Thread adapters: Why the hate?

[86indy]

I have trust issues working in the manufacturing world I just opted to skip adapters. Less variables the better, it’s that simple for me.


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[Firth]

I left the 6.5 CM at 22” long because I have the ZG 6.5 and OG 6.5 I can use with it. I knew from using my little gauge, that it would be 1/2x28 and I was okay with that. I also had already ordered a good (UM) 1/2x28 to 5/8x24 adapter for it.

As far as I know, Kampfeld (that’s the name I couldn’t remember) is the only trustworthy smith who does them collared like that.

Shooter71 on here has done a couple for me. They came out great.

 

[Kurts86]

I was worried until I used a few and now I’m fine with them assuming you check alignment.

 

[Jimbee]

Anyone have the thread adapters that caused them issues lying around?

I’ll pay shipping costs if you want to send them my way.

I had a cheapo thread adapter that made my supressor crooked enough to take a little hunk out of the end cap. I can see if I still have it. It was obvious after I pulled the bolt and just looked down the bore through the supressor. You're welcome to it but why are you wanting adapters that caused issues?

 

[WoodlandCritter]

I'm clearly one of the guys you're complaining about. I have had baffle strikes with thread adapters and have avoided baffle strikes because I've checked the alignment of other adapters before using them. My background is in manufacturing with a focus on precision CNC machining. Put simply, I do not trust the average lathe operator to even be able to read GD&T callouts in the US anymore. I use adapters when necessary, but tolerance stack is real.

Lets look at some numbers. Its pretty average to see a suppressor be 0.060" overbore. Than gives you 0.030" of clearance per side. If the shoulder of your barrel is perpendicular to the bore with a max error of ~0.2 degrees, that gives you an additional error of only ~0.1 degrees with an 8" can before you get an endcap strike (feel free to check my trig). Of course that's assuming you get very unlucky and the high spot of the adapter clocks perfectly with the high spot of your shoulder. But its possible, and cans are expensive and difficult to buy. So do I want to rely on some guy making 13$ an hour to make sure he's using a fresh insert when he makes my adapter? Nah. Not really.

 

[Shortschaf]

I'm clearly one of the guys you're complaining about. I have had baffle strikes with thread adapters and have avoided baffle strikes because I've checked the alignment of other adapters before using them. My background is in manufacturing with a focus on precision CNC machining. Put simply, I do not trust the average lathe operator to even be able to read GD&T callouts in the US anymore. I use adapters when necessary, but tolerance stack is real.

Lets look at some numbers. Its pretty average to see a suppressor be 0.060" overbore. Than gives you 0.030" of clearance per side. If the shoulder of your barrel is perpendicular to the bore with a max error of ~0.2 degrees, that gives you an additional error of only ~0.1 degrees with an 8" can before you get an endcap strike (feel free to check my trig). Of course that's assuming you get very unlucky and the high spot of the adapter clocks perfectly with the high spot of your shoulder. But its possible, and cans are expensive and difficult to buy. So do I want to rely on some guy making 13$ an hour to make sure he's using a fresh insert when he makes my adapter? Nah. Not really.

How could you possibly get the rearward shoulder out of square with the threads, or the internal threads non-concentric with the external threads on a CNC lathe?

Isn't it all done in one operation?

Genuine questions from a manual lathe novice. Curious how we end up with bad adapters

 

[WRO]

I have trust issues working in the manufacturing world I just opted to skip adapters. Less variables the better, it’s that simple for me.


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Barrell threads can be mismatched as well.

 

[Marbles]

Check alignment by looking down the barrel and out the muffler.

Do it regardless of adapter or not.

It is easy.

Barrel threads can be off. Suppressor threads can be off.

Good adapters are less than $30. https://precisionarmament.com/m4-muzzle-thread-adapter/

If you have an OTB can then get the Unknown Suppressors adapter.

 

[Pookie]

Many people use thread adapters. I use a thread adapter on 5.56 to run my 7.62 can. As with any new setup for a can, you should check to make sure it's aligned through the entire barrel and can path.

 

[WoodlandCritter]

How could you possibly get the rearward shoulder out of square with the threads, or the internal threads non-concentric with the external threads on a CNC lathe?

Isn't it all done in one operation?

Genuine questions from a manual lathe novice. Curious how we end up with bad adapters

Good question although not necessarily the right one. The issue is alignment to the bore, not the threads. When a barrel is drilled with a gun drill, the drill will wander a bit. So the bore isn't always perfectly aligned with the outer diameter of the barrel. And, of course, the OD is generally what you're holding in the chuck.

Therefore, both your shoulder AND threads can potentially be misaligned to the bore even though they're cut in the same setup. You gotta get used to really considering what your primary datum is.

Then as far as the adapter goes, there's a whole host of ways you could mess that up between changing setups and changing tools.