Silencer Saturday 341: The Case For (Some) Non-standard Thread Pitches

Welcome back to another installment of Silencer Saturday. This time we will look at some standard thread pitches and some less-standard ones. Why would any manufacturer use a non-standard thread pitch? Let’s find out.

Silencer Saturday @ TFB:

Silencer Saturday #340: The SHUSH Act Reintroduced In Congress SILENCER SATURDAY #337: The HUXWRX FLOW 556 Ti Preview SILENCER SATURDAY #327: YHM Mounts & Muzzle Devices – Locking In The Bad Larry SILENCER SATURDAY #306: The KAC QDC MCQ-PRT Ultra Compact 5.56mm Suppressor Silencer Saturday #339: SilencerCo’s Little-known A2 ASR Flash Hider

Disclaimer: NFA items like silencers are highly regulated. You can end up in prison if you break the law in this space. Please speak to a competent attorney if you need advice on your specific situation. I am not your attorney, and I do not and will not represent you.

Standardization

Standardization is usually a good thing. Whether it is cell phone chargers, railroad gauges, or sizes of nuts and bolts, when people use the same type of equipment it is easier for everyone involved. Economies of scale make replacement parts cheaper, and there is more competition in the market when different companies sell goods that are compatible.

This is very true in the gun industry as well. “Does it take Glock mags?” has become a running joke because it is asked so frequently when new guns are announced. Most of us already have a pile of those magazines and multiple guns to use them with, and if the new gun can use them too that is a major expense avoided. It is also one less thing to forget when loading up for the range. We also standardize scope tube diameters so that rings and mounts are easier to find, and when a scope uses a main tube other than 1-inch, 30mm, 34mm, or 35mm, people ask a lot of questions.

In the world of suppressors, standardization is common with muzzle thread pitches. Just reading 1/2-28, 5/8-24, and .578-28 probably made you involuntarily think of the common calibers each one pairs with.

Why Go Non-standard?

While standardization may make sense in most situations, it is not always the answer. This article was inspired by the Ruger Hawkeye Alaskan. I have been looking at various big-bore hunting rifles and the price point, all-weather construction, and shorter barrel with muzzle threads of the Alaska caught my eye. But the next thing I noticed was the thread pitch: the .300 Win Mag model has 1/2-24 threads. That is not a misprint, 1/2-24 is correct. Not 1/2-28, as we would expect on other guns, or 5/8-24 as is generally on .30 caliber guns, 1/2-24.

The non-standard threads also show up on the other caliber models. The .338 Win Mag is threaded 1/2-32, and the .375 Ruger has 5/8-18 threads. But there is a good reason for these choices: to prevent accidental shooting of bullets too big for the muzzle device. Had Ruger put 1/2×28 threads on the .300 Win Mag, there is a 100% chance that someone would put a 1/2-28 muzzle device intended for a .223 on the gun. A heavy, fast .308 bullet going through an opening sized for .223 would destroy the silencer and possibly the gun too. By making the threads non-standard, that cannot happen.

Instead, people who want to put silencers on these guns must find an adapter that goes to a normal thread pitch. Those adapters are designed for this exact situation and have bore diameters that accept those larger bullets. Adding the extra step of finding that adapter is hopefully enough to make the end user stop and think about what muzzle device is being used, and it probably saves Ruger a lot of expense by avoiding warranty work.

Another gun that has a weird muzzle thread is the original Steyr Scout. That gun has 1/2-20 threads, which is not the most common pitch but is used on some .22 rifles. It is not generally used on centerfire rifles though. The Scout is typically chambered in .308 or 6.5 Creedmoor, and 5/8-24 would be the standardized thread pitch for those cartridges. However, the Scout’s barrel profile is quite thin, too thin for the 5/8 of an inch outer diameter of those threads.

Steyr needed a thread pitch with a smaller outer diameter, but the most common thread pitch that would fit is 1/2-28. Much like the Ruger Alaskan there is a risk that a muzzle device or direct thread silencer with a .223 bore could be unwittingly put on those threads. To remedy this, Steyr sold a 1/2-20 to 5/8-24 thread adapter with a suitable bore diameter. Those who want to use a silencer can do so with the adapter, and everyone else can enjoy a thin barrel profile.

Non-standard thread pitches are rare, but there are good reasons why a manufacturer would choose to use them. When you see one in the future take a step back and think about why the manufacturer decided to do that. There just might be a reasonable explanation.