MDT TIMBR Frontier Stock Overview *AND* 6mm ARC Build

I’ve been talking about my coming 6mm ARC build for some time. This time it’s here, featuring the MDT Timbr Frontier stock!


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About the MDT Timbr Frontier

This wooden stock is an interesting departure from MDT’s chassis, but features the same level of quality. The fit and finish of the birch hardwood laminate stock is tight. It has an aluminum micro-chassis and bottom metal, MLOK forend, adjustable length of pull and cheek riser and V-block bedding/inlet.

Also included are interchangeable rubber over-molded grips.  The Timbr logo burned into the wood on the side of the stock is also a nice touch. 

From MDT

The MDT Timbr Frontier has been developed to provide the look and feel of a traditional stock while incorporating the precision and repeatability of the modern V-Block bedding from a chassis. The buttstock and forend are made of Birch hardwood laminate giving every stock a unique wood grain and warm feel. They are then finished with a high-quality clearcoat and attached to the aluminum micro chassis and bottom metal.

This is a new generation of wood stocks with a fully tool-less adjustable Length of pull, cheek riser height and interchangeable rubber over-molded grips to fit you and your style of shooting. At just 4lb the Frontier allows you to use it for anything from hunting to target shooting with the ability to add accessories to the M-LOK forend and buttstock. The stock uses standard AICS pattern magazines and has an easy to manipulate ambidextrous magazine latch.


    • Remington 700 Short Action
    • Savage Short Action – Coming Soon
    • Tikka T3/T3X Short Action – Coming Soon
    • Tikka T1X – Coming Soon 

This stock is ideal for cold-weather use and hunting with foam on the cheekpiece, a rubber grip and wood forend. 

What’s in the Box 

There are two colors of the Timbr stock available: charcoal and green mountain camo. Included is the hybrid  main stock assembly with user manual, a wooden velcro patch and interchangeable vertical grip. The slanted grip is pre-installed. My plan is to switch out the slanted grip for the vertical grip during the actual build and swap the included MLOK forend for ARCA. Also a nice touch are the nylon nuts holding the action screws in place. 

6mm ARC Specs and Considerations

Before starting any build, I take the time to study the SAAMI specifications and think about the entire process. As both an AR and bolt gun cartridge, there is a wide range of tolerance for 6mm ARC. When chambering my 6mm ARC barrel, I realized I didn’t have a go-gauge for this cartridge, making my research even more important. I took some brass cases I had and used a Hornady headspace comparator to determine where I wanted headspace to be. I started with a piece of brand new Hornady brass measuring 1.1805”. I also measured resized 6mm ARC brass (1.18850″) and brass fired through my 6mm ARC AR (1.1935”). SAAMI specifies the chamber min at 1.1901” and the max at 1.2001” base to datum.  When considering headspace, I decided I wanted to be able to easily swap ammunition between the 6mm ARC AR and bolt gun and decided to cut the chamber close to SAAMI minimum, using the brass cases as go and no-go gauges. 

Tools & Machinery

Big surprise – I’m using the Precision Matthews TL-1660 lathe and true bore alignment system. I’m also using an Alpha Munitions carbide reamer, custom pressure flush system and Short Action Customs modular barrel vise and action wrench. I’m taking my .223 trainer rifle and using it as a basis for this build in terms of the barreled action parts. 

About the Build

Besides the MDT Timbr Frontier Short Action Stock, this build has a BAT TR action, Bartlein 1:7.5 barrel blank (24” finished), TriggerTech Diamond 2-stage trigger, Athlon Cronus 4.5-29x56mm scope, MDT magazine and MDT GRND Pod Bipod

Athlon Cronus 4.5-29x56mm FFP Scope:

Barrel Work

If you take a look at the .223 Trainer Build, you’ll see much of the same barrel work as I did on this 6mm ARC build with the exception of the pressure flush system. I start with the muzzle end first and thread it  ⅝” x 24. You’ll notice I’m also using custom 3-D printed sleeve adapters for the 6-jaw chuck. These have an internal taper and straight outside profile for even pressure and forces on the barrel with a secure hold. 

Finished Muzzle End

After completing the muzzle end, I used a barrel extension to reach through the long spindle on the Precision Matthews. I decided to run the Alpha Munitions reamer in a rigid reamer holder with no bushing to allow  for good oil flow. 

Chambering the Barrel

I opted for classic graphite black Cerakote once again, but this time did the Cerakote first and the laser engraving afterwards to preserve as much detail as possible.

Putting it All Together 

At this point, it was time to put it all together.

I first removed the Picatinny section from the stock and replaced it with a full-length ARCA rail as well as swapped out the grip. I then torqued the barrel onto the action (90 ft-lbs), adjusted the length of pull, mounted the Athlon Cronus and added a 6mm brake from Area 419. The 6 Dasher magazine from MDT did not feed the 6mm ARC rounds well, but my .224 Valkyrie magazine did. Besides this, the entire build went together very smoothly.

Breaking it In 

I’ve made it about halfway through the break-in process on this rifle. I started with Hornady 108 grain ELD-M match ammunition, firing three shot strings and cleaning in-between. My second three-shot group measured 0.216” at 100 yards. I was particularly impressed with Hornady’s match ammunition. The chronograph recorded SD’s in the 8 ft/s range. 

We also did a bit of loading with Sierra 107 grain MatchKings and they performed impressively. I loaded three different charge weights of 8208-XBR, firing five shots at 100 yards. The first group (26.7 grains) measured 0.643”, the second group (26.9 grains) measured 0.457” and the third (27.1 grains)  measured 0.244”.

6mm ARC Results with Sierra 107 Grain MatchKings

Here’s my full video covering these bullets:

All of these groups were five shots fired at 100 yards using the LongShot Target Camera System.


Gavin breaking in the MDT Timbr 6mm ARC build with Sierra 107 grain MatchKings.

Looking forward, I’ll be collecting more data to hopefully get consistent quarter MOA groups at 100 yards. It has very little recoil and is very pleasant to shoot. I’m planning positional shooting and rock chuck slaying with this gun! 

Get the Gear

Find the MDT Timbr Frontier at


Alpha Legacy Reamer

 BAT TR Action


Area 419 Brake

Athlon Cronus 4.5-29x56mm FFP Scope

Hornady Match Ammunition from Midsouth Shooters Supply 

Hornady 6mm ARC Brass from Midsouth Shooters Supply or Creedmoor Sports 

Hornady Headspace Comparator from Midsouth Shooters Supply

Find Sierra 6mm 107 grain HPBT MatchKings at Creedmoor Sports!

Short Action Customs Modular Action Wrench

Short Action Customs Modular Barrel Vise

Cerakote Certified Applicator Training 

Cerakote Coatings 

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Gavin Gear

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