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35NCO · 03-10-2014, 11:49

FlagDayNCO reminds me of another important portion,

Some points on Threading and mounting from experience:

-Make sure the barrel shoulder, threads, and crown are all perfectly concentric to the bore. Many mass manufactured run off guns are not concentric to the bore and could cause baffle strikes due to misalignment. AK47’s and 74’s are notorious for this. Just threading the mount on does not mean it is safe. It would be good to have a good gunsmith that is good with a lathe to check the concentricity of these points. The point of this is that the outer barrel profile is typically not concentric to the bore. Surprisingly to many, when companies drill and rifle the barrels they are not dead center. For this reason the threading must occur concentric to the bore by either indexing from the bore or by threading between centers. The only part that you can get away with without between centers is the crowning. This can be achieved with a good pilot and
crown tool. It can be done in or out of a lathe if done carefully. Surf youtube for some videos on barrel threading as well if you want to have a better understanding of the how and why this takes place.

-If the suppressor is a thread on, often many companies have different standards of thread lengths that are required for a proper mounting. AAC published a PDF that you can download that has the threading specifications for all their suppressors. While this may not apply directly to your case, it is worth review to understand the aspects of threading in relation to concentricity to the bore and therefore concentric to the bore of the suppressor.

-The length of thread can also be cut in a manner that the muzzle break, flashhider or mount is properly timed to the correct orientation to the barrel. This is useful for a rock solid professional mounting. This is also useful in mitigating POA to POI shift as much as possible.

-Avoid taps and dies as this will not do what you want if you need to thread or correct a situation. Also remember that for a suppressor mount you really want tight threads, generally a class III thread. For ½ 28 you want to be close to .500 or better. There are international standards that cover these tolerances. A class II thread may be okay for a muzzle break or flashhider, but it will be far too loose for a suppressor.

-Finally, make sure you have a relief cut behind the threads. This is necessary so the threads do not run out inside the internal thread. The relief cut is typically .100 from the shoulder of the barrel to the first thread.

03-10-2014, 11:49	#15
35NCO Guerrilla Join Date: Nov 2010 Location: CONUS Posts: 403	Threading and Mounting FlagDayNCO reminds me of another important portion, Some points on Threading and mounting from experience: -Make sure the barrel shoulder, threads, and crown are all perfectly concentric to the bore. Many mass manufactured run off guns are not concentric to the bore and could cause baffle strikes due to misalignment. AK47’s and 74’s are notorious for this. Just threading the mount on does not mean it is safe. It would be good to have a good gunsmith that is good with a lathe to check the concentricity of these points. The point of this is that the outer barrel profile is typically not concentric to the bore. Surprisingly to many, when companies drill and rifle the barrels they are not dead center. For this reason the threading must occur concentric to the bore by either indexing from the bore or by threading between centers. The only part that you can get away with without between centers is the crowning. This can be achieved with a good pilot and crown tool. It can be done in or out of a lathe if done carefully. Surf youtube for some videos on barrel threading as well if you want to have a better understanding of the how and why this takes place. -If the suppressor is a thread on, often many companies have different standards of thread lengths that are required for a proper mounting. AAC published a PDF that you can download that has the threading specifications for all their suppressors. While this may not apply directly to your case, it is worth review to understand the aspects of threading in relation to concentricity to the bore and therefore concentric to the bore of the suppressor. -The length of thread can also be cut in a manner that the muzzle break, flashhider or mount is properly timed to the correct orientation to the barrel. This is useful for a rock solid professional mounting. This is also useful in mitigating POA to POI shift as much as possible. -Avoid taps and dies as this will not do what you want if you need to thread or correct a situation. Also remember that for a suppressor mount you really want tight threads, generally a class III thread. For ½ 28 you want to be close to .500 or better. There are international standards that cover these tolerances. A class II thread may be okay for a muzzle break or flashhider, but it will be far too loose for a suppressor. -Finally, make sure you have a relief cut behind the threads. This is necessary so the threads do not run out inside the internal thread. The relief cut is typically .100 from the shoulder of the barrel to the first thread.
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