionate enough about this that I suggested it to Magpul. Note: To utilize this stock the rifle will need to be fitted with an AR15 carbine length buttstock extension tube. This will require a special buffer and an Armalite AR-10 spring
Below is the little stuff you don’t want to forget about
- Gas Tube
- Gas Tube Roll Pin
- Butt Stock Extension Tube
- SI DEFENSE Stainless Steel Bolt Catch Screw
- David Tubb Superior Shooting AR-10 CS Buffer Spring
- Barrel Nut – note: Some free float handguard’s require a proprietary barrel nut that is either provided with the handguard or needs to be ordered at the same time. In our case the Daniel Defense Lite Rail is supplied with a special barrel nut.
SI Defense Stainless Steel Bolt Catch Screws
JP VTAC Modular Hand Guard System JPHG-6D
Visitors may recall I had originally specified a Daniel Defense “Lite Rail” for this project. I have since changed my mind and decided while as nice as that would be it is simply not the right setup for this rifles intended use. It would be having quad rails for the sake of quad rails. I will save the Lite Rail for the 3rd build. Since originally starting this project there has been a new free float handguard to hit the market. That new handguard is a 15.5″ version JP Enterprises Handguard JPHG-6D of their rifle length free float handguard JPHG-1D.
Note: If you follow the link to brownells read the specs to select the correct one and don’t rely on the JP part numbers here. The “D” part numbers specify DPMS LR-308. The “A” part numbers specify Armalite.
I have a 12″ JP VTAC on an AR-15 and I like it ver much. You can see that here.
Falcon Industries ERGO AR-LF Tactical Deluxe Grip, SUREGRIP – with Spacer – Pistol Grip
Falcon Industries ERGO AR-LF Tactical Deluxe Grip, SUREGRIP 4060LF Im a big fan of the Falcon ERGO GRIPS. They fit my hand perfectly and have the perfect texture to mate up with your hand.
DPMS SASS Gas Block 308 Micro 936 Gas Block. DPMS reports that the SASS barrel requires a “Special Gas Block”. Naturally they are the only ones to produce it. Well I cant confirm what they say at the moment but I will get to the bottom of this. A quick check of my SASS barrel didn’t find any unusual dimensions but I will investigate thoroughly when I get a non dpms gas block. I have confirmed that the DPMS SASS barrels do in fact require a special gas block. The issue is the diameter of the barrel is between the receiver and the step down to .936 is greater than that of a typical barrel. This results in the hole in the gas block for the gas tube being obstructed in a manner preventing the gas tube from being installed. The DPMS gas block raises the gas tube position to compensate. Note the wall thickness in the image below.
To comply with local laws I can not have a threaded muzzle. This leaves me with two options. The first would be to send the barrel out of state and have a muzzle device pinned and welded to make the attachment permanent. The second option is to have the muzzle threads removed and replaced with a sharp 11 degree crown. For a few reasons I’m opting to remove the threads and go with the 11 degree crown. The biggest issue for me is the total cost of getting the muzzle device attached. First there is the cost of shipping the barrel two ways. Second is the cost of the muzzle device itself. Third cost of the installation (Pin & weld). Lastly the heat from the process of the silver soldering the muzzle device to the barrel would damage the teflon finish of the barrel. This would require the barrel to be refinished. All this would easily double the cost of the barrel. Now if I was to buy a muzzle device for this weapon It would be the Primary Arms FS30 Flash Hider Muzzle Brake.
308 AR Magazines
I opted for two different brands of magazines, the official DPMS MA-3082 19 round and MagPul Pmag 20LR 308 AR Magazines. The Magpuls have become a real game changer in these big rifles. Perfect function and reliability.
Below is a list of the manufacturers I used for this build.