It’s finally begun! My next rifle build is a super precision 6GT with an MDT ACC chassis and Bat TR action. Let’s kick off the series! 

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MDT ACC Unboxing and Overview 

We have several pieces to the chassis puzzle — the MDT ACC short action chassis for Remington 700 in FDE, SRS-X Elite buttstock in FDE and the vertical grip elite. 

From MDTtac.com: 

Designed for competitors, the Adjustable Core Competition (ACC) is the result of endless testing and collaboration with competition shooters, implementing the most crucial and results-driven features while ensuring accuracy and precision remain unparalleled.

The MDT ACC Chassis System was created with an integrated weight management system, allowing shooters to fine-tune their chassis’ weight and balance point. Add weights to the buttstock as well as the forend on both the interior and exterior. With an original weight of 4.5 lbs, it can be fitted for a maximum of 12.3 lbs, but that’s only for the chassis itself. Add your action, barrel, scope, and other accessories and you could be pushing 25-30 lbs.

All of this modularity can be achieved without taking your barreled action out of the chassis system. Internal forend weights can be inserted for the front of the forend and screwed in place, while external weights are designed to be M-LOK compatible and easily attached on either side of the forend. This allows shooters to rapidly adjust the feel and recoil of their system, even while at the range.

For more on this chassis, see my video on the MDT ACC long action chassis. 

The assembly process (adding buttstock and vertical grip) was pretty simple. I immediately fell in love with the vertical grip. I have larger hands and it was easy and comfortable for me to hold with a rubberized textured grip on the outside. 

This chassis is designed for PRS and NRL competitors and similar to the long-action ACC we’ve previously tested, has an integrated ARCA rail. It is nearly endlessly customizable and is optimized for weight systems. The chassis itself has an integrated barricade stop, ambidextrous mag release button and an adjustable buttpad. 

Project Goals

I wanted to use the existing Bat TR action we used in a 6mm Dasher build. I’ve chambered a number of barrels for the Bat TR action thus far including .223, 6 Dasher and 6.5 Creedmoor. By adding the 6GT to this family, we’ll have the ability to directly compare various 6mm cartridges. 

On every rifle I build, I monitor the process extremely closely with utmost precision in mind. For this project I’ll be chambering an ultra-match GT barrel and showing that process. By the end of this project, I’ll have an amazing PRS rifle with the ability to try out new gear (ex. Baker Wings) as well as further load development and compare the MDT ACC short action and long action chassis. 

Why 6GT? 

I’ve personally had a lot of experience with the 6mm Dasher and wanted to compare it to 6GT.

The 6GT, unlike the 6mm Dasher, is SAAMI certified. While I love the 6mm Dasher for its longer barrel life and lower recoil than 6mm Creedmoor, it has some magazine and feeding issues. The creator of the 6GT, George Gardner, specifically targeted resolving these feeding issues in cartridge development. Building on the capabilities of the 6mm Dasher, the 6GT has slightly more velocity than the 6mm Dasher. The shoulder on a 6GT round is approximately 0.108” longer than the 6mm Dasher. As a result, the 6GT cartridge is a little longer, preventing the nose-diving experiences prevalent with 6mm Dasher. Given all this, no surprise you can use a 6GT reamer to convert a 6mm Dasher chamber to a 6GT Chamber. 

SAAMI certification allows for more consistency in the cartridge itself and relevant equipment/components. As the 6mm Dasher isn’t SAAMI certified, Manson Precision Reamers put together a 6mm Dasher reamer for me.

 

On this build, I’ll be using an Alpha carbide 6GT reamer that is optimized for the slower-speed manual machine I have with 0.170” freebore.

This geometry was specifically recommended to me by Tom Danielson at Alpha Munitions while we discussed what bullets I would run in Alpha Munitions’ brass. 

Build Components

We’ve already highlighted the MDT ACC short action chassis, but I also have the following: 

• AICS MDT mag with extension
• TriggerTech Diamond Remington 700 Trigger 
• BAT TR action (stolen from 6mm Dasher barreled Action)
• Krieger Match Grade 1:7.5 twist, 5-groove barrel (which I plan to finish off at 26”)
• Area 419 Hellfire Muzzle Brake

To put all this together, I need tools. At the heart of this project is the Precision Matthews TL1660 lathe.

Precision Matthews TL-1660 Ultra-Precision Lathe

Again I’m using my preferred manual lathe for chambering, the Precision Matthews TL-1660!

This lathe is a beast! Here are some of the specs for the Precision Matthews TL-1660:

• Ultra Precision, made in Taiwan
• 16″ swing, 60″ between centers capacity
• D1-6 high precision spindle
• English and Metric threading without gear changes
• One shot lube on the carriage
• 3-Phase 5hp motor

*Note: for most gunsmiths, the TL-1640 would be a great choice. You likely won’t need 60″ between centers like the TL-1660 offers. The TL-1640 can save both space, and significant money on freight! I opted for the larger lathe because I wanted to have a lathe on hand with extended capacity between centers.

Straight Shot Gunsmithing “True Bore Alignment System” and Range Rod

Recently I’ve become a huge fan of the SSG True Bore Alignment System (TBAS). This unique articulating chuck system allows you to dial in your barrel with both radial and axial adjustments.

Above you can also see the SSG Range Rod (see bottom of page HERE) which is used in conjunction with the TBAS system to indicate barrels (I used this on both the breech and and the  muzzle end of the barrel.

This top quality lathe has a 16” capacity swing and 60” between centers. On this lathe I have the Straight Shot Gunsmithing true-bore alignment system and will be using the Straight Shot Gunsmithing range rods as well. I also have a Greg Tannel (Gre-Tan) fixed holder for the specialized Alpha Munitions carbide reamer with 0.170” freebore. This was recommended by Alpha Munitions for use with the Berger 105’s, Berger 109’s and Hornady 110 A-Tips. For verification purposes, I also have the Dave Manson 6GT Go gauge, which can easily be converted into a no-go gauge with some masking tape. This tool was featured in my 22 GT build. Finally, I have a Mitutoyo Precision measurement and an Aloris CXA size tool post and tool holder system I splurged on when I bought my lathe. 

Load Components

We’ve addressed the rifle build components and tools, but what about load components? 

I’ve got 200 pieces of Alpha Munitions brass I’ll be loading with a combination of Berger 105 and 109 grain 6mm Hybrid Target bullets and Hornady 110 grain A-Tip Match. 

What’s Next 

In the next part of this series, I’ll cover barrel work: 

• Muzzle threading
• Cut down of barrel
• Chambering 
• Polishing 
• Laser engraving 
• Checking headspace

Don’t worry! I won’t tell the same, long story each time but will change it up with each build. I’ll focus closely on one or two things as well as include a process overview on a higher level. 

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Thanks,
Gavin Gear