Gunsmithing 1/2x28 for .243/6mm???

[WB300]

I know it's not usually recommended, but why isn't threading a muzzle 1/2x28 for a .243 or 6mm (short action cartridge at 22" bbl length) more common?

I have several .308 caliber rifles threaded 9/16x24 for a suppressor and was told that it's the minimum recommended for .308.

By my math... 9/16 = .5625". .5625"-.308" = .2545". This should give at least the recommended .1" preferred for a shoulder.
Now.... 1/2 = .500". .500"-.243"=.257". So there is more meat than 9/16 on a .308.

I am not a machinist, but I understand there is more math to it than I've illustrated above, but can someone please help me out?

Is threading a 22" barrel 1/2x28 on a .243 Win rifle a bad idea??? Let's assume the barrel profile isn't big enough to support 9/16 or 5/8 threading.

Thanks in advance.

 

[chevy_man]

I'm sure you can find a smith to do whatever you want.

Most stick with 5/8” because it's common and easy to find.

 

[TheOfficeT-Rex]

Probably because the muzzle under the threads is getting pretty thin and has potential to open up and do funny things.
Yes, the nominal is 1/2 inch… but the minor for 1/2x28is .457. Subtract bore diameter, divide by 2, and you only have .107 of barrel material between bullet and muzzle device. 5/8x24 gets you and extra 60k on each side. Plus or minus.

I’d always go with the largest threads I can get cut. YMMV.

 

[WB300]

Thanks for the reply.

Does that mean my current 9/16 on a .308 is a bad idea??

 

[Wannashootit]

Thanks for the reply.

Does that mean my current 9/16 on a .308 is a bad idea??

What T-Rex said.
Not a bad idea, but not ideal, either. If you can go 5/8", and still have adequate shoulder- do it. To me, "adequate" depends on the muzzle device. I'll do brakes with as little as .050 shoulder and rely on Rocksett rather than torque (which would deform a minimal shoulder) to make sure it stays put. Cans, generally double that to .100 shoulder but I always go by the mfg. specs. Obviously due to length alone, concentricity and the shoulder being precisely 90 degrees to the bore is more critical.

For me, .100 barrel wall thickness is minimal and again- more is better. Well documented (and I've seen it myself testing with gage pins) that a muzzle can bell-mouth from too little barrel wall thickness.

 

[Easy_E]

All 350 Legends come threaded 1/2-28 and that's a .355 bore so I wouldn't think doing a 1/2-28 on a .243 would hurt anything other than not matching the adapters that come with bigger bore cans .

 

[WindstormSCR]

the best reason I can think of to go 5/8x24 is because then you or a future owner are far less likely to accidentally put a .223 dia muzzle device on the thing.

 

[Geno C.]

the best reason I can think of to go 5/8x24 is because then you or a future owner are far less likely to accidentally put a .223 dia muzzle device on the thing.

But being stupid should hurt and/or be expensive

 

[Geno C.]

If your cans are already 9/16 I’d stick with that. 1/2 won’t hurt anything. Mike from tac ops threads his stuff 9/16 fwiw

 

[roostercogburn98]

All 350 Legends come threaded 1/2-28 and that's a .355 bore so I wouldn't think doing a 1/2-28 on a .243 would hurt anything other than not matching the adapters that come with bigger bore cans .

That’s funny, my 350 legend was 5/8-24?

 

[LeftyJason]

There is also the possibility of a face mount muzzle brake.

Thunderbeast cb brake on my Tikka T3x lite. Muzzle diameter of 0.616". Threaded 9/16 under but uses face of muzzle as shoulder. Installed and threaded by Thunderbeast.

 

[iceng]

1/2x28" is common for rimfire stuff. Last thing you want is to accidently put a 223 can with 1/2x28 onto a 6mm.

Thats a common reason why.

 

[FuhQ]

5/8-24…And don’t look back.

 

[kswaterfowl]

I had a t3x lite in 243 threaded 1/2-28 by Longrifles Inc. Had no issues with it, and it was one of my best shooting factory barrels that I've owned.

 

[kthomas]

Thanks for the reply.

Does that mean my current 9/16 on a .308 is a bad idea??

No, it's not bad.

TacOps cuts their muzzle threads to 9/16x24, to maximize shoulder engagement with their suppressors.

They use quality cut rifled Krieger barrels, so the risk of the muzzle "belling" or flaring out is minimal. And TacOps rifles shoot very well.

 

[LeftyJason]

No, it's not bad.

TacOps cuts their muzzle threads to 9/16x24, to maximize shoulder engagement with their suppressors.

They use quality cut rifled Krieger barrels, so the risk of the muzzle "belling" or flaring out is minimal. And TacOps rifles shoot very well.

Bolded is a bit of an understatement

 

[WB300]

I had a t3x lite in 243 threaded 1/2-28 by Longrifles Inc. Had no issues with it, and it was one of my best shooting factory barrels that I've owned.

Exactly the rifle I have and exactly what I was wanting to do.

 

[kswaterfowl]

It killed a few critters

 

[WB300]

Lefty...

I have another Tikka T3x that TBAC did the same as yours with a 9/16 brake on a 7-08. Came out awesome.

 

[david walter]

You can mess up and put a 223 hole on a 6mm barrel that way. And blow the end of the barrel up.

I don’t know if any 5/8-24 brakes with less than a 6mm hole.

So there’s that.

 

[kswaterfowl]

You can mess up and put a 223 hole on a 6mm barrel that way. And blow the end of the barrel up.

I don’t know if any 5/8-24 brakes with less than a 6mm hole.

So there’s that.

That's a good point. Mine was threaded for a silencerco harvester, so I didn't have to worry about that. But you do have to pay attention to the muzzle device you plan using.

 

[LuvDog]

I had a T3x 6.5. Superlite barrel threaded 1/2” and it was fine

 

[Easy_E]

That’s funny, my 350 legend was 5/8-24?
View attachment 8247677

Funny thing is my grandsons 350 is 5/8-24, just the way I threaded it . I didn't say 1/2-28 threads were the way to go just making a point some factory guns come with 1/2-28 threads so the wall thickness must be safe.

 

[msgriff]

Funny thing is my grandsons 350 is 5/8-24, just the way I threaded it . I didn't say 1/2-28 threads were the way to go just making a point some factory guns come with 1/2-28 threads so the wall thickness must be safe.View attachment 8248164
View attachment 8248163

The issue is that you posted "All 350 Legends come threaded 1/2-28", which is factually incorrect, even for off-the-shelf factory barrels.

 

[Easy_E]

The issue is that you posted "All 350 Legends come threaded 1/2-28", which is factually incorrect, even for off-the-shelf factory barrels.

Your right I should have said many of them come threaded 1/2-28 .