The T1 rifle in my previous article is one of the finest rifle builds I have undertaken. It was designed to be the best it could be. As much as I like the 16″ carbine with an LPVO mounted to it, I really do prefer a short barreled rifle for duty use. I carry a modified Mk18 (pronounced Mark Eighteen) rifle in my patrol vehicle for work on a nightly basis. For the ranges at which I expect to engage targets a short barrel offers plenty of performance, but as with anything it is a compromise. That being said, I wanted a comparable T1 SBR to be be a part of the Tier Rifle Project.
The parts between the T1 in my previous article are all present, but the specs change a bit for the SBR model. Unfortunately Griffin does not produce a 10.3″ HEDP barrel. For the initial build of the T1 Mk18 I wanted to maintain close specs to the original Mk18, so a 10.3″ barrel was essential. I opted to use a Ballistic Advantage Hanson Profile 10.3″ Barrel for this build. I liked that the gas block came with a pin for more solid mounting to the barrel. The barrel is said to offer better balance and performance than most barrels on the market. I look forward to seeing how it performs once I begin range testing the rifles.
Rather than opting for the LPVO setup on the SBR I decided to go with an Eotech EXPS0-3. With the limitations of the short barrel I did not feel there would be a benefit or advantage to mounting a large, magnified optic on the SBR. I also opted for a smaller light. I used a Surefire M300 Pro body, DS07 tailcap, a Modswitch, and a Malkoff Devices head. I also decided to try a new QD mount that I haven’t used before. The Strike Industries Link Angled QD mount is an interesting mount. I like that is angled back toward the operator rather than putting the socket at a 90° angle to the rail. It makes it a little more streamlined. Like it’s T1 big brother, I equipped the SBR with a Burn Proof Gear rail wrap. When high volume of fire is sent through an AR, especially one with a low profile rail, it tends to get quite hot. Having a way to mitigate the heat become essential. This becomes even more important when a suppressor is installed.
For this rifle, unlike the rest of the Tier rifles, I decided to go for a proprietary suppressor mounting muzzle device. I opted to go for the Hammer Comp taper mount from Griffin Armament. I’ve opted to get a Griffin Armament Recce 5 suppressor for this project. I wanted a suppressor I could mount and remove while it has a heat wrap installed. I am waiting for the ATF to release the suppressor from NFA purgatory. Once I do I plan to install it and have it covered by a Burn Proof Gear Suppressor Cover. I’ve had the experience of a hot suppressor brushing across my forearm while changing positions shooting under a car. I prefer not to have that experience again.
Aside from the changes mentioned, the platform remains the same from the T1 to the SBR. It varies from the modified Mk18 that I carry for work a good bit and I look forward to stacking them up against each other once I have the entire SBR assembled with its suppressor. It wouldn’t be fair to compare the T1 SBR to my duty rifle until I have the suppressor for it. My duty rifle is equipped with a Surefire SOCOM 556-SB2, which I am hoping the Griffin Recce 5 will be comparable to.
I will eventually make an 11.5” T1 upper for the T1 Mk18. It will use the Griffin barrel just like I used on the actual T1. I will be able to compare the Hansen profile 10.3” barrel to the 11.5” Griffin barrel and see which one really offers better performance. Modern studies show that the 11.5” is the more ideal length to really take advantage of 5.56 ammunition. It allows a longer dwell and higher muzzle velocity, which equates to better terminal performance. There is also research that shows the 10.3” Mk18 functions best with heavier ammo, like 77gr OTM rounds that are intended to be used in the Mk12 SPR. The 77gr bullets hit with more energy and break up better, so they function well out of a 10.3” barrel that doesn’t offer the higher muzzle velocity that a 5.56 really needs in order to shine.
All of the lessons I’ve learned have been applied to the T1 rifles, now it will be a development platform for me to really hone in the “perfect” platform. By the time I’m satisfied with the end product it should be quite a fighting rifle.