It’s very common to have pistols and rifles with threaded muzzles. A very common thread pattern for .22, .204, .223/5.56 and even some 9mms is 1/2×28. This means the thread is 1/2″ wide and has 28 threads per inch (TPI). This is the most common pattern for AR rifles for example as .223/5.56 rifles tend to follow the original military specification thread pattern. There are many patterns out there so you always want to confirm.
For a variety of reasons, you may not want to install a muzzle device. If this is the case, I would recommend installing a thread protector, sometimes called a “muzzle nut” to protect the threads.
For example, here is a 10.5″ AR pistol upper receiver assembly. You can see the 1/2×28 thread and I did not plan on installing a muzzle device.
Thread protectors simply screw onto the end of the barrel. The only thing I do is to apply some Blue-Loctite to reduce the odds of the nut rattling off. Yes, the heat of the barrel will soften the Loctite but the “gummy” nature of it will do the job. If you plan on taking the thread protector off and putting it back on a lot, then don’t use a thread locker.
I hope this helps you out. The Amazon listing is the product I used on the above build and really like.
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Amazon product links are at the bottom of the post.