Best Thread Patterns for Pistol barrels?

General Firearms NFA
1

I see that OEM and aftermarket threaded barrels are available in a wide array of thread patterns. So, for 9mm and .45 ACP, what are the more “desirable” thread patterns, assuming the user has a choice?

Looking around on the internet, I see:

HK45 & HK45C uses: 16x1 LH
FNP-45 Tactical uses: 0.578x28 RH

If I buy an aftermarket barrel for my Glocks (9mm and .45) what patterns would you recommend?

Thanks,
Jason

2

0.578x28 RH

I would ask one of the AAC dudes though.

3

9mm = 1/2x28
.45 = .578x28

4

Like Robb said, if you want standard threads (slightly more common here):
9mm = 1/2x28
.45 = .578x28

I prefer metric (reverse) threads, so:
9mm = M13.5x1LH
45 = M16x1LH

5

9mm = M13.5 x 1 LH
45 = M16 x 1 LH

Is the only way to go.

6

LH threads are terrible for me. I will always turn it the wrong way when I want to make sure it’s tight.

Then there is the complexity of the metric threads. Ridiculously over engineered if you ask me, with no gain. There are literally over twice as many dimensions at half the tolerances (that don’t need to be that tight) compared to standard American threads.

7

Well I bought a OEM Glock threaded G19 barrel from Robb’s company. I got the TiRant .45. I got the correct 9mm piston for the TiRant.

However, I’m still clueless as to the pros and cons of the metric vs standard threads.

For those of you who prefer the metric threading, what makes that superior in your eyes? What is the purpose behind the metric threads being left handed instead of right handed?

I’m trying to educate myself beyond “well these guy on the Internet said it’s better.”

Thanks.

8

The metric threads have a “pad” (flat band) at the end of the barrel that the o ring in the silencer rests on and keeps tension on the connection so it won’t come unscrewed.

Metric threads also index off the muzzle instead of a thin shoulder behind the threads that evenually wears down (gets a rolled over edge).

9

this.

Plus, arguably, the threads are opposite to the rifling direction and MAY stay tighter while shooting… may.

10

Correct

11

I’ve got two USP Tacticals and using my KAC USP45T can with LH metric thread, it still comes loose.

12

Sorry to hear.

My Evo does not loosen on my M13.5x1 LH Sig Barrel.

No matter what threads you have, you still need to be vigilant about checking it periodically.

13

Does the KAC have an o ring?

14

It does indeed. It’s more effective at staying tight with a new one, so I have a bag of spares.

15

I use an o-ring in the thread relief of my 1/2-28 barrels.