What barrel thread pitch and calibres is the GrovTec GTHM323 jam nut designed for?

The GrovTec GTHM323 jam nut is specifically engineered for centrefire rifle barrels featuring 5/8"-24 TPI muzzle threads. It is ideally suited for .30-calibre and .308 Win platforms, as well as popular Australian hunting and target calibres like 6.5 Creedmoor and .300 AAC Blackout.

Can I use the GrovTec GTHM323 jam nut with a 1/2"-28 barrel or metric threaded rifles?

No, this specific model will not fit barrels threaded in 1/2"-28, which require the GrovTec GTHM322 instead. It is also incompatible with common European metric thread standards such as M14x1, M15x1, and M18x1, so you must verify your rifle's muzzle thread pitch prior to purchase.

Is the GrovTec GTHM323 suitable for mounting direct-thread sound suppressors?

Using a jam nut is generally avoided for direct-thread sound suppressors that require tight concentricity tolerances to prevent baffle strikes. For suppressors, manufacturer-specific precision shim kits or direct shoulder indexing are preferred over the GTHM323, which is primarily designed for timing directional muzzle brakes and compensators.

Does this firearm accessory require any electrical certifications or compliance checks for the Australian market?

No, the GrovTec GTHM323 is a completely unpowered, passive machined steel firearm accessory. Standards such as 240V compatibility, Australian mains plugs, and SAA or RCM electrical certifications are entirely not applicable to this product.

GrovTec Jam Nut GTHM323 - GrovTec GTHM323

The GrovTec Jam Nut – 5/8"-24 (.308) is a machined steel locking collar engineered to index and secure muzzle devices on threaded centrefire rifle barrels. Designed with standard 5/8"-24 TPI internal threads, this low-profile hardware allows shooters to precisely time directional muzzle brakes, compensators, and flash hiders without relying on single-use crush washers or variable peel shims. Finished with a durable black coating, it enables repeatable alignment, simple removal, and straightforward mechanical re-timing on .30-calibre platforms.

Key Features

Reusable Hex-Profile Design: Enables mechanical indexing and firm locking of directional muzzle devices without requiring single-use crush washers.
Standard Calibre Threading: Machined with internal 5/8"-24 TPI threads for compatibility with common centrefire sporting and precision rifle barrels.
Machined Steel Construction: Delivers rigid, durable lockup with a protective black finish for field and range use.
Adjustable Port Timing: Facilitates fine orientation of brake ports for optimal recoil management and quick muzzle device swaps.

Specifications

Brand: GrovTec US, Inc.
Manufacturer Part Number (MPN): GTHM323
Thread Pitch: 5/8"-24 TPI
Calibre Compatibility: .30-calibre / .308 Winchester (also suits 6.5 Creedmoor, .300 AAC Blackout, and 7.62 NATO barrels with 5/8"-24 threads)
Material: Machined steel
Finish: Black

Who is the GrovTec Jam Nut 5/8"-24 for?

Long-range precision shooters — Need to index directional muzzle brakes on barrels threaded in 5/8"-24 TPI to achieve level port alignment without stacking uneven shims, using this muzzle brake jam nut for repeatable positioning.
Hunters — Require a simple, reusable locking method when configuring .30-calibre or .308 Win centrefire rifles with 5/8"-24 TPI threaded muzzle devices that may need periodic field adjustment or maintenance.

Less suitable for: Barrels threaded in 1/2"-28 TPI (which require 1/2"-28 jam nuts) or metric profiles such as M14x1, M15x1, and M18x1, as well as direct-thread sound suppressors requiring tight concentricity tolerances, where precision-ground shoulder shim kits are preferred over jam nuts.

SKU	GT40838LP
Model #	GTHM323
Brand	Grovetec
Shipping Weight	1.0000kg

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Grovtec Gthm323 Jam Nut 5/8-24 .308 Calibre Muzzle Hardware

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