Introduction
My first real rifle, used a laminate wood stock. Not too long after, the fiberglass craze took off, as did the mainstreaming the entire custom rifle industry. It was a radical decade or two where aluminum bedding blocks eventually turned into complete chassis with carbon and other materials added in. Big growth from many companies involved was inevitable, as was the next logical step. Today we are talking about one of those products, The Grayboe Universal Mini Chassis system, and the stocks that go with it. A relatively new product offering, that offers all the precision of an aluminum chassis, and the fit and feel of a synthetic composite stock. Because of the modularity of the UMC stock system, I decided to combine two options into a single review.

Grayboe and Innovation
Grayboe’s founder comes from the McMillan family, yes that one. I expect his exposure to the stock industry, as well as time spent behind rifles and in service influenced the company’s direction.
What Grayboe has done with their Universal Mini Chassis (UMC) is brilliant for several reasons. Everything in the gun industry is going to modular designs; multi-caliber rifles, interchangeable suppressor hubs, serialized fire control units for pistols and so on. Grayboe has brought that premise into the rifle stock market with their UMC stock design.

The Mini Chassis
The UMC is exactly what it sounds like; a minimized chassis that incorporates mounting the action against a custom machined fit. Allowing a perfectly supported action while supporting the magazine and trigger within.

The UMC incorporated AICS magazines even for actions that used proprietary magazines in their stock configuration. They also have little options like adjustable magazine release levers. Weight of the UMC can vary depending on what action/inlay you choose, but its around 14 ounces.

The UMC is only as big as it needs to be to accomplish those features, because it is then bolted into one of Grayboe’s many stock options. Currently these are the actions with a Grayboe UMC option.
- Remington 700 Short Action
- Remington 700 Long Action
- Tikka T3 / T3x
- Howa 1500 Short Action
- Howa 1500 Long Action
- Ruger American Short Action
- Ruger American Long Action
- Savage 110 Short Action
- Savage 110 Long Action
- Mossberg Patriot
- CVA Cascade Short Action
The Stock Options
Grayboe’s composite fiber and impact resistant polymer stocks incorporate the light weight and strength of composites, married to all the features that shooters want. They have a variety of different stocks designed for different purposes and budgets in mind.
- Core – Competition focused
- Flagstaff – Hunting application lightweight
- Halo – Hunting/crossover
- Phoenix 2- Hunting/crossover
- Renegade 2 (Unreleased at publication)
All of these stocks accept the UMC using two screws. That means if you have two different Grayboe stocks, you can transfer your rifle from one to the other in under a minute if you’re quick. All the UMC’s have the same external footprint, fitting any of the Grayboe stocks. And they make UMC’s for most of the popular rifle actions.

The Innovative Bit
So you might have already imagined, if you have a couple UMC’s, and a few stocks, you can mix and match. This brings options to the American rifleman who lusts for customization and modularity. You could use the exact same stock on your Ruger American 7PRC elk hunting rifle and your favorite Tikka 22-250 varmint rifle. And they can be changed out quick and without needing to re-zero the rifle.
Unboxing Grayboe Stock
Grayboe recently released a UMC for the CVA Cascade short action, and since I am currently on a Cascade kick it was perfect timing. And as a glutton for modular rifle systems, I tested both the Grayboe Flagstaff and Core stocks with the CVA UMC. My two CVA Cascade rifles would both benefit from the Grayboe system. The exact rifles used are the CVA Cascade SB .65CM and the CVA Cascade Long Range Hunter 25CM, you can read the reviews of the individual rifles here.

You can buy the Grayboe stocks with or without the UMC of your choice. The different stocks come with different accessories, depending on the stock. For example, the Core stock came with spacers to adjust the length of pull. Both stocks came with M-Lok slots under the forearm to allow attachment of accessories like bipods and ARCA rails. They also have QD cups to attach slings both front and rear.

The UMC comes with hardware to attach the rifle action, as well as connecting the UMC to the stock itself. As well as some simple instructions to assemble the whole thing.
Features
These two stocks have some differing features as they are built for very divergent purposes. The Flagstaff is built with hunters in mind, while the Core is built for competitive and professional shooters. They share the footprint of the UMC, and the same stylings but are otherwise pretty different.
The Flagstaff
Keeping the weight down on the Flagstaff was obviously a priority, but it is still pretty feature rich all things considered. On the flat-bottomed forend you will find four M-Lok slots for attaching things like ARCA rails or your favorite bipod. It also has QD sling cups on the bottom front and rear to attach your favorte sling.

The textured grip is built at a 35 degree angle, and comb height is fairly traditional. I found that the polymer Flagstaff has a slight compressed fit when installing the UMC, adding a bit of a squeeze to it. Whereas in the carbon fiber Core, it dropped in like a machined fit.
The Core
By comparison, the Core stock has a lot going on. It can be had in either fiberglass or carbon, with a significant weight difference between them. Since it has a focus on the professional shooter, there are many added little features.
The length of pull can be adjusted using provided spacers, moving the gel recoil pad to fit the shooter. The comb height can be adjusted on the fly with a thumb-screw, keeping the luxuriously soft cheek-rest at the perfect height for your sight picture. On the bottom of the buttstock you will find a traditional butt-hook to keep the recoil pad in your shoulder pocket.

On the right side of the stock, there are threaded mounting bosses to install a HopticUSA cartridge quiver. An accessory that has become quite popular over the last few years. Up front the Core also features M-Lok slots under the broad and flat forend. It also has multiple QD cups on all sides of the stock so you can carry it different ways. The barrel channel is cut wide, to allow heavy barrel profiles often used in competition.
| Grayboe Core | Grayboe Flagstaff | |
| Weight | 4.5lb Fiberglass/6lb Carbon | 2.5lbs |
| Material | Fiberglass or Carbon fiber | Impact resistant polymer |
| Barrel Channel | Under 1.330 inches | Sendero under .925 |
| Sling QD Cups | 7 total front and rear | Front and rear |
| M-Lok Slots | Full length on forend | 4 M-Lok slots on forend |
| Length of Pull | 12.75 min Plus .25” spacers | 13.5 |
| Comb Height | Adjustable (tooless) | Fixed |
| Overall Length | 32.5-inches | 31.5-inches |
Installation
Since I got the system for my CVA Cascade rifles, I would end up installing two different rifles in various configurations. And swap both of them back and forth between the different stocks to get additional experience.

One of the first intricacies that I noticed was a necessity by the manufacturer to make each UMC fit the different action options. For example; the CVA Cascade action screws are in front of and just behind the magwell. This required an engineering solution because a traditional trigger guard like on typical floorplates would be right on top of the rear action screw.

Unlike tang-mounted rear action screws like on a Remington 700 that go behind the trigger guard. So Grayboe’s solution was to install the trigger guard after marrying the UMC to the action. The trigger-guard incorporating the mag release are pinned in place after attaching the UMC and action.

I expect that other UMC’s for other actions have a regular trigger guard as part of it, or perhaps there are several differences like this depending on the action. The UMC can then be dropped right into any of the compatible stocks. There are two cap-screws that connect the UMC and the stock that once torqued down, make it into one solid structure.

It really wasn’t very hard at all to figure out the installation, or to swap them between the two stock options I had. I hadn’t even gotten to the range yet and I was already contemplating other UMC’s for some of my other rifles.

After the installations process, its simply a matter of adding the accessories you would like for the stock. For example, on the Core stock, I installed one of my Hoptic USA cartridge quivers on the side. I was surprised that this little bonus was added, and that they even put stub-screws in to protect the threads from getting damaged or filled with crud.

Additionally, I decided to add an Area 419 ARCA lock rail to the Core stock. It is already pretty heavy (which is common for competition guns) so adding a little more wasn’t a big deal. I might add a lightweight short ARCA rail to the Flagstaff, but that one I’m trying to keep light in hopes of carrying it this hunting season.

Shooting with Grayboe Stocks
Putting the Grayboe stock system to work, would take place over various trips to the range in open country of the Rocky Mountains. I like to practice where I hunt, so the Flagstaff would get used in the same rugged country where we chase deer and elk. The Core on the other hand isn’t exactly a hunters best choice, but it too would get used for some long range shooting in big country.
Ergonomics
I used just about every option there is when it comes to stocks and chassis. I don’t consider myself to be particularly picky as in general I like most of them. The Grayboe Flagstaff has a pretty traditional feel to it with some added features for handling.

Grayboe Flagstaff
The grip area has a textured pad for added purchase. And the forearm of the stock has two finger grooves running down the side, this gives your fingers something to hold on to when carrying by the stock. The rubber buttpad is nice, sticking where it should.

I ended up using a Triad Tactical stock pack on the back to get better comb height. This turned out to be a suitable situation for my hunting purposes. I also used a few different AICS pattern magazines, all of which worked great.

Grayboe Core
Grayboe’s Core stock on the other hand feels a bit more like a nice leather couch compared to the Flagstaff. That should come as no surprise as most competition focused stocks have many comfort features.

The adjustable comb is as luxurious as it is practical. Making the rifle fit you is quick and simple, and a comfortable place to rest your cheek while shooting. The vertical grip feels fantastic, keeping your finger perfectly presented to the trigger. The magazine release of the UMC is easily reached with your trigger finger, and has enough resistance to avoid being accidentally engaged.
It wouldn’t hurt my feelings if there was a touch more texture in the right spots, as most guns put into this stock are going to be heavier. A nice texture on the grip areas would help for holding tight. It was nice to carry on a sling though, without it dragging or pulling at clothing.

The wide front end of the Core stock allows you to rest the rifle on any surface it will fit, and get a good rest. Once I’d added the ARCA rail, it was even bigger around which could be a challenge for small handed individuals.
Putting the soft gel recoil pad into your shoulder feels quite suave. My two CVA’s don’t recoil very hard but if you had one that did, this recoil pad would definitely soften the blow. I also like the butthook under the stock, it allows you to pull the stock into your shoulder when you need it.

Quality
Both of these stocks are quite rigid, giving that stiff platform to launch your shots from. I was surprised to find out the Flagstaff was made from polymer, I initially thought they were both carbon fiber. But even though it is made of a “lesser” material, I was quite happy with it. Minimal flex of the stock make the Flagstaff a great option, and its polymer production is likely why it is more affordable than the carbon options.

The Grayboe Core stock takes it to the next level, with all the best materials and features. Everything from the finish of the stock, to the supplied fasteners and little instruction cards to help those mechanically challenged out there. The soft parts of the the Core are so nice I’d hate to take them hunting, as they might get sweat soaked or even torn hiking through brush. It does feel built like tank, if you ran out of ammo you could certainly beat your antagonists into a fine paste with it.

Machine work as seen in the Universal Mini Chassis is excellent. All the aluminum parts were nicely anodized and smooth. Both of my rifles fit perfectly into the UMC, and functioned flawlessly. You can tell they spent time designing each different UMC to interact with the action it was meant to fit. And in the CVA case, makes them work perfectly with AICS magazines.

Durability
Grayboe offers a lifetime warranty on their products, which is very comforting. It covers both craftsmanship and accidental damage for those who like to leave their rifle propped against truck tires. If you do happen to use your stock to beat someone into pâté and wear some of the finish off however, that would be considered normal wear. So don’t expect to abuse the warranty.

The only thing I found during my time with these Grayboe stocks that made me pause for durability concerns was the trigger guard. I could see somebody not being careful enough and damaging or breaking the trigger guard when in stalling it in the UMC. Again this might just be the CVA option as others are built into the UMC.
Value
If you browse some of the popular custom stock options you can find stocks that cost significantly more, and some that cost less. The Flagstaff is definitely a more affordable option, with not many less expensive options that offer an aluminum mini chassis.
The Core stock on the other hand has a lot more competition from many of the big names. Even so, the Core is not as expensive as other options. At this level, there is a lot of subjectivity and usually folks can choose based solely on their preference and looks. Many of the Core’s competitors offer similar features, but they don’t offer the modularity. That may be reason enough to choose the Grayboe option.
Pros and Cons
| Pros | Cons | Comment |
| Strong and rigid construction | (Core) Can be heavy | Comp guns are heavy so… |
| Great fit and finish | Trigger guard thing I mentioned | May only be the CVA version |
| (UMC) Precise machinework | I’d like more exterior texture | For grip areas and in general |
| Excellent modularity | ||
| Huge step up from original equipment | Both stock and magazine system improved | |
| Comfortable to carry and shoot | ||
| Excellent warranty | ||
| Great value | ||
| Great Feature set | M-Lok, QD cups, etc. |

Final Thoughts
Different designs appeal to different individuals tastes, I definitely found the Grayboe products to fit into mine. I really enjoy configurable rifles, and the ability to interchange and customize them. But that is certainly not a requirement, as you can setup you rifle in one of these Grayboe chassis systems and never mess with it.
There is definitely a style to their designs, like any manufacturer. And whether one style or another appeals to you, the function of the Grayboe system is fantastic and innovative. Whether you choose to mix and match as I have, or if you are just looking for a solid stock/chassis to improve your factory rifle these will work great. They are well built, and offer great features for a reasonable price made by Americans right here in America.

















































































