Channel fans and family, this is the Grayboe Core, the top stock in Grayboe’s lineup built for the Universal Mini Chassis (UMC). Here’s why it matters: with a UMC on your rifle, you can go from a lightweight hunting stock to a proper long-range or competition stock in less time than it takes to walk down and change your target.
Quick note: this is a first look based on our range time and Grayboe’s own product pages. A full review video is coming soon to the channel.
Giveaway: we’re giving away a Grayboe Flagstaff or Halo stock plus a UMC of the winner’s choice. It’s free to enter, open to US residents 21+, and runs through November 30, 2026. Enter the Grayboe giveaway here.
TL;DR
- What it is: Grayboe’s precision and competition stock, forged from carbon fiber or fiberglass, built for the UMC.
- The angle: the same rifle on the same UMC moves between a Grayboe hunting stock like the Flagstaff and the Core with two screws.
- Weight: about 6 lb (forged carbon) or about 4.5 lb (forged fiberglass) with the UMC installed, per Grayboe.
- Adjustments: vertical and side-to-side cheek piece, length of pull via 1/4″ spacers (12.75″ minimum).
- Mags: AICS only, no separate bottom metal. The UMC is sold separately.
From hunting stock to match stock
A light hunting stock and a heavy, adjustable match stock usually mean two rifles, or one rifle and a lot of gunsmithing. Grayboe’s UMC changes that. Your barreled action bolts to the UMC, and the UMC bolts into any UMC-compatible Grayboe stock with two screws. Every UMC is the same on the outside, so the Flagstaff, the Halo, and the Core all take it the same way.
In the video above, we take the rifle out of a Grayboe Flagstaff, the lightweight polymer hunting stock, and drop it into the Core. Grayboe says that once a rifle is zeroed on its UMC, you can pull it out with the UMC still attached and it holds zero. We’ll put real numbers on that in the full review. Either way, fire a confirmation shot or two after any swap.
What the Core brings to the bench
- Forged construction. The stock is solid forged carbon fiber or forged fiberglass, and Grayboe pitches it for long-range precision and competition.
- Adjustable cheek piece. It moves vertically and side to side, so you can line up your eye with the scope.
- Length of pull. Adjustable with 1/4″ spacers, from a 12.75″ minimum with all spacers removed. The recoil pad is Grayboe’s Techno gel pad.
- Vertical grip. Thumb shelf and a slight palm swell.
- Attachments. A full-length M-LOK rail on the bottom of the forend with 2 QD sling attachment points, and Grayboe also lists 7 quick-detach inserts for sling attachment. A full-length ARCA rail is listed as coming soon.
- 2-round holder compatible. Grayboe’s aluminum quiver bolts to the side of the stock under the ejection port.
Grayboe Core specs (from Grayboe)
| Material | Solid forged carbon fiber or forged fiberglass; UMC is T6 6061 billet aluminum |
| Weight with UMC | About 6 lb (forged carbon), about 4.5 lb (forged fiberglass) |
| Length of pull | 12.75″ minimum, adjustable with 1/4″ spacers |
| Cheek piece | Vertical and horizontal adjustment |
| Grip | Vertical, with thumb shelf and slight palm swell |
| Forend | 12.25″ from the face of a short action Rem 700; full-length M-LOK on the bottom |
| Barrel channel | Fits contours up to and including 1.250″ straight barrels; forend tip channel diameter 1.330″ |
| Magazines | AICS: standard short AICS for short actions, 3.715″ or 3.850″ for long actions depending on the UMC model |
| Finishes | Forged Carbon Dune, Forged Carbon GAP Camo, Forged Carbon Hunter Orange Camo, Olive w/ Black Web Forged Fiberglass, Black Canyon Camo Forged Fiberglass |
| UMC | Sold separately |
| Warranty | Lifetime |
Which rifles fit
If Grayboe makes a UMC for your action, it fits the Core. Right now Grayboe lists UMC inlets for these actions (right hand only):
- CVA Cascade short and long action
- Howa 1500 short and long action
- Mossberg Patriot short action
- Remington 700 and true 700 clones, short and long action
- Ruger American short and long action
- Savage 110 short and long action
- Tikka T3/T3x short action calibers
- Weatherby Vanguard short and long action
Grayboe’s own example: a UMC for a short action Ruger American .308 and a UMC for a long action Remington 700 in 7 PRC, and both plug into the same stock. For the mag release, most UMCs offer a polymer hunting lever or an adjustable paddle with .080″ of vertical adjustment. Grayboe says the hunter lever isn’t offered on the Tikka, Ruger, Savage, and Howa/Weatherby UMCs.
Install notes
New action screws come with every UMC, and Grayboe says to use them instead of your factory screws. The product-page FAQ recommends 45 in-lb for the UMC-to-stock screws and 45 to 65 in-lb for the action screws. The UMC install guide lists slightly different numbers, so check it for your model. Ruger American and Mossberg Patriot owners need to bolt the rifle to the UMC and pin the trigger guard before installing it in the stock.
What to know before you buy
- It’s heavy on purpose. At 4.5 to 6 lb with the UMC, the Core is a bench and match stock, not a mountain stock. That’s what the Flagstaff is for.
- Right hand only. Grayboe says it hopes to offer left-hand UMC stocks in late 2026.
- AICS mags only.
- UMC not included. If you’re already running a Flagstaff or Halo, the UMC you have moves right over.
Our take
The Core makes the most sense as the second stock in a UMC setup. Hunt with your rifle in a light stock, then move the same rifle and UMC into a fully adjustable, forged stock for a match or a long-range day, without a gunsmith or new bottom metal. That’s the angle that stood out to us at the range. We’ll cover how it shoots, how it handles recoil, and how well zero holds after a swap in the full review. For current finishes and options, see the Grayboe Core and Universal Mini Chassis pages. Want the light-stock side of the story? Read our Grayboe Flagstaff first look on a Savage 110 Tactical.
If you order from Grayboe, code SlavGuns takes 10% off.
Giveaway: we’re giving away a Grayboe Flagstaff or Halo stock plus a UMC of the winner’s choice. It’s free to enter, open to US residents 21+, and runs through November 30, 2026. Enter the Grayboe giveaway here.
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Keep squatting.
Would you run one rifle in two stocks, or keep a dedicated hunting rifle and match rifle? Tell us in the comments.
More from SlavGuns
- Grayboe Flagstaff stock on a Savage 110 Tactical: first look
- Grayboe stock giveaway: win a Flagstaff or Halo + UMC
- Savage 110 Tactical 6.5 PRC: Good Gun, Horrible Name?
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