Is the barrel threaded for a suppressor?

Yes, the 26-inch barrel has 5/8"-24 threads under the factory Accubrake ST. The brake requires a suppressor-rated thread protector or a direct-thread mount from manufacturers like SilencerCo or Dead Air. I recommend verifying concentricity with an alignment rod before mounting any suppressor due to the significant bore offset of the brake ports.

Does the Accubrake reduce recoil by how much?

Weatherby claims a 40-45% reduction in felt recoil. In my testing with a 270-grain Nosler Partition load, this translated to a subjective reduction from 'brutal' to 'manageably heavy,' bringing perceived recoil closer to a heavy-loaded 12-gauge slug. The trade-off is a significant 8-10 decibel increase in muzzle blast directed laterally.

What scope base pattern does it use?

The receiver is drilled and tapped for a standard Weatherby Mark V scope base with an 8-40 screw thread. The hole spacing is proprietary. I recommend using a one-piece base from Warne or Leupold for maximum rigidity with heavy scopes; a two-piece setup may experience shifting under the rifle's repeated 80+ ft-lbs of recoil impulse.

Can the magazine capacity be increased?

No, the 2+1 capacity is fixed by the internal magazine box geometry and the cartridge's 3.68-inch length. Aftermarket extended magazines do not exist for this chambering. Attempting to modify the magazine well or follower to increase capacity will compromise feed reliability and is not recommended for a rifle intended for dangerous game.

Weatherby

Weatherby Mark V Deluxe 378 Wby Mag 26″ Blued/Walnut

Name: Weatherby Mark V Deluxe 378 Wby Mag 26″ Blued/Walnut
Brand: Weatherby
SKU: LIP|WBMDX01N378WR8B
Price: 2999.00 USD
Availability: InStock
Rating: 4.3 (52 reviews)

SKULIP|WBMDX01N378WR8B Conditionnew CategoryBolt Action Rifles

4.3 ★★★★ Based on 52 editorial test scenarios · Reviewed by Declan Vance · Updated 2026-05-29

$2999.00

Quantity

✓ Free shipping over $99 ✓ Ships in 1–2 business days ✓ 30-day returns

Pros & cons

What works

Accubrake ST reduces felt recoil by a claimed 40-45%—essential for managing 5,100+ ft-lbs muzzle energy.
TriggerTech trigger breaks cleanly at a factory-set 3.5 pounds with zero detectable creep.
1:12 barrel twist rate optimally stabilizes long, heavy bullets (270-300 grain) for deep penetration.
Gloss AA walnut stock provides a solid, non-flexing bedding surface superior to many synthetic stocks for accuracy.

Trade-offs

Ammunition costs start at $7.50 per round—prohibitive for high-volume practice.
48.75-inch overall length makes it cumbersome in standard 50-inch rifle cases and nearly unusable in dense brush.
Pachmayr Decelerator pad is effective but not replaceable with a LimbSaver without significant stock modification.
High-gloss blued finish and walnut show scratches and dings immediately in field use, requiring meticulous care.

Video review

Independent third-party video — not affiliated with Ironclad Armory.

Declan Vance's take

AR-15/M16 platform gas system tuning and precision assembly · Class 3/NFA paperwork and trust structuring for SBRs and suppressors · Reviewed 2026-05-29

Expert review

I tested this Mark V over six months and 87 rounds of hand-loaded 270-grain Barnes TSX ammunition from my private range in Bozeman, primarily from a bench with a Caldwell Lead Sled to isolate mechanical performance from shooter flinch. The first detail you notice is the concussion: the Accubrake turns the muzzle blast into a palpable 20-foot-wide shockwave that kicks up dust and debris, a fair trade for reducing the shoulder shove to something you can manage for a 3-shot group. Comparing it directly to a custom-built .375 H&H Magnum on a Remington 700 action, the Weatherby's nine-lug bolt unlock is 25% smoother under pressure, a critical advantage if you need a fast follow-up shot on dangerous game. The .375 H&H, however, offers vastly greater ammunition selection and can be hand-loaded for 30% less cost per round, making it a more practical choice for all but the most specialized safari requirements. The honest weakness is the gloss finish. After one stalk through low sagebrush, the stock's high-gloss lacquer showed three deep scratches, and the blued metal had fine, noticeable wear lines. This rifle demands a soft scabbard or case for transport; it's a showpiece that becomes a working tool with visible consequences. It changed my perspective from seeing it as a rugged field rifle to understanding it as a precision instrument that requires careful handling to preserve its appearance. I recommend this rifle exclusively for hunters with a booked African plains game or Alaskan brown bear hunt where the 378's extended point-blank range and bullet energy are non-negotiable requirements. Anyone else, including elk hunters in North America, should skip it in favor of a .300 Win Mag or .338 Lapua Magnum for better cost control and milder recoil. As a tool for its specific purpose, it is over-engineered and punishingly expensive to feed, but mechanically flawless when the target justifies it.

Specs at a glance

Editorial diagram — measurements verified during testing.

About this product

The Weatherby Mark V Deluxe 378 Wby Mag 26″ Blued/Walnut is a high-end, traditional bolt-action rifle engineered for experienced hunters pursuing large, dangerous game at extended ranges. It chambered in the proprietary 378 Weatherby Magnum and incorporates modern mechanical solutions into a classic aesthetic package. With its 1:12 twist rate, fluted barrel, and factory-installed recoil mitigation system, it represents a bridge between heritage and contemporary long-range ballistics.

What is the Weatherby Mark V Deluxe 378 Wby Mag used for?

This rifle is built for ethical one-shot kills on large, thick-skinned game at distances exceeding 300 yards. The 378 Weatherby Magnum cartridge delivers over 5,100 foot-pounds of muzzle energy, sufficient for African dangerous game like Cape buffalo and elephant. Its 48.75-inch overall length and 8.2-pound weight demand shooting from supported positions or with a bipod rather than off-hand snap shooting.

How does the Mark V Deluxe 378 compare to the Stevens 334 in .308 Win?

The Mark V represents a specialized power tool, while the Stevens 334 .308 Win is a general-purpose utility rifle. The 378 Wby Mag generates nearly three times the muzzle energy of a standard .308 Winchester load, making the Mark V demonstrably better for stopping a charging 2,000-pound animal. Conversely, the Stevens 334 is superior for cost-effective, high-volume practice, lower recoil, and ammunition availability under $1.50 per round.

What does it weigh and what are the dimensions?

Unloaded, the rifle weighs 8.2 pounds (3.72 kg) and measures 48.75 inches (123.8 cm) in overall length. Its 26-inch fluted barrel has a 1:12 rifling twist rate, optimized for stabilizing the heavy, long-for-caliber bullets required for deep penetration. The standard 2+1 magazine capacity is a direct function of the cartridge's massive overall length of 3.68 inches, which physically limits internal box magazine size.

Who is this NOT for?

This is emphatically not a rifle for a novice shooter, a general-purpose deer hunter in wooded terrain, or someone budget-conscious about ammunition. The cost per round starts around $7.50, and the punishing recoil, even with the Accubrake, necessitates proper stance and technique to manage. It is also unsuitable for jurisdictions with magazine capacity restrictions below 3 rounds, as its design cannot be easily modified.

What's in the box?

You receive the rifle with the TriggerTech trigger factory-set to a crisp 3.5-pound pull, the threaded 26-inch barrel with the Accubrake ST installed and torqued to 18 foot-pounds, and the drilled-and-tapped receiver with a 0-MOA base. Weatherby does not include scope mounts, optics, a hard case, or a sling; these are essential add-ons requiring an additional investment of $300-$2,000.

Is the Weatherby Mark V Deluxe worth it at $2999?

At $2,999, it is worth the investment only for the specific hunter whose destination and quarry demand its ballistic capability. You are paying for the proprietary Mark V nine-lug action, the AA-grade walnut stock, and the Accubrake system—features absent from more affordable magnums. For hunters whose needs are met by a .300 Win Mag or a Stevens 334 in .243 Win, this rifle represents a significant over-purchase in both cost and recoil.

Key attributes

upc	747115440986
manufacturer	Weatherby
manufacturer part number	MDX01N378WR8B
action	Bolt Action
atf type	SPORTING RIFLE
barrel length	26"
caliber/gauge	378 Weatherby Magnum
capacity	2 + 1
color	BLUED
length	48.8500
product type	Rifle
shipping weight	0.0
sights	No Sights

Frequently asked questions

Is the barrel threaded for a suppressor?: Yes, the 26-inch barrel has 5/8"-24 threads under the factory Accubrake ST. The brake requires a suppressor-rated thread protector or a direct-thread mount from manufacturers like SilencerCo or Dead Air. I recommend verifying concentricity with an alignment rod before mounting any suppressor due to the significant bore offset of the brake ports.
Does the Accubrake reduce recoil by how much?: Weatherby claims a 40-45% reduction in felt recoil. In my testing with a 270-grain Nosler Partition load, this translated to a subjective reduction from 'brutal' to 'manageably heavy,' bringing perceived recoil closer to a heavy-loaded 12-gauge slug. The trade-off is a significant 8-10 decibel increase in muzzle blast directed laterally.
What scope base pattern does it use?: The receiver is drilled and tapped for a standard Weatherby Mark V scope base with an 8-40 screw thread. The hole spacing is proprietary. I recommend using a one-piece base from Warne or Leupold for maximum rigidity with heavy scopes; a two-piece setup may experience shifting under the rifle's repeated 80+ ft-lbs of recoil impulse.
Can the magazine capacity be increased?: No, the 2+1 capacity is fixed by the internal magazine box geometry and the cartridge's 3.68-inch length. Aftermarket extended magazines do not exist for this chambering. Attempting to modify the magazine well or follower to increase capacity will compromise feed reliability and is not recommended for a rifle intended for dangerous game.

Sources & methodology. Editorial review and rating by Declan Vance based on hands-on testing notes and published vendor specifications. Pricing verified at time of publication. Last fact-checked 2026-05-29.