Threading

[Allen in MT]

Looking at getting my .223 Rem 700 threaded. What is the average length of threads from muzzle of barrel to barrel shoulder. I've heard 0.500" to 0.600" is there one standard length of threads. thanks

 

[LocoGringo]

Edit to say my reply did not apply.

 

[rbernie]

Paging @MachIVshooter.

 

[Hugger-4641]

He's not asking about pitch or thread diameter, he's asking about depth from crown to shoulder, which could also be expressed as total number of threads.
As a general rule the length should be roughly the same as the diameter, so a 1/2-28 would be about 0 .4 to 0.55, or about 14 full threads.. A 5/8-24 would be 0.6 to 0.65, or 15 full threads.

 

[horsemen61]

Ttrl

 

[Hugger-4641]

Ttrl

Not familiar with this acronym, can you explain ?

 

[jmorris]

Around 5/8 length (.625”) on .223’s. I have seen as short as 3/8” (.375”) on .22 long rifle. Both using 1/2-28 but there are other thread pitches used.

 

[gotboostvr]

Not familiar with this acronym, can you explain ?

Tagged to read later

 

[Hugger-4641]

Tagged to read later

Thanks!

 

[MachIVshooter]

Paging @MachIVshooter.

Sometimes there's a reason to run a different length, but generally I cut tenon lengths as follows:

Centerfire rifle: .55
Pistol caliber carbine: .45-.5
Centerfire handgun: .45
Rimfire: .4

The .625 tenon length of the AR is meant to accommodate the 1/8" crush washer. There's no reason to make them that long for any other muzzle device, and there are several muzzle devices not threaded deep enough to take all of a 5/8" long tenon.

Sometimes magazine tubes, sights or other components and features dictate a shorter tenon.

There is also a specific rimfire tenon spec for O-ringed SilencerCo cans, but unless someone mentions it, I don't do that one, and they work just fine on a normal tenon.

The other important aspect is the undercut. I put one fore and aft, but the rear one is critical, because not all muzzle devices are sufficiently counterbored and may bottom out before contacting shoulder if there is no undercut. The front is done for a cleaner look and to aid with installation of cans.

 

[12Bravo20]

As stated by others, between 0.400" and 0.500" or the same length as the major thread diameter. The exception as mentioned is the AR or others that use a crush washer.

Yes having the undercut at the shoulder is very important. Another thing that is super important is to have a small radius at the corner of any shoulder. A squared corner/shoulder can and will lead to failures and parts breaking off. Squared corners induce a weak spot. I have seen this on things as small as th CMMG AR22 firing pins up to very large roller shafts that are 24+ inches in diameter at the smallest point (bearing surface).

 

[BigBlue 94]

As a basic rule, any threaded item needs approximately the diameter as the tenon length. Too short and you risk misalignment and improper stability.

Think about nuts and bolts. A 1/4-20 nut is about 1/4" thick, etc.

 

[sarduy]

If i were you, I would do the same as the AR have, that way i can use the same accessories with crush washers

 

[Zak Smith]

Industry standard specs:
https://thunderbeastarms.com/tech/thread-specifications

^^ Centerfire. Rimfire also at link

 

[lysanderxiii]

Looking at getting my .223 Rem 700 threaded. What is the average length of threads from muzzle of barrel to barrel shoulder. I've heard 0.500" to 0.600" is there one standard length of threads. thanks

There is no "standard", but if you plan on an AR-type muzzle device, 0.62-0.63" to the shoulder and thread as far as a standard die will go. This gives room for full threading of the device and a washer.

 

[lysanderxiii]

Industry standard specs:
https://thunderbeastarms.com/tech/thread-specifications
^^ Centerfire. Rimfire also at link

That's not an "industry" specification, that is a local, or company, specification. Colt uses a different specification . . .

 

[Zak Smith]

It is.

You can tell because it being the norm is what makes the weird ones stand out.